Corrosion behavior of low pressure cold sprayed Zn-Ni composite coatings

In this study, Zn-Ni composite coatings with different Ni contents were deposited on low-carbon steel using Low pressure cold spray (LPCS) method. The morphology, element distribution and phase compositions of powders and as-sprayed coatings were analyzed by using scanning electron microscopy, energy dispersive spectrometer and X-ray diffraction respectively. The corrosion protection mechanism of these composite coatings were investigated using electrochemical technique and their corrosion morphologies. The results show that Zn-Ni composite coatings exhibited a better sacrificial anodic protection and physical shielding effect, where the corrosion resistance of the coating with 10 wt% Ni in the feedstock was best. The corrosion products were mainly composed of Zinc hydroxide Zn(OH)2, basic zinc chloride hydrate ZnCl2·4Zn(OH)2·H2O, basic zinc carbonate hydrate Zn4·CO3(OH)6·H2O and the corrosion products is not mixed with alumina. The corrosion process mainly includes active dissolution of zinc, zinc cathodic protection, physical shielding caused by corrosion products.