Inhibition of filiform corrosion on polymer coated AA2024-T3 by hydrotalcite-like pigments incorporating organic anions

Benzotriazolate, ethyl xanthate, and oxalate anion-exchanged hydrotalcite (HT) pigments are evaluated with respect to their ability to inhibit filiform corrosion (FFC) on organic coated AA2024-T3 aluminum alloy. Following FFC initiation by application of aqueous HCl to a penetrative coating defect, the time-dependent extent of coating delamination was determined both optically and by repeated in situ measurements performed using a scanning Kelvin probe (SKP). Inhibitor efficiency is shown to increase in the order ethyl xanthate << oxalate < benzotriazolate. Benzotriazolate is also shown to interact specifically with the alloy surface, depressing Volta potential values by up to 0.4 V. (c) 2004 The Electrochemical Society.