Corrosion resistance of Zn–Al co-cementation coatings on carbon steels

Zn–Al co-cementation coatings on carbon steels have been obtained by pack cementation method. The coatings possess a two-layered structure. The outer layer is composed mainly of Fe 2Al 5 and FeAl intermetallics with a small amount of Zn and the inner layer consists of Zn, Fe and a small amount of Al. The corrosion resistance of the Zn–Al co-cementation coatings was studied with rotary corrosion test in water and NaCl and H 2S containing solutions. High-temperature oxidation and sulphidation were carried out in air and H 2S containing atmosphere at 500 °C. The experimental results were compared with the coatings produced by Zn sherardizing and aluminizing, showing that the Zn–Al co-cementation coatings have much better corrosion resistance in both aqueous solutions and high-temperature environments.