Zinc Flake Coating Technology Black Finishes for Fasteners
Mr. Hermann Donsbach Business Manager
BTT F&S, 2010/01, Hermann Donsbach
Dr. Leo Liu ZF manager
Zinc Flake - Coating
? Introduction
? Products ? Technology ? Bulk application ? Requirements ? Approvals ? Summary
BTT F&S, 2010/01, Hermann Donsbach
Zinc flake coating systems
Alternative to zinc or zinc alloy plating
Zinc flake coating is a method to deposit a cathodic protecting layer electrolessly. Additional top coats increase the performance. The trend to high strength steel requires suitable layer systems which cause no stress corrosion and fracture by hydrogen embrittlement. ,
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Zinc flake coating systems
Comparison plating – coating (1/2)
Zn Plating Corrosion protection Hydrogen embrittlement Brightness +++ 240 h red rust in Zn deposit + Need heat treatment Zn/Ni Plating +++ 1000 h red rust + Need heat treatment ++ Alkaline +++ Acid + Iridescent/blue/black/ clear ++ Skip plating problem may happen unless alkaline zinc/zinc alloy used + Poor Zinc Flake Coating +++ 1000 h red rust +++ No hydrogen embrittlement ++ ++ Multi colour on finish +++ Zinc flake covered with the use of facilitated equipment
+++ ++ Iridescent/blue/black/ clear ++ Skip plating problem may happen unless alkaline zinc/zinc alloy used ++ Fair
Appearance
Complicated shape part
+++ Good
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Zinc flake coating systems
Comparison plating – coating (2/2)
Zn Plating Waste water + ++ Less number of chemicals
Zn/Ni Plating + Strong complexing agents + Lot of additives
Zinc Flake Coating +++ No waste water +++ Only small number of chemicals ++ Low cost only in large scale production (+++) New low cost finishes under introduction
Handling
Running cost
(related to required protection)
+++ High productivity Low cost in acid zinc relatively
+ Low productivity High cost in zinc nickel
+++ Good
++ Fair
+ Poor
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High corrosion protection systems
Atotech is world wide the single chemical supplier for corrosion resistance coatings, able to offer both
ZINC and ZINC ALLOY PLATING with POSTTREATMENT
as well as a full range of
ZINC FLAKE COATING and MECHANICAL PLATING PROCESSES ,
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Zinc flake coating systems
Base coat Zintek?
Zinc flake base coats are high reactive systems containing zinc and aluminum flakes. After application and curing at approx. 200°C the dry film contains no lead, mercury, cadmium and chrome. , The flakes lay close-packed parallel to the substrate boundary. The substrate is cathodic protected. , . A top coat can fulfill additional properties.
For example: Containing an internal lubricant allowing to achieve different friction coefficients
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Zinc flake coating systems
Structure of the Zintek? layer
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Zinc flake coating systems
Top coats
Techseal? is an organic top coat, which was developed for application on zinc flake base coats as well as on electrolytically zinc or zinc alloy layers available in different colors. , Zintek? Top is a reactive, inorganic silicate based top coat developed for application on Zintek? base coats. After curing the layer thickness is < 1 μm with a good barrier effect against oxygen. , Multifunctional properties:
Increased corrosion resistance Defined lubrication Excellent adhesion Available in different colors Increased scratch resistance Very good chemical resistance
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Zinc flake coating systems
Examples of use – bulk production
Automotive industry: Zintek? 300 B + Techseal? Black
Fastening systems Stamping parts Brake drums Drive shafts Lock parts …
Traditional application: Silver base coat + black top coat Photo shows screws coated as above after mechanical load (e.g. oscillating conveyor): The silver base coat appears.
+
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Zinc flake coating systems
New products
Techseal? Black SL 28 V
Product request from OEM for sophisticated screws: small screw with internal drive integrated washer Properties: deep black color less sticky integrated lubricant increased corrosion protection
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Zinc flake coating systems
Process sequence
Pretreatment
Coating
Pre-drying
Curing
Cooling
Degreasing Shot blasting Phosphating
Bulk material dip-spin Bulk material spray Rack material dip-spin Rack material dip-drain Rack material spray
Box oven Conveyor oven Inductive curing
The dip-spin process sequence (without pretreatment) will be repeated in order to cover touch marks.
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Zinc flake coating systems
Dip-spin process 3-basket-centrifuge
Dip-spin processes are economically efficient coating processes for bulk and mass goods materials.
Centrifugal basket will be loaded with parts Dipped into the coating-medium Basket moves out of coating-medium Basket stays in the upper region of the tank Excess material will be spinned off Drying and curing Repetition of these process steps
The coating thickness can be regulated by variations of viscosity, solids and setting of defined spinning parameters. , .
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Zinc flake coating systems
Dip-spin process
parts
Loading of parts
Dip 5 – 30 s at 35 rpm
Spin 8 - 20 s at 250 rpm
Unloading of parts
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Zinc flake coating systems
Application process: Bulk material dip-spin
(by courtesy of BETEO GmbH)
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Zinc flake coating systems
Application process: Bulk material dip-spin Example planetary system
(approx. LxW: 28x6m only coating line) 28 x6
After burning
3-basket-centrifuge Pre-heating zone Curing area Cooling zone Conveyor belt Loading and unloading zone
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Zinc flake coating systems
3-basket-centrifuge
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Zinc flake coating systems
Standard equipment – improvements
Equipment Original Output 1998 Evolution 2009
Planetary
ZT-8 ZT-16 ZT-50 800 kg/h 1600 kg/h 5000 kg/h 40 x 40 = 1600 kg/h 60 x 40 = 2400 kg/h 80 x 80 = 6400 kg/h
Classic Tilting
ZT-12 ZT-36 ZT-48 1200 kg/h 3600 kg/h 4800 kg/h 30 x 180 = 5400 kg/h 40 x 180 = 7200 kg/h
Classic Still
ZT-9 ZT-3 900 kg/h 300 kg/h
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Zinc flake coating systems
Evolution of planetary ZT equipment
NEW ZT-50
3 baskets, diameter 514 (S) – 580 (K) mm Part range up to 250 mm L 250 Planetary motion 360° instead of 180° 50 baskets / hour (simple geometry) 80" dip-spin 130" load - unload 100 kg / basket, 100 / 360 40 baskets / hour (recess parts) 140" dip-spin 130" load - unload
Useful dipping volume: 'K' basket 74 L / 'S' basket 55 L
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Zinc flake coating systems
ZT equipment offered by Atotech – comparison with other European dip-spin unit suppliers
ZT-16 1998 Load/Basket Load/Basket Load/Batch Load/Batch Min Cycle Max Cycle Planetary Max Length Max Output 25 kg 13 L 75 kg 40 L 4,5' 5' 180° 150 mm 1,3 t/h ZT-16 2009 40 kg 21-25 L 120 kg 63-75 L 2,5' 3' 180° 150 mm 2,8 t/h ZT-50 80 kg 42-50 L 240 kg 126-150 L 2,25' 3' 360° 250 mm 6,4 t/h NEW ZT-50 100 kg 55-74 L 300 kg 165-222 L 3,5' 4,5' 360° 250 mm 5 t/h** 350-4 30 kg 15 L 120 kg 60 L 3,5' 4,5' 360° 150 mm 2 t/h 350-8 30 kg 15 L 120 kg 60 L 2' 3,5' 360° 150 mm 3,6 t/h TULZ 250 kg 140 L 250 kg 140 L 2' 3' No 250 mm 7,5 t/h ZT-48 180 kg 100 L 180 kg 100 L 1'30" 2' No 250 mm 7,2 t/h
** New further improvement ZT-50 with 6 baskets has an output of 8 t/h with planetary motion. 8 /
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