In the list below, it is my understanding that the metals at the bottom of the chart are the ones most susceptible to corrosion. That's why silicon bronze corrodes so little, and why zinc is so useful in protecting other metals. The zinc corrodes and gets used up instead of the stuff you're counting on. Examples of this are the "sacrificial zincs" which are put on outboard motors to protect them, and therefore must be replaced from time to time.
Steve Tyree In a message dated 8/3/2005 10:23:12 AM Central Standard Time, [EMAIL PROTECTED] writes: In a message dated 8/2/2005 6:53:18 PM, [EMAIL PROTECTED] writes: << I wonder if I need worry about galvanic corrosion at all since I'm a freshwater sailor (?) ... --Craig >> Too hot for any sailing here (Arizona), but I am sending some additional information re your topic/question: Galvanic action is the process of electrolysis that takes place between two dissimilar metals when placed in salt water or non-pure fresh water. Although galvanic action is a problem faced primarily by boats used in salt water, freshwater boaters cannot be totally ignorant of the problem: not all fresh water is chemically pure, and water that is even slightly brackish can set galvanic action into motion. The following is an electrolytic table which rates metals from "most noble" to "least noble." In non-pure water current will flow from the less noble to the more noble metal, and in the process, the less noble metal will be destroyed. Metals close together in the table can be used together. Metals far apart cannot. Yellow brass, for example, is composed of zinc and copper. Over time galvanic action will erode the zinc. For that reason brass screws, valves, etc. would be useless in salt water. mercury monel nickel bronze (silicon) copper brass (red) bronze (aluminum) gun metal brass (yellow) bronze (phosphor) tin lead steel (stainless) iron steel (mild) aluminum cadmium galvanized iron and steel zinc magnesium Regards, Diane Kerr High Barbaree M15 #625 _______________________________________________ http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats
