Improved corrosion resistance through microstructural modifications induced by codepositing SiC-particles with electrolytic nickel

Micron and submicron-sized SiC-particles (5 and 0.3 mum respectively) were codeposited with nickel from a Watts electrolyte. The Ni-SiC composite coatings showed a better corrosion resistance in a 0.6 M NaCl solution than nickel electrodeposited under the same conditions. The corrosion rate of Ni-SiC decreases by two orders of magnitude with respect to pure Ni coatings. This improved corrosion resistance is quite independent of the size and amount of embedded particles, except for the smallest SiC-particles investigated. In that case, the pitting corrosion potential shifts to more noble values indicating a notable reduction of the localized corrosion susceptibility. This improved corrosion resistance of Ni-SiC coatings containing submicrometric SiC-particles is linked to a change in grain morphology and texture of the coatings. That morphology evolves from columnar grains to small and equiaxed grains. (C) 2003 Elsevier Science Ltd. All rights reserved.