accelerated saltwater corrosion testing - pitting around seals

[rmetzger]

We are looking at a seal design in one of our products that incorporates two o-ring radial gland seals between 316 stainless steel and a PBT plastic housing. This unit will most probably only be submersed in short intervals in saltwater (and allowed to dry in between uses) but can also be left for as long as two years under water. Generally it's less than 30 meters below the water line on deployments - most often less than 4 meters but can possibly see use down to 100 meters on rare occasions. As this is a different seal / material concept for this design we wanted to increase our pre-release testing to best simulate long life under the worst conditions and hence want to speed up the saltwater corrosion cycle (specifically low-oxygen pitting around the seals). Any advice?

 

[EdStainless]

316 is not suitable for crevice corrosion resistnace in sea water. period.

You need a better alloy, at least a 6%Mo grade to stand up to this. The intermitent service is the worst. When it dries out the trace of fluid under the seals will be 26% salt.

You need to simulate the conditions after it has been in service a while, high salt, low pH, low oxygen. Sounds like G48 is the ticket, though an acidified seawater may also be a good solution.

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http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[mshimko]

1. Can you be a bit more specific about the application?

2. If you want excellent pitting & crevice corrosion protection, here's an option (although it may be expensive): grind out and weld-clad the surfaces that will contact the o-ring, using a relatively nobel material for the cladding such as inconel. This is easily accomplished in production, the inconel has very good resistance to pitting and crevice corrosion, and the inconnel will be cathodically protected by the stainless.