Powder Coating Q&A: Can Powder be Applied Over Zinc Plating?
Can powder coating be applied over steel parts that have been zinc plated type II SC2 black?
Q. Can powder coating be applied over steel parts that have been zinc plated type II SC2 black?
A. Plated surfaces are always a challenge for adhesion of an organic coating such as powder. There are certain types of plating that powder will not bond with very well. Type II zinc plating indicates a colored chromate conversion coating.
In general, the answer is yes, you can powder coat it. However, caution is advised. A chromate conversion coating can be a very good corrosion inhibitor, but may not be very good for powder adhesion. The chemistry is not conducive to good adhesion.
I would do a sample to check if the powder wants to stick to the zinc plated surface. If the adhesion is not good, you may need to roughen the part with a very light blast, tumbling operation or something similar to create some surface roughness. The roughness may help you overcome the lack of chemical compatibility and provide a good surface for mechanical adhesion.
Originally published in the February 2016 issue.
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