Behaviour of nickel coatings made by brush plating technology in conditions of cavitation erosion and corrosion

The basic hypothesis of the research was that the structure of the coating, i.e. the type of defects, affects the mechanical and electrochemical properties, as well as the resistance to cavitation erosion and corrosion. For this purpose, nickel coatings produced by brush-plating technology using two different electrolytes and deposited on X20Cr13 steel were tested. The electrolytes affected the structure and properties of the coatings: one coating had a network of cracks, and the second one had a cauliflower-like structure. The hardness and Young's modulus of both coatings were investigated under multi-cycle loading modes. Cavitation erosion resistance was tested in a cavitation tunnel equipped with a barricade system at an inlet pressure of 600 kPa and outlet pressure of 120 kPa. Both nickel coatings protected the substrate against cavitation erosion. The lowest rate of cavitation erosion had a coating with a network of cracks and high hardness. Microscopic examinations showed no influence of the net of cracks on the degradation process. Electrochemical tests confirmed the better corrosion resistance of the compact coating. The compact coating had about an order of magnitude lower corrosion potential and about 100 mV higher corrosion current density than that of the agglomerate coating. The agglomerate coating had electrochemical parameters comparable to the substrate.

Automated summary

The research hypothesized that the structure of the coating affects its mechanical and electrochemical properties, as well as resistance to cavitation erosion and corrosion. Nickel coatings produced using two different electrolytes on X20Cr13 steel were tested. The coatings exhibited different structures and properties, with one having cracks and the other a cauliflower-like structure. Both coatings provided protection against cavitation erosion, with the one having cracks and high hardness showing the lowest erosion rate. Microscopic examinations showed no influence of the cracks on the degradation process. Electrochemical tests confirmed that the compact coating had better corrosion resistance compared to the agglomerate coating. The agglomerate coating had electrochemical parameters similar to the substrate.