The corrosion characteristics of electro codeposited cobalt-silicon nitride composites in neutral sodium chloride and sulphuric acid solutions are presented. The electro composites showed greatly improved corrosion resistance over pure cobalt in nondeaerated 3.5% sodium chloride solution, but they induced significantly less galvanic corrosion on steel in the same medium. Galvanic current and dissolution current measurements showed a linear variation with the cathode-to-anode area ratio, while the galvanic potential showed a logarithmic variation with the same. Composites of cobalt-silicon nitride also showed improved passivation properties in 1 N sulphuric acid. © 1995.

Amita Iyer

Suresh Krishnamoorthy Seshadri

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Corrosion characteristics of cobalt-silicon nitride electro composites in various corrosive environments

Materials Chemistry & Physics

The frictional and wear behaviour and hardness of cobalt and cobalt-titania (anatase) particulate composites, developed by sediment electro-codeposition method, were studied. Frictional and wear studies, performed on a disc-on-disc type machine, show that the microhardness of the composite increases as the titania content in the composite increases. A decrease in both the coefficient of friction and specific wear rate was observed for the composites with increasing titania content in the cobalt matrix. The effect of sliding velocity and load on the coefficient of friction and specific wear rate of cobalt and cobalt titania composites was also investigated. The optical microphotographs and X-ray diffractogram reveals that the tribo-deformation is oxidation dominated for cobalt. A probable mechanism is discussed. © 1991 Chapman & Hall.

Journal of Materials Science

A study of the tribological properties of cobalt-titania composite

Journal of Materials Science Letters

Transformation-toughened cobalt-partially stabilized zirconia electrocomposite coating

The electrochemical behaviour of sediment electro- deposited nickel-silicon nitride composite coatings on mild steel has been studied. These composite coatings provide better corrosion resistance in both 3∙5% NaCl and 0∙5M H2SO4 solution than nickel coatings. The higher the percentage of silicon nitride in the composite, the better is the corrosion resistance. Microstructural studies on these composite coatings have revealed the retention of silicon nitride particles in the coating after corrosion tests, which was indicative of very little or no galvanic corrosion. A reduced tendency to pitting of the composite coatings as compared to nickel coatings was also observed. X-ray analysis of composite coatings exposed to 0∙5M H2SO4 revealed the presence of silicon dioxide in them, leading to enhanced passivation of the composite coatings with respect to pure nickel. © 1991 The Institute of Metals and the Wolfson Institute for Surface Engineering.

Journal	Materials Chemistry & Physics
ISSN	02540584
Open Access	No