ROHS & Yellow Chrome Plating

[CVPEngineering]

We are in the process of looking to eliminate "Hexavalent" from our yellow chrome finish parts. I need more information on Zinc Trivalent Dichromate Plating. How many hours of salt spray can the Zinc Trivalent Dichromate Plating withstand? 72hrs, 96Hrs or 120hrs?

What would be an industry call-out that I can use on my drawings to if I want to have the yellow finish on ROHS compliant chrome finish parts?

 

[SwinnyGG]

Without knowing specifically which salt spray test you use as a baseline, it is impossible to give a hard number- but if you are changing from hex to tri chromates, you're going to see an increase in free-body corrosion life between 10 and 20%. Trivalent chromates are, however, softer than hex chromates are, so there is a slightly higher danger of scratch-induced failures of the coating.

The callout I would use is "Trivalent Yellow Zinc Chromate"

 

[CVPEngineering]

jgKRI, Thank you. We reference ASTM B117 for the salt spray chamber and test based ASTM B633 Table 2 for corrosion resistance requirement.

 

[Screwman1]

Are you looking for hr. to white or to red rust- there is a big difference. If red rust- how thick is your base plating.

 

[CoryPad]

You need to obtain the latest version of ASTM B633, or ASTM F1941 if this is for fasteners. These standards provide a lot of new information.

An example drawing note would be Fe/Zn 5CN according to ASTM F1941.

 

[CVPEngineering]

Thank you everyone for some great feedback. Regards.

 

[SwinnyGG]

Not sure if CoryPad had a typo or something, but per ASTM F1941, the code suffix for Trivalent Chromium is "T"

So Fe/Zn 5CT

 

[CoryPad]

jgKRI,

Not a typo. ASTM F1941/F1941M − 15 Standard Specification for Electrodeposited Coatings on Mechanical Fasteners, Inch and Metric is the most recent revision. It now uses suffix N, not T.

 

[SwinnyGG]

Not a typo. ASTM F1941/F1941M − 15 Standard Specification for Electrodeposited Coatings on Mechanical Fasteners, Inch and Metric is the most recent revision. It now uses suffix N, not T.

Wow, thanks for that info. I was unaware the suffix had changed.