EFFECT OF THE ADDITION OF OXO-ANIONS ON THE CORROSION BEHAVIOR OF AN ALUMINUM-ALLOY-6063 IN BICARBONATE MEDIUM

Effect of the addition of oxo-anions CrO42-, MoO42-, WO42- and HPO42- on the corrosion behaviour of an aluminium 6063 alloy has been studied by electrochemical methodes in bicarbonate - chloride medium. The results show that aluminium 6063 alloy manifest a passivation phenomenon with ruptur of passivity. Addition of chromate ions leads to the inhibition of general and pitting corrosion of this alloy. Molybdate or tungstate anions inhibit pitting corrosion but stimulate cathodic process. Phosphate ions give good efficiency for general corrosion and increase simultaneously pitting sensitivity of the aluminium alloy. On the basis of these results a mecanism of oxo-anions action has been proposed.