Letter 24036

Are there other methods to acquire a high chrome, low Ra surface finish? [California] 

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We work with high purity 316L SST to manufacture gas flow products that meet or exceed the Semiconductor Industry standards for internal wetted surfaces. Electropolish and acid Passivation is the process method presently used. Are there other methods that are being researched such as CVD (Chemical Vapor Deposition) of chrome, that may be used in creating a passive layer with a high chrome/nickel finish and a sub 1uin Ra on internal surfaces?

Thank you,

Raul Mercado
Manufacturing - Livermore, California, USA

A low Ra surface produced via mechanical polishing and then electropolishing is currently your best option. By reducing micro-pits and cracks and removing sub-surface impurities, there is reduced chance for corrosion to begin and to take hold in the base metal. When comparing methods, consider a salt spray test or other accelerated corrosion test. Comparison of corrosion is your only sure way to know if any method is superior.

David Pokvitis
- Chicago, IL, USA

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