Synthesis and Characterization of Nanocrystalline Pure Cobalt Coating: Effect of pH

By Hyie, Koay Mei; Resali, Nor Azrina; Abdullah, Wan Normimi Roslini & Chong, W.T.
Published in Procedia Engineering NULL 2012

Abstract

Nanocrystalline cobalt (Co) has been developed as an environmental alternative to replace hard chromium due to its higher cathode efficiency and corrosion resistance properties. This study aims to determine the corrosion behaviour, mechanical and magnetic properties of Co coatings. Nanocrystalline Cobalt (Co) coatings were synthesized by electrodeposition technique. The electrodeposition technique was applied in different pH of 3, 5 and 7, respectively. The Co coatings were deposited on stainless steel substrate at 50oC and the deposition was performed at current density of 0.145 A/cm2. The Co coatings are identified as hexagonal close packed phase. The crystallite sizes of pure Co calculated using Scherrer formula are between 30.1 nm to 50.1 nm. FESEM micrograph reveals that the nanoparticles are irregular and almost spherical in shape. From the FESEM results, average grain size of Co coating prepared at pH 3 is smaller compared to the others. Besides, this coating exhibits the highest hardness (240 HV) and performs the smallest corrosion rate. The magnetic result shows the Co coating prepared at pH 3 exhibit low coercivity and high saturation magnetization. It is found that the effect of pH parameter in Co coatings plays an important role to obtain better hardness, corrosion behavior and magnetic properties.

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