Galvanic corrosion only occurs where an exchange of electrons is set up in a working fluid or medium. This mechanism works not too dissimilar from a typical voltage cell or two poled battery.
In the case of stainless steel, a thin layer of oxidation develops shortly after the metal is poured at the foundry. This layer, the passification layer, shields stainless from the rest of the world, hence the inertness of the metal relative to others. The passification layer is extremely tough but can be breached by heavy wear, scratching or some chemical action.
Also, the relative closeness of stainless steel in the Galvanic Series with carbon steel make for a poor coupling. In our case, the carbon steel would be anodic (active) and the stainless cathodic (noble). In the case of 13% Cr stainless, there is neglegable potential with iron in a carbon steel composition. 18-8 stainless is slightly more noble, but again, I would not expect much in the way of strong electronic coupling between the dissimilar metals.
Therefore as London2002 correctly points out, this is not an issue in our particular case.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
