* Galvanic corrosion occurs between weld metal and base metal, between different areas of the same metal and between different metals in water.
* The intensity of galvanic corrosion is determined by the conductivity, oxygen content and the effective anode-to-cathode area ratio.
* Galvanic effects are spread over a large area in brackish and seawater; are confined to the immediate area of the junction in fresh water; and are often negligible in deaerated brines.
* Steel, Ni-Resist, zinc and aluminum are very effective in suppressing crevice corrosion on stainless steels except types 303 and 303Se.
* Carbon, graphite-lubricated gaskets, packing, greases etc. are very effective in initiating severe corrosion of stainless steels.
* Galvanic effects can be significantly reduced by removing coatings from the anode and by coating the more noble (cathodic) material.
* Stainless steel (or titanium) tubing increases copper alloy tube sheet attack to the point where impressed current cathodic protection is normally required to control tube sheet corrosion.
* Galvanic corrosion between different grades of nickel stainless steels mechanically joined is rare, but can be severe when welded. Caution and exposure tests are suggested.
* Avoid use of types 303 and 303Se.