Oxygen corrosion cautions

Galvanic corrosion is an accelerated corrosion of a metal due to formation of a corrosion cell with a metal or non-metallic conductor that exhibits a higher corrosion potential. For example, if a water pipe made of zinc-coated steel (galvanized steel) is connected to a brass fixture and caution is not taken to electrically isolate the two metals, a corrosion cell is established (Figure 7.5). To simplify the situation, we have replaced, in Figure 7.5, the zinc-coated steel by pure zinc and the brass by copper. The cathodic reaction is the reduction of dissolved oxygen, which takes place on both metals. The corrosion cell formed between the zinc and the copper leads to an accelerated corrosion of zinc near the joint. 

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