Corrosion of s/steel 316
Corrosion of s/steel 316
(OP)
Hello,
we have a motor housing made of s/steel aisi 316. It is a thin metal body about 2mm thick and cold formed (deep drawn and spun). Two holes are also cold worked (punched)for the electrical cables to go through. Recently we've seen pitting around these holes (where the rubber cable gland sits) forming an o-blong shaped pitting area where the seal contacts the housing. Close to the holes we also spotweld 2 studs. The studs have also corroded and fallen off.
The motor which is part of a pump operating in sea water, has its cable coming out of these 2 holes around which corrosion was seen.
Can anybody explain what initiated the corrosion?
thanks for your help!
ELv
we have a motor housing made of s/steel aisi 316. It is a thin metal body about 2mm thick and cold formed (deep drawn and spun). Two holes are also cold worked (punched)for the electrical cables to go through. Recently we've seen pitting around these holes (where the rubber cable gland sits) forming an o-blong shaped pitting area where the seal contacts the housing. Close to the holes we also spotweld 2 studs. The studs have also corroded and fallen off.
The motor which is part of a pump operating in sea water, has its cable coming out of these 2 holes around which corrosion was seen.
Can anybody explain what initiated the corrosion?
thanks for your help!
ELv





RE: Corrosion of s/steel 316
Either eliminate them or use a more Cl resistant SS, such as 254SMO.
RE: Corrosion of s/steel 316
The punched holes create surfaces perpendicular to the rolling plane of the metal. This exposes inclusions which make such a surface pit more readily. Lastly the welds which hold the studs are the least corrosion resistant even if properly cleaned. Unless they are laser welds they will have a crirical pitting temperature 10C lower than the wrought metal. The cold work on the housing has a negligible effect.
316 is marginal in seawater. You could move up to 2205 to eliminate the problem or try 316Ti if you can locate any.
RE: Corrosion of s/steel 316
btw - This phenomenon is not well known outside of the metallurgical world. I set up an experiment for my son to do for his high school science project on this. It won the state! We used 316L with 10.1% Ni content, solution annealed. It had no attraction to a magnet in that condition, but he showed that increasing deformation induced increasing response to a magnet.
RE: Corrosion of s/steel 316
RE: Corrosion of s/steel 316
really helpful!
cheers.
RE: Corrosion of s/steel 316