Corrosion Behaviour of Three Kinds of Arc Sprayed Coatings in Soil

摘要

The corrosion resistance of a pure Zn coating, a ZnAl alloy coating and a ZnAl pseudo-alloy coating ina Beijing area was studied. The corrosion products were analysed by XRD, and the electrochemicalprocesses of the three coatings were analysed by measuring the electrochemical impedance andpolarization curves. The results showed that the surface corrosion products of the pure Zn coating weremainly composed of Zn 5 (OH) 8 Cl 2 H 2 O, ZnCO 3 , ZnO and Zn 5 (CO 3 ) 2 (OH) 6 , while the surface corrosionproducts of the ZnAl alloy and ZnAl pseudo-alloy coating similarly consisted of Zn 5 (OH) 8 Cl 2 H 2 O,Zn 0.71 Al 0.29 (OH) 2 (CO 3 ) 0.145xH 2 O and ZnO·Al 2 O 3 . Before and after corrosion, the order of the coatingcorrosion resistance was as follows: ZnAl alloy coating > ZnAl pseudo-alloy coating > pure Zn coating.It was found that a "self-sealing" protective effect of the ZnAl alloy coating was better than that of theZnAl pseudo-alloy coating because the composition was more uniformly distribution. The main reasonfor a weaker “self-sealing” protective effect of the ZnAl pseudo-alloy was that galvanic corrosionoccurred between the Zn-rich phase and the Al-rich phase of the pseudo-alloy, which accelerated theelectrochemical reaction. Meanwhile, the pure Zn coating did not have the "self-sealing" effect.Consequently, the corrosion resistance of the ZnAl alloy coating was the best.