Effect of Standoff Distance on Corrosion Resistance of Cold Sprayed Titanium Coatings

Abstract

A titanium protective layer was deposited onto Al7075 substrate (Al7075/Ti) by a cold spray method (CS) with different standoff distances (SoD) of the nozzle from the specimen surface. The aim of this research was to study the influence on the mechanical properties and corrosion resistance of the Ti coating on Al7075 substrate. The surface and microstructure of Al7075/Ti was observed by a scanning electron microscope (SEM). The corrosion test of the materials was carried out by using the electrochemical method. The SoD had a significant effect on the microstructure of the coatings and their adhesion onto Al7075 substrate. The highest level of microhardness (248 HV0.3) value was achieved for deposits obtained with the SoD of 70 mm. The corrosion tests showed that the mechanism of electrochemical corrosion of titanium coatings is a multi-stage process, and the main product of the corrosion process was (TiO2)ads. However, the polarization resistance (Rp = 49 kΩ cm2) of the Al7075/Ti coatings was the highest, while the corrosion rate (υcorr = 13.90 mm y−1) was the lowest, for SoD of 70 mm.