Letter 12184

Zinc Plate Flaking Off 12L14 Carbon Steel During Forming 

I have a problem/question regarding zinc plate of 12L14 steel. We have a cylindrical case made of 12L14 that is zinc plated 200-400 microinches (our specifications). During the subsequent assembly process, we place a plastic cap into the case ends and roll the case ends using a pneumatic press and mandrel to capture the plastic caps. The rolling operation causes flaking of the zinc plate, which can cause electrical failures due to metallic particles inside the case. What are my alternatives to zinc plate that will not flake off during the rolling of the case ends, and what are the tradeoffs?

Mike McMonagle
- Houston, Texas

Machinists love leaded steel. Platers hate it for exactly the problems you have. Normally, using a fluoboric acid dip will remove enough lead to give better adhesion. This is a more expensive acid and may have to be in addition to the muriatic or sulfuric the plater is using. Most tank lines do not have the capability of adding another acid tank and associated rinse tanks. Two main choices: 1. go to a NON free cutting steel or 2. go to a plater that can use the fluoboric treatment.

James Watts
- FL

Maybe a more ductile plate? Try Zinc Iron... if the specification does not allow a plating change, are you getting it plated with acid or alkaline zinc? Are there cosmetic concerns for the finished assembly?

Brian Lucas
- Wolcott, CT

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