Evaluation of cavitation/corrosion synergy of the CrC-25NiCr coating deposited by HVOF process.

Wear processes are always present in components exposed to different work situations. Hydraulic turbines in electric power generation and ship propellers are good examples of components subject to wear and corrosion. One way to protect these components, for example, is the deposition of coatings by thermal spray processes. Indeed, there are several wear or corrosion mechanisms acting simultaneously, and the validation of the mechanisms separately, is not the best way to select the better material. When materials have passivation as protective mechanism against corrosion, the mass loss due erosion can affect the materials selection. This paper study the combined effect of the corrosion on the cavitation mass loss, as well as, the cavitation mass loss influence on the corrosion properties of a chromium carbide CrC-25NiCr coating. Despite of the modification of the erosion mechanism on the cavitated samples under 3,5% NaCl solution, the volume loss did not show any significant alteration. Cavitation mass loss increase the corrosion process, reducing significantly the corrosion potential and raising the corrosion current. It was observed that the cavitation of the CrC-25NiCr HVOF coating influences much more the corrosion kinetics, than the corrosion affects the cavitation resistance.