CORROSION RESISTANCE OF BINARY AND TERNARY ALLOY COATINGS FROM ACID SULPHATE BATH

Abstract

Electroplating of three binary (Zn-Ni, Zn-Co and Zn-Fe) and two ternary (Zn-Ni-Co and Zn-Co-Fe) alloy coatings were developed onto mild steel substrate using 2-((4-chlorophenyl) amino)-1-(6-methyl-1H-pyrazolo [3, 4 - b] quinolin-1-yl) ethanone (CME) as an additive. Hull cell technique was used to optimize the bath constituents and operating conditions. Corrosion rate of binary and ternary alloy coatings were determined using potentiodynamic polarization method. Corrosion rate of ternary Zn-Ni-Co alloy coating was ~18 times less than Zn-Ni and Zn-Co and Zn-Co-Fe coating was ~32 times less than Zn-Co and 11 times less than Zn-Fe coatings. The good corrosion resistance of the of ternary coating was ascribed to its phase structure. A simple sulphate baths have been suggested for smooth and uniform binary and ternary alloy coatings were produced and result has been discussed.

Key words: Binary coating, electroplating, SEM, XRD, corrosion