Letter 14026

Red indicates corrosion site in hard chrome deposit [Canada] 

I recently witnessed a test used on a Hard Chrome deposit, where a clear solution was dabbed onto the deposit. The deposit was approx 1mil thick. If pores or potential corrosion sites existed, the solution indicated this by turning red at the site. It sounds similar to the ferroxyl test, but red not blue. Could the solution contain phenolphthalein? I asked, but of course got no answer from the tester. I would like to make some of this solution for my own use, and I'm sure others would as well. Can anyone help?

Steve Delaney
- Beamsville, Ontario, Canada

Sounds a lot like a copper sulfate test, but that should have been a light blue solution.

James Watts
- FL

I assume that the basis metal is steel. The solution could be sodium or potassium thiocyanate. This will react with corrosion products of iron (compounds in the ferric state) to give a deep red color.

Dave Wichern - Bronx, NY, USA

  

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