Optimization of Dispersing of SiC Particles in Aqueous Electrolytes Using Surfactants for the Application in Composite Coatings

From the earliest development of a composite solid, the goals for composite development have been to achieve acombination of properties not achievable by any of the materials acting alone [1]. Deposition of electrochemical compositecoatings (ECC) is not a newly developed technique , but has been in continuous development since the 1970s [2]. One of them isnickel coatings that are used in the range of mechanical (preventing wear) and chemical (protecting against corrosion) toelectrical and magnetic (storing electronic data in magnetic media) [3]. These coatings, which can be produced via combinedelectrodeposition and electrophoretic deposition have demonstrated enhancements in tribological, physical, chemical, andelectrochemical properties. A wide range of particles are available including (a) solid lubricant materials e.g. PTFE, graphite,MoS2, (b) hard oxide, nitride or carbide particles e.g. SiC, TiO2, SiO2, Si3N4, WC and (c) metallic particles, e.g. Al, Cr [4].SiC has a high resistance to abrasion due to its high toughness, chemical resistance to corrosion and its high stability at hightemperatures (melting temperature is about 2730 ° C) and because of its covalent bonding properties [4].Due to their high wear resistance and the low cost of ceramic powder, Ni–SiC composites have been investigated to thegreatest extent and successfully commercialised for the protection of friction parts [5]. In this study, the sliding wear corrosionbehaviour of a pure nickel and nano-structured SiC–nickel composite coatings were studied. Both measurements ofelectrochemical corrosion and wear corrosion show a better resistance of nancomposite coating compared with pure nickelcoating [2].The addition of metal cationic accelerants and organic surfactants in an electrolyticbath improved the amount and the distribution of co-deposited particles[1]. It was confirmed that suitable surfactants could notonly improve the stability of a suspension by increasing the wettability and the surface charge of suspended particles but alsoenhance the electrostatic adsorption of suspended particles on a cathode surface by increasing their positive charge[5].Addition of the surfactants into electrolyte changes the polarization potentials at the cathode andalters the grain size, rate of grain growth, smoothness and adhesion of the coating. The most common application of surfactant inelectroplating is to reduce the surface tension of the bath to produce smaller hydrogen bubbles, thus preventing pitting. Hence, italso helps in improving the current efficiency of the electrodeposition. The most common surfactants used in theelectrodeposition bath are sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and sodium lauryl sulfate(SLS) [4,5].

Keywords:

Dispersion , SiC , Surfactant , Composite Coatings