Electrochemical Characterizations of Epoxy Coatings Embedded by Modified Calcium Carbonate Particles

In this paper, electrochemical behavior of epoxy paints embedded by modified calcium carbonate particles was investigated during exposure to 3.5 wt% NaCl solution. The precipitated calcium carbonate (PCC) and ground calcium carbonate (GCC) particles were utilized as inexpensive filler for epoxy paints. Electrochemical impedance spectroscopy (EIS), polarization tests and pin-on-disk method were used to determine the protective properties of epoxy paints on carbon steel substrates. GCC particles with the concentration of 20 wt% were more effective than PCC particles in increasing the corrosion resistance of epoxy paints; however, PCC particles affected obviously the reduction of friction coefficient of epoxy paints under wet condition (3.5 wt% NaCl solution). This behavior may be attributed to the small size and spherical shape of such particles. Values of the friction coefficient for epoxy paints were about 0.5-0.6 under dry condition. The coating resistance increased by about 99 % in the presence of GCC particles in 20 wt% after 3 days of the immersion. In addition, equivalent electrical circuits suggested that the ion transport through defects in the paint layer is the controlling factor in the corrosion process after immersion for 7 days.