On Wed, 14 May 2008 17:47:45 +0200, "Steve Lusardi"
wrote:

Will urine ie human waste corrode 316L valves and pipe? The question is
asked because waste tanks are typically plastic, but Lloyds A1 certification
requires all through hull valves to be fire proof. Fireproof valves are
typically 316L. I have purchased all my valves from the chemical industry. I
have been told that urine will corrode 316 over time. I don't believe it. If
316 is good enough for corrosives in industry, why would it not stand up to
human waste? If anybody knows for sure, please let me know.
Steve


Greetings Steve,
Stainless steels will corrode faster if not exposed to free oxygen.
Stainless that is constantly submerged in salt water will corrode when
the same piece above water will not. This corrosion can also be from
biological processes. Science News had an article several years ago
about stainless piping that had to be replaced in some nuclear power
plants because of corrosion induced largely by bacteria. I have
machined many stainless prop shafts that were replacements for shafts
that had what appeared to be worm holes in them that ran roughly
parallel with the shaft axis and were anywhere from 3 to 18 inches
deep. Washington State had to have a bunch of stainless pipe replaced
on some ferries because the boat builder used it in a salt water
system where the inside of the pipes were always flooded.
ERS