Characterization of inhibitor release from Zn-Al-[V10O28]6- hydrotalcite pigments and corrosion protection from hydrotalcite-pigmented epoxy coatings

A Zn-Al-[V10O28](6-) hydrotalcite ion exchange compound was synthesized as a corrosion inhibiting pigment additive for protective organic coatings. A simple aqueous coprecipitation method was used to synthesize the compound in particulate form. Ion exchange experiments showed that the compound is an amphoteric exchanger that releases Zn2+ and vanadates in millimolar concentrations when contacted by 0.0001 M to 1.0 M sodium chloride (NaCl) solutions. The Zn2+ and vanadates released into solution inhibit corrosion of AA2024-73 (UNS A92024) substrates. In potentiodynamic polarization measurements, Zn2+ and vanadates are modest inhibitors of oxygen reduction and vanadates are anodic inhibitors, particularly under neutral and allcaline conditions. Hydrotalcite pigments were added to epoxy resins as an inhibiting additive. applied as rudimentary coatings on AA2024-T3 substrates, and subjected to salt spray exposure testing. Electrochemical impedance measurements made as a function of time suggested that hydrotalcite-pigmented coatings provide both barrier protection and active protection from released Zn2+ and vanadate.