EVALUATION OF POTASSIUM PERMANGANATE (KMnO_4) AS A GREEN CORROSION INHIBITOR/SEALANT FOR ANODIZED AI 2024 AND Al 6061 AT DIFFERENT pH VALUES

摘要

Increasing awareness about the toxicity, lack of biodegradability, health hazard andcarcinogenic character of chromium (VI) or chromate based inhibitors has led to the worldwideresearch on the suitable alternatives. These alternatives are expected to be environmentallyfriendly, biodegradable, non-toxic and easily available. Various oxoanion (MO_4~(-n)) basedinorganic compounds are being studied in this context. Potassium permanganate (KMnO_4)isone such inorganic compound, which is used commonly as a green corrosion inhibitor.However, due to the proprietary nature of the field of inhibitors, adequate information about itsefficacy as a corrosion inhibitor is not available in the literature.In this paper extensive electrochemical studies on KMnO_4 have been presented.Aluminum alloys like AI 2024 and AI 6061 are anodized in order to raise their corrosionresistance. The anodic oxide coating is made of an inner thin, non-porous barrier layer and anouter porous layer. It is important to seal the porous layer using inhibitor containing sealingsolutions in order to increase its corrosion resistance in chloride containing environment. Inorder to determine the appropriate concentration of the KMnO_4 solution (to be used as asealant), potentiodynamic anodic polarization and electrochemical impedance spectroscopic(EIS) studies were carried out on AI 2024 and AI 6061 in aerated solutions of KMnO4 in theconcentration range of 0.02M to 0.1M with pH values of 2.88, 4.20 and 9.16 in presence of 100