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topic 9104

Chrome plating is peeling off in sheets


(2001)

We have connector plates (CRS) that are chrome plated with a zinc underlayer. The plates are used to connect a metal band together with spot welds. After the band is finished it goes to the customer where it is thermally expanded. After the thermal expansion process, all of the chrome plating falls off. Before the process of thermal expansion, you cannot remove the chrome plating, even if you scratch it. The customer is blaming our plater and wants us to send out a corrective action. I think that the customer is overheating the band during the process causing the chrome to debond.

Is there anyone that can offer any explanation for this peeling? This is not mild flaking, the whole surface is debonding in one sheet.

Thanks in advance,

Randall Hardin
Englewood Precision - Englewood, Ohio, USA


(2002)

Dear Randall,

Zinc is a metal with the hexagonal close packed structure, which has very directional characteristics. If there is grain growth in the zinc during the thermal expansion process, perhaps the cleavage planes of the zinc are growing parallel to the substrate. It might be a question for a local analysis lab or engineering college.

On the production side of the question, could the underlayer be another more ductile metal, like nickel?

Best regards,

Dave Hass
- Oklahoma City, USA



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