Developments in the electrochemical noise method (ENM) to make it more practical for assessment of anti-corrosive coatings

Abstract

Interest in the electrochemical noise method (ENM) as a technique for assessment of anti-corrosive properties of organic coating is constantly increasing. This is because it has advantages such as quickness, a non-intrusive nature and ease in gathering and interpretation of data. There are a number of available arrangements of the ENM that can be used to perform noise measurements. Two of them, called successively single substrate (“SS”) and no connection to the substrate (“NOCS”) have been examined and compared with DC resistance method in order to determine whether the ENM is attractive and accurate enough to be accepted as a convenient way to test organic coatings in site situations. Results have shown good correlation between these two ENM arrangements and the DC resistance method. As the most promising arrangement, the NOCS has been considered in more detail. NOCS involves taking measurements from three areas on the coated substrate without the need of electrical connection to the substrate. The aim of this part was to check if the individual values of resistance can be computed by varying the way the cells are connected to the measuring equipment. The results obtained allow the suggestion to be made that the result of a single measurement of NOCS is dominated by the cell which acts in this configuration as a working electrode 1 (WE1). In this work also an attempt has been made to deal with the practical considerations involved in making measurement in the field. Dismountable cells to act as temporary connectors to the substrate, in the form of “copper pads”, have been developed and are discussed. These “copper pads” have indicated their potential usefulness in conducting ENM measurements in site situations. To make ENM usable in the field, good reproducibility of obtained results is required. Therefore, experiments have been conducted to consider this aspect as well. It has been proven that ENM results are reproducible.