Impressed Current Cathodic Protection of Low Carbon Steel in Conjunction with Conducting Polyaniline based Paint Coating

Abstract

Epoxy, Fusion bonded epoxy and conducting polyaniline based paints were applied on low carbon steel sample. Conducting polyaniline and conducting polyaniline based paint was characterized by UV-visible absorption spectroscopy and scanning electron microscopy respectively. Cathodic polarisation was used to determine cathodic protection potential range of the uncoated and painted low carbon steel samples dipped in 3.5% NaCl. Cathodic impressed current range was found out using galvanostatic technique and used to impart cathodic protection to non coated and painted samples. Iron loss of uncoated and painted samples without cathodic protection and under cathodic protection was measured using spectrophotometry. It was found that conducting polyaniline based paint exhibits negligible iron loss ~0.06 ppm in 3.5% NaCl solution under impressed current cathodic protection. Conducting polyaniline based paint can be used in association with impressed current technique to protect low carbon steel cathodically in neutral medium. However, conducting polyaniline, as a pigment, becomes less effective in presence of coating defects due to exposure of the metallic surface to the electrolyte.