MgSO4とNaHCO3を含む孔食抑制剤のアルミニウム合金に対する効果

概要

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The effects of inorganic inhibitors on pitting corrosion of aluminum and its alloys were studied in NaCl solutions with and without ethylene glycol and a trace of cupric ions. The addition of MgSO4 and NaHCO3 was effective as of either Na2CrO4 or NaNO3 in preventing corrosion. The addition of ethylene glycol resulted in some increase in pit depth but had virtually no effect on the effectiveness of these corrosion inhibitors. An oxide film composed of a basic salt of Al and Mg was deposited on the alloy surface when the specimen was exposed to dilute NaCl solution containing MgSO4 and NaHCO3 at temperatures higher than 40°C, and ethylene-glycol did not affect the formation of this film. When the specimen was covered with this protective film, the corrosion potential moved to the negative and the pitting potential tended toward the positive, so that the resistance to pitting corrosion was markedly improved.