Zinc-aluminium-coatings as corrosion protection for steel

An analysis was made to investigate the influence of the alloying of sprayed coatings on the corrosion performance in climates of practical relevance and to evaluate the optimised alloy compositions. Furthermore, the mechanism of corrosion and coating formation was evaluated. The protective effect increased up to an aluminium content of 15 and 22 wt%, respectively, with corrosion rates below 1 mu m per year. Electrochemical investigations found a distinctive decrease in the cathodic reaction together with an accumulation of aluminium in per cent and a depletion of zinc. Due to the increasing concentration of aluminium within the layer and the correlated presence of inhibitive corrosion products, the cathodic reaction and therefore the corrosion of the sprayed zinc-aluminium coatings can be increasingly eliminated.