Re: Compatibility of distinct materials

>My question relates to the Compatibility of distinct materials when
>used in assembly. To be specific, there is a case where a SS tube is
>joined to a Copper tube wit a brass coupling. At the joint, corrosion
>has set in.

Make sure it's corrosion. I just finished having some copper water line replacedwhich had eroded due to cavitation. Copper doesn't respond well to ordinary water moving at high speed, and the turbulence and cavitation associated with small obstructions like sudden changes in diameter or joints which haven't been deburred are a real problem. Brass, including red brass, corrodes preferentially to straight copper and stainless, so if you had a galvanic corrosion problem I'd expect the brass fitting to corrode.

Galvanic corrosion is an electrolytic process where the two materials form a sort of battery and material is transferred from the more electropositive material by a small current flow. If you have metal fillings, try biting down an some aluminum foil to see what I mean. You should do your own homework on galvanic corrosion, Here are some places to start

http://www.ocean.udel.edu/mas/masnotes/corrosion.html
http://www.ocean.udel.edu/mas/masnotes/corrosion.pdf
http://www.thelenchannel.com/1galv.html

There are a couple of file on <http://www.pipingdesign.com/> dealing with corrosion

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