Study on Cavitation and Corrosion Resistances of Thermally Sprayed Coatings and Electroplated Coatings

Abstract

In the field of material protection coating, there is a market demand for replacing the traditional electroplating process with the thermal spraying process, but supporting information in the aspects of the cavitation and corrosion resistances of corresponding coatings is inadequate. To solve this problem, Nickel - based coatings with similar chemical compositions were prepared respectively by HVOF (High Velocity Oxygen Fuel) thermal spraying and traditional electroplating process. The microstructure, cavitation resistance and corrosion resistance of the thermally sprayed and electroplated coatings were researched by XRD, ultrasonic cavitation test and electrochemical corrosion test. Results showed that the hardness of thermally sprayed coating was about 50% higher than that of the electroplated coating and the cavitation wear mechanisms of these two coatings were different. After cavitation, the surface of thermally sprayed coating was obviously brighter and smoother than that of the electroplated coating, and the cavitation mass loss of thermally sprayed coating was only 30% of that of the electroplated coating. Moreover, the results of an electrochemical corrosion test on these two coatings carried out in 3.5% NaCl solution showed that, comparing with the electroplated coating, the thermal sprayed coating showed slightly lower corrosion potential, larger impedance and one order of magnitude smaller corrosion current density. Therefore, the coating prepared by thermal spraying process had higher hardness, better cavitation resistance and corrosion resistance than electroplated coating. This paper could provide a strong support for the application of thermal spraying instead of traditional electroplating process in the manufacturing of material protection coatings.

Keywords

• thermal spraying|electroplating|cavitation|corrosion