Craig, Every metal has an associated potential, or voltage property.
Here are simplified examples of potential values in sea water: -0.05: 304 Stainless -0.30: Copper -0.76: Aluminum The greater the difference in potential between metals, the faster the rate of corrosion of the metal with the lower number. The lower one is the one with the most negative number. There are three combinations of metal of interest: 1) Stainless and aluminum will cause corrosion in the aluminum. 2) Stainless and copper will cause corrosion in the copper. 3) Copper and aluminum will cause corrosion in the aluminum. However, the rate of corrosion of (3) is less than (1). The fact that the higher metal (stainless) is smaller in size than the lower metal (aluminum) is helpful. If the situation were reversed, that is if you had some sort of aluminum fasteners in a stainless spar, it would corrode faster than an aluminum spar with stainless fasteners. steve Steve R. M-15 #119 Lexington, KY ********************************************* I'd like to know more about galvanic corrosion, if any M-List metallurgists can explain: Why would copper prevent galvanic corrosion between steel and aluminum, and why wouldn't copper cause galvanic corrosion to both? _______________________________________________ http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats
