Synthesis of a dibenzimidazole compound and its corrosion inhibition behavior on AZ91D Mg alloy in 3.5 wt.% NaCl solution

In this work, a low-cost and easily purified small molecule dibenzimidazole compound (BBI) was synthesized by the condensation of o-phenylenediamine and malonic acid. BBI was a new corrosion inhibitor for magnesium alloys and its corrosion inhibition behavior on AZ91D magnesium alloy was studied by electrochemical measurements, surface analysis and theoretical calculations in 3.5 wt.% NaCl solution at 30 °C. The adsorption behavior and corrosion inhibition mechanism of BBI molecules were discussed. It was found that BBI exhibited excellent inhibition effect on the corrosion of magnesium alloy. When BBI concentration was 0.25 g/L, the optimal corrosion inhibition efficiency was 86.2%. The adsorption of BBI molecule obeyed Langmuir adsorption on the surface of magnesium alloy, and one side of BBI molecule was adsorbed on the surface of magnesium alloy in parallel through physical and chemical mixed adsorption.