High-pressure cold-sprayed Ni and Ni-Cu coatings - Improved structures and corrosion properties

Cold spraying is a promising technique for the production of dense metallic coatings. In cold spraying, coating formation is based on high velocity impacts of solid particles with high kinetic energy. During the impacts, particles deform plastically and adhere, building-up the coating. This makes it possible to form pure and dense coating structures. Full impermeability of the coatings is required e.g. in corrosion protection applications. Nickel and nickel-copper alloys have good corrosion resistance and therefore, as dense coatings, they have a high potential for employment as corrosion barrier layers. In this study, the structural and corrosion properties of high-pressure cold-sprayed (HPCS) Ni and NiCu coatings are characterized. NiCu alloys are known to have good corrosion resistance e.g. in sulphuric and hydrochloric acids whereas Ni is resistant to e.g. caustic soda and alkaline salt solutions. This study also shows the effect of heat treatments on the coating performances. FESEM studies of cross-sectional samples reveal structural details of dense coatings while corrosion properties are evaluated with polarization measurements. Corrosion behaviors are compared with corresponding bulk materials and substrate material in order to perceive the real corrosion protection potential of the coatings.