NACE International, CORROSION, 3(60), p. 219-228, 2004
DOI: 10.5006/1.3287724
Full text: Unavailable
Abstract Novel anion-exchange anticorrosion pigments consisting of nitrate-, carbonate-, and chromate-exchanged hydrotalcite (HT) are shown to inhibit the propagation of filiform corrosion (FFC) effectively on organic-coated aluminum alloy 2024-T3 (AA2024-T3 [UNS A92024]) alloy. The HT-pigments are dispersed in polyvinyl butyral (PVB) coatings applied to the AA2024-T3 surface. Following FFC initiation by application of controlled amounts of aqueous hydrochloric acid (HCl) to a penetrative coating defect, the time-dependent extent of coating delamination is determined both optically and by repeated in-situ scanning using a scanning Kelvin probe (SKP) apparatus. All the HT-pigments profoundly reduce rates of coating delamination by comparison to unpigmented samples. However, inhibitor efficiency is dependent upon the exchangeable anion and increases in the order: carbonate < nitrate < chromate. It is also shown that by using SKP potentiometry, exchangeable chromate anions interact specifically with the metal surface to depress free corrosion potential values.