Paint electrochemical data

Table I. Summary of Electrochemical Data in Bulk Paints...

Electrochemical tests This group includes the various electrochemical tests that have been proposed and used over the last fifty or so years. These tests include a number of techniques ranging from the measurement of potential-time curves, electrical resistance and capacitance to the more complex a.c. impedance methods. The various methods have been reviewed by Walter . As the complexity of the technique increases, i.e. in the above order, the data that are produced will provide more types of information for the metal-paint system. Thus, the impedance techniques can provide information on the water uptake, barrier action, damaged area and delamination of the coating as well as the corrosion rate and corroded area of the metal. However, it must be emphasised that the more comprehensive the technique the greater the difficulties that will arise in interpretation and in reproducibility. In fact, there is a school of thought that holds that d.c. methods are as reliable as a.c. methods. 

ASTM G53-77, Salt Spray and Electrochemical Impedance Measurements). The results indicate that electrochemical impedance measurements provide a satisfactory correlation with the behaviour of paint coatings as evaluated by visual examination. In addition, it appears that, in certain cases, data obtained by this technique will allow prediction of the metallic corrosion underneath the paint coating when no changes in the appearance of the coating can be externally observed. 

Figure 6.3.4.S The electrochemical approach curves of a Pt UME insulated with electrophoretic paint to an air/solution interface, (a) Electrode insulation is good, (b) Electrode insulation is poor. The solution contained 10 mM K3pe(CN)5 and 0.1 M KCl. The tip potential was 0.1 V vs. Ag/AgCl. (The data was from the Electrochemistry Laboratory of the Department of Chemistry and Biochemistry, University of Austin at Texas.)...

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