[TheForge] where do I get?

[Bruce Freeman]

Peter,

Take two pieced of (clean) metal.  Connect them to a millivolt meter.  Dangle them (NOT touching each other) in any conductive solution - like table salt in water.  If a voltage is seen on the meter, then the potential for corrosion exists.  For two pieces of the same metal, there should be no difference at all.  (If there is, your apparatus is at fault.)   For metals as different as zinc and copper, this will be on the order of 1 to 2 volts - a battery. The smaller the difference, the smaller the problem.  Brass and copper are considered compatable (need not be separated by a dielectric in a plumbing installation), yet I'd bet a small voltage difference would be apparent on this apparatus.

Like all such tests, getting it to work right is the key.  Clean metal is essential - clean it with detergent, then acid.  Keep the meter leads and clips out of the brine.  When you get a voltage reading, exchange the pieces of metal between the lead clips and see if you get the identical negative voltage.

I think you'll find that stainless is stainless is stainless, but I could be wrong.

Bruce
NJ

>>> Peter Fels And Phoebe Palmer <artgawk at thegrid.net> 8/1/2007 3:34 AM >>>
<snip>

A second question for the knowledgeable folks here...
I'm assembling a semi submerged water intake for my system out of 
assorted scrap stainless. It's pretty clear that there are 
several, quite different alloys going into the assembly...hard, 
softer, magnetic and non magnetic.
What are the corrosion consequences of the mixed stainless? 
(Stainlesses?)

The prior intake ( the frog coffin) was enameled steel, galv 
steel, brass and copper. It lasted about 15 years. The steel 
parts are crumbling...1" galv schedule 40 pipe is perforated...
A fine demonstration of the drawbacks of mixed metal assemblys.
pete f