430 stainless steel bolt corrosion after salt-spray test

[mrippo]

After a recent salt-spray test, the 430 stainless steel bolts (passivated) which fasten a clam-shell enclosure design together for the outdoor environment have shown signs of rust (particularly in the bolt head region). The entire unit was suspended in a salt-spray chamber and subjected to a salt-spray condition of 95 degrees F for 14 days within a salt-fog solution containing 5% sodium chloride (salt), per BellCore.

Can anyone shed some light why the passivation process in the 430 stainless may have been interrupted and the salt-spray solution was allowed to attack the underlying metal?

 

[WKTaylor]

Mrippo...
I think You may get better a much better response to this question in the corrosion forum.. forum338.

I'm speculating that the natural passivation affect of SSTL is mitigated when the film is constantly erroded by the salt spray [directed onto the bolts?]. The bolt heads may also be corroding agressively due to affects of cold-heading [imbedded stresses] or other heat-treatment issues.

What Spec bolt [SAE, ASTM, etc..] are You using???... that may say a lot to others listening in! Regards, Wil Taylor

 

[WKTaylor]

Mrippo...

Duhhh, Sorry about ref to corrosion forum... I though I was in the mechanical forum... finally had my cup of coffee... Regards, Wil Taylor