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AES study of passive films formed on a type 316

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J O U R N A L O F M A T E R I A L S S C I E N C E34(1999)1073–1079AES study of passivefilms formed on a type316 austenitic stainless-steels in a stressfieldF.NAVA¨I∗,O.DEBBOUZLaboratoire de G´enie des Mat´eriaux,ISITEM,Universit´e de Nantes,La Chantrerie,C.P.3023,44087Nantes Cedex03,FranceThe type AISI316stainless steel,in addition to the principal alloying elements chromium and nickel,contains2.5–3.5%of molybdenum.This element is added to improve the mechanical properties and the pitting resistance of austenitic alloys.Concerning the Stress Corrosion Cracking(SCC)resistance of austenitic stainless steels,molybdenum additions to alloys have a variable effect:the effect is detrimental for small additions of Mo,and it is beneficial for the alloy containing more than4%Mo.Thus the Mo concentration on passive film plays an important role on the SCC resistance of steels.On the other hand,in a previous investigation,it was shown that the composition of passivefilms formed on the stressed302alloy depended on the compressive or tensile nature of stresses. Consequently,the aim of the present work is to study the composition of passivefilms formed on316steel and the migration of molybdenum in a stressfield.Thus,Auger electron spectroscopy spectra were recorded to determine the chemical composition of the passivefilms formed on both sides of the type AISI316stainless steel U-bend samples.The results obtained show that the behaviour of chromium and oxygen in passivefilms formed on316steel in the stressfield was nearly similar to that formed on302steel.Concerning the molybdenum diffusion outwards the passivefilm formed on the316steel was reduced by either the tensile or compressive stressfield.C 1999Kluwer Academic Publishers1.IntroductionGenerally,molybdenum added to stainless steels in-creases their passivating ability and decreases the activity of the weak points of the passivefilms.Conse-quently,molybdenum assists passivation of the stain-less steels but does not constitute the passivefilm.When passivity failure occurs at weak points of passivefilm, the localized active dissolution of all the alloy con-stituents leads to a corrosion productfilm formation,in which molybdenum ions are significantly concentrated. The molybdenum enriched corrosion productfilm is due probably to the fact that molybdenum is pas-sive in the active region of chromium and iron.It acts as an effective diffusion barrier against further active dissolution of the alloy[1–2].Vanslembrouck et al.[3] studied the behaviour of several austenitic stainless steels in neutral chloride solutions.They found that the molybdenum presence improves the resistance of steels against pitting attack.Cieslak et al.[4]found also a beneficial effect of alloyed molybdenum.However,Latanision and Staehle[5–6]suggested that molybdenum has a vari-able effect on the stress corrosion cracking(SCC)resis-tance of austenitic stainless steels.Above5%,the effect is beneficial,while below5%it is rather detrimental. In this way,Loginow and Bates[7]have shown that a small addition of molybdenum(0.1%)to a18Cr-8Ni ∗Author to whom all correspondence should be addressed.steel exposed to MgCl2solutions had a detrimental effect on the failure time of this steel.Kowaka and Fujikawa[8]found identical results.On the contrary, Staehle et al.[9],and Desesteret and Wagner[10], found that somewhat larger percentages of Mo in stain-less steels tested still had a detrimental effect. Concerning the effect of cold work on the corrosion resistance of alloys,many papers shown that cold work decreases the ability to passivate the austenitic stainless steels[11].Cigada et al.[12]correlated the SCC resistance re-duction to an increase in concentration of internal micro-stresses.Hawkes et al.[13]showed that the cold work stretching effect on stress corrosion cracking of type316stainless steel was deleterious by boiling mag-nesium chloride solution.On the contrary,there are some indications showing that beneficial effects of cold work could be observed[14–15].This is mainly,the case for cold rolling or extrusion,which produce com-pressive residual stresses and enhance the resistance of the samples to aggressive environments. Concerning the effect of the compressive stress on the corrosion resistance of stainless steels,it has been shown in a previous investigation[16],that the com-position of passivefilms formed under stress on302 alloy depended on compressive or tensile nature of stresses.It was also shown that the beneficial effects0022–2461C 1999Kluwer Academic Publishers1073of compressive stress was both related to the increas-ing chromium enrichment and the decreasing thickness of the passive film.2.Experimental 2.1.Base materialRectangular specimens of 100mm long,8mm wide and 0.25mm thick,investigated in the present study were cut from a type 316stainless steel sheets from Goodfel-low,supplied in a ductile pure austenitic structure state (annealed at 1050◦C and quenched).The longitudinal axes of the samples were oriented parallel to the prior rolling direction of the sheet.The chemical composi-tion of the investigated steel is given in Table I.Fig.1presents the stress-strain curve of the investi-gated base material,where elastic and plastic domains are clearly shown.It can be noticed that the offset yield-ing point is about 300MPa and the ultimate tensile strength is ≈625MPa corresponding to a failure strain of 0.49mm/mm.2.2.Surface pretreatmentAfter cutting the sheets to rectangular specimens,the tested samples received the following initial prepara-tion.They were washed with soap,rinsed with water,and ultrasonically degreased in an acetone bath.They were then electropolished for 3minutes with a current den-sity of 1A cm −2,in a 15%sulphuric acid (R.P.Norma-pur,95%minimum,d =1.83)and 85%orthophos-T A B L E I Chemical composition of the investigated steel (wt %)Composition (%)Cr Ni Mn Mo C S P Fe 16–208–14<22.5–3.5<0.12<0.03<0.045BalanceFigure 1Stress strain-curve for 316stainless steel,straining rate ε◦=1.3910−3s −1.phoric acid (R.P.Normapur,85%minimum,d =1.70)mixture at temperature 35◦C.The samples were then washed in doubly distilled water,and finally dired in a hot air flow.2.3.Mechanical stressingBefore immersing in the acidic bath,the samples (ex-cepted R sample)were subjected to a loop test.They were first plastically deformed into a U-shape at a curvature radius of ρ=7±0.25mm (Fig.2a),then the two extremities were clamped together in order to add the elastic stress (Fig.2b).The superficial stress due to the bending of the spec-imen is estimated to be slightly higher than the base material yielding point (about 350MPa).Table II indi-cates the maximum external stress in the outer layers of the U-bend sample.For a realistic comparison,an un-stressed sample,denoted R,was prepared and studied as a referencespecimen.Figure 2Mechanical straining of sample:(a)rolled specimen plastically deformed before stressing;(b)stressed specimen after adding the elastic stress.T A B L E I I Strain and stress of U-bend specimenRadius of curvature Strain Estimation of stress Sample(mm)(mm/mm)(MPa)U-bend 7±0.5≥0.02Residual ±350R∞Residual1074Figure3Potentiodynamic polarization curve for the type316stainless steel in1N sulphuric acid.Sample potential were measured against the satured calomel electrode(SCE).3.Results and discussion3.1.Polarization curvesIn order to determine the passivation potential do-main,anodic potentiodynamic measurements,were done on the unstrained sample at a scanning rate of 100mV min−1and the current density versus poten-tial is recorded.These measurements were conducted by placing the samples as the working electrode,in the presence of a platinum electrode and a saturated calomel reference electrode(SCE)in the electrolyte. The results in Fig.3show that the passivation domain ranges from about−250mV to nearly+900mV,with a minimum current of19µA at−150mV/SCE.How-ever,the passivation potential of+450mV,for which the anodic current is about31µA and the passive layer is more stable,was chosen as an electrode potential in the potentiostatic tests to study the passivation kinetics of the samples.It can be noticed from the polarization curve that the passivation critical current peak is ab-sent.This signifies that this alloy is easily passivated in normal sulphuric acid solution.3.2.Passivation of the samplesAfter the initial preparation,each tested sample was quickly immersed in1N H2SO4solution.Then,in order to eliminate the thin oxidefilm formed on the sample surface between the end of the electropolishing and its introduction into the bath,the sample wasfirst cathod-ically pretreated at−550mV/SCE.The cathodization was stopped when the current density reached the value of−200µA cm−2,and then,the anodization treatment was begun.Each sample was passivated under a voltage of+450mV/SCE during20minutes,at room temper-ature.The stable passive layers grown on the sides of the tested samples were studied subsequently by means of Auger electron spectroscopy(Vacuum Generators).3.3.Surface physical analysisAfter anodization,the samples were immediately rinsed in water,dried in airflow,and then introduced into an Auger electron spectrometer,where the composition depth profiles measurements were carried out.The AES analysis were,in addition of unstrained sample,done on both compressive and tensile strained surfaces of samples.The elemental depth profiling was obtained from a series of repeated cycles of argon ion abrasion and AES analyses.The results were plotted from the peak-to-peak heights of the principal Auger lines against the ion milling time(Fig.4).Each ion abrasion time period wasfixed to60seconds,corresponding to the removal of approximately0.48nm of silicon.Error estimation is not reported on thefigures for better clarity and it ranges from2to4%.The peak-to-peak heights of the principal Auger lines (the703eV Fe line,the529eV Cr line,the848eV Ni line,the510eV O line,and the272eV C line)are plotted against the ion milling time in Fig.4.The car-bon and sulphur peak are not reported for clarity.In fact,the concentration of sulphur in the alloy is very low(<0.03%)and that of carbon is less than0.16% and does not seem to influence significantly the passive layer[7–9].It has previously been shown that the pres-ence of sulphur in passivefilm is principally due to bath contamination and that of the carbon results from ex-ternal contamination produced due to exposure to CO2 from the atmosphere[16].The study of iron AES depth concentration profiles of the passivefilm is important,because iron is not only the principal constituent of steels,but also its peak is usually used to determine the ratios of the Auger peak heights of the alloying elements.As it can be seen from Fig.5,the iron concentration of the passivefilm is substantially weak in the outer layer of passivefilm,its Auger line intensity increases strongly with the increasing depth.The Fe bulk/Fefilm ra-tio varies from1to5.It was shown previously that the iron impoverishment of the passivefilm was rather due to the higher diffusion rate of chromium than the iron preferential dissolution[17,18].In fact,this phe-nomena is also observed in the case of dry oxidation, where the dissolution of all elements is excluded.For1075(a)(b)(c)Figure 4AES depth concentration profiles of the passive film formed on Type 316steel specimens in 1N H 2SO 4solution.The profiles were measured on (a)reference sample,(b)the compressive strained side of the sample,(c)the tensile strained side of the same sample.example,the Cr(529eV)/Fe(703eV)pronounced de-pendence ratio for the oxide films formed on a 302stainless steel during an oxidation of 45minutes (at a temperature of 928K under an oxygen partial pres-sure of about 0.2Pa),indicated that there is an im-portant selective enrichment in chromium with a max-imum value of 4.6for the compressive strained side [19].1076Figure5Normalized iron AES depth concentration profiles of the passivefilm formed on the compressive,tensile and non strained sides of samples.(a)(b)Figure6Ratios of the Auger peak heights(a):Cr(529eV)/Fe(703eV),(b):Ni(848eV)/Fe(703eV),(c):Mo(eV186)/Fe(703eV)and(d): O(510eV)/Fe(703eV)as a function of the ion milling time for the R sample and compressive and tensile strained sides.1077(c)(d) Figure6(continued)According to the Fig.4a,b and c,it can be observed that,in general,the passivefilm region was relatively enriched in chromium and depleted in nickel.In addi-tion,thesefigures show also that the chromium enriched layer due to the chromium migration outwards through the passivefilm,is followed by a chromium deple-tion region.This depletion occurred only at high depth where the chromium content reaches its bulk value. Fig.6a and b present the Auger peaks heights ratio changes of Cr(529eV)/Fe(703eV)and Ni(848eV)/ Fe(703eV)of all samples as a function of the ion milling time.From Fig.4b–c,it can be observed that the width of the region affected by the chromium en-richment is greater on the tensile strained surface than it is on the compressive strained one.The Cr(529eV)/ Fe(703eV)ratio indicates also that there is a selective enrichment of chromium,because of its migration to-wards the oxidefilm(Fig.6a).Moreover,according to the Ni(848eV)/Fe(703eV)ratio depth profile(Fig.6b), it is shown that there is also a selective enrichment of nickel.The real concentration of nickel,as it was men-tioned above,is depleted in the passivefilm,never-theless a Ni enrichment can be observed in m´e tal/film interface(∼5.5nm)(Fig.4a,b,c).Consequently,the selective enrichment of nickel in this region is rather due to the iron concentration decrease in passivefilm (cf.Fig.5).Concerning the supplementary alloying element molybdenum,as can be seen from Fig.4a,the reference sample passivefilm is relatively enriched in molybde-num.This enrichment disappears after an ion milling time of about500s(∼4nm).On the contrary,the ten-sile strainedfilm is impoverished in this elements,but less than the compressive strained side(Fig.4b,c). The depletion of this element occurred at high depth (about5–7nm).Similarly and according to the Fig.6c, the Mo(186eV)/Fe(703eV)ratio point out a selective enrichment of molybdenum,for the reference sample, R.Concerning the tensile and compressive strained sides of samples,Fig.6c shows that,in a stressfield, whatever the nature of stress,the Mo/Fe ratios are re-duced in outer layers of passivefilm.However,the Mo/Fe ratio of tensile stressed side remains slightly higher than the ratio of compressive strained side.1078AES depth profiles for oxygen show(see Fig.4a,b,c)a similar effect of the stressfield on the passivelayer growth.This effect was already observed in thecase of302stainless steel:the passive layer of non-stoichiometric formula is richer in oxygen and morethicker on the tensile strained surfaces than it is on theunstrained or the compressive strained one[16].But,inthe present investigation,the width difference betweenthe tensile and compressive sides of the316steel,is lessthan the case of302alloy.This is probably due to theyield stress of316steel(∼=300MPa),in comparison with302steel(∼=900MPa).Fig.4b and c show the Auger peak height change of oxygen,O(510eV),as afunction of the ion milling time.This value indicatesthat the increase in relative depth of the oxide thicknessis about:(d tens−d comp)/d comp≈16%where d tens and d comp are the average thickness of ox-idefilms formed on tensile and compressive sides ofspecimen,respectively.4.ConclusionThe results obtained in this investigation allow the fol-lowing conclusions to be drawn:1.The passive layer formed on316stainless-steel insulphuric acid is thicker on the tensile strained surfacethan it is on the compressive strained one or on thereference sample.2.The apparent thickness of the oxidefilm,devel-oped on the unstrained sample,was found to be similarto that formed on the compressive stressed side,andgreater than that formed on the tensile stressed one.3.The molybdenum concentration in the outer lay-ers of passivefilms is higher on the unstressed samplethan it is on the compressive or tensile stressed sides.Consequently,the molybdenum migration outwards in passivefilm was reduced in a stressfield,whatever the tensile or compressive nature of stresses. References1.K.A S A M I,M.N A K A,K.H A S H I M O T O and T.M A S U M O T O,J.Electrochem.Soc.127(1980)p.2130.2.K.H A S H I M O T O,in“Passivity of Metals and Semiconducteurs,”edited by M.Froment(Elsevier Science Publishers B.V.Amester-dam,1985)p.246.3.P.V A N S L E M B R O U C K,W.B O G A R T S and A.V A NH A U T E,ibid.p.393.4.W.R.C I E S L A K and D.J.D U Q U E T T E,ibid.p.405.5.R.M.L A T A N I S I O N and R.W.S T A E H L E,“Fonda-mental Aspects of Stress Corrosion Cracking,”edited by R.W.Staehle,A.J.Forty and D.Van Rooyen(NACE,Houston,1969) p.214.6.“Stress Corrosion Cracking and Hydrogen Embrittlement of IronBase Alloys”(NACE5,Unieux Firminy,1973&1977).7.A.W.L O G I N O W and J.F.B A T E S,“Influence of AlloyingElements on the Stress Corrosion Behaviour of austenitic Stainless Steels,”(NACE Conference,Cleveland,Ohio,1968),preprint. 8.M.K O W A K A and J.F U J I K A W A,The Sumitomo Search7(1972)10.9.R.W.S T A E H L E,J.J.R O Y U E L A,T.L.R A R E D O N,E.S E R R A T E,C.R.M O R I N and R.V.F A R R A R,Corro-sion,26(1970)451.10.A.D E S E S T E R E T and G.H.W A G N E R,Werkst.Korro.20(1969)300.11.W.D.F R A N C E,Jr.,Corrosion NACE26(1970)189.12.A.C I G A D A,N.M A Z Z A,P.P E D E F E R R I,G.S A L V A G O,D.S I N I G A L A L I A and G.Z A N N I,Corr.Sci.23(1983)195.13.H.P.H A W K E S,F.H.B E C K and M.G.F O N T A N A,Corrosion NACE9(1963)247t.14.J.C.C H A R B O N N I E R.M´e moires et Etudes Scientifiques Revuede M´e tallurgie3(1981)121.15.H.L.L O G A N and M.J.M c B E E,Materials Research andStandards,ASTM Special Technical Publication264,Case History No.49.(1961)p.38.16.F.N A V A¨I,J.Mater.Sci.30(1995)1166.17.A.C I G A D A,Corr.Sci.22(1982)559.18.J.C.L A N G E V O O R T,T.F R A N S E N and P.J.G E L L I N G S,Werkstoffe und Korrosion34(1983)50.19.F.N A V A¨I,Thesis,ISITEM,Universit´e de Nantes,1997. Received28August1997and accepted8October19981079。

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ASTM+D+4065-2001

ASTM+D+4065-2001

1 This practice is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.10 on Mechanical Properties. Current edition approved September 10, 2001. Published November 2001. Originally published as D 4065 – 82. Last previous edition D 4065 – 95.
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*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1. Scope* 1.1 This practice is for general use in gathering and reporting dynamic mechanical data. It incorporates laboratory practice for determining dynamic mechanical properties of specimens subjected to various oscillatory deformations on a variety of instruments of the type commonly called dynamic mechanical analyzers or dynamic thermomechanical analyzers. 1.2 This practice is intended to provide means of determining the transition temperatures, elastic, and loss moduli of plastics over a range of temperatures, frequencies, or time, by free vibration and resonant or nonresonant forced vibration techniques. Plots of elastic and loss moduli are indicative of the viscoelastic characteristics of a plastic. These moduli are functions of temperature or frequency in plastics, and change rapidly at particular temperatures or frequencies. The regions of rapid moduli change are normally referred to as transition regions. 1.3 The practice is primarily useful when conducted over a range of temperatures from −160°C to polymer degradation and is valid for frequencies from 0.01 to 1000 Hz. 1.4 This practice is intended for materials that have an elastic modulus in the range from 0.5 MPa to 100 GPa (73 psi to 1.5 3 107 psi). 1.5 Apparent discrepancies may arise in results obtained under differing experimental conditions. Without changing the observed data, reporting in full (as described in this practice) the conditions under which the data were obtained will enable apparent differences observed in another study to be reconciled. 1.6 Test data obtained by this practice are relevant and appropriate for use in engineering design. 1.7 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the
Letter of Amendment #2 to Protocol HPTN 058说明书

Letter of Amendment #2 to Protocol HPTN 058说明书

DATE 日期: March 24, 2011 2011年3月24日TO: 送：Protocol HPTN 058 Principal Investigators, Study Coordinators and Study Staff HPTN058方案主要研究者、研究协调员和研究工作人员FROM: 从：HPTN 058 Protocol Team: HPTN058方案小组SUBJECT: 主题：Letter of Amendment #2 to Protocol HPTN 058, Version 2.0 dated 16 September 2008 (IND # 73,797), entitled A Phase III randomized controlled trial to evaluate the efficacy of drug treatment in prevention of HIV infection and death among opiate dependent injectors《评价药物治疗对注射阿片类制剂人群预防HIV 感染和死亡效果的Ⅲ期随机对照临床试验》2008年9月16日2.0版本(IND # 73,797)的第2号修订信The following information impacts the HPTN 058 study and must be forwarded to your institutional review board (IRB)/ethics committee (EC) as soon as possible for their information and review. This must be approved by your IRB/EC before implementation.以下信息影响HPTN058研究，必须尽快将信息递交你处伦理审查委员会（IRB/EC）审查。

ASTM F1545-97

ASTM F1545-97

Designation:F1545–97(Reapproved2009)An American National Standard Standard Specification forPlastic-Lined Ferrous Metal Pipe,Fittings,and Flanges1This standard is issued under thefixed designation F1545;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(´)indicates an editorial change since the last revision or reapproval.1.Scope1.1This specification covers factory-made plastic-lined fer-rous metal pipe,fittings,andflanges intended primarily for conveying corrosivefluids.Requirements for materials,work-manship,dimensions,design,fabrication,working pressure and temperatures,test methods,qualification requirements,and markings are included.1.1.1This specification does not define the suitability of different liner materials to various chemical and operating environments.Refer to the manufacturer’s chemical resistance data for suitability recommendations.1.1.2This specification does not include products coated with plastics.1.2This specification covers plastic-lined pipe,flanges,and fittings as listed in Table1.Pressure limitations shall be in accordance with ANSI/ASME B16Standards,except reduced pressure limitations may be established by the manufacturer, considering both pressure and temperature limitations of the ferrous metal housing and the sealing ability of the liner.N OTE1—In this specification,propylene plastics cover those materials defined as both polypropylene plastics and propylene plastics in Termi-nology F412.Both materials are identified as“PP”on the product.Note that this is at variance with Terminology D1600,where“PP”is the abbreviation for polypropylene.1.3The plastic-linedflanged pipe andfitting assemblies are limited to temperatures shown in Table2.End users should consult with manufacturers as to the likely result of using a particular lined piping component at temperatures below the rated minimum.N OTE2—The temperature limitations are based on noncorrosive test e in specific aggressive environments may alter temperature limitations.In such instances,specific temperature limits shall be estab-lished by mutual agreement between the purchaser and the manufacturer.1.4The values stated in inch-pound units are to be regarded as standard.The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.5This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1ASTM Standards:2A48/A48M Specification for Gray Iron CastingsA53/A53M Specification for Pipe,Steel,Black and Hot-Dipped,Zinc-Coated,Welded and SeamlessA105/A105M Specification for Carbon Steel Forgings for Piping ApplicationsA106/A106M Specification for Seamless Carbon Steel Pipe for High-Temperature ServiceA126Specification for Gray Iron Castings for Valves, Flanges,and Pipe FittingsA135Specification for Electric-Resistance-Welded Steel PipeA182/A182M Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges,Forged Fittings,and Valves and Parts for High-Temperature ServiceA216/A216M Specification for Steel Castings,Carbon, Suitable for Fusion Welding,for High-Temperature Ser-viceA234/A234M Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature ServiceA278/A278M Specification for Gray Iron Castings for Pressure-Containing Parts for Temperatures Up to650°F (350°C)A312/A312M Specification for Seamless,Welded,and Heavily Cold Worked Austenitic Stainless Steel PipesA351/A351M Specification for Castings,Austenitic,for Pressure-Containing PartsA395/A395M Specification for Ferritic Ductile Iron Pressure-Retaining Castings for Use at Elevated Tempera-tures1This specification is under the jurisdiction of ASTM Committee F17on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.11on Composite.Current edition approved Aug.1,2009.Published September2009.Originally approved st previous edition approved in2003as F1545–97(2003).2For referenced ASTM standards,visit the ASTM website,,or contact ASTM Customer Service at service@.For Annual Book of ASTM Standards volume information,refer to the standard’s Document Summary page on the ASTM website.Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.A403/A403M Specification for Wrought Austenitic Stain-less Steel Piping FittingsA513Specification for Electric-Resistance-Welded Carbon and Alloy Steel Mechanical TubingA536Specification for Ductile Iron CastingsA587Specification for Electric-Resistance-Welded Low-Carbon Steel Pipe for the Chemical IndustryD729Specification for Vinylidene Chloride Molding Com-pounds3D792Test Methods for Density and Specific Gravity(Rela-tive Density)of Plastics by DisplacementD1457Specification for Polytetrafluorethylene(PTFE) Molding and Extrusion Materials3D1505Test Method for Density of Plastics by the Density-Gradient TechniqueD1600Terminology for Abbreviated Terms Relating to PlasticsD2116Specification for FEP-Fluorocarbon Molding and Extrusion MaterialsD3159Specification for Modified ETFE-Fluoropolymer Molding and Extrusion MaterialsD3222Specification for Unmodified Poly(Vinylidene Fluoride)(PVDF)Molding Extrusion and Coating Mate-rialsD3307Specification for Perfluoroalkoxy(PFA)-Fluorocarbon Resin Molding and Extrusion MaterialsD4101Specification for Polypropylene Injection and Ex-trusion MaterialsD4894Specification for Polytetrafluoroethylene(PTFE) Granular Molding and Ram Extrusion MaterialsD4895Specification for Polytetrafluoroethylene(PTFE) Resin Produced From DispersionD5575Classification System for Copolymers of Vi-nylidene Fluoride(VDF)with Other Fluorinated Mono-mersF412Terminology Relating to Plastic Piping Systems 2.2ANSI/ASME Standards:B16.1Cast Iron Pipe Flanges Flanged Fittings4B16.5Steel Pipe Flanges and Flanged Fittings4B16.9Factory-Made Wrought Steel Butt Welding Fittings4 B16.28Wrought Steel Buttwelding Short Radius Elbows and ReturnsB16.42Ductile Iron Pipe Flanges and Flanged Fittings—Section IX of the ASME Boiler and Pressure Vessel Code4 2.3Manufacturers Standardization Society(MSS)Stan-dard:MSS SP-43Wrought Stainless Steel Butt-Welding Fittings53.Terminology3.1General—The definitions used are in accordance with Terminologies F412and D1600,unless otherwise indicated.4.Materials4.1Lining:4.1.1Material—The lining shall be made from a resin conforming to one of the requirements in Table3.4.1.2Mechanical Properties—The minimum tensile strength and minimum elongation at break when tested in accordance with the specifications outlined in 4.1.1shall conform to Table4,except the test specimens shall be obtained from extruded or molded liners.Sample orientation is not critical except for PTFE liners made using the paste extrusion process.For paste-extruded PTFE liners,test specimens with their major axis cut longitudinally shall meet the mechanical property criteria listed in Table4,and specimens cut circum-ferentially shall have a minimum tensile strength at break of 2500psi(17.3MPa)and a minimum elongation of200%.4.1.3Specific Gravity—Specific gravity for polytetrafluoro-ethylene(PTFE)resins,when tested in accordance with Test Methods D792or D1505,shall be as follows:Lining Material,Resin Type Specific Gravity Polytetrafluoroethylene(PTFE)Types I andIV2.14to2.19Polytetrafluoroethylene(PTFE)Type III 2.13to2.214.2Ferrous Pipe and Fittings:4.2.1Mechanical Properties—The mechanical properties of the pipes andfittings shall conform to the appropriate specifi-cations listed in Table5,except as they are influenced by accepted methods of processing in the industry(for example, Van Stoneflaring,bending,swaging,welding,and threading). The carbon steel pipe and wroughtfittings shall be welded or seamless steel,Schedule40or80,except Schedule30pipe may be used in8,10,and12-in.nominal size.Schedule20or standard wall may be used in nominal sizes12in.and larger.4.2.2Finish—The interior surfaces of all housings shall be clean and free of mold burrs,rust,scale,or other protrusions, which may adversely affect the integrity or performance of the lining.4.2.3General—All pipe andfitting end connections shall be manufactured to provide a minimum1⁄8-in.radius or chamfer in the transition from pipe wall toflange or lap face.This radius or chamfer is required to reduce stress concentrations in the plastic liner as it isflared or molded over theflange face or stub end.For PTFE-lined pipe andfittings,a1⁄8-in.minimum radius must be provided.A perforated metal collar which seats over theflange chamfer may be used to provide this required radius.4.2.4Dimensional—Flanges andfittings used for plastic-lined pipe shall conform dimensionally(Note3)to the follow-ing industry ferrousflange andfitting dimensional standards: Metallurgy SpecificationSteel ANSI B16.5Ductile iron ANSI B16.42Cast iron ANSI B16.1N OTE3—Center-to-face dimensions include the plastic lining.4.2.5Welding—All metal welding shall be done by welders or welding operators using welding procedures qualified under the provisions of the ASME Boiler and Pressure Vessel Code (Section IX).3Withdrawn.The last approved version of this historical standard is referenced on .4Available from American Society of Mechanical Engineers(ASME),ASME International Headquarters,Three Park Ave.,New York,NY10016-5990,http:// .5Available from Manufacturers Standardization Society of the Valve and Fittings Industry(MSS),127Park St.,NE,Vienna,V A22180-4602,http://www.mss-.5.Requirements5.1Dimensions:5.1.1Housing—Housing installation dimensions are as re-quired in the applicable material specification in accordance with4.2.4.5.1.2Plastic Wall Thickness—Pipe andfitting liners shall have a minimum wall thickness and face thickness in accor-dance with Table6.5.1.3Lining Flare Diameter—The outside diameter of the flare covering the gasket portion of theflange or the full face of the lap-joint stub end shall not be less than the diameter specified in Table7.Theflared portion of the lining shall be concentric with theflared portion of the pipe within1⁄16in.(1.6 mm).5.1.4Tolerances—Tolerances for pipe,flanges,andfittings shall be in accordance with Table8.Bolt holes in bothflanges on afixedflange spool shall straddle the same center line to facilitate alignment.Finished lined(plasticflare to plasticflare) fabricatedfittings shall conform to the nominal center-to-face dimensions as specified in ANSI B16.1,B16.42,or B16.5 with the applicable tolerances.5.2Flange Construction:5.2.1Threadedflanges shall be secured in position to prevent inadvertent turning of theflange.5.2.2Socket-typeflanges,except threaded,shall be fully back-welded to the pipe housing and the inside surfaces of the socketflanges shall be ground smooth.5.2.3Slip-onflanges shall be fully back-welded.N OTE4—No welding shall be done on lined components in thefield.5.2.4Modified slip-onflanges used as lap-jointflanges may be used withflared laps formed byflaring the pipe.The backingflange for theflared metallic lap shall have a1⁄8-in. bevel or1⁄8-in.corner radius at the bore to provide clearance for thefillet of theflared lap.The outside diameter of theflared lap shall be in accordance with the dimension of an ANSI B16.9 lap-joint stub end.5.2.5Lap-joint(or Van Stone)flanged ends may be manu-factured by standard forming techniques or by using fully welded Type A MSS SP-43or ANSI B16.9lap-joint stub ends. Van Stoneflares shall have afillet radius compatible with the corner radius of the matingflange and shall not contain any cracks or buckles.Van Stoneflares and stub ends shall have a radius to provide a smooth transition for the plasticflare.Only lap jointflanges in accordance with ANSI B16.42and B16.5 shall be used.5.3Venting—Each pipe andfitting shall be provided with a venting system that will release any pressure between the liner and the housing.N OTE5—One or more holes in the housing,or a helical groove system inside the housing,that connectsflange vents,has provided adequate venting.N OTE6—Venting is not required with PVDF,PP,ETFE,or PVDC liners.5.4Workmanship:5.4.1Pipe andfittings shall show no evidence of pinholes, porosity,or cracks when inspected in accordance with5.5.2. The linings shallfit snugly inside the pipe andfitting housings.Any bulges or other obvious indications of poor contact with the housing shall be cause for rejection.5.4.2The gasket seating surface of the lining shall be free of surface defects that could impair sealing effectiveness. Scratches,dents,nicks,or tool marks on the seating surface shall not be deeper than10%of the face thickness.5.5Performance:5.5.1Qualification—Lined pipe andfittings must be ca-pable of meeting the qualification requirements specified in Section6.5.5.2Inspection—Each spool andfitting,prior to shipment, shall be hydrostatically or electrostatically tested in accordance with Section7and shall subsequently be inspected visually to verify conformance to the requirements of5.4.6.Test Methods6.1High-Temperature Test:6.1.1Cycle representative production samples of lined pipe andfittings in an oven from room temperature to the test temperature of the liner type(Table9)to determine the ability of the lined components to withstand heat aging and tempera-ture cycling.Test a minimum of two pipe spools,tees,and90°elbows in each size.6.1.2Procedure—Install companionflanges at the manufac-turer’s recommended torque value,and affix a thermocouple in the ferrous housing to measure the temperature.Pipe spools shall be at least3ft(1m)long.After3h in an oven at the test temperature(Table9)as indicated by the thermocouple,air cool the lined components to122°F(50°C)maximum.Repeat this test for a total of three cycles.6.1.3Inspection—Inspect lined pipe andfittings after each cycle for distortion or cracks in the lining.At the completion of the third cycle,subject tested specimens to the hydrostatic or electrostatic test described in Section7.6.2Low-Temperature Test:6.2.1After the high-temperature test,subject the same parts used for6.1to a cold test at0°F(−18°C)for a minimum of48h.New parts may also be used.6.2.2Procedure—Install companionflanges at the manufac-turer’s recommended torque value,and affix a thermocouple to the ferrous housing to measure the temperature.Pipe spools shall be at least3ft(1m)long.After48h at or below0°F (−18°C),as indicated by the thermocouple,allow the parts to warm to a minimum of60°F(16°C).6.2.3Inspection—Inspect lined pipe andfittings for distor-tion or cracks in the lining.Subject tested specimens in the hydrostatic or electrostatic test described in Section7.6.3Steam-Cold Water Cycling Test:6.3.1Subject representative production samples of lined pipe andfittings to steam-cold water cycling to determine the ability of the lined components to withstand rapid temperature changes.Test a minimum of two pipe spools,tees,and90°elbows in each size.6.3.2Procedure—Assemble lined pipe andfittings with suitableflanges having provision for the introduction of steam air,cold water,and for drainage.Install theflange using the manufacturer’s recommended torque value.Pipe spool length shall be10ft(3m)minimum.Mount the sample in such a manner as to permit complete drainage and venting.Thensubject the sample to100consecutive steam-cold-water cycles, each consisting of the following in the sequence given:6.3.2.1Circulate gage saturated steam at the pressure listed in Table10through the sample until the ferrous housing skin temperature adjacent to theflange at the outlet end of the sample has not changed more than5°F(3°C)in10min.6.3.2.2Close off the steam.6.3.2.3Circulate water at a maximum temperature of77°F (25°C).Circulate the cooling water until the ferrous housing skin temperature adjacent to theflange at the outlet end of the sample measures122°F(50°C)or lower.6.3.2.4Vent and introduce air to purge the sample for a minimum of1min making certain that it is completely drained of water.6.3.3Inspection—There shall be no evidence of leakage from the venting system or from behind the plastic faces during the100cycles.At the completion of the test,the liner shall exhibit no buckling or cracking.On PFA,PTFE,and FEP, formation of water blisters shall not be cause for rejection.N OTE7—These surface blisters are formed due to absorption of the steam vapors by the liner and subsequent condensation in the liner.The blisters do not adversely affect liner performance.6.3.4Subject the lined pipes orfittings to either the hydro-static test described in Section7or,after drying,to the electrostatic test described in Section7.6.4Vacuum Testing:6.4.1Test representative samples of lined pipe andfittings to determine the vacuum ratings of the lined components.Test a minimum of two pipe spools,tees,and90°elbows in each size.Conduct tests at room temperature,at the manufacturer’s maximum recommended service temperature,and at one inter-mediate temperature level.Full vacuum is defined as29.6in. Hg corrected to sea level.N OTE8—Vacuum temperature ratings for pipe andfittings are pub-lished in the manufacturer’s literature.N OTE9—The vacuum test is performed on pipe andfittings that have not been exposed to prior e in specific environments may alter the vacuum-temperature ratings.6.4.2Procedure—For pipe spools,specimen lengths shall be at least10pipe diameters.Install aflange incorporating a sight glass at one end and aflange suitable for drawing a vacuum at the other end.Affix a thermocouple to the ferrous housing to measure the temperature.Heat the specimens uniformly externally with the sight glass end visible.Begin the test after the desired ferrous housing temperature has been reached.Hold a selected initial vacuum level for8h,and if no failure occurs,increase the vacuum by5in.Hg.Repeat this every8h until failure or full vacuum is reached.Failure is defined as any buckling or collapse of the liner.If failure occurs at the initial vacuum level selected,test a new test specimen at a lower vacuum level to determine the failure threshold.The vacuum failure threshold is defined as1in.Hg below that at which failure occurs.N OTE10—The external pressure method to simulate higher than full vacuum can be used to establish the failure threshold when full vacuum is achieved.With the use of pressure taps,a pressure is applied between the plastic liner outside diameter and the pipe inside diameter.6.4.3The vacuum rating shall be80%of the failure threshold value.6.4.4At the test completion and after establishing the vacuum rating,place a duplicate specimen in an oven at the test temperature.Apply the rated vacuum to the specimen after the desired skin temperature has been reached.Achieve the rated vacuum within2min and apply continuously for48h.If no liner buckling or collapse occurs,the rated vacuum shall be considered acceptable.6.5Retest—When a test specimen fails to meet the require-ments of either6.1.3,6.2.3,6.3.3,6.3.4,6.4.2,or6.4.4,correct the cause of failure and repeat the specified test.7.Inspection Tests7.1Hydrostatic Pressure Test—The internal test pressure shall be250psi(1.7MPa)minimum for Class125(0.9-MPa) components and425psi(2.9MPa)minimum for Class150 (1.0-MPa)and Class300(2.1-MPa)components.Conduct the test at ambient pletelyfill the pipe andfitting with clean water and bleed the system free of all air prior to the application of pressure.Reach full test pressure within1min and maintain for a further3min.Observe the pressure gage throughout the test for any evidence of leakage,which shall be cause for rejection.7.2Electrostatic Test—Conduct the test with a nondestruc-tive high-voltage tester at an output voltage of10kV.A visible or audible spark,or both,that occurs at the probe when electrical contact is made with the housing because of a defect in the liner shall be cause for rejection.8.Finish8.1The outside surface of all lined pipe andfittings,other than stainless steel,shall be coated with a corrosion-resistant primer over a properly prepared surface.9.Quality Assurance9.1When the product is marked with this designation,F 1545,the manufacturer affirms that the product was manufac-tured,inspected,sampled and tested in accordance with this specification and has been found to meet the requirements of this specification10.Marking10.1Quality Assurance—When the product is marked with this ASTM designation,it affirms that the product was manu-factured,inspected,sampled,and tested in accordance with this specification and has been found to meet its requirements 10.2Quality of Marking—The markings shall be applied to the pipe in such a manner that it remains legible(easily read) after installation and inspection have been completed.10.3The pipe andfittings shall be marked with the follow-ing information:10.3.1Nominal pipe size,10.3.2Liner material identification,10.3.3Manufacturer’s name(or trademark),10.3.4Length(on pipe only),and10.3.5ASTMdesignation.10.4Other information such as order numbers,part num-bers,item numbers,and so forth shall be provided at the request of the purchaser.10.5Pipe liner identification shall be provided on a band utilizing raised letters.The band shall typically be located near the flange.11.Packaging11.1The gasket face of each spool shall be protected by end plates or other suitable protective means.11.2Fittings shall have the same protective covers on the gasket faces unless protected by other means,such as indi-vidual boxing.12.Keywords12.1plastic-lined ferrous metal fittings;plastic-lined ferrous metal flanges;plastic-lined ferrous metal pipeTABLE 1Specification CoverageMaterialANSI Class Nominal Pipe Size,in.(mm)Ethylene Tetrafluoroethylene Copolymer (ETFE)150/3001to 10(25to 254)Perfluoro (Alkoxyalkane)Copolymer (PFA)150/3001/2to 12(13to 305)Perfluoro (Ethylene-Propylene)Copolymer (FEP)150/3001to 12(25to 305)Poly(Vinylidene Chloride)(PVDC)125/150/3001to 8(25to 203)Poly(Vinylidene Fluoride)(PVDF)150/3001to 10(25to 254)Poly(Vinylidene Fluoride)Copolymer (PVDF)150/3001to 10(25to 254)Polytetrafluoroethylene (PTFE)150/3001/2to 24(13to 610)Propylene and Polypropylene (PP)125/150/3001/2to 16(13to406)TABLE2Temperature SpecificationsMaterial Temperature Range,°F(°C) Ethylene Tetrafluoroethylene Copolymer(ETFE)−20to300(−29to149) Perfluoro(Alkoxyalkane)Copolymer(PFA)−20to500(−29to260) Perfluoro(Ethylene-Propylene)Copolymer(FEP)−20to300(−29to149) Poly(Vinylidene Chloride)(PVDC)A0to175(−18to79) Poly(Vinylidene Fluoride)(PVDF)0to275(−18to135) Poly(Vinylidene Fluoride)Copolymer(PVDF)−20to275(−29to135) Polytetrafluoroethylene(PTFE)−20to500(−29to260) Propylene and Polypropylene(PP)0to225(−18to107)A Storage or handling below20°F(−7°C)of uninstalled4,6,and8-in. components should be avoided.TABLE3Polymer Standard Specifications ALining Material—Resin Type Standard ResinSpecification Allowable ResinClassificationStandard Liner Color Maximum Filler Material(byweight)Polypropylene(PP)ASTM D4101Type I and II orange<30%glassfiberPoly(Vinylidene Chloride)(PVDC)ASTM D729gray<20%glassfiberPoly(Vinylidene Fluoride)(PVDF)ASTM D3222blackPoly(Vinylidene Fluoride)Copolymer(PVDF)ASTM D5575blackPolytetrafluoroethylene(PTFE)ASTM D1457ASTM D4894ASTM D4895whitePerfluoro(Ethylene-Propylene)Copolymer(FEP)ASTM D2116Type III greenPerfluoro(Alkoxyalkane)Copolymer(PFA)ASTM D3307Type II naturalEthylene Tetrafluoroethylene Copolymer(ETFE)ASTM D3159Type I naturalA A maximum of1%by weight of additives or colorants,or both,is permissible.Colorants,if used,shall be identified in the manufacturer’s specification.Clean,reworked resins may be used provided all mechanical property requirements are maintained.Only virgin PTFE resin may be used.TABLE4Polymer Mechanical PropertiesLining Material—Resin Type Minimum TensileStrength atBreak,psi(MPa)Minimum Elongation at Break,%Polypropylene(PP)Type I4000(27.6)A10A Polypropylene(PP)Type II3000(20.7)A10A Polypropylene(PP)30%GlassFilled2500(17.3)A2A Poly(Vinylidene Chloride)(PVDC)1500(10.3)A2A Poly(Vinylidene Fluoride)(PVDF)4500(31.0)10 Poly(Vinylidene Fluoride)Copolymer(PVDF)4000(27.6)300 Polytetrafluoroethylene(PTFE)3000(20.7)250 Perfluoro(Ethylene-Propylene)Copolymer(FEP)3000(20.7)250Perfluoro(Alkoxyalkane)Copolymer(PFA)3800(26.2)300Ethylene TetrafluoroethyleneCopolymer(ETFE)6500(44.8)275 A Minimum tensile strength and elongation at yield.TABLE 5Approved Ferrous Metal Flange and Fitting MaterialStandards (ASTM)Lining MaterialPipeSpecificationsFlange SpecificationsFitting Specifications PVDF,PTFE,FEP ,ETFE,A 53/A 53M A 105/A 105M A 105/A 105M and PFAA 106A 135A 182/A 182M A 182/A 182M A 312/A 312M A 216/A 216MA 216/A 216M A 513A 395/A 395M A 234/A 234M A 587A 536(60-40-18)A 351/A 351M A 395/A 395M A 403/A 403M A 536(60-40-18)PP and PVDCA 53/A 53M A 105/A 105M A 48/48M A 106A 105/A 105MA 135A 182/A 182M A 126A 312/A 312MA 216/A 216M A 513A 395/A 395MA 182/A 182M A 587A 536A 216/A 216M A 234/A 234M A 278/A 278M A 351/A 351M A 395/A 395M A 403/A 403MA 536TABLE 6Minimum Liner Wall Thickness,in.(mm)ASize,in.Liner MaterialPTFEPVDF PP PFA FEP PVDC ETFE 10.120(3.05)0.100(2.54)0.125(3.18)0.100(2.54)0.100(2.54)0.094(2.39)0.100(2.54)11/20.120(3.05)0.100(2.54)0.125(3.18)0.100(2.54)0.100(2.54)0.094(2.39)0.100(2.54)20.120(3.05)0.100(2.54)0.125(3.18)0.100(2.54)0.100(2.54)0.094(2.39)0.100(2.54)21/20.120(3.05)0.100(2.54)0.125(3.18)0.100(2.54)0.100(2.54)0.094(2.39)0.100(2.54)30.120(3.05)0.100(2.54)0.125(3.18)0.100(2.54)0.100(2.54)0.094(2.39)0.100(2.54)40.120(3.05)0.100(2.54)0.125(3.18)0.100(2.54)0.100(2.54)0.094(2.39)0.100(2.54)60.125(3.18)0.100(2.54)0.125(3.18)0.100(2.54)0.100(2.54)0.094(2.39)0.100(2.54)80.125(3.18)0.100(2.54)0.125(3.18)0.100(2.54)0.100(2.54)0.094(2.39)0.100(2.54)100.125(3.18)0.100(2.54)0.125(3.18)0.100(2.54)0.100(2.54)......120.125(3.18)...0.125(3.18)...0.100(2.54)......140.125(3.18)..................160.125(3.18)..................180.125(3.18)..................200.150(3.81) (24)0.150(3.81)..................AMinimum liner face thickness shall be 80%of minimum liner wall thickness.TABLE 7Lining Flare DiameterNominal Pipe Size,in.Minimum Flare Diameter,in.(mm)1⁄211⁄4(31.8)3⁄419⁄16(39.7)117⁄8(47.6)11⁄2211⁄16(68.3)237⁄16(87.3)345⁄8(117.5)4515⁄16(150.8)68(203.2)8101⁄16(255.6)10121⁄4(311.2)12143⁄8(365.1)14151⁄2(393.7)16173⁄4(450.9)18201⁄4(514.4)20221⁄4(565.2)24261⁄4(666.8)TABLE8Tolerances for Pipe,Flanges,and Fittings,in.(mm)Pipe Length61⁄8(63.2)Fixedflange bolt hole alignment61⁄16(61.6)Flange perpendicularity(with pipe3⁄32in./ft(7.8mm/m)of diametercenterline)Flanges:All dimensions see ANSI B16.42or ANSI B16.5Fittings:All dimensions see ANSI B16.1,B16.5or B16.42TABLE9Test Temperatures,°F(°C)PVDC PP PVDF FEP PTFE PFA ETFE17565225652756530065500655006530065(7963)(10763)(13563)(14963)(26063)(26063)(14963)TABLE10Steam Test Pressures,psig(kPa)PVDC PP PVDF FEP PTFE PFA ETFEA4613062506312565125655063(2867)(207615)(300620)(862635)(862635)(300620)A The thermocycling test for PVDC lined pipe andfittings should be run usingwater at17565°F(7963°C).ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this ers of this standard are expressly advised that determination of the validity of any such patent rights,and the risk of infringement of such rights,are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed everyfive years and if not revised,either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters.Your comments will receive careful consideration at a meeting of the responsible technical committee,which you may attend.If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards,at the address shown below.This standard is copyrighted by ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959, United States.Individual reprints(single or multiple copies)of this standard may be obtained by contacting ASTM at the above address or at610-832-9585(phone),610-832-9555(fax),or service@(e-mail);or through the ASTM website ().。

Surface & Coatings Technology

Surface & Coatings Technology

Surface & Coatings Technology Influences of binder on fire protection and anticorrosion properties of intumescent fire resistivecoating for steel structureArticleinfo：Article history:Received 31 May 2009Accepted in revised form 23 October 2009Available online 30 October 2009Keywords:IntumescentFire resistive coatingBinderFire protectionAnticorrosion propertyAbstract：The combination of epoxy emulsion and self-crosslinked silicone acrylate (SSA) emulsion was used as mixed binder for preparing water-borne intumescent fire resistive coating. The influences of binders on the properties and char formation of the coatings were investigated in detail by using thermo gravimetry (TG), scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), rheological measurement, fire protection test and anticorrosion property test. It was found that the fire protection and foam structure of the coating was significantly improved by adding 14% SSA (by mass). The TG results showed that adding SSA increased the residue weights of the coatings. The XRF results demonstrated that anti-oxidation of the coatings was improved by adding SSA into the mixed binders. The results of anticorrosion property test indicated that the anticorrosion property of the coatings was enhanced with increase of content of SSA.Crown Copy right . 2009 Published by Elsevier B.V. All rights reserved.1. IntroductionIntumescent fire resistive coatings have been found widespread used as passive fire protection for steel structure which applied in civil buildings, chemical plants and other facilities [1,2]. Intumescent coatings were composed of three fire retardant additives: an acid source(such as ammonium polyphosphate, APP), a carbon source (such as pentaerythritol, PER) and a blowing agent (such as melamine, MEL) bound together by a binder. During the intumescent process, the binder became important due to two effects: it contributed to the char layer expansion and ensured the formation of uniform foam structure [3–5]. However, hydrophilic fire retardant additives (APP and PER) in the coatings were very sensitive to corrosive substances, such as water, acid and alkali [6]. They could easily migrate to the surface of the coatings in corrosive environment [7]. This would significantly depress the expected effect of intumescent coatings. The binder as a film-forming component could prevent or remarkably reduce migration of fire retardant additives and access of the corrosive substances [8,9]. However, somepolymer binders, such as acrylic resin,were not efficient enough to provide good corrosion resistance [10].The objective of this work was to develop a highly protective intumescent coating, which not only had advantages of good fireproof performance, but also showed great anticorrosion property. To achieve this objective, epoxy emulsion and self-crosslinked silicone acrylate (SSA) were selected as mixed binders. Epoxy was used to bind fire retardant additives and provided a carbon source of the intumescent system. Moreover, the chemical structure of epoxy imparted them high chemical resistance against severe corrosive conditions [11]. The crosslinking structure of SSA could increase intumescent rate of coating and improve the foam structure of char layer. Furthermore, when SSA was mixed with epoxy emulsion, the reaction might occur between the two resins, which could enhance crosslinking degree of the mixed resin and lead to an increase of corrosion resistance of the coatings [12,13]. The influences of the mixed binder on the fire protection and anticorrosion properties of intumescent coating were analyzed. Based on the obtained results, the effects of mixed binder on the coatings were evaluated.2. Experimental2.1. MaterialsEpoxy emulsion was supplied by Anbang New Material Development Co., Zhejiang, China.SSA was supplied by Duokete Chemical Reagent Co., Jiangsu, China.APP (nN1000) was supplied by Weidong Chemistry Co., Shandong, China.MEL was supplied by Luming Chemistry Co., Shandong, China.PER and titanium dioxide (TiO2, rutile) were supplied byGuoyao Chemical Reagent Co., Shanghai, China.Kaolin was supplied by Sanbao Kaolin Co., Neimenggu, China.Expandable graphite (EG) was supplied by Baoding Action Carbon Co., Hebei, China.The particle size and expansion volume of EG were 0.18 mm and 180 cm3/g, respectively (specified by the suppliers).2.2. Samples preparationThe composition of intumescent coatings was listed in Table 1. APP, MEL, PER, TiO2, kaolin, EG and distilled water were mixed by high-speed disperse mixer. The mixture was added into the mixed binder composed with epoxy emulsion and SSA, then the coatings were dispersed by high speed disperse mixer. Prepared coating was coated on steel board (35# carbon steel, 15 cm×7 cm×1 mm) and then the sample boards were dried. This process was repeated 10–15 times until dry film thickness of 2±0.1 mm was reached.2.3. Measurement and characterizationPyris 1 TGA analyzer (Perkin Elmer Co., America) was used for TG analysis, which was performed from 50 to 800°C at a heating rate of 20°C/min under nitrogen gas (40 mL/min). XRD measurements were performed on D/max2550VB3+/PC X-ray diffract to meter (Rigaku International Co., Japan) in the range (10°b2θb70°). XRF measurements were performed on SRS3400 X-ray fluorescence spectrometer (Bruker Co., Germany). S-2360 N SEM (Hitachi Co., Japan) operated at 15 kV was used to observe the morphologies of char layers and the distribution of the cell size was characterized with SEM pictures of char layers.Rheological measurement was recorded on EQUINOXSS/HYPERION2000 ARES rheometer (TA Co., American) from 1 to 100 rad/s at 270 °C. The testing temperature (270 °C) was selected based on the DTG results. According to the DTG curves (derivatives of the TG curves) of the coatings, the decomposition of APP/PER/MEL system began at 230 °C. The inert gases (NH3, H2O) sent out and the coatings began to expand. The mixed emulsion was dried and formed film at room temperature for 240 h. The swelling ratio (SR)was determined by immersing the film in toluene for 48 h. After immersing, the swollen film was patted dried and weighed. The ratio of the mass of swollen film to that of the unswollen film was SR. Moreover,the initial film was extracted in Soxhlet extractor with acetone for 24 h. The film after extracting was dried at 100 °C for 5 h in oven and then weighed. The ratio of the mass of dried film to that of the initial film was the gel content (GC),which was a measurement of crosslinking degree of the film.2.4. Fire protection testThe fire protection test was carried out using the equipment in Fig.1 and the gas consumption of the gas lamp was 130 g/h. The side of steel board coated by intumescent coating was exposed to the gas lamp and burned for 1 h. During the test, the temperature of backside of steel board was recorded by digital thermometer (Center305, Center Co., Taiwan) and drawn as a function of time and the time–temperature curve of uncoated steel board was drawn as Fig. 2. Moreover, the intumescent process of coating was recorded by video camera (FS10, Canon Co., Japan) and the time–intumescent rate curve of coating was drawn to characterize the speed of intumescent process of coating.Moreover, the intumescent rate (I) was calculated by Eq. (1).I = （d2-d0）/（d1-d0）（1）In Eq. (1), d0 was the thickness of the steel board, d1 was the thickness of the sample board coated intumescent coating, d2 was the thickness of the sample board after fire protection test.2.5. Anticorrosion property testThe sample broads of coatings were weighed and then immersed in alkali liquor (5% sodium hydroxide solution by mass) at room temperature for 24 h and where after dried at room temperature for 12 h. The weight change rate x (%) was calculated by Eq. (2) and the anticorrosion property of coating was evaluated.X（%）= （m1-m2）/m1 × 100 （2）In Eq. (2), m1 was the weight of coating before test, m2 was the coating weight after a specific time of test.The sample broads of coatings were immersed in 5% hydrochloric acid solution (by mass) until the coatings were blistered, cracked or split, and the immersed time was defined as acidproof time.3. Results and discussion3.1. Influences of content of SSA on properties of bindersBoth epoxy emulsion and SSA had crosslinking structure and formed three-dimensional network structure which could significantly improve anticorrosion property of themselves [14,15]. Moreover, it has been reported that the reaction might occur between the two resins [12]. Six kinds of films (marked as A1–A6) were prepared according to the composition in Table 2 and the GC and SR of films were shown in Table 2.From Table 2, there was a continuous increase in GC value of films with increase of content of SSA. The GC values of A1 film and A6 filmwere 28.55% and 32.24% respectively, and both of them were less than 33%. But the GC of A5 film was 51.97% and almost two times higher than that of A1 film. This suggested that the crosslinking reaction (as shown in Fig. 3) has occurred between epoxy emulsion and SSA [16,17] and led to an increase of crosslinking degree of binders. This would contribute to improvement of anticorrosion property of binders. Moreover, it was shown that there was a gradual decrease in SR values of films with increase of content of SSA. This indicated that the solvent resistance of films was gradually improved because of increase of crosslinking degree of binders.3.2. Fire protection of coatingsAccording to the composition in Table 1, five kinds of coatings (marked as F1–F5) were studied by the fire protection test. During the test, the temperature of backside of steel broad was plotted as a function of time (as shown in Fig. 4) and the influences of content of SSA on fire protection of coatings were showed in Table 3.The shape of the temperature profiles was similar for all the coatings. During the first 300 s, there was no difference in the temperature of each coating, and the temperature increased rapidly and attained 180 °C. Then after 20 min of the test, the temperature reached an equilibrium value and almost remained unchanged at a long time. The experimental results showed that the equilibrium temperatures of F1, F2, F3, F4 and F5 were 270 °C, 255 °C, 243 °C, 272 °C and 290 °C respectively. It indicated that the equilibrium temperature of coatings was firstly decreased and then increased with increase of content of SSA, and the equilibrium temperature of F3 was obviously lower than that of other coatings.3.3. Thermal analysis of coatingsThermal degradation of F1 and F5 was analyzed by DTG curves in Fig. 5. In the case of F1, two weight loss peaks at 248.7 °C and 285.1 °C were attributed to the decomposition of APP and MEL, respectively. APP began to decompose at about 230 °C and liberated phosphoric acid, NH3 and H2O at the same time. The phosphoric acid took part in the dehydration of PER by esterification and induced char formation of the coating.MEL decomposed to yield gaseous products such asNH3 andH2O at about 290 °C. The inert gases caused fused char to swell and formed an expanded char layer [18]. The thirdweight loss peak at 394.5 °C in Fig. 5a was due to thermal degradation of the binder. Epoxy was a kind of high carbon-yielding polymer, which was helpful to char formation.SSA could react with epoxy and increased crosslinking degree of the mixed binder [12]. The binder with high crosslinking degree could enhance anti-oxidation and residue weight of the coatings at high temperature. Compared with decomposition temperatures of F1, the decomposition temperatures of F5 were much higher than those of F1. The results indicated that increasing SSA content could improve thermal destabilization of fire resistive coating and was favorable to fire protection of the coatings [19,20].TG curves of the coatings were presented in Fig. 6. The curves of the coatings were similar at 50–250 °C and weight loss of each coating was less than 20% at 250 °C.When the temperature was higher than 250 °C, the TG curves of the coatings were obvious different. The TG curves demonstrated that the residue weight of coating was increased with increase of content of SSA at high temperature. The residue weight of F1, F3 and F5 at 750 °C was 26.3%, 32.1% and 40%, respectively. The higher residue weights of F3 and F5 indicated that increasing SSA content in mixed binder could enhance anti-oxidation of the coatings [21].3.4. Rheological properties of bindersIt has been reported that the viscoelastic behavior of the binder significantly affects the fire protection of intumescent coating [22,23]. Thus, high temperature rheological measurements of the binders were performed in order to identify changes in the rheological properties of the binders under burning condition. Loss tangent (tanδ) was the ratio of loss modulus and storage modulus, which represented the deformation capacity of materials [22]. The tanδ values of different binders were shown in Fig. 7 and the intumescent rates of coatings were presented in Table 3.It was shown that the tanδ values of binders increased at first, and then turned to decrease with increase of content of SSA, and the trend of intumescent rate of coatings was similar. The tanδ value was increased from 0.24 to 0.26 with increase of content of SSA from 0 to 14% when shear frequency was 10 rad/s. Meanwhile, the intumescent rate was increased from 10.7 to 14, which was improved by 30.8%. However, when the content of SSA continued to increase from 14% to 28%, the tanδ value was reduced to 0.16 and the intumescent rate was also decreased to 10.7. In fact, the binder with appropriate crosslinking degree could improve its melt rheological property and increased the intumescent rate of coatings [24,25].The melting viscosity of binder had a close relation with the rate and speed of intumescent process of coating [26,27]. The relationship between intumescent rate and time under fire protection test for different coatings was presented in Fig. 8 and the melting viscosity of different binders was showed in Fig. 9. When the content of SSA was increased from 0 to 14%, the melting viscosity of binders was obviouslyenlarged, and the required time of intumescent process of coating was increased from 263 s to 390 s. This suggested that the speed of intumescent process of coating became slowly. Moreover, the melting viscosity of binder was continued to significantly enlarge owing to increasing of content SSA to 28%, and the required time of intumescent process of coating was also increased to 502 s. The results showed that the required time of intumescent process of coatings was significantly increased with increase of content of SSA. These indicated that increasing viscosity of binder could slow the speed of intumescent process of coating.3.5. Morphology of intumescent char layersThe efficiency of char layer depended strongly on its physical structure [28]. The SEM micrographs of foam structure (a, b, c) of char layers of F1, F3 and F5 were shown in Fig. 10 and the cell size distribution of foams was presented in Fig. 11. It was shown that the cell size of char layers was gradually bigger due to the significantly enlargement of the melting viscosity of binders with increase of content of SSA [29,30]. The char layer of F1 had a uniform distribution of the cell size, but a tiny foam structure with some cracks was observed in Fig. 10a. The tiny foam structure could insulate steel substrate from heat and fire. However, heat and fire might transfer to steel substrate through the cracks in foam structure, which could lead to a decline of fire protection of F1. A dense foam structure of char layer was found in Fig. 10b and the cell size distribution of F3 was uniform too. This foam structure could isolate steel substrate from fire and provide a better fire protection of F3. Moreover, the char layer of F5 showed a broad distribution of the cell size and had a lot of large cells (Fig. 10c). This foam structure demonstrated that some cells burst and coalescedtogether [31],which could increase efficiency of heat transfer and damaged fire protection of F5.3.6. Elemental analysis of intumescent char layersXRF analysis could provide the detail information about element composition of char layer. The element composition of surface material of char layers obtained from F1, F3 and F5 was shown in Table 4. It was shown that the silicon content was increased from 0.35% to 2.64% with increase of content of SSA. However, there were no obviously differences among the main elements of surface material of char layers such as oxygen, phosphorus and titanium. The results indicated that increasing content of SSA in mixed binder had little influence on the element composition of surface material of char layers.The element composition of interior material of char layers was shown in Table 5.When the content of SSA was increased from0 to 28%, the carbon content in interior materials of char layers was increased from 39.14% to 50.1% and that of oxygen content was decreased from 32.77% to 22.86%. The values of C/O were increased from 1.19 to 2.19. Carbon content in char layer indicated residue degree, while oxygen content in char layer implied oxidation degree of char layer at high temperature, so higher carbon content and lower oxygen content in char layer contributed to improve anti-oxidation of char layers [32].After the char layers of coatings were burnt by fire, only some amorphous carbon and inorganic materials were remained [33] and the inorganic materials might be the main protecting layer at later stage of fire protection test. XRD results of char layer of F3 were shown in Fig.12. Several XRD peaks (marked a) and other peaks (marked b) were assigned to titanium pyrophosphate (TiP2O7) and TiO2, respectively. According to spectrum (3), TiO2 and TiP2O7 were mainly distributed on the surface of char layer. It was shown that TiO2 could react with APP or phosphoric acid and formed a ceramic material at high temperature which could enhance the strength of char layer.3.7. Anticorrosion properties of coatingsThe corrosion mediums, such as water, acid and alkali, could destroy some components of hydrophilic fire retardant additives and break some bonds of binders, so the corrosion resistance of intumescent coatings decreased significantly [7].The differences of weight change rate as a function of immersion time for the coatings were shown in Fig. 13. When F1 was immersed in alkali liquor, two main processes (permeation and migration) took place simultaneously. In the permeation process, water and corrosive ions could infiltrate into the pore structure of coating, which led to the increase ofweight of coating. Moreover, some hydrophilic fire retardant additives might migrate from coating and be solved in alkali liquor during the migration process, which resulted in weight loss of coating [34,35]. During the first 100 h of test, the permeation process of water and corrosive ions exceeded the migration process of fire retardant additives, the weight of coating was continuously increased and its weight gain rate was 4.7% at 100 h. After 100 h of test, the migration process became stronger, so the weight of coating was gradually decreased and its weight loss rate was 18% at 504 h. Furthermore, weight loss rate of coating maintained relatively constant between 504 and 576 h when the two processes of F1 reached equilibrium. After immersed in alkali liquor for 576 h, the cracking and blistering phenomena did not happen in any coating. However, the weight loss rate of coatings was gradually decreased with increase of content of SSA.It has been reported that the appropriate crosslinking degree of polymer binders could not only improve compactness of coatings, but also slow down permeation of water and ions and migration of fire retardant additives, which led to an improvement in corrosion resistance of coatings [36]. The influences of content of SSA on GC of binders and weight change rate of coatings were shown in Fig. 14. The GC of binders was increased linearly with increase of content of SSA, and the final weight loss rate of coatings was decreased gradually. The final weight loss rate of F2, F3, F4 and F5 was 16.7%, 12%, 10.5% and 9.1%, respectively. These results proved that increase of crosslinkingdegree of polymer binders was benefit to the alkali resistance of coatings. Furthermore, the acidproof time of intumescent coatings was listed in Table 6. It was shown that the acidproof time of coatings was gradually increased with increase of content of SSA. The acidproof time of F5 was remarkably achieved 219 h, which was improved by 52.1% compared with that of F1. Owing to the linear increase of GC of the mixed binders with increase of content of SSA, the results indicated that increase of crosslinking degree of the mixed binders was favorable to improve acid resistance of the coatings.4. ConclusionsThe combination of epoxy and SSA led to an increase of crosslinking degree of polymer binder. This could significantly improve compactness of coating and slow down permeation of water and migration of fire retardant additives, which resulted in an improvement in corrosion resistance of coating. The interaction of fire retardant additives and the mixed binder led to formation of foam structure of char layer. The TG results showed that adding SSA increased the residue weights of the coatings. 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