Abstract
Maximum protection efficiency for the cathodic polarization of 6351 aluminium alloy in sea water was achieved in the potential range −′1·0 to −1·1 V (SCE). Protection efficiency declined at both more electropositive and more electronegative potentials because of pitting and an increase in the rate of cathodic corrosion respectively. Determination of changes in the pH of the sea water close to the surface of the cathodically polarized alloy at different potentials in the range ′−1·1 to −1·5 V(SCE), revealed that calcium and magnesium compounds were deposited only after prolonged polarization to potentials at or more negative than −1·2 V(SCE), during which surface pH increased to values in excess of the theoretical values for the deposition of these compounds from sea water. Once formed, magnesium compounds were more effective than calcium compounds in buffering the sea water close to the surface against increase in pH.
Get full access to this article
View all access options for this article.