Letter 26590

Removing hard chromium  

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We have an automatic hard chromium plating plant for engine valves production in Istanbul. In our plating process we have some problems. Some of our valves have small visual defects. When we strip chromium to restore the plated surface, Which method must we use to prepare surface before replating for the good results. Thanks for your kind reply.

Best regards.

Muammer Ozkan
Engineer - Istanbul, Avcilar, Turkey

+++ There are only two methods that I know of: alkaline electrolytic stripping and hydrochloric acid stripping. What is the substrate of these valves, hardened steel?   Ted Mooney, P.E. finishing.com Inc. - Brick, NJ

Hard Chromium Plating, Robert K. Guffie

Stem hardened tempered and head solution aged for bimetallic valves. We apply both of your stripping methods. But for the better results that needs extra polishing.We don't prefer to apply it.

Muammer Özkan
- Turkey

I think it is extremely unlikely that you are going to take a part from being stripped straight back to the chrome tank without further mechanical finishing. Having stripped a lot of hard chrome over the years in both NaOH and HCl I have never seen it done without the surface being smutted or tarnished. I suppose you could get a bright dipping or electropolishing tank to replace the mechanical finishing but the convention is to repolish, hone or blast the surface after stripping

Daryl Spindler
decorative chrome plating for truck industry - Portland, TN

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