Alternatives to hex chromate for mechanical tin / zink plating

[WillCole]

Could anyone suggest an alternative topcoat for a mechanical tin / zink plating? Most of the suppliers I have contacted about trivalent chromate have said they aren't recommending them for tin / zinc mixtures.

 

[CoryPad]

Why do you want it topcoated? What is the application?

 

[WillCole]

Corrosion protection. I am hearing the trivalents aren't preforming as well for tin /zinc mixtures.

 

[CoryPad]

If you want higher corrosion resistance, try using a higher performance zinc electroplating like ZinKlad or a zinc-nickel electroplating.

 

[WillCole]

Thank you for the reply. I do understand there are other options with electroplating. I was specifically wondering about mechanically plated parts.

The application I was thinking about was mechanically plated flat springs of extremely high tensile steel. They are not electroplated because of hydrogen embitterment / baking issues.

Cost is a bit of a factor, so exotic processes like solvent based aluminum plating are not viable.

 

[CoryPad]

The extra information supplied allows better responses. There are inorganic and organic topcoats that can improve corrosion resistance, try Magni and Dorken. If you want really good corrosion resistance with low embrittlement risk, try zinc-rich coatings from Magni and Dorken.