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.

Subject
Anions, Water, Coatings, Pigments, Metal surfaces, Constants, Coating defects, Aluminum alloys, Delamination, Corrosion inhibitive pigments, Electrolytes, Samples, Anodic inhibitors
Keywords:
aluminum, filiform, hydrotalcite, inhibitor, Kelvin probe
NACE International
2004
You do not currently have access to this content.