The Characterization of Co-Ni-Fe Coating in Different pH Environment

This study aims to produce a Co-Ni-Fe alloy coating on a mild steel hollow cylinder shape by electrodeposition process and analyze the effect of different pH on the corrosion performance of the alloy coating. During the electrodeposition process, the temperature and time are set to 50°C and 30 minutes, respectively. Different pH value consisting of pH 2.1 (strong acid), 5.2 (weak acid), 6.9 (neutral), 8.4 (weak alkali) and 12.3 (strong alkali) are used. From the results obtained it was found that the deposited Co-Ni-Fe alloy has excellent corrosion performance. Corrosion rate obtained for strong acid, weak acid, neutral, weak alkali and strong alkali are 5.88 mmpy, 2.95 mmpy, 1.17 mmpy, 2.16 mmpy and 5.72 mmpy, respectively. Hence this studied showed that Co-Ni-Fe coating alloy could be used as an alternative to prevent against corrosion due to its high corrosion resistance as well as high microhardness.

INFLUENCE OF MICROSTRUCTURE OF FRICTION STIR WELDED JOINTS ON GROWTH AND PROPERTIES OF MICROARC OXIDATION COATINGS ON AZ31B MAGNESIUM ALLOY

Ceramic coatings on friction stir welded (FSW) joints of AZ31B magnesium alloy were fabricated by microarc oxidation (MAO) method in silicate electrolyte. Microstructure, phase constituents, microhardness and electrochemical corrosion behaviors of bare and coated magnesium alloys at different zones of FSW joints for different oxidation time were investigated. The influence of microstructure at different zones on the growth of MAO coatings was analyzed. The results show that the MAO coatings on FSW joints are uniform, and they have almost the same morphology, phase constituents, hardness and corrosion resistance at base metal, stir zone and heat-affected zone. The properties of MAO coatings are independent on the microstructures of AZ31B alloy. In addition, the microstructures of magnesium alloy near the coating/alloy interface at different zones of FSW joint was not changed by microarc discharge process.