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Re: Galvanic Actions

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On Feb 22, 2010, at 5:54 PM, Thor Tandy wrote:

I have a connector system which is hot-dipped galvanized and I am proposing
to use stainless steel Hilti Kwik Bolts-TZ for connection to concrete.
Would I be better to use Carbon steel anchors instead? Is there significant galvanic action between stainless and the galvanizing? What about between
carbon steel and galvanizing?

The corrosion mechanism for stainless is pitting rather than general wastage as for carbon steel. Galvanizing protects carbon steel because the zinc coating corrodes preferentially until it's mostly gone then the corrosive medium starts on the steel. Chlorides are the big bugaboo for stainless and the mechanism is intergranular corrosion. Stress aggravates the effects of chlorides and I've seen instances where stainless simply fell apart after exposure to low pressure steam which basically just caused the metal to disintegrate. Crevices are bad things for stainless. They trap fluid and chemistry of the trapped fluid is very damaging.

Architectural stainless subject to road salt and similar contaminants get pretty ugly after a couple of winters, which confuses architects who take the 'stainless' moniker at face value.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania 1864)

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