Research on Corrosion Inhibitors for Coatings on Hot-Dip Aluminized-Galvanized Steel in Marine Environment

Galvanized steel is one of the commonly used material in the field of corrosion protection, but it's prone to corrosion in heavily corrosive environments. Hence, the Hot-Dip Aluminized-Galvanized Steel (HDAGS) was developed, which is less susceptible to corrosion, by adding aluminum to the galvanizing solution. But in marine environment, the HDAGS still requires further protection. In this article, the effect of nine common corrosion inhibitors on HDAGS was evaluated by Immersion corrosion test, Tafel polarization, EIS test, XRD, SEM&EDS firstly. The results showed that the adsorbed film inhibitors and the deposited film inhibitors were effective, but the oxidized film inhibitors were not ideal because the Al-Zn coating was hard to oxidize. The corrosion rate of HDAGS in simulated seawater containing 1 wt % zinc phosphate was 3.333 x 10(-7) g/(m(2) h), while it was 6.072 x 10(-4) g/(m(2) h) in simulated seawater without inhibitor, and the inhibition efficiency was 99.94%. Three most effective inhibitors were then added to the waterborne poly-urethane coating (WPUC) for HDAGS, and the performance was evaluated by EIS and Immersion corrosion test. The impedance of WPUC containing inhibitors all decreased fast at the beginning of immersion. The subsequent action of the corrosion inhibitor in the corrosion process extended the service life of WPUC by 2-3 times.