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17-4 Stainless Steel Corrosion in a Marine environment

September 28, 2010

Hi I work for a company that manufactures Survival Capsules for the Offshore Industries.
These Capsules are supported by a Release Mechanism or "Hook". In this particular application, the Hook Nose is manufactured from 17-4 Stainless Steel which rotates around a 17-4 Pin which in turn is supported by a 316 Stainless Steel Housing. The 316 housing remains in a good condition, but after only a week or so, the 17-4 Hook Nose looks "bad". It looks like it has considerable corrosion. I know it's only surface "tarnish", but the customer wants his hook to look "nice & Shiny".
Any thoughts on how I can keep the Hook Nose looking "nice & shiny" would be much appreciated.

Sid Medley
Engineer - Vally Center, California, USA

September 30, 2010

Hello, Sid. It's molybdenum in the 316 alloy that is responsible for the extra corrosion protection in marine (chloride) environments. The 17-4 simply lacks that key component. Sorry about that.

Jon Barrows
Jon Barrows, MSF, EHSSC
GOAD Company
supporting advertiser
Independence, Missouri

October 11, 2010

We can suggest special passivation process. Such passivation creates strong corrosion protection layer on the surface of 17-4 stainless steel (parts look shine and bright). Based on the corrosion tests results the passivated parts can stand such test 3 times longer than non-passivated ones.

Anna Berkovich
Russamer Lab
supporting advertiser
Pittsburgh, Pennsylvania
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October 21, 2010

Passivation and alloy choice are both of major importance in marine environments. Even 304 stainless doesn't hold up as well as 316.

ray kremer
Ray Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
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