The localized corrosion behavior of Al-Mg-Si alloy (Al 6063, UNS A96063) in five types of ground waters found in Japan was studied in terms of the relationship between chemical composition of the ground water and the electrochemical characteristics. Localized corrosion (nodular pitting corrosion surrounded with white corrosion products) occurred in all aerated, original ground water after immersion for 480 h, but weight loss of the specimens differed according to the type of ground water. Weight loss was inversely proportional to the difference between pitting potential (Epit) and corrosion potential (Ecorr). Epit was dominated mainly by chloride ion concentration, and Ecorr increased with an increase in calcium hardness. From electrochemical studies in ground water and synthetic waters, the increase of Ecorr was caused by enhancement of dissolved oxygen reduction in the presence of calcium ions, bicarbonate, and dissolved oxygen.

Subject
Pits, Water, Ions, Calcium, Chemical composition, Polarization curves, Ion concentrations, Weight loss, Pitting, Dissolved oxygen, Copper, Hardness, Samples
Keywords:
Al 6063, aluminum, corrosion potential, ground water, localized corrosion, magnesium, pitting corrosion, pitting potential, polarization, silicon
NACE International
1999
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