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Titanium reaction with HCl and HF

We use descaler (mixture of acids : 50% HCl and 5% HF) in the titanium heat exchanger. We noticed that the titanium discolorized. By this reaction, thus it means that the metal composition of titanium (Grade 7 and 12) be attacked? Can it result in breakdown of titanium?

Ben Riva
- Philippines
2006

Yes. Titanium is attacked by both acids.

Guillermo Marrufo
Monterrey, NL, Mexico
2006

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The discoloration may be hydrogen attack from the acids.
Suggest a 30 wt% sulfuric acid + 1% copper sulphate ⇦ on eBay or Amazon [affil link] solution at 28 °C (100 °F) for cleaning, and a 33.2% nitric acid + 1.6% hydrofluoric acid solution for final brightening.

See letter 38318 and ASTM B600(2002) Standard Guide for Descaling and Cleaning Titanium and Titanium Alloy Surfaces.

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.
2006

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