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"Red striations on "cleaned" brass"
I am new to metal finishing but am looking to expand existing plating endeavors into restoration and finishing.
I recently used a 5% HCl solution in an attempt to remove build up and tarnish from a brass casting (ships clock)
I used a 12 min bath and the piece came out very smooth, no pitting however there were many dull red striations through the piece. I do not know if it is oxidation but it does appear to be. Has anyone seen this discoloring before ?
I am considering doing reproductions of some pieces and also restoring existing nautical pieces and am curious to what these striations may be.
New Plating and restoration shop - LOrignal, ON, Canada
You have dezincified the brass. This means that the zinc in the brass has dissolved out, leaving just copper. This has caused your red striations. You may be able to polish them out until you get back to the brass, but you will lose all the copper thickness. Cleaning brass should be done with care; use a neutral cleaner or very slightly alkaline, but do not leave the article in the solution too long. It is best to buy a proprietary brass cleaning solution. If you want to do this on a professional basis, I suggest you seek professional advice and materials before you lose a lot of money. Doing things on the cheap only leads to failure unless you have already developed the expertise.
R&D practical scientist
Chesham, Bucks, UK