Reliability of maintained ship hull girders subjected to
corrosion and fatigue
C.Guedes Soares*,Y.Garbatov
Unit of Marine Technology and Engineering,Instituto Superior Te ?cnico,Av.Rovisco Pais,1096Lisboa,Portugal
Abstract
A formulation is presented to account for the e ect of corrosion and fatigue on the reliability of ship hulls.A time variant formulation is presented in which the e ect of these degradation phenomena on the hull section modulus is quanti?ed.The e ect of maintenance actions is accounted for by considering that the repaired elements are restored to a state as new.Di erent repair policies can be studied and the approach can be used as a tool to plan the maintenance actions based on reliability results.#1998Elsevier Science Ltd.All rights reserved
Keywords:Maintained ship hull girders;Corrosion;Fatigue.
1.Introduction
The degradation of the ship hull is a result of the combined e ect of corrosion and fatigue crack growth.These two phenomena have the common characteristic that they are a monotonic function of time inducing a systematic decrease of strength.
This paper considers the reliability of a ship hull girder subjected to the simultaneous action of corrosion and of fatigue in longitudinal members.The e ect of both phenomena on the section modulus is accounted and it is used as the reference variable to measure the reliability of the ship hull against collapse.In resisting the longitudinal bending due to waves and weight distribution,the ship hull bends as a beam and as such,the levels of stresses in the deck and bottom depend on the moment of inertia of its cross section which is very much dependent on the amount of continuous longitudinal material in the deck and bottom.The degrading e ect of general corro-sion is reˉected in the decreased thickness of the plating which in turn decreases the moment of inertia of the ship cross section and thus induces higher stress levels for the same applied moments.The e ect of cracks on the longitudinal strength is accounted in a similar manner.The propagation of cracks in sti eners or in the plates makes them unsuitable to contribute to the longitudinal strength with similar consequences.
0167-4730/98/$Dsee front matter #1998Elsevier Science Ltd.All rights reserved PII:
S0167-4730(98)00005-8
STRUCTURAL
SAFETY
Structural Safety 20(1998)201±219
*Corresponding author.Tel.:003518417607;Fax:003518474015.
There is however interaction between these phenomena in that thickness reduction will induce an increase of nominal stresses which in turn produces a larger speed of crack propagation.On the other hand,if fatigue cracks grow in longitudinally resistant members,they will decrease the resisting longitudinal material,increasing the stresses on the e ective material and precipitating the ultimate collapse of the structure.However,this formulation does not account for the inter-action between corrosion and fatigue in which the speed of crack growth in the presence of cor-rosion is changed.
The normal approach towards dealing with the e ect of degradation is to have maintenance actions which,during the ship lifetime,restore some damaged part to their intact status.There-fore a realistic modelling of the degradation phenomena during the lifetime of a structure requires that maintenance actions are also considered.
This paper builds upon earlier results that developed a time variant reliability formulation accounting for maintenance.The time variant approach was initially applied to the fatigue crack growth problem in Ref.[1]and was extended to include the e ect of maintenance actions in Ref.[2].The corrosion problem was dealt with considering ?rst its steady state e ect in reducing the plate thickness considered at a random point in time during the ship life in Ref.[3].This for-mulation was developed in connection with time invariant reliability formulation of the type proposed in Refs.[4±5].A time dependent approach was proposed in Ref.[6]where corrosion was considered to induce a monotonic decrease of ship scantlings and the ship reliability was determined from a sequence of time invariant reliability formulations in each of which the ship scantlings were decreasing.In Ref.[7]a time variant formulation was proposed to deal with the reliability of hull girder subjected to corrosion and maintenance,adopting a method based on the same principles as in Ref.[1].
The present work will extend the earlier proposals by formulating the problem of combined corrosion and fatigue including the e ect of the maintenance actions.Since the earlier papers contain an adequate presentation of the present state of the art,this is omitted here.2.Time dependent section modulus of a hull
To predict crack propagation and the fatigue life the Paris-Erdogan equation has been adopted [8]:
d a
d N
C áK m Y áK !áK th I
where a is the crack size,N is number of cycles,áK the stress range intensity factor.C and m are material parameters and áK th is the stress range threshold intensity factor.The stress intensity factor is described by the following equation:
áK á'Y a
%X a p P where á'is the stress range and Y(a)is the geometry function.
If Y a Y is a constant,N #o t where #o is the mean zero upcrossing rate and t is the time and after substitution of Eq.(2)into (1)and integration of Eq.(1)one obtains:
202 C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219
a t
a 1àm 2
o 1àm 2
C á'm Y m %m 2#o t h
i 11àm
2Y m 2 Q a t a o exp CY 2á'2%#o t Y m 2
à
R
where á'm is the m th moment of the stress range which can be written:
á'm m
á'à1 m á'Y á'th á'
á' !
S
where the stress range threshold á'th in Eq.(5)is related with the stress range intensity factor in
Eq.(1),and à is the incomplete Gamma function.The scale parameter á',of the Weibull distribution of the stress range is obtained from the shape parameter á'and a reference stress response á'0,exceeded once in the corresponding reference number of the stress cycles N O ,
determined as the N à1
0probability level:
á' á'0
vn N 0 1
á'
T Two modes of possible failure after fatigue crack initiation in structural elements can be con-sidered.The ?rst one is the loss of e ectiveness of the element on the local structure because the crack reaches a size larger than its critical value a cr :
a t
b a cr
U
The second one is unstable crack growth that can occur when the stress intensity factor K reaches the critical value K cr :
K t b K cr
V
In the assessment of the failure of structural elements the second mode is not the governing one in most cases,because the steels used in ships are very ductile and thus the associated critical crack size is very long.In this paper the critical crack size is considered to be the height of the sti ener or the breadth of the plate.
The crack size at a random point in time is given by Eqs.(3)and (4),which depend on para-meters such as the initial crack size,the stress range,the crack geometry,the material constants of the crack growth law and the number of cycles.Since there is a signi?cant uncertainty associated with some of these parameters it is reasonable to model them as random variables and as a consequence,the crack size becomes a function of random variables.
The mean and variance of the crack size can be obtained by second moment methods,which are an appropriate approximation in many situations but their accuracy decreases as the coe -cient of variation (COV)of the variables increase.In the present case some COVs may be large and thus the results must be interpreted with https://www.doczj.com/doc/ce18659574.html,ing Eq.(3)the mean and variance of the crack propagation size are given [1]by:
E a t
E a o
è
é1àm 2
1àm 2
E C E á'm Y m %m 2#o t h i 11àm
2 W
C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219203
'2a t
E a o è
éàm
2
a t E a o èé1àm 2 1àm 2
àáE C E á'm Y m %m 2#o t 4
52'2
a o
E á'm Y m
%m 2
#o ta t
E a o èé1àm 2
1àm 2àáE C E á'm Y m %m 2#o t 452
'2c
E C Y m
%m
2
E á'm
E a o
è
é1àm 2
1àm 2àáE C E á'm Y m %m 2#o t 452
'2á
IH
where E []is the mean value operator and '2a o
,'2c ,and '2
áare the variance of a o ,C and á'm ,respectively and the derivatives are to be evaluated at the mean values of the random variables.It is considered that general corrosion will occur in all structural elements,both in the plating and in the sti eners,by decreasing the plate thickness at a rate that may be di erent from element to element.In the foregoing formulation localised pit corrosion will not be accounted for.
The sti ening elements are considered to be ˉat bars.The crack will propagate across its width decreasing therefore its net sectional area available to carry longitudinal stresses.The variation of the area with time will be dependent on the crack size a i (t )and on the corrosion rate r i .The net area of the element,which decreases with time,is the product of the horizontal dimension of the plate s yi t by the vertical direction s zi t :
A i t s yi t s zi t II
The dimensions of the elements start from initial value s yoi and s zoi and they decrease with time at a rate of corrosion r i and due to a crack size a i t :
s yi t s yoi àa 11a i t a 12r i IP s zi t s zoi àa 21a i t a 22r i
IQ
where the coe cients in Eqs.(12)and (13)are given depending of the location of an element as follows:
a 11 0Y a 12 t Y a 21 1Y a 22 0for the verti l elements IR a 11 1Y a 12 0Y a 21 0Y a 22 t for the horizont l elements
IS
The mean value and standard deviation of the net sectional area of the elements are given as:
E A i t E s yi t ??
E s zi t
IT '2A i t
s 2zi t '2s yi t s 2yi t '2
s si t IU
204 C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219
and the mean value and variance of the moment of inertia are presented below:
E i i t
E s yi t ??
E s zi t 3
12
IV '2i i t s 3zi 12 2'2s yi i s yi s 2zi 4 2
'2
s zi t IW
The variances that are considered in Eq.(19)are given by:
'2s yi t p 11'2C p 12'2r i p 13'2a o p 14'2á' p 15'2
s yoi PH '2s zi t p 21'2C p 22'2r i p 23'2a o p 24'2á' p 25'2
s zoi
PI
where '2s yoi ,'2
s zoi
are the variance of the initial geometry s yoi ,s zoi of an element.In the case of a vertical element the coe cients will be given as:
p 1k m 2k for k 1to 5 PP p 2k m 1k for k 1to 5
PQ
and in the case of an horizontal element they can be written:
p 1k m 1k for k 1to 5 PR p 2k m 2k for k 1to 5
PS
The parameters included in Eqs.(22)±(25)are described by:
m 11 E á'm Y m %m
2#o ta t
E a o èé1àm 2 1àm 2
à
áE C E á'm Y m %m 2#o t 452
PT m 12 0 PU m 13
E a o èéàm
2
a t
E a o èé1àm 2 1àm 2à
áE C E á'm Y m %m 2#o t 4
52 PV
m 14 E C Y m
%m
2
E á'm
E a o è
é1àm 2 1àm 2
àá
E C E á'm Y m %m 2#o t 452
PW m 15 m 21 m 23 m 24 m 25 0 QH m 22 t 2 QI m 25 1
QP
C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219205
To assess the properties of sti eners it is enough to note that they are made of plate elements to which the above formulas can be applied.In the case of T or L sti eners it is only necessary to consider separately the web and the ˉange and to apply Eqs.(11)to (32)according to the position of each of them.
The mean value of the ordinate of the neutral axis Z n is given by the ratio of the mean moment of area M to the mean value of the total area:
E Z n t
E M t E A t
The mean value of the area and the moment of area are given by:
E A t
n i 1E A i t QR
E M t n i 1
z i E A i t QS
where z i is the ordinate of the centre of gravity of each element and E A i t is the expected area
at an instant of time t given by Eq.(16).The variance of the moment of area is:
'2M
t
i
z 2i '2
Ai t
n i 1 n j 1
z i z j 'A i t '2
Ai t &ij
QT
where &ij is the correlation coe cient between plate elements,which is equal to 1when i j and
the variance is given by Eq.(17).It is important to account for the correlation between di erent plate elements because the elements that will be subjected to the same conditions will be likely to have similar corrosion rates and crack growth rates.The variance of Z n is obtained from:
'2Z n
t '2M t E A t èé2 E M t èé2
E A t èé4'2
A t à2E M t E A t 3'A t 'M t &AM QU where the correlation coe cient &AM is expected to be very high and as an approximation can be
taken equal to 1.0.
The moment of inertia of the hull section is obtained from the product of the area of the plate elements multiplied of their ordinate and from their own inertia and mean value and variance are given by:
E I b t
n i 1
z 2i E A i t
E i oi t
èé
QV
206 C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219
'2I b
t
n i 1 n j 1
z 2i z 2
j 'A i t 'Aj t
'i oi t 'i oj t h i
&ij
QW
The moment of inertia with respect to the neutral axis is obtained by transporting the moment of inertia in relation to the base line by the ordinate of the neutral axis:
E I n t E I n t àE Z n t èé2
E A t RH and the variance is obtained from:
'2I n t '2
I b t E Z n t èé4'2A t 4E Z n t 2E A t èé2'2
Z n
t n n RI
Finally the probabilistic descriptors of the section modulus W are obtained from:
E W D t
E I n t
E Z n t
RP
'2W D t '2I n
t E Z n t èé2 E I n t èé2
E Z n t èé4'2
Z n
t RQ
E W B t
E I n t
n RR
'2W B
t '2I n
t D àE Z n t
èé2 E I n t
èé2
D à
E Z n t èé4'2
Z n t RS
where subscripts B and D stand for bottom and deck,respectively,and D is the depth of the hull.3.Time variant reliability of the ship hull girder The limit state for global hull failure is de?ned as:M T
W
b 's RT
where M T is the total vertical bending moment,W is the midship cross-section modulus and 's ,is the allowable stress.After transformation Eq.(46)may be written:
M T b 8 t RU
where:
8 t 's W t
RV C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219
207
This limit state condition deals only with the wave induced loads and with the respective allow-able stresses.This is a simpli?cation of the real problem that should consider the combined wave induced and still-water bending moments and the total allowable stress.The simpler load model was chosen because the aim of the paper is to deal with the strength model since the load combination problems have been dealt in Refs.[9,10].
There will be a failure if Eq.(46)is ful?lled and the probability of the wave induced vertical bending moment exceeding 8 t during the period of the time [0,T ][11]is:
P f T 1àexp à T 0
#8 t d t
!
RW
where #8 t is the mean upcrossing rate of the threshold 8 t .
If the loading is a stationary Gaussian process or even non-stationary and non Gaussian process,as shown in Ref.[12],the mean upcrossing rate may be written:
#8 t #o exp à8 t
! SH
for the case of a two parameter Weibull distribution.
This expression was adopted for the amplitude of the vertical bending moment MT which is assumed to follow the Weibull distribution [1]:
#8 t #o exp à
8 t àE M T L L
!
SI where L andy L are the Weibull parameters.
The two main components of the vertical bending moment are the still water (M SW )and the wave induced (M W ).Both can be modelled as stochastic but the ?rst one has a much larger typical duration than the wave induced load cycles.Therefore,in a voyage,for example,one can consider that the still-water is constant and,since the mean of the wave induced load is zero,the mean of the total moment will be equal to the still-water value.
Considering now that during the ship lifetime the still water loads can be described by a normal distribution,the upcrossing rate can be calculated by unconditioning on the still water as is given in Ref.[7]:
#8 t
I
àI
#8 t j m SW f M SW m SW d m SW SP where f M SW m SW will be a normal distribution,the parameters of which are given in Ref.[13].
Using now Eqs.(51)and (52)it can be obtained:
#8 t I
àI
#o exp à8 t àm SW L L
!f M SW m SW d m SW SQ
208 C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219
It has been shown in several occasions [14],that an exponential distribution is an adequate approximation for the long-term distribution of wave induced loads.Therefore,this distribution was adopted and,making L 1in Eq.(53)and substituting:
R t 1àP f t
SR
in Eq.(49),the reliability after crack initiation can be derived as:
R a t exp à t 0
#8 ( d (
Y t b t i 1
SS
where t i 1is the time of the ?rst initiation of crack propagation.
For t t i 1,the midship section is still intact and the section modulus is equal to its value at t 0,i.e.,W t W 0 and when t t i 1,8 t is given by Eq.(48),depends only of the corrosion rate.
Therefore,the reliability before crack initiation is given by:
R b t exp à t 0
#8 ( d (
Y t t i 1
ST It is assumed that the probability distribution of the time to crack initiation is approximated by
the Weibull distribution [15]:
F T i t i 1àexp àt i
T i T i !
SU
Since the time to crack initiation is a random variable,the reliability given in Eq.(56)is in fact conditional on the time to crack initiation,R T j t i .Therefore the unconditional reliability of a hull is:
R T
I
R T j t i f T i t i d t i SV where R T j t i is given by Eqs.(55)and (56).
The total reliability R(t)includes the reliability of the hull with cracks plus the reliability of the hull without cracks,which has a probability of 1àF T i T .Thus,the ?nal expression is given by:
R T 1àF T i T ??
R b T T
R b t i R a T àt i f T i t i d t i SW
The ?rst term of this equation represents the probability that no cracks are present and that failure does not occur in time [0,T ].The second term represents the probability of non-failure under the condition that the cracks are initiated.
The probability of failure P f t of the hull structure is obtained by substituting Eqs.(59)in (54).The reliability of the structure can be related with the generalised index of reliability which is
C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219209
calculated from a multinormal distribution [16].Under this assumption the reliability index can be written by:
t àèà1P f t ??
TH where èis the standardised normal distribution.4.Modelling inspections and repair
Inspections are routinely made for structures in service and they may result in the detection or
no detection of cracks.The size of a detected crack is measured by a non-destructive method.For welded structures,cracks are generally assumed to be present after fabrication.Fatigue damage is expressed in terms of fatigue crack size that increases with time and by the midship section modulus,which decreases with time.
The purpose of periodic inspections is to detect the fatigue cracks.It is assumed that if a fatigue crack is detected,it is repaired and its contribution to the midship section modulus is restored,thus increasing the reliability of the ship structure.
The inspection quality depends on detecting the crack and quantifying its size.In principle each detection technique will have a limit size of detection a d ,under which cracks will not be detected,i.e.,in general for detection it is necessary that
a i t !a d
TI
The state of general corrosion in a panel is assessed by measuring the plate thickness at several points.There are two sources of uncertainty in this procedure.One results from the precision of the measuring instrument and the other from sampling variability.Measurements are made at few points of a panel and they are considered to be representative of the thickness in the whole plate.
Inspections are routinely made for structures in service and they may result in detection or no detection of a plate that has a thickness smaller than the acceptable value that is a fraction k of the original value.
s i t ks oi Y k 1X 0
TP
The uncertainty of this method of detection is considered to be small and in this work it is assumed not to inˉuence plate detection.
It is assumed that all elements will be inspected every 4years and the method of inspection is such that all plates with thickness lower than a limit value are detected.The detected plates will be replaced by new ones with a thickness equal to their original value.
The reliability of the hull after repair will be smaller than the initial value for the new ship because it will contain several cracks,that are already larger than the initial crack size but still smaller than the limit to repair the crack,as well as corroded elements which however have not yet been replaced.After repair,the cracks are assumed to start propagation after the time of
210 C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219
crack initiation,which for simplicity is taken here as a percentage of the time of crack propagation to the critical size.
The reliability after the inspection j th at time T j is the same as the reliability of the hull before repair at the time t ej .Therefore,the reliability of the repaired hull for times larger than T j is the same as the reliability of the unrepaired hull for times larger than t ej .To assess the reliability of the ship hull girder after inspection,the repaired midship section modulus will be denoted by W r t e where t e ,is an e ective time that is related to the status of the midship section modulus without repair.This means that the more extensive the repairs are made the smaller t e ,will be,i.e.,the section modulus will be restored to a situation similar to which it was at an earlier stage of the ship life.Until the time T 1of the ?rst inspection,t e t and:
W r t e W t 0 t `T 1
TQ
At the ?rst repair,the midship section is restored to a situation that it had some years earlier.The e ective age of structure t e ,will now be reduced according to the repair that was made.From then on t e `t and the repaired midship section modulus decreases at a rate that depends on t e instead of t ,i.e.,
W r t e W t for T j à1 t `T j
TR
where the e ective time is given by:
t e t àTr j à1
TS
and
Tr j à1
j à1k 1
áT k TT
where the T j is the time of the j th inspection and Tr j is the total ``recovered''time that at the j th
inspection has been accumulated due to all previous repairs.The repair that was made at the time of the j th inspection restored the structure to the condition that it had áT j years earlier,for example the ?rst inspection Tr 1 áT 1and if there is no repair then áT 1 0.
The reliability is computed for each period between inspections by using Eq.(59)being a function of the e ective time [2]:
R t 1àF T i t àTr j à1àá??R b t àTr j à1àá t àTr j à1
0R b t i R a t àTr j à1àt i àá
f T i t i d t i for T j à1 t `T j
TU
where R a and R b are given by Eqs.(55)and (56)also as a function of t e .It is important to note
that t e is a discontinuous function of the real time t because at each inspection j ,Tr j can change its value that will then be constant until next repair.
C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219211
At each repair operation,a value of áT k ,has to be determined by assessing the age of the structure that has a section modulus equal to the value that resulted from the repair.This value will represent the decrease of the e ective age of the structure,and will update Tr j à1,as given by Eq.(66).This updated value is substituted in Eq.(67)and the reliability can be evaluated for the next interval between inspections.In Eq.(67)the ?rst term denotes the probability of non-failure when some cracks are not initiated in the service interval before T j à1Y T j ??
and the second term denotes the probability of non-failure when some cracks are initiated in the service interval T j à1Y T j ?
?.
5.Numerical example
The formulation presented in this paper has been applied to the assessment of the reliability of a tanker with a deadweight of 369,000tons,a length of 340m,breadth of 56m,depth of 22.45m and a block coe cient of 0.84and a service speed of 16knots.The yield stress was considered to be 390MPa.
The maximum and minimum still water bending moment are in the sagging condition and were considered to be 7.28GN m and 0.7GN m,respectively.The still-water bending moments were modelled by a normal distribution with mean of 3.13GN m and a standard deviation of 1.6GN m,following the results in Ref.[13].
The wave induced bending moment was calculated using the expression prescribed by the Classi?cation Society Rules resulting in 11.3GN m.It is assumed that the long-term distribution of wave induced bending moments is exponential.The cross-section used in this example is shown in Fig.1where the numbering of the elements have also been indicated.
The sti eners,which are all bar elements are numbered from 1to 118.The numbers following those ones from 119to 238correspond to the plate elements that are between sti eners (i.e.,119is the plate element between sti ener 1and 2and so on).The initial dimensions of the longitudinal elements of the deck are 2000?24mm for the sti ener no.1and for the rest of them 400?24mm.The dimensions of the plate elements are 1000?22mm.The sti eners which are located in the side structure have thickness ranging from 18to 24mm,heights from 320to 580mm and the dimen-sions of the plate elements are 22and 1000mm,respectively.The sti eners of the bottom have a thickness of 24mm and height 400mm,except element no.86which is 2500?25mm.The plate elements from the same structure have thickness 22mm and breadth 1000mm.The thickness of the sti ener elements which are located on the longitudinal bulkhead vary from 18to 27mm and their height from 320to 560mm.The thickness of the plate elements from the same area vary from 14to 22min and the height is 1000mm.The distance between transversal frames is 4900mm.The corrosion rates are modelled as normal random variables with a degree of correlation that decreases with distance between the elements.However,it is expected that within one zone of the ship,subjected to comparable conditions,the corrosion rates would have a high correlation and thus perfect correlation was assumed in the present numerical example.The mean value of corrosion rate r in each element is given on Fig.2.The corrosion rates were assumed to be the same in all elements in a given area in the ships but they vary with the zone of the hull under consideration.A constant value of 0.10was assumed for the coe cient of variation of the corrosion rate in all elements.
212 C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219
Fig.1.Midship section of a
tanker.
Fig.2.Rate of corrosion in various elements of the hull.
C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219213
Applying Eqs.(42)and (43),the calculated time variation of the mean section modulus and standard deviation as functions of time are shown in Figs.3and 4which at each time instant de?ne a normal distribution that is seen in Fig.5.
Figs.3and 4show discontinuities in the mean value and standard deviation of the midship section modulus at the time of repair.This is explained with the fact that the net section of the ship is degraded by corrosion in a linear way and by crack growth in a non-linear manner.At
the
Fig.3.Mean value of the midship section modulus as a function of
time.
Fig.4.Standard deviation of the midship section modulus as a function of time.
214 C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219
time of inspection if the plate thickness or the crack size of the element reaches the allowable level for detection then the element is replaced with new one.At the beginning of their life elements have full thickness and the initial crack size that corresponds to their initial standard deviation.Relatively larger or smaller peaks and jumps are related with di erent number of repaired
elements.
Fig.5.Probability density function of the midship section modulus as a function of
time.
Fig.6.Reliability of the ship hull as function of time and depending of di erent criteria without inspections.
C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219215
The strong inˉuence of crack growth,corrosion,and the combined e ect is easy to see from Fig.6,which shows that the inˉuence of crack growth and corrosion on reliability is similar.However,when the calculations are carried out for the combined e ect of cracks and corrosion,it can be seen from Fig.6that after 7±9years the rate of decreasing of the reliability is larger than in the cases when only one of these factors is
considered.
Fig.7.Reliability of ship hull structure as a function of time with inspection at every 4th
year.
Fig.8.The reliability of ship hull structure as a function of time depending of di erent criteria with inspection at every 4th year.
216 C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219
If now the e ect of repair is considered the reliability is computed for each period between repair by using Eq.(67)as shown in Fig.7.
Figure 7also shows the variation of the corresponding reliability index.These can be used to have repair criteria based on a limit value of .If this limit was set for instance at 3X 35,then the ?rst plate replacement should be made at about 2years in the present example,instead of at 4years,which is when,individual plates start having thickness lower than the allowable value or crack size is larger than detectable value.
The formulation presented here can be applied to assess the e ect of crack growth,corrosion or the combined e ect in the reliability of the repaired structure as shown in Fig.8.As can be seen (curve ``Cracks'')the crack detection policy dominates and results in higher reliability level.In the case when only repair on corroded plates is made (curve ``Corrosion'')the reliability is signi?cantly lower and the ?rst replacement of some elements is at 20years because of the consideration that elements will be replaced if their thickness is less than 75%of its original value.The third case (curve ``Cracks and corrosion'')combines detection policies for cracks and corrosion which reˉects into relatively higher reliability level during the whole ship life.6.Conclusion
A formulation has been presented which accounts for the combined e ect of fatigue crack growth and of corrosion on the reliability of the ship hull girder.It is shown that the formulation accounts for the interactions between the phenomena in that their combined e ect result in an increased rate of strength degradation.The repair actions are taken into account showing how the reliability of the structures is changed at each repair operation.The formulation can be used to study the e ects of di erent maintenance policies and di erent intervals between repair actions on the hull reliability.7.Notation a ij coe cients in Eqs.(11)±(18)a t crack size depending on time a o initial crack size a cr critical crack size
a d detection limit of the crack size
i oi
moment of inertia with respect to its centre of gravity
f M SW m SW probability density function of the vertical bendin
g moment in still-water f T i probability density function of time to crack initiation k coe cient in Eq.(62)
m exponent in Paris H equation m ij coe cients in Eqs.(22)±(25)
m SW mean value of vertical bending moment in still water during one speci?c sea state p ij coe cients in Eqs.(22)±(25)r i
corrosive rate of each element
C.Guedes Soares,Y.Garbatov/Structural Safety 20(1998)201±219217
218 C.Guedes Soares,Y.Garbatov/Structural Safety20(1998)201±219 s yi t horizontal dimension of the plate
s zi t vertical dimension of the plate
s yoi t horizontal initial dimension of the plate
s zoi t vertical initial dimension of the plate
t time
t ej e ective time
z j Ordinate of the centre of gravity of each element
Z n distance of the neutral axis from the base line
A t total sectional area
A i t sectional area of each element
C constant in Paris H equation
D depth of the ship
E mean value operator of[]
I n t moment of inertia relative to neutral axis
I b t total moment of inertia with respect to the base line
M t total?rst moment of area
M SW vertical bending moment in still-water
M W vertical bending moment
N number of stress cycles
P f t probability of failure
K cr critical value of stress intensity factor K
R t reliability
R a t probability of non-failure after crack initiation
R b t probability of non-failure before crack initiation
T f fatigue life
T i time to crack initiation
T j time for j th inspection
Tr j total``recovered''time
W B midship section modulus(bottom)
W D midship section modulus(deck)
W r t ej repaired midship section modulus
Y geometry factor
Y a geometry function
?shape parameter of Weibull distribution function of*
?scale parameter of Weibull distribution function of*
à incomplete Gamma function
áK stress range intensity factor
á'stress range
á'm m th moment of the stress range
á'o stress range which is exceeded once out of the stress cycles N o á'th threshold stress range
's allowable stress
'?2variance of*
#o mean zero-upcrossing rate
8 t
threshold
# t j m SW mean upcrossing conditional rate of the threshold level t "M W mean value of the vertical wave bending moment &ij correlation coe cient between plate element i and j &AM correlation coe cient between A t and M t
Acknowledgements
This work has been performed as part of the research project (B/E 4554)Reliability Methods for Ship Structural Design (SHIPREL),which has been partially ?nanced by the Commission of the European Communities under the BRITE/EURAM programme (Contract no 91-501),and which involves the following additional participants:Bureau Veritas,Germanischer Lloyd,Registro Italiano Navale and the Technical University of Denmark.References
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钢结构的防腐蚀措施 钢结构的发展使得钢结构工程逐渐取代了传统建筑工程。那么，为了使得钢结构建筑更好，更耐用，钢结构的防腐蚀措施要如何执行呢？ （1）耐候钢：耐腐蚀性能优于一般结构用钢的钢材称为耐候钢，一般含有磷、铜、镍、铬、钛等金属，使金属表面形成保护层，以提高耐腐蚀性。其低温冲击韧性也比一般的结构用钢好。标准为《焊接结构用耐候钢》（GB4172-84）。 （2）热浸锌：热浸锌是将除锈后的钢构件浸入600℃左右高温融化的锌液中，使钢构件表面附着锌层，锌层厚度对5mm以下薄板不得小于65μm，对厚板不小于86μm.从而起到防腐蚀的目的。 这种方法的优点是耐久年限长，生产工业化程度高，质量稳定。因而被大量用于受大气腐蚀较严重且不易维修的室外钢结构中。如大量输电塔、通讯塔等。近年来大量出现的轻钢结构体系中的压型钢板等。 也较多采用热浸锌防腐蚀。热浸锌的首道工序是酸洗除锈，然后是清洗。这两道工序不彻底均会给防腐蚀留下隐患。所以必须处理彻底。对于钢结构设计者，应该避免设计出具有相贴合面的构件，以免贴合面的缝隙中酸洗不彻底或酸液洗不净。造成镀锌表面流黄水的现象。热浸锌是在高温下进行的。对于管形构件应该让其两端开敞。 若两端封闭会造成管内空气膨胀而使封头板爆裂，从而造成安全事故。若一端封闭则锌液流通不畅，易在管内积存。 （3）热喷铝（锌）复合涂层：这是一种与热浸锌防腐蚀效果相当的长效防腐蚀方法。具体做法是先对钢构件表面作喷砂除锈，使其表面露出金属光泽并打毛。再用乙炔-氧焰将不断送出的铝（锌）丝融化，并用压缩空气吹附到钢构件表面，以形成蜂窝状的铝（锌）喷涂层（厚度约80μm~100μm）。 最后用环氧树脂或氯丁橡胶漆等涂料填充毛细孔，以形成复合涂层。此法无法在管状构件的内壁施工，因而管状构件两端必须做气密性封闭，以使内壁不会腐蚀。这种工艺的优点是对构件尺寸适应性强，构件形状尺寸几乎不受限制。 大到如葛洲坝的船闸也是用这种方法施工的。另一个优点则是这种工艺的热影响是局部的，受约束的，因而不会产生热变形。与热浸锌相比，这种方法的工业化程度较低，喷砂喷铝（锌）的劳动强度大，质量也易受操作者的情绪变化影响。 （4）涂层法：涂层法防腐蚀性一般不如长效防腐蚀方法（但目前氟碳涂料防腐蚀年限甚至可达50年）。 所以用于室内钢结构或相对易于维护的室外钢结构较多。它一次成本低，但用于户外时维护成本较高。涂层法的施工的第一步是除锈。 优质的涂层依赖于彻底的除锈。所以要求高的涂层一般多用喷砂喷丸除锈，露出金属的光泽，除去所有的锈迹和油污。现场施工的涂层可用手工除锈。涂层的选择要考虑周围的环境。不同的涂层对不同的腐蚀条件有不同的耐受性。涂层一般有底漆（层）和面漆（层）之分。底漆含粉料多，基料少。成膜粗糙，与钢材粘附力强，与面漆结合性好。 面漆则基料多，成膜有光泽，能保护底漆不受大气腐蚀，并能抗风化。不同的涂料之间有相容与否的问题，前后选用不同涂料时要注意它们的相容性。涂层的施工要有适当的温度（5~38℃之间）和湿度（相对湿度不大于85%）。涂层的施工环境粉尘要少，构件表面不能有结露。涂装后4小时之内不得淋雨。涂层一般做4~5遍。 干漆膜总厚度室外工程为150μm，室内工程为125μm，允许偏差为25μm.在海边或海上或是在有强烈腐蚀性的大气中，干漆膜总厚度可加厚为200~220μm.。
船舶阴极保护 现代海船船体绝大部分由钢质材料焊装而成，船舶营运的特殊环境使船舶船体和机械设备的腐蚀破坏相当严重。据加拿大运输安全委员会(Transportation Safety Board of Canada)对1995年到2004年发生的事故原因统计，船体结构损害导致的事故平均约占总数的8%，而其中有相当一部分是由于船舶腐蚀造成船体强度降低引起的。一项由英国海洋工程营运公司BRITOIL所作的失效分析表明：在所有设施失效的例子中，33%是由腐蚀造成的。根据船舶具体情况，从防护效果、要求、施工难易程度以及经济性等各个方面出发，选择船舶防腐蚀方法，进行合理的防腐蚀设计，对于增强船舶抗腐蚀的能力，确保营运安全，具有重要的意义。 目前，国内外船舶防腐的主要方法是有机涂料、牺牲阳极及外加电流保护或者它们的组合等几种传统的方法。由于安全的原因，船舶上一般采用的是牺牲阳极阴极保护，外加电流阴极保护一般不被采用。安装较多阳极块会增大船舶航行阻力，造成过度保护，少了则保护不足，船体仍然遭受腐蚀。因此，必须安装适量的阳极，这就需要进行合理的设计。 根据阴极保护的原理，在对金属实施阴极保护的时候，为了到达最佳的保护效果，需要注意阴极保护的最小保护电位和最小保护电流密度两个主要参数。而在实际中考虑到其它因素的影响，还要选择合理的最大保护电位和最大保护电流密度。 1. 最小保护电位 为使腐蚀完全停止，必须使被保护的金属电极电位极化到活泼的阳极“平衡”电位，即保护电位，对于钢结构这一电位就是铁在给定电解质溶液中的平衡电位。保护电位有一定的范围，铁在海水中的保护电位在-0.80～-1.0V 之间，当电位大于-0.80V时，铁不能得到完全的保护，该值称为最小保护电位。选择保护电位需根据已有的实验数据和经验加以确定。 我国近年来规定钢船在海水中的保护电位为- 0.75～-0.95V( Ag/AgCl电极)，最佳保护范围为-0.85～-1.0V，其保护情况如表1所示。 表1 钢船体在不同保护电位下的保护效果
浙江东方造船有限公司船舶防腐蚀 施工组织设计方案 第一章根据船舶的工艺流程、图纸的设计要求、标准塑造施工方案。 第二章 第三章 第四章工人进入现场前必须配戴统一服装、安全帽。施工前把各种工作设备配送到施工现场，进行安装、整齐牢固，试验后确保安全生产顺利工作，一切就绪，由专业技术工人到应当的岗位上，高空作业2米以上的部位，必须配戴安全带，检查脚手架是否牢固，光线不足的地方应及时安全照明，密封室内必须有良好的通风、照明、专人看护条件。 第五章上层建筑机舱内一般不要喷砂，用电动纲丝轮磨光，具体边、角、焊缝部位、表面清除干净。 船舶通常长期处于海洋中，海洋对于船体金属是非常严厉的腐蚀环境。海洋有盐雾，有呈微碱性的海水和强烈的紫外线;在海水中还有各种海洋附着物，它们会在船底上附着，影响船只速度，增加燃料消耗;船体流水线以下部位，长期浸浸在海水中，遭受海水的电化学腐蚀。 5.1上层建筑（房舱等）及桅杆、机舱内防腐涂料保护配套施工方案5.1.1中国船舶涂料配套防腐施工方案
5.2油仓、边水仓、压水仓、主仓首先照明、通风，大多数是喷砂，一些死角部位用磨光机工作达到甲方施工要求。甲板、外壳表面可喷砂、可磨光，根据曱方的施工需要进行工作、具体部位根据现场情况，合定工作方法，做到简便快优。 5.2.1内舱涂料 油舱运载石油及其产品往往含有水分和酸性腐蚀介质，有些舱内交替接触油水，有时用冷水或热海水、洗涤剂刷洗，这些因素导致钢铁结构的严重腐蚀。因此必须选择附着力好、耐油、耐海水性能好的涂料来保护油舱。目前国内外使用的油舱及压载舱涂料的品种有环氧型、聚氨酯型、乙烯系列及无机富锌涂料等。 5.2.1.1、货舱、油舱涂料配套施工方案
船舶上材料保护研究进展作者姓名卜祥星 专业班级材研1302 指导教师姓名乔宁 学号 摘要：船舶海上腐蚀是影响其寿命的最大因素之一。因腐蚀导致结构损坏和破坏， 严重影响船舶性能和安全。本文介绍了当前船舶防腐蚀技术措施的实际应用情况。探讨在船体防腐蚀新技术的发展情况，如船体防腐涂料技术、防腐涂装技术、阴极保护功能和涂膜结合技术、防腐蚀监测新技术等方面的新技术应用。 关键词：船舶，防腐蚀新技术，阴极保护，防腐蚀检测 ABSTRACT：The ships marine corrosion is one of the biggest factors that affect its life span，The structure damage and the destruction caused by corrodes affects the ships performance and security seriously．This article introduces the practical application situation of the current ships corrosion preventing technology and methods，discusses the development situation of new hull anticorrosion technology and new technology application，such as the hull an corrosion painting technology ，the anticorrosion painting and camouflage technology ，the cathode protection function and the painting film combination technology ，the new anticorrosion monitor technology and so on． Key words: ship,new technology of corrosion protection ,catholic protection, corrosion test 目前，大多数船舶都采用金属外壳。而金属在海洋环境中，受海水温度、海水含盐度、海洋大气温度、海洋大气湿度的影响，腐蚀程度很严重，腐蚀不仅降低了船舶钢结构的强度，缩短了船舶的使用寿命，同时还会使航行阻力增加，航速降低，影响使用性能[1]。更为严重的是，一旦出现穿孔或开裂，还会导致海损事故的发生，造成惊人的损失[2]。这已引起国内外防腐专家的极大关注，并积极研究探索解决金属腐蚀的各种防护技
管线防腐施工技术措施 1.编制依据及工程概况 1.1编制依据 1.1.1国家发展计划委员会国家物资储备局设计院设计相关工艺图纸图纸 1.1.2GB8923-88《涂装前钢材表面锈蚀等级和除锈等级》 1.1.3SY/T0407-97《涂装前钢材表面预处理规范》 1.1.4SY/T0447-96《埋地钢质管道环氧煤沥青防腐层技术标准》 1. 2工程概况及实物量 1.2.1国家成品油储备库安全改造湖南一五四处安装工程工艺管线及给排水部分由国家发展计划委员会国家物资储备局设计院设计，图号为：艺总施02。工艺管道为热扎无缝钢管ф273×7，410米；ф219×6，370米；ф159×6，320米；ф89×4，270米；焊接钢管DN150，200米；DN25，100米材质均为20号钢。给排水为焊接钢管ф377×9，25米；ф325×8，25米；ф273×7，25米；无缝钢管ф194×7，900米；ф89×3.5，700米；ф57×3.5，20米；镀锌钢管DN100，700米；铸铁排水管DN200，450米。该工程受监理和一五四处质监站共同负责质量监督。中国石化集团第四建设公司承担工艺管线及给排水安装工程，本措施只针对工艺管道和给排水管道防腐工程，施工中做好质保体系运行，防腐过程严格受控，确保防腐工程优良。 1.2.2工程特点及施工技术关键
本工程属新建工程，质量要求严格，其中工艺管道除锈和给排水管道防腐直接影响防腐施工质量，为技术关键工序。 2. 防腐施工工序 3.施工工艺 3.1材料检验 施工所用的油漆，应具有产品质量证明书或出厂合格证，油漆应检查有效期，严禁超期使用，油漆等规格型号必须符合设计或甲方要求。 3.2基层除锈 钢材表面采用砂轮机除锈达St3级，即钢材表面应无可见油脂、污垢并且没有附着不牢的氧化皮、铁锈，底材显露部分的表面应具有金属光泽、除锈应全面无遗漏。 对于焊道补漆除锈要求同上。 3.3防腐刷漆 管道表面刷漆应符合设计要求：地下及室内工艺管线涂H06-4环氧富锌底漆一道,环氧厚膜中间漆一道,B04-33丙烯酸聚氨脂面漆二道,涂层总厚度>180微米,埋地、管沟及套管内管线防腐采用环氧煤沥青防腐涂层特加强级；埋地排水铸铁管及消防泵房内埋地管道做环氧煤沥
编号：SM-ZD-19741 防腐漆施工的危险因素及 一般防护措施 Through the process agreement to achieve a unified action policy for different people, so as to coordinate action, reduce blindness, and make the work orderly. 编制：____________________ 审核：____________________ 批准：____________________ 本文档下载后可任意修改
防腐漆施工的危险因素及一般防护 措施 简介：该方案资料适用于公司或组织通过合理化地制定计划，达成上下级或不同的人员之间形成统一的行动方针，明确执行目标，工作内容，执行方式，执行进度，从而使整体计划目标统一，行动协调，过程有条不紊。文档可直接下载或修改，使用时请详细阅读内容。 防腐漆喷涂是一个危险的过程，其主要的危险是可能会接触到那些对人体健康造成危害的物质。喷涂作业时的危害可能来自于：火灾与爆炸、喷涂设备、人工搬运、噪声及有限空间作业。 因此，使用防腐漆及有关化学品的人员应查询产品安全标签、安全技术说明书和涂装作业可能危及安全与健康的相关资料，接受相关安全技术培训。在作业过程中应始终严格遵守安全生产、工业卫生的规章制度，及时报告可能造成危害和无法处理的情况 本章旨在帮助建立安全的工作方法和环境，主要内容包括：危险印度及防护措施；个人防护用品；使用防腐漆时的安全工作指导和环境；环境保护和污染预防。 防腐漆施工的危险因素
Q/DNS 大连新船重工有限责任公司企业标准 Q/DNS.J0×.×××-2002 船体保护设计指南 Guide for cathodic protection design （审查稿） 2002- - 发布 2002- - 实施
目次 前言 (1) 1 范围 (1) 2 定义 (1) 3 设计依据 (1) 4 设计内容 (1) 5 设计方法 (2) 参考文献 (6)
前言 为规范牺牲阳极阴极保护的布置设计过程中应遵循的技术准则﹑方法和要求，并为设计工作和控制设计质量提供依据，特制定本标准。 本标准中的设计方法是公司多年来大中型散货船﹑油船以及集装箱船的牺牲阳极阴极保护的布置经验的总结。 本标准按Q/DNS.J01.007.1-2002《设计规范编制规定》的要求编制。 本标准由大连新船重工有限责任公司标准化委员会提出。 本标准由船研所标准室归口。 本标准起草单位：船研所标准室 本标准起草人：×××校对：×××审定：×××批准：××× 本标准标审、编辑：×××编校：×××编审：××× 本标准由船研所标准室负责解释。
牺牲阳极阴极保护设计指南 1.范围 本标准规定了船体保护设计布置以及设计时的依据﹑保护参数﹑布置原则和设计方法。 本标准适用于各种大中型船舶（散货﹑油船以及集装箱船）的牺牲阳极阴极保护设计。 1定义 2.1牺牲阳极保护法: 是采用一种比被保护金属电位更负(化学性更活泼)的金属或合金和被保护的金属连接在一起,依靠该金属或合金不断地腐蚀融解所产生的电流使其他金属获得阴极极化而受到保护的方法。而这种自身被腐蚀的金属或合金,称为牺牲阳极。 目前世界各国生产的牺牲阳极主要是锌基合金阳极和铝基合金阳极两大类。 2.2外加电流阴极保护： 采用外加电流使船体处于保护电位而不至于被腐蚀的方法。 2.3保护电流密度： 使被保护结构达到最小保护电位所必须的极化电流密度。单位mA/m2 2.4牺牲阳极使用寿命： 牺牲阳极的消耗率达到利用系数1/K时的使用时间。也就是被保护结构安装一次牺牲阳极后的有效保护时间。 2.设计依据 4.1 合同建造技术说明书及其指定的建造规范 4.2 主要图纸和文件 a) 总布置图 b) 相关船体结构图纸 c) 螺旋桨﹑舵图纸
第一章概述 (1) 第二章舰船的主要防腐措施 (2) §2.1舰船的涂漆防腐 (2) §2.2舰船的阴极保护 (2) §2.2.1牺牲阳极法 (2) §2.2.2外加电流阴极保护法 (3) §2.2.3阴极保护 (4) §2.3船体的结构设计防腐 (4) §2.4船底微生物清除 (5) 第三章现代的舰船阴极保护系统设计 (5) §3.1阴极保护系统 (5) §3.2计算机仿真技术在阴极保护系统的应用 (5) 第四章国内外舰船阴极防腐技术发展 (6) §4.1国外舰船防腐 (6) §4.2国内舰船防腐 (7) 第五章结语 (7) 致谢 (7) 参考文献 (7)
舰船腐蚀与防护 摘要：随着科技的发展，舰船的应用越来越广泛，但同时我们也面临着新的考验。现在大多数舰船都是金属外壳，而海水这个恶劣环境，海水盐度、湿度、海洋大气等，都容易使金属腐蚀，是舰船的杀手。船体造成舰船的受损，每年为人类造成了巨额损失。因此，舰船防腐成为了许多行业的研究热点之一。现在人们根据电化学腐蚀原理，以阴极保护为主，涂层防护为辅来防腐。 关键字：舰船腐蚀与防护、腐蚀、阴极保护、涂层保护 Ships corrosion and protection Abstract: with the development of science and technology, ship used more widely, but at the same time we also face new test. Now most ships are metal shell, and the bad environment water, salinity, humidity, Marine atmosphere, easy to make metal corrosion, are the killer. The hull of the ship's damaged, caused a year for a human caused a huge loss. Therefore, ships anticorrosive became many industry the hotspot. Now people by electrochemical corrosion principle, according to cathodic protection is given priority to, complementary to corrosion protection coating. Key word: ships corrosion protection, and corrosion, cathodic protection, coating protection 第一章概述 腐蚀是材料由于环境的作用而引起的破坏或变质，材料所处的环境越差，则对其耐腐蚀性和需要采取的防护措施要求越高。大多数舰船的外壳都是金属，它们处于海水这个苛刻的腐蚀环境之中，受海水盐度、湿度、海洋大气等影响，腐蚀成为了它们使用寿命的一个严重威胁。舰船结构的强度下降，阻力增大，更有甚能导致灾难性的危害。每年我国舰船腐蚀造成的损失可达几百亿。因此，腐蚀一直是造船业和腐蚀专业研究的重点之一。 舰船处于海水环境和海洋大气环境之中，其各个结构遭受着不同程度的腐蚀危害。而且如果不采取有效的防护措施，腐蚀会越来越快。人们根据腐蚀原理，将舰船的腐蚀分为了化学腐蚀和电化学腐蚀两大类。海洋中的舰船多发生电化学腐蚀，由于舰船水线一下部分，长期受到海水的直接作用，腐蚀最为严重。
船舶上材料保护研究进展 作者姓名卜祥星 专业班级材研1302 指导教师姓名乔宁 学号2013200313
摘要：船舶海上腐蚀是影响其寿命的最大因素之一。因腐蚀导致结构损坏 和破坏，严重影响船舶性能和安全。本文介绍了当前船舶防腐蚀技术措施的实际应用情况。探讨在船体防腐蚀新技术的发展情况，如船体防腐涂料技术、防腐涂装技术、阴极保护功能和涂膜结合技术、防腐蚀监测新技术等方面的新技术应用。 关键词：船舶，防腐蚀新技术，阴极保护，防腐蚀检测 ABSTRACT：The ships marine corrosion is one of the biggest factors that affect its life span，The structure damage and the destruction caused by corrodes affects the ships performance and security seriously．This article introduces the practical application situation of the current ships corrosion preventing technology and methods，discusses the development situation of new hull anticorrosion technology and new technology application，such as the hull an corrosion painting technology ，the anticorrosion painting and camouflage technology ，the cathode protection function and the painting film combination technology ，the new anticorrosion monitor technology and so on． Key words: ship,new technology of corrosion protection ,catholic protection, corrosion test
混凝土结构一直被认为是一种节能、经济、用途极为广泛的人工耐久性材料,是目前应用较为广泛的结构形式之一.但随着结构物的老化和环境污染的加剧,其耐久性问题越来越引起国内外广大研究者的关注.由于勘察、设计、施工及使用过程中多因素影响,很多混凝土结构都先后出现病害和劣化,使结构出现了各种不同程度的隐患、缺陷或损伤,导致结构的安全性、适用性、耐久性降低,最终引起结构失效,造成资金的巨大浪费.从国外情况来看[1],美国与钢筋腐蚀有关的损失占总腐蚀的40%;前苏联工业建筑的腐蚀损失占工业固定资产的16%,仅混凝土和钢筋的腐蚀损失占GDP的1·25%; 1999年,澳大利亚公布的腐蚀损失为GDP 的4.2%.除此之外,北欧、英国、加拿大、印度、日本、韩国及海湾地区等不少国家都存在以基础结构设施为主的腐蚀.中国面临的问题同样很严峻.根据中国工程院2001~2003年《中国工业和自然环境腐蚀调查与对策》中的统计, 1998年中国建筑部门(包括公路、桥梁建筑)的腐蚀损失为1000亿人民币[2].近年来,中国建筑行业的发展速度突飞猛进,一批批建筑物拔地而起,但钢筋混凝土基础的耐久性问题也逐渐暴露出来.所以,重视和加强钢筋混凝土基础结构的腐蚀性与防腐措施的研究已迫在眉睫. 1 腐蚀机理分析 1·1 混凝土的腐蚀机理 混凝土的腐蚀是一个很复杂的物理的、物理化学的过程.由于混凝土腐蚀机理的复杂性,对混凝土腐蚀的分类还没达成一个共同的认识,但一般都倾向于采用前苏联学者B·M.莫斯克文为代表所提出的分类方法[3].将混凝土的腐蚀分为3类:溶蚀性腐蚀、某些盐酸溶液和镁盐的腐蚀、结晶膨胀型腐蚀. 所以,混凝土的腐蚀机理可从以下3类入手:物理作用、化学腐蚀、微生物腐蚀. 1·1·1 物理作用 物理作用是指在没有化学反应发生时,混凝土内的某些成分在各种环境因素的影响下,发生溶解或膨胀,引起混凝土强度降低,导致结构受到破坏.物理作用主要包括2类:侵蚀作用和结晶作用. (1)侵蚀作用:当环境中的侵蚀性介质(如地下软水,河流、湖泊中的流水)长期与混凝土接触时,将会使混凝土中的可溶性成分(如Ca(OH)2)溶解.在无压力水的环境下,基础周围的水容易被溶出的Ca(OH)2饱和,使溶解作用终止.侵蚀作用仅仅发生在混凝土表面,影响不大.但在
船舶的腐蚀与防腐措施 摘要：船舶的腐蚀问题日益受到人们和有关部门的关注，国内外研究人员对船 舶的腐蚀机理和防腐措施进行了大量的研究.随着科学技术的发展和研究的深入， 对腐蚀类型的更深刻的认识，防腐技术措施的持续发展，船舶的防腐问题会逐步 的得到更好的预防和控制。 关键词：船舶腐蚀；防腐措施 引言 金属在海洋环境中，受海水温度、海水含盐度、海洋大气温度、海洋大气湿 度的影响，腐蚀程度很严重，腐蚀不仅降低了船舶钢结构的强度，缩短了船舶的 使用寿命，同时还会使航行阻力增加，航速降低，影响使用性能。更为严重的是，一旦出现穿孔或开裂，还会导致海损事故的发生，造成惊人的损失。这已引起国 内外防腐专家的极大关注，并积极研究探索解决金属腐蚀的各种防护技术方法和 措施。 1概述 随着世界冶金技术的不断发展，就目前来看，绝大多数的船舶都采用金属外壳，金属外壳不仅有较强的耐磨性，美观性，更重要的是具有强大的抗打击能力，在远洋运输中能够抵抗海浪的冲击。但是，金属材质并不是完美无缺的，因长时 间受到海水侵蚀（包括海水温度、盐碱性、海洋大气湿度等），船舶的腐蚀程度 非常严重，这种长时间的腐蚀，一方面降低了船舶钢结构的强度，严重威胁着船 体的稳固性，缩短了船舶的使用寿命，另一方面腐蚀形成的金属锈垢严重阻碍了 航行速度，船舶的使用性能急剧下降，一旦船体出现漏孔，就会导致大量海水倒灌，即威胁着船中货物的安全，也对船员生命安全造成极大的威胁。例如上世纪80年代末期的埃克森尔瓦尔迪兹号漏油事件，因船员操作失误再加上船体年久失 修腐蚀严重，当船舶撞到冰山上时，船体立马就出现了裂缝导致大量的原油泄漏，这不仅造成了巨大的经济损失，更重要的是给当地环境造成了不可估量的破坏。 我国作为远洋贸易大国，每年因船体金属腐蚀而造成的直接经济损失就高达300 多亿元。现阶段如何防治并减少海水对船体的腐蚀，已经引起国内外有关学者的 重视，我国政府也投入大量的资金来对防腐蚀进行研究，以期能够早日解决这方 面的难题。 2船舶腐蚀的类型 2.1电化学腐蚀 2.1.1电偶腐蚀 船舶的部件仅需可以组成异金属接触电池，便会产生电偶腐蚀。此类腐蚀是 最为常见的，比如：离心泵的叶轮与泵轴、冷凝器的黄铜管和碳钢外壳等所形成 的腐蚀，也就是电偶腐蚀。 2.1.2氧浓差腐蚀 金属部件和含氧量不一样的溶液之间的相互接触，便会产生氧浓差电池。溶 液中含氧量越多，电极的电位也就会更加之高，转变成阴极。比如：柴油机的气 缸套和气缸体下部密封圈位置处之间的缝隙，由于冷却水的增多而造成氧浓度的 不断减少，金属转变成了阳极，与周围含氧量较多的金属产生相应的氧浓差电池，形成氧浓差腐蚀。
陕西铸丰创新节能有限公司 防腐、防锈处理操作工艺说明 公司针对招标产品在高湿度、温度、阳光等及腐蚀环境中工作，产品对防锈、防腐能力要求高，因此，在生产装卸式垃圾箱时，对金属材料都进行磷化工艺处理，经过磷化处理的工件，提高了漆膜附着力和涂漆层的耐腐蚀性能力。 金属表面常常会生锈、腐坏，如何让金属防腐防锈是一个困扰了人们很多年的难题。传统的金属表面处理技术主要以电镀为主，但由其产生的高能耗、高污染等负面影响也越来越大，所以公司引进一种先进的金属表面处理技术，对生产垃圾箱的材料进行磷化工艺处理。经过磷化处理的工件，提高了漆膜附着力和涂漆层的耐腐蚀性能力。与没有进行磷化工艺处理的工件相比较，耐腐蚀性能提高了3-5倍，耐腐蚀周期长，大大提高了产品的使用寿命。 一、金属表面处理工艺流程： 1、净化脱脂，活化除锈工艺流程：除油→酸洗→水洗→钝化→水洗→烘干→磨砂→表调→磷化→钝化→水洗（离子水洗净）→干燥 2、工艺要求：按照每升投放3g-7g的比例，将合成缓蚀剂放入有机酸池或者碱池中；将金属件放在有机酸池或者碱池中，进行酸洗；酸洗3-5h后，将金属件捞出来，然后用冷水冲洗30-60min ;冲洗完成后，用温度在90-100°C的
热水冲洗金属件30-60min ;按照重铬酸钾溶液2_4份、磷酸1_2份和温度在80-90°C的热水4-8份的比例配置钝化液；将金属件浸溃在钝化液中2-3min ;取出后，先用冷水冲洗再用热水冲洗，冲洗后，将金属件烘干；利用喷丸或者喷砂的方式对金属件进行磨砂处理，然后涂上保护油待用；根据金属件的材质选择合适PH值的脱脂剂；对金属件进行加热，当温度超过70°C时，将脱脂剂喷射在金属件上，进行喷射脱脂；L-3min后，将金属件浸溃在脱脂剂中；用循环泵搅动脱脂剂，每小时的循环量为脱脂剂体积的5-8倍；每隔4-8min，捞起金属件，检查是否彻底脱脂；彻底脱脂后，用清水将金属件清洗干净；将金属件浸溃在表面调整剂中30-90S，进行表面调整处理；利用磷化液和促进剂对金属件进行10-15min的磷化处理，形成磷化膜，其中，磷化温度控制在60_80°C，总酸度为:35_55Pt，游离酸度为:5_7Pt，磷化膜的膜层厚度为:8-15 Μ M;利用钝化液对金属件表面的磷化膜进行补充处理；2_3min后,将金属件用去离子水洗净,并将其烘干,烘干温度在130_150°C。 二、喷漆涂装工艺流程 金属表面在喷漆涂装前已经经过净化脱脂，活化除锈等前处理及表面处理工艺，有效地改善喷漆涂装金属的防腐抗蚀性能。公司生产实践证明：喷漆涂装金属防腐性的优劣与其涂装前基体前处理质量的好坏影响极大，金属表面涂装
防腐蚀工程安全技术措施 姓名：XXX 部门：XXX 日期：XXX
防腐蚀工程安全技术措施 1)操作人员必须身体健康，并经过专业培训考试合格，在取得有关部门颁发的操作证或特殊工种操作证后，方可独立操作。学员必须在师傅的指导下进行操作。 2)树脂类防腐蚀工程中的许多原料都具有程度不同的毒性或刺激性，使用时或配制时要有良好的通风。操作人员应在施工前进行体格检查，患有气管炎、心脏病、肝炎、高血压者以及对某些物质有过敏反应者均不得参加施工。研磨筛分、搅拌粉状填料最好在密封箱内进行。操作人员应穿戴防尘口罩、防护眼镜、手套、工作服等防护用品，工作完毕应冲洗淋浴。 3)施工过程中不慎与腐蚀或刺激性物质接触后，要立即用水或乙醇擦洗。采用毒性较大的材料施工时，应适当增加操作人员的工间休息。施工前制定有效的安全防护措施，并应遵照安全技术及劳动防护制度执行。 4)在配制使用乙醇、苯丙酮等易燃材料的施工现场，应严禁烟火并应备置消防器材，还要有适当的通风。 5)配硫酸时应将酸注人水中，严禁将水注入酸中。在配酸现场应备有10％碱液和纯碱水溶液，以备中和洒出的酸液之用。配制硫酸乙醇时，应将硫酸慢慢注人酒精中，并充分搅拌，温度不可超过60CC，以防止酸雾飞出。配制量较大时应设有间接冷却装置(如循环水浴槽)。 6)生漆毒性较大，能使接触者产生过敏性皮炎。严重者手脚、面部形成水肿、生出疮疹，即所谓漆疹。操作人员必须穿戴好防护用品，操作时严防生漆接触皮肤，面部可涂防护油膏保护。 第 2 页共 4 页
7)使用毒性或刺激性较大的涂料时，操作人员应穿戴防护用品，执行有关安全技术及劳动保护制度外，现场应注意通风，并适当采取操作人员轮换、工间休息，下班后冲洗、淋浴等安全防护措施 8)施工现场应注意防火，严禁吸烟和使用电炉等 材料库应能适当通风并备置消防器材。 第 3 页共 4 页
内河船舶船体阴极保护系统的应用研究 文章从船舶阴极保护分析入手，论述了内河船舶船体阴极保护系统的应用。期望通过本文的研究能够对船舶使用寿命的进一步延长有所帮助。 标签：船舶;恒电位仪;阴极保护 1船舶阴极保护 在内河上行驶的船舶，不可避免地会受到水体的腐蚀，一旦船体遭受腐蚀，不但会缩短船舶的使用寿命，而且还会导致安全风险增大。所以必须采取行之有效的措施，对船体进行防蚀处理。防腐涂层与阴极保护是船舶腐蚀防护较为常用的方法，通过在船体上涂刷防腐涂层，能够有效降低船体腐蚀的几率，而阴极保护系统则是对防腐涂层的补充。不同的金属有着不同的电势，阴极保护系统就是通过对这些不同电势的合理运用，对船体上的金属起到保护效果。船舶可以采用的阴极保护方式有两种，一种是外加电流，另一种是牺牲阳极。外加电流是以直流电源对电流进行输出，由于电源本身的输出具有可调的特性，加之阴极数量相对较少，整个系统的使用寿命更长，故此在船体防蚀中应用的阴极保护系统基本上采用的方式都是外加电流。阴极保护系统中，外加电流方式的结构如图1所示。 2内河船舶船体阴极保护系统的应用 2.1系统设计思路 对于船体阴极保护系统而言，保护电位是非常重要的指标之一，该指标除了能够对系统的性能进行评估之外，还能对整个系统起到一定的控制作用。实践表明，内河船舶采用阴极保护系统时，只有保护电位达到一定范围时，船体才能够得到有效保护。通过对现有外加电流阴极保护系统的构成情况进行分析后发现，系统中保护电位的检测是相关工作人员以手动的方式完成。同时，根据检测到的结果，对保护状态进行判断。当发现保护电位超出预先设定好的范围时，需要以人为的方式对电源的输出进行调节，从而达到改变保护效果的目的。针对现有系统的不足，并在充分考虑船舶运行需要的基础上，在系统设计开发过程中，增加一个监测模块，借助该模块对保护电位进行实时监测，确保阴极保护的评估效果更加准确。同时还能减轻工作人员的劳动强度。基于这一思路，本次设计开发的船体阴极保护系统由两个部分组成：一部分是保护控制，另一部分是监测。 2.2保护控制系统的设计 保护控制系统由供电装置和辅助阳极组成，前者具有反馈调节功能，后者需要具备稳定的性能。 2.2.1供电装置
船舶金属腐蚀失效与防护研究 摘要：目前，大多数船舶都采用金属外壳。而金属在海洋环境中，受海水温度、海水含盐度、海洋大气温度、海洋大气湿度的影响，腐蚀程度很严重，腐蚀不仅 降低了船舶钢结构的强度，缩短了船舶的使用寿命，同时还会使航行阻力增加， 航速降低，影响使用性能。更为严重的是，一旦出现穿孔或开裂，还会导致海损 事故的发生，造成惊人的损失。所以，加强对船舶防腐新技术的研究具有重大意义。 关键词：船舶金属；腐蚀失效；防护； 船舶由于长期处于盐度较高的海洋环境中，腐蚀极为严重，腐蚀不但能够降 低船舶钢结构的强度，缩短船舶寿命，还会增加航行阻力，降低航速，影响船舶 性能和航行安全。因腐蚀导致结构损坏和破坏，财产甚至生命的损失屡见不鲜， 可以说船舶腐蚀是影响其寿命的最大的因素之一。 一、船舶金属腐蚀失效 1．在船体钢结构上的电化学腐蚀主要有以下几种。（1）氧的浓差电池作用。由于氧有夺取电子的能力，且水面的氧较水下的氧多，故近水面部分的金属得到 电子成为阴极，而水中部分的金属失去电子成为阳极而发生腐蚀。腐蚀发生后， 缝隙或缺口处的氧多，而底部氧少，从而底部继续腐蚀，最后成为锈坑或锈穿。（2）两种不同金属或钢种的腐蚀。在海水中，两种不同成分的金属接触时，电 势较低的金属成为阳极发生腐蚀，例如铆钉和焊缝处容易锈蚀，原因即于此。（3）氧化皮引起的腐蚀。由于氧化皮的电极电位比钢铁的高0.26V，所以成为阴极，而钢铁本身成为阳极发生腐蚀。（4）涂膜下的腐蚀。由于实际上涂膜表央 有微孔存在，所以海水仍可缓慢穿过涂膜产生电化学腐蚀。此时，含涂膜的部分 成为阴极，不含涂膜的部分成为阳极而发生腐蚀，在涂膜未损坏或失效时，这一 过程是缓慢的。涂漆前未除尽的氧化皮、锈蚀物、污物、水分、盐类等，在涂膜 下加速进程，破坏涂膜。涂装时漏涂等施工缺陷也会加速腐蚀进程，从而过早破 坏涂膜。涂膜损坏后，将产生前述各种腐蚀，这种腐 2．机械作用腐蚀。机械作用的腐蚀包括腐蚀作用和机械磨损，二者相互加速。其中包括冲击腐蚀，这是由于液体湍流或冲击所造成；空泡腐蚀，高速流动的液体，因不规则流动，产生空泡，形成“水锤作用”，常常破坏金属表面的保护膜， 加速腐蚀作用，如螺旋浆、泵轴等处易发生；微振磨捐腐蚀，两个紧接着的表面 相互振动而引起的磨捐；应力腐蚀开裂，是在拉伸应力和腐蚀介质作用下的金属 金属腐蚀破坏，金属内会产生沿晶或穿晶的裂纹。 3．生物腐蚀。生物腐蚀是由海洋生物的船底附着引起的，这种腐蚀包括化学腐蚀和电化学腐蚀两种。由于海洋生物在船底的附着，破坏了漆膜，造成钢板局 部电化学腐蚀；由于微生物的新陈代谢作用，分泌出具有侵蚀性的产物如CO2、NH4OH、H2S等以及其他有机酸和无机酸引起钢板的腐蚀作用等。 4．化学腐蚀。化学腐蚀的特点是：腐蚀反应产物是直接地参与反应的金属，在表面区域生成，无电流产生。一般分为气体腐蚀和在非电解质溶液中的腐蚀两 大类。例如钢铁在高温蒸汽中产生的氧化皮，在有机液体中浸泡的破坏等。 二、防护技术 1．防腐蚀涂料技术。采用合适的船舶涂料，以正确的工艺技术，使其覆盖在船舶的各个部位，形成一层完整、致密的涂层，使船舶各部位的钢铁表面与外界 腐蚀环境相隔离，以防止船舶腐蚀的措施，称之为船舶的涂层保护。目前，船舶
船舶合理防腐蚀设计 尹建平 （湛江市吉达科技发展有限公司，广东湛江524009） [摘要] 船舶合理的防腐蚀设计是船舶腐蚀控制的关键措施，它主要包括合理选材、结构设计、布置设计和保护方法四个方面；针对船舶电偶腐蚀与缝隙腐蚀进行了合理防腐蚀设计，实现了对该两种典型腐蚀预防和有效控制。 [关键词] 船舶；防腐蚀设计；电偶腐蚀；缝隙腐蚀 前言 在海洋环境中使用的船舶，腐蚀非常严重，直接影响安全和营运，甚至缩短船舶寿命，因而受到造船和腐蚀界的高度重视。船舶腐蚀控制是一项复杂的系统工程，不仅涉及合理选材、结构设计、布置设计和保护方法选择，而且贯穿设计建造、使用维修，直至退役全过程，对船体、装置系统、舾装等均有密切关系。合理防腐蚀设计是腐蚀控制的关键措施，它关系船舶“优生优育”，是一项从源头抓起，投入少、效费比高、“终身受益”积极主动的措施，越来越受到世界各造船国家的高度重视。国内目前尚无国外船舶合理防腐蚀设计方面的专著翻译，国内无此方面的专著问世。笔者在上世纪九十年代初，结合船舶维修进行了该方面的尝试，从十五年的效果看，结果令人满意。凡进行合理防腐蚀设计与保护新技术结合治理的船体易腐蚀部位，15年无腐蚀，而非治理部位，已经修换过两次。据测算，在维修中实施该项措施，效费比为3：1，若在造船中实施，效费比更高，可达6：1。 1 船舶合理防腐蚀设计的几个主要方面 1.1合理选材 造船材料品种繁多，即使在同一艘船上使用的材料也多种多样。设计选材时除了考虑强度、刚性、韧性等力学性能外，还必须考虑材料的耐蚀性和匹配问题，特别全浸积水和潮湿环境部位，由于选材不当，往往出现某种材料的加速腐蚀。在船舶修理中出现这种情况的可能性更大，由于材料供应和现场材料限制，在局部更换或挖补时，使用了相对原船体材料电位较负的其它材料，由于直接接触和大阴极小阳极，换上去的材料腐蚀会更快。值得一提的是焊接材料也有类似问题，焊接接头部位，焊缝金属电位负于母材时，会出现焊缝腐蚀。 1.2 结构设计 腐蚀余量 船舶设计中，通常在船体易腐蚀部位，局部增加钢板厚度，即腐蚀余量，以保证船舶使用强度和寿命。其实，腐蚀余量并非上策，因为增加钢材消耗和船舶的排水量。由于船舶结构所处的具体环境多样性，还必须考虑腐蚀余量的特殊性，在有如尾轴填料函、海水设备
防腐防潮 建筑工程中的防腐主要是对易腐蚀的材料采用一定的措施，防止材料被腐蚀。比如：木门窗后面刷沥青漆、木门窗刷油漆、钢门窗刷防锈漆、管道拴防锈漆等都是属于防腐的措施； 2、防潮主要是地下水的侵蚀，一般是通过做防潮层来实现的。 3、区别： a、钢材防腐蚀主要是防氧化，木材防腐主要是防腐烂，腐蚀原因多来自空气； b、防潮主要是防止地下水的侵蚀。 防腐措施 1、热浸锌 热浸锌是将除锈后的钢构件浸入600℃左右高温融化的锌液中，使钢构件表面附着锌层，锌层厚度对5mm以下薄板不得小于65μm，对厚板不小于86μm.从而起到防腐蚀的目的。这种方法的优点是耐久年限长，生产工业化程度高，质量稳定。因而被大量用于受大气腐蚀较严重且不易维修的室外钢结构中。如大量输电塔、通讯塔等。近年来大量出现的轻钢结构体系中的压型钢板等。也较多采用热浸锌防腐蚀。热浸锌的首道工序是酸洗除锈，然后是清洗。这两道工序不彻底均会给防腐蚀留下隐患。所以必须处理彻底。对于钢结构设计者，应该避免设计出具有相贴合面的构件，以免贴合面的缝隙中酸洗不彻底或酸液洗不净。造成镀锌表面流黄水的现象。热浸锌是在高温下进行的。对于管形构件应该让其两端开敞。若两端封闭会造成管内空气膨胀而使封头板爆裂，从而造成安全事故。若一端封闭则锌液流通不畅，易在管内积存。 2、热喷铝(锌)复合涂层 这是一种与热浸锌防腐蚀效果相当的长效防腐蚀方法。具体做法是先对钢构件表面作喷砂除锈，使其表面露出金属光泽并打毛。再用乙炔-氧焰将不断送出的铝(锌)丝融化，并用压缩空气吹附到钢构件表面，以形成蜂窝状的铝(锌)喷涂层(厚度约80μm~100μm)。最后用环氧树脂或氯丁橡胶漆等涂料填充毛细因而管状构件两端必须此法无法在管状构件的内壁施工，以形成复合涂层。孔， 做气密性封闭，以使内壁不会腐蚀。这种工艺的优点是对构件尺寸适应性强，构件形状尺寸几乎不受限制。大到如葛洲坝的船闸也是用这种方法施工的。另一个优点则是这种工艺的热影响是局部的，受约束的，因而不会产生热变形。与热浸锌相比，这种方法的工业化程度较低，喷砂喷铝(锌)的劳动强度大，质量也易受操作者的情绪变化影响。 3、涂层法 涂层法防腐蚀性一般不如长效防腐蚀方法(但目前氟碳涂料防腐蚀年限甚至可达50年)。所以用于室内钢结构或相对易于维护的室外钢结构较多。它一次成本低，但用于户外时维护成本较高。涂层法的施工的第一步是除锈。优质的涂层依赖于彻底的除锈。所以要求高的涂层一般多用喷砂喷丸除锈，露出金属的光泽，除去所有的锈迹和油污。现场施工的涂层可用手工除锈。涂层的选择要考虑周围的环境。不同的涂层对不同的腐蚀条件有不同的耐受性。涂层一般有底漆(层)和面漆(层)之分。底漆含粉料多，基料少。成膜粗糙，与钢材粘附力强，与面漆结合性好。面漆则基料多，成膜有光泽，能保护底漆不受大气腐蚀，并能抗风化。不同的涂料之间有相容与否的问题，前后选用不同涂料时要注意它们的相容性。涂层的施工要有适当的温度(5~38℃之间)和湿度(相对湿度不大于85%)。涂层的施工
高耗能 1.绪论 腐蚀会造成材料和能源的消耗以及设备的失效，而且还会进一步污染环境、爆炸以及人员伤亡等重大问题。基于这一点，工业发达国家都对腐蚀所造成的损失进行了调查。1990年美国由CC Technologies Laboratories 和NACE International 负责执行，由交通部（DOT）的FHAW（Federal High Way Administration）管理的腐蚀调查数据表明，1998年总的腐蚀损失为每年2757亿美元，直接经济损失为1379亿美元。 我国于1999年启动的中国工程学院咨询项目“中国工业与自然环境腐蚀问题调查对策”，历时3年，于2001年基本完成。腐蚀调查涉及了自然环境，化工，交通运输，基础设施，电力系统和能源系统，机械制造以及军事设施与设备等。用Uhlig方法推算，我国的腐蚀约为5千亿元，相当于600多亿美元。这是不完全统计，如果加上矿山，冶金，轻工，食品和造纸等的腐蚀，我国的年腐蚀损失会更大。 浩瀚的海洋是人类生存的摇篮。“人口剧增，资源匮乏，环境恶化”是当今人类社会所面临的三大难题。人们越来越深刻地认识到海洋是人类生命的源泉，海洋是世界资源的宝库，海洋的开发和利用是国民经济发展的一个新的增长点。未来将是海洋的世纪，这已成为全球的共识。 近年来，随着国家经济发展战略从陆地转向海洋，船舶工业的发展得到了越来越多的重视。但由于海洋严酷的腐蚀环境，船舶防腐蚀
一直是困扰人类的重大难题。船舶在海洋上航行，与海水接触部分不仅受海水强烈的电化学腐蚀，还受海洋生物附着的污损。海水对于钢质材料来说是一种非常强的腐蚀性介质，而许多海洋生物和微生物能吸附于船底、螺旋桨、船舶管路及其他金属结构表面并生长和繁殖。特别是在温暖的海域和春夏两季，这些有害生物迅速生长繁殖，污损特别严重。除此之外船体还受到风浪的冲击，日光的暴晒等等。造成的腐蚀降低了船舶的使用寿命，增加了维护、维修的费用，更严重危害着船舶的安全。 船舶是一个整体，它的各个部分腐蚀的情况各不一样。（1）船底部位，船底分为平底和直底部位，长期处于海水的浸泡之中，受到海水的电化学腐蚀和冲刷作用。当船舶停泊时，还会受到海生物的污损作用。（2）水线区，水线区处于海水浸泡、海浪冲刷以及阳光暴晒之下，还要受到漂浮物的撞击。还有可能处于冰区航行，受到更大的冲击作用。（3）大气区，大气区指水线以上的干舷部位、露天甲板、甲板漆装件、上层建筑外部等。这些部位长年累月的处于含盐的潮湿海洋大气中，经常受到日光暴晒，干舷和甲板还经常受到海浪冲刷。（4）油舱，船舶内部的油舱主要指燃油舱，润滑油舱和污油水舱等；原油舱，装载原油的货舱内，粘稠的原油油膜对钢板有一定的保护作用。但是，原油中如果含硫量高，其中的无机硫化物，硫醇和噻吩等有机硫化物有较大的侵蚀性。原油中一般还混有油田咸水，其中含有氯化镁。除了油品本身的腐蚀外，往往有一个舱是进行荷油和压载的油水兼用舱。装过油的空舱由于表面有一层油膜对钢板有一定的保护作用，