Investigation of defects in organic anti-corrosive coatings using electrochemical noise measurement

Performance of solvent-borne and water-borne coatings at defects produced by laser and by a new mechanical technique was investigated when immersed in Harrison's solution (3.5% (NH4)2SO4, 0.5% NaCl) diluted 10× and in 0.4% NaCl. The main technique employed as the electrochemical noise method (ENM). This method is virtually non-intrusive. Using noise resistance (Rn) values gives a quantitative indication of how the coating is performing: the higher the value the more effectively it was found to be protecting at the scribe. Some results have also been obtained using electrochemical impedance spectroscopy (EIS) and good correlation was obtained with ENM values. Also, analysis of the distribution of some of the data sets obtained from the electrochemical noise measurements has been conducted.