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Re: Stainless shapes at sewage plants

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> Re:  stainless steel structural
> shapes, for a wastewater treatment plant:

I presume there's agood reason to go to stainless steel, but have you considered
aluminum as an alternative?

The aluminum members I've seen at our local sewage (sorry - wastwater) treatment
plant look as good as new, even when they constantly dip in and out of that
unmentionable stuff. My friend, who designs maintenance equipment there, says
that they use aluminum now, whenever they can. 6061-T6 is the most common alloy.

There are also lots of aluminum geodesic - style domes, built from 6061-T6,
serving as roofs over aeration and digester tanks. Temcor is a leading
manufacturer who may be able to advise on performance-

SS 316 Stainless Steel will probably do fine, but beware of applications where
there may be limited circulation around the metal. I think corrosion results
because stagnant water allows ambient oxygen to get used up, so the protective
oxide coating isn't maintained.

One of my submarine manufacturing clients uses aluminum ballast tanks for their
tourist submersibles, which spend their days in sea water. The aluminum
generally does well, although corrosion is a problem when bimetallic galvanic
action occurs. A competitor used stainless steel for their ballast tanks, but
this proved to be a mistake. When the sub sat inactive for a few months at their
dock, the tanks corroded - I think it sank when it wasn't supposed to.

Jim Warne