corrosion protective coatings a practical approach 5-12-2007
TRANSCRIPT
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Corrosion protective coatings a practical approach
5-12-2007
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© TRW Automotive Inc. 20072
ELV
Change to Passivation due to ELV legislation
Hexavalent chromium (Cr6)
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© TRW Automotive Inc. 20073
Cr6
• Hexavalent Chromium in corrosion protective finishings:
• Cr6 used in many hundreds of components made-in, calipers, and bought out as bolts, tie rods, washers, levers, abutment plates,……
• Main applications are chromate passivations for Zn and Al, some Dacromet finishes,…
• Annex I I distinguishes between parts with / without thread for the expiring date of the exemptions:
• COMPONENTS AND SPECS HAVING Cr6 (NOT THREADED) TO BE CHANGED BEFORE 01-07-2007
• COMPONENTS AND SPECS HAVING Cr6 (WITH THREAD) TO BE CHANGED BEFORE 01-07-2008
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© TRW Automotive Inc. 20074
Cr6 to Cr3
Problems with Cr3
• Not self healing
• Original TRW standard for calipers (without seal) will not meet corrosion requirement due to handling damage.
• All Calipers now have sealer as standard unless they are to be painted. (New standard finish for TRW)
• Externally plated parts: Bolts, Push Rods, levers etc. Do not meet corrosion requirements in all cases due to handling damage.
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© TRW Automotive Inc. 20075
Cr3
Problems with Cr3
Threaded parts parts.
• Can’t put a sealer on as external suppliers use different sealers/ concentrations, which may change the torque etc.
Parts without threads.
• In some cases a sealer is now being added to improve the corrosion performance.
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© TRW Automotive Inc. 20076
Cr3
Colour
• Need to differentiate between parts (left/right hand thread)
• A dye can be added. Not evaluated by TRW and will be an additional cost.
• Cr6 used clear or yellow passivate.
• Now we specify Black (ZnFe) or clear/normal passivate
• Cr3 Black passivate now available but not evaluated by TRW
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© TRW Automotive Inc. 20077
Example of Cr3 bought out parts
Requirement 96 hrs to white 144 hrs to red
72 Hours salt spray
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© TRW Automotive Inc. 20078
Example of Cr3 bought out parts
24 hours salt spray
Barrel plated
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© TRW Automotive Inc. 20079
ZnNi
• Trend with Vehicle Manufacturers towards ZnNi.
• More Customers looking for longer time to red corrosion.
• TRW now have in house ZnNi capability. (Duplex process).
• Standard finish for parts that have contact with aluminium.
• Harder to control in production.
• Standard finish under painted calipers
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© TRW Automotive Inc. 200710
Global warming is not just confined to ELV