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"Removing rust and restoring yellow chromate color"

April 27, 2018

Q. Dear sir, I have a quantity of cold rolled job with zinc yellow passivation in my end. When I was dumped more than one year, so still occurs rust on some of the areas on this job. It was assembled with plastic components, so we aren't able to re-plate this job.

1. How I get clear the rust and recolor this job related origin?

- chennai, tamilnadu, india.

April 2018

A. Hi cousin Parthiban. Simply removing the rust will not accomplish anything because they will rust again immediately; further, you will not be able to passivate them because the chromate conversion chemistry only works on the zinc plating it doesn't work on cold rolled steel. Finally, although some plastics like PVC and polyethylene are resistant to the acids you would use for the clean-up, other plastics like nylon do not offer acid resistance.

Please tell us what these assemblies are and where they are used so someone can make a positive suggestion. For example, it might be possible to clearcoat them, or preferably zinc phosphatize and then paint them, but neither of those ideas will work if the parts must be conductive, those and other ideas might be a problem if there are critical dimensions. Finally, replating may be possible despite the assembled plastic pieces. Good luck.


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Ted Mooney, P.E. RET
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finishing.com - Pine Beach, New Jersey

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