Study of the inhibition mechanism of benzotriazole for the protection of Zn-Mg coated steel

摘要

In automotive and construction industries, zinc coated steel is largely used thanks to its high corrosion resistance and sacrificial protection. However, consumption of zinc is very intensive and coating prices are increasing. A large number of new coated steel formulations have consequently been studied for many years in order to reduce the consumption of zinc and its cost in coatings. Several studies have shown that the addition of magnesium into the metallic coating allows to improve corrosion resistance in atmospheric conditions without increasing coating thickness. However, the corrosion mechanisms of these alloys in immersion conditions are not entirely understood yet. In literature, there is very few information about the corrosion protection of these substrates, in particular as regards the action of corrosion inhibitors. The action of benzotriazole (BTA) on the corrosion resistance of Zn-Mg coated steel was investigated in sodium chloride solution. Electrochemical and analytical measurements combined with surface analyses prove that BTA inhibits the corrosion reactions by reacting with zinc to form a protective layer. At sufficient concentration, the presence of BTA is always assured in the chloride medium and the protective layer offers sustainable barrier properties. A corrosion protection mechanism is proposed.