Corrosion protective coatings a practical approach 5-12-2007.

Corrosion protective coatings a practical approach

5-12-2007

© TRW Automotive Inc. 20072

ELV

Change to Passivation due to ELV legislation

Hexavalent chromium (Cr6)


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


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.


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.


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


Example of Cr3 bought out parts

Requirement 96 hrs to white 144 hrs to red

72 Hours salt spray


Example of Cr3 bought out parts

24 hours salt spray

Barrel plated


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


Global warming is not just confined to ELV

Corrosion protective coatings a practical approach 5-12-2007.

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