Effect of halide ions on the corrosion inhibition of aluminium in alkaline medium using polyvinyl alcohol

The corrosion inhibition of aluminum in NaOH in the presence of polyvinyl alcohol (PVA) at 30 and 40 degrees C and the effect of addition of halides (KCl, KBr, KI) were studied using weight loss and hydrogen evolution methods. Results obtained showed that PVA acts as a corrosion inhibitor in the alkaline environment. The inhibition efficiency increased with increase in concentration of PVA and synergistically increased on the addition of the halides but however decreased with rise in temperature. The phenomenon of physical adsorption is proposed from the obtained E-a and Q(ads) values. PVA was found to obey Freundlich and Frumkin adsorption isotherms. The increase in inhibition efficiency I (%), surface coverage 0 values as well as synergistic parameter, S, were found to be in the order I- > Br- > Cl-, which clearly indicates that the radii and electronegativity of the halides play a significant role in the adsorption process. (c) 2006 Wiley Periodicals, Inc.