The corrosion resistance of nanocrystalline composite Ni/diamond coatings produced by electrochemical method

The paper presents results of studies of nanocomposite nickel/diamond coatings produced by electrocrystallization method on carbon steel. For comparison purposes, the tests also included a layer of nickel exhibiting nanocrystalline structure. The nanocomposite coatings were prepared in a bath containing different amounts of diamond disperse phase. The structure of the diamond disperse phase was characterized by using a transmission electron microscope. The construction of the produced coatings and the chemical composition were investigated by optical microscopy and scanning electron microscopy with an EDS attachment. Micro-hardness of produced coatings and their corrosion resistance were studied by the Vickers method and potentiodynamic method in the environment of 0.5M NaCl, respectively. The results of corrosion testing of produced coatings are presented in the form of potentiodynamic polarization curves j = f(E) and the value of the potential and current corrosion. Damages of the coatings after tests in a corrosive environment were identified. The results of performed investigations indicate on a compact and uniform thickness of the produced coatings on the whole coated surface and good adhesion to the steel substrate. The diamond built into coating and its contents significantly affect their microhardness and corrosion resistance.