Metal finishing Q&As since 1989

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CLEANING OF INCONEL 625 HEAT EXCHANGER

We have a client who intend to clean heat exchanger (tubes of Inconel 625)having a different scale of carbonate, carbons, silica.....etc. we are intend to do heavy degreasing using caustic soda [affil links] followed by picking using HCl to dissolve these scale which proven by lab will dissolve the scale...my question will Caustic and HCl affect the Inconel 625 metal due to high chlorides includes. as you may know we can not use these with SS metals.

REDA ABDEL SALAM
Halliburton - EGYPT
2005

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The ASM Metals Handbook, 9th Ed. Vol. 5, Surface cleaning, finishing and coating, has a section on cleaning and finishing of Heat-Resisting Alloys. For removing oxide scale they recommend alkaline conditioning using NaOH and KMnO4, followed by 3 pickling operations using H2SO4, HCl, nitric acid, then nitric plus Hydrofluoric Acid. The concentrations of the acids are fairly low, temperatures are about 150F. The text mentions that most of the time, the acids are a nitric and hydrofluoric mix. Excessive roughening is a problem, according to the text.

  
Tom Pullizzi
Falls Township, Pennsylvania
2005

You could try phosphoric acid?

Dale Windrdge
- Magate, Kent, UK
2005