Research on Corrosion Behavior of Cold Sprayed Copper Coating on Aluminum Substrate

 Due to its low processing temperature, cold spray has many advantages over traditional thermal spray, such as low porosity, low oxidation, high density, free of residual stress. Above characteristics make the cold spray coating a better anti-corrosion performance than thermal sprayed coating. As we all know that there exists serious risk to apply noble metal on negative metal by traditional thermal spray methods because of galvanic corrosion if there has penetrated porosity. But it is not known whether cold spray has such problem too. And now few people care about the electrochemical behavior difference between cold and thermal spray coating. It is necessary to study the influence of coating structure on the corrosion behavior of cold spray. In this article, as-cold spraying copper coating, polished cold-spraying copper coating, aluminum bulk material and arc sprayed copper coating and pure copper are tested with electrochemical methods to compare their electrochemical behavior in natural seawater, the electrochemical methods including dynamic polarization curve and electrochemical impedance spectrum. The results indicate that: there is no significance difference in corrosion potential between cold sprayed coating and bulk copper material. The potential of cold spray coating is much different from arc spray copper coating. Polarization curves indicate that the corrosion rate in much higher for arc spray copper coating. The electrochemical impedance spectrum shows that there is no difference in electrode interface structure. From above we infer that the higher corrosion rate for arc spray copper coating mainly attribute to its high porosity and oxidation degree.