Letter 32019

Repair of Hard Chrome Plating  

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We have a part that has been constructed of several plates welded together in layers. After welding some edges were machined and then the entire assembly was Hard Chrome plated. After plating some of the seams between layers continued to seep what we assume to be Chromic Acid. We have tried baking the part at 250 deg. F to dry out the acid. This has helped but we are still getting some seeping. Any suggestions?

We are considering grinding into the seams and welding them shut, but aren't sure of our options to repair the chrome plating in these areas. Any suggestions?

Mike Iverson
Major Tool and Machine - Indianapolis, IN, USA

Try dipping the part in 10% sodium meta bisulphite solution then remove after say 10 minutes and rinse in clean water. It converts the hex Cr in chromic acid to tri Cr which is firstly not brown and will not stain your comp.

ALL THE BEST

VIKRAM
- INDIA

There is no cost effective way of preventing or removing chrome solution that has wicked into the crevice of welded components.. You might try a directed medium pressure spray jet at the joint. It could be automated at a high initial cost, or, manually done at a lower cost that continues forever. Engineers should avoid butt or T joints on parts that will later be plated. The reducing agent suggested in the first reply will convert some of the hex chrome solution which will rinse slightly better, but I will bet that you will get additional seepage that will be green along with orange/yellow.

James Watts
- Navarre, Florida

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