PERFORMANCE EVALUATION OF TWO COATING SYSTEMS ON CARBON STEEL IN SEAWATER

Abstract

This research investigated the effectiveness of nickel plated carbon steel and spray coated mild steel with base coat paint in sea water. Carbon steel samples were grinded and polished to obtain a mirror-like surface; which is necessary for effective and uniform electroplating and spray coating. The polished mild steel samples were then electroplated with nickel using watts solution as a standard for the composition of the electroplating bath. The plating time and voltage were varied with different samples in order to obtain varied thickness of nickel plating in accordance with Faraday’s law of electrolysis. Other samples were spray coated with base coat paint, in which the thicknesses of the coating were also varied base on the number of coating applied. Scanning electron microscope (SEM) images was used to study the surface morphology of the coatings. Linear potentiodynamic polarization tests were carried out on the Ni plated and spray coatedsamplesas well as the as-received sample. Measurements were done using Verstatpotentiostat (computer controlled) with the General Purpose Electrochemical Software (GPES). Measurements were made at room temperature using seawater as an electrolyte. The result showed that base coat paint coatings had homogeneous distribution of the fine particles deposited and also be able to display lower corrosion rate and corrosion current density (icorr). These coatings had higher corrosion resistance over the Ni deposited coating as well as the substrate.