Corrosion-erosion resistance of coated magnesium by autocatalytic Ni-P/Ceramic nanocomposite coatings

摘要

Ni-P-nanocomposites coatings were deposited on commercial purity magnesium by a chromium-free electroless process in order to study the effect of the presence of ceramic nanoparticles of Ti02, SiC and diamond on the corrosion-erosion resistance of Mg/Ni-P system. The effect of the concentration and the nature of ceramic nanoparticles on erosion-corrosion damage with respect to Ni-P coatings was also investigated. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), micro-Raman spectroscopy, infrared spectroscopy (IR) and X-ray diffraction (XRD) were employed to study the characteristics of the coatings. The corrosion-erosion behavior of the coated specimens was evaluated by means of in-situ polarization and electrochemical impedance spectroscopy in a 3.5 wt. % sodium chloride solution. According to the electrochemical tests the nanocomposite coatings exhibit a better corrosion-erosion resistance compared with Ni-P coatings due to the formation of a hydroxide film which is formed independently of nature and concentration of the nanoparticles.