"301, 316, 316L, Elgiloy, corrosion resistance to certain chemicals"

Question:

"I'm part of a medical device development engineering team investigating failure modes of stainless steel belts (301, high yield - 270K psi min). The belts are subjected to a repeated stress of 14K psi with a target life of 20K cycles. The device is cleaned every 2 weeks (2yr life) and the belts are exposed indirectly to cleaning solutions. Mist from a spray bottle can find it's way to the belts where it cannot get wiped off. The solutions in question are: Ammonia(50%), Saline(.9%), and a cleaning solution called Wexcide (.1%, active ingredients: ortho-Phenylphenol & ortho-Benzyl-para-Chlorophenol) We know that stress concentrations have lead to premature failures in some belts and but wish to understand how these chemicals influence or contribute to this failure and how belts without any stress concentrations will fare. Are 316, 316L or Elgiloy better in resisting chemical attack from these solutions?"

Answer:

Any corrosion that will introduce geometric stress concentrators (pits) will reduce fatigue life. Chlorides and hypochlorites are especially harmful pitting agents. The chemicals should not be harmful in the absence of corrosion. Type 316SS will be more resistant to pitting corrosion than 301SS; however, you may not achieve the same strength levels, based on cold working.

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