Improved Corrosion Protection of Acrylic Waterborne Coating by Doping with Microencapsulated Corrosion Inhibitors

Herein, a waterborne acrylic coating doped with pH sensitive colophony microcapsules containing corrosion inhibitors was studied on carbon steel plates. The changes in the physical properties of the coatings were studied. The microcapsule coating specimens maintained more noble E-corr values compared to the control in deionized water and simulated concrete pore solutions with -513 and -531 mV(SCE), respectively. Additionally, the microcapsule polarization results for both pH 12.6 and 6.2 electrolyte solutions showed lower i(corr) values of 1.20 x 10(-6) and 3.24 x 10(-6) A center dot cm(-2), respectively, compared to the control sample (1.15 x 10(-5) and 4.21 x 10(-5) A center dot cm(-2)). Therefore, the microcapsule coating provided more protection from chloride attack on the substrate as well as the deleterious effects of low pH on carbon steel. The electrochemical impedance spectroscopy analysis corroborated the DC polarization results, showing increased corrosion resistance for the microcapsule coated specimens compared to the control. Moreover, the R-pore and R-ct are much higher than the control, indicating the protection of the inhibitors. The C-eff,C-dl also shows lower values for the microcapsule coating than the control, showing a more protective and less doped double layer.