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302 stainless steel springs salt water corrosion [Italy] 

August 5, 2008

Hi everibody,
we are stainless steel springs maker and we've a great problem with a corrosion resistance test asked for some customers. This test is quite simple. The springs have to pass 24 h without develop any form of corrosion in a salt water solution ( 150 gr NaCl / 1 l water ) at 55 ° C. Springs are made of 0.5 - 0.9 mm 302 cold drawn wire. The surface is of course stearate. We temper the springs in air at 380 ° C to improove the mechanical properties. After we utilize the standard cleaning/degreasing system. Sometimes the spings don't pass the test developing rust. We're thinking about a passivation step after cleaning...
Any suggestions?
thanks a lot for your help

Marco Giudici
tecnician - Italy

If they're already passing part of the time without passivation, I have no doubt that passivating them will get you the rest of the way there. Nitrc acid and citric acid based processes are available. Let us know if we can help.

Ray Kremer Stellar Solutions, Inc. Algonquin, IL, USA