Results using a rotating disk electrode (RDE) clarify the mechanism of corrosion of commercial Cu‐9.4Ni‐1.7Fe alloy in aerated 3.4 weight percent NaCl solution at room temperature. The loosely adherent corrosion product (mainly Cu 2 ( OH ) 3 Cl ) formed under rotating conditions consists of two layers. Additional support is obtained for the existence of a third inner layer which is very thin and adherent to the metal surface. The anodic Tafel slope on this corrosion‐product‐covered sample is 60 mV decade −1 and is independent of rotation speed, consistent with a slow step for the anodic reaction being ionic transport in electrolyte within the porous corrosion‐product layer. Results using Pd deposits on the corrosion‐product surface show that the rate of the cathodic reaction (oxygen reduction) may be under reaction (charge transfer) control rather than transport control through a corrosion‐product inner layer. It follows that the good corrosion resistance of the cupronickels in seawater may be due to a poor catalytic nature of the corrosion‐product surfaces for the oxygen‐reduction reaction.
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Kato et al. (1984) studied this question.