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Chemical Polishing of 2014 aluminum alloy

I need some enlightenment on the chemical polishing of 2014 Al alloy. Is it natural that I obtain a rough surface, with a good light reflection but nevertheless far away from the 60xx series? I'm using a proprietary composition based on sulfuric, phosphoric and accelerated by nitrates, at 80-90 °C.

Marco J.N. Antunes
consumer - Porto, Portugal
2006

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2006

The 2xxx Al-Cu alloys are rather unsuitable for chemical polishing (bright dip) due to microstructural heterogeneities. Also, some proprietary bright dip solutions operate with Cu concentrations of 100-200 ppm, which is rapidly exceeded with Al-Cu alloys.

The microstructure of 2014 is described and shown on pages 70 and 76-79 in Aluminum Properties and Physical Metallurgy [affil link on Amazon] (1984). It contains intermetallic phases such as (Mn,Fe)3SiAl13 and Cu2Mn3Al20 which are not dissolved during the solutionizing heat treatment.

Recommended alloys for bright dip are 5357, 5457, 5657, 6463, 7016 and 7029.  This is based on primarily on experience with automotive trim using phosphoric-nitric acid bright dips.
-- The Surface Treatment and Finishing of Aluminum and Its Alloys, 6th Edn., p. 139 (2001).
Other alloys chemically polished include 1100, 1175, 3002, 5005, 5252 and 6063. All of the customary bright dip alloys anodize better and resist corrosion better than the 2xxx alloys.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.

Thank you Ken!

Marco J.N. Antunes
- Porto, Portugal
2006

 

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