Modifications of the hydrotalcite film on AZ31 Mg alloy by phytic acid: The effects on morphology, composition and corrosion resistance

An environmentally friendly corrosion inhibitor phytic acid (PA) has been successfully added to modify the hydrotalcite (HT) film by adsorption and ion exchange approaches. In alkali PA solution, PO 4 3 - cannot substitute CO 3 2 - in the HT, but adsorb to the external surface; H 2 PO 4 - / HPO 4 2 - can insert into the HT after decarbonation under acidic condition. Partial decomposition occurs under both conditions. The PA/pH 11-HT film shows superior stability and lasting protective efficiency, and also can provide self-healing effect associated with the P adsorption in the filament. The worse resistance of the PA/pH 6.5-HT film may be related to the micro-cracks.