INFLUENCE OF CHLORIDE AND HYDROXIDE IONS CONCENTRATIONS ON THE CORROSION BEHAVIOR OF AL AND AL-SI ALLOY

The electrochemical behavior of Al and Al-Si alloy in NaCl and NaOH solutions have been studied in the absence and presence of some amino acids as corrosion inhibitor. Open-circuit measurements showed that both immersion potential (Eim.) and steady state potential (Es.s.) decreased and become more negative as the concentration of NaCl and NaOH increased, while the rate of film thickening independed on the solutions concentrations. Cyclic anodic polarization curves indicated a small hysteresis loop raising the possibility of pitting as well as crevices corrosion. The studies revealed that both glycine and valine adsorbed on the electrode surface and inhibited both anodic and cathodic reactions. Due to the electron donating effect of methyl group in valine, valine was more effective in inhibition than glycine.