Polysulfide Sealant and Steel Corrosion

[Busman]

I was recently on a project observing test cuts in a strand-wound shotcrete tank structure (~50 yrs old) with an embedded steel diaphragm. The diaphragm is severely corroded at the vertical diaphragm joints adjacent to what was reported to be polysulfide sealant. The corrosion decreases with distance from the joint. Does anyone have experience or know of online references that I could use in determining if the polysulfide has accelerated corrosion. I read that it can induce stress corrosion cracking, but I can't use that reference.

 

[unclesyd]

your material is probably Thiokol Rubber base on installed date. The early OSR material had a relatively short useful life. It Probably had a half life of 7 to8 years with total failure in 12 years.
The original material was not recommended for immersion use. If used in immersion service it could deteriorate in several years. This process would allow the entrance of H2O into areas where the rubber was trying to protect. I Think this is what you are seeing.

One other point is that some of the sealants of that time peroid had a lot of PCB"s in the aged product. The presence of PCBs should be verified. I think the cut off date for finding PCBs in the sealant market was around 1980.