Studying dual active/barrier and self-healing reinforcing effects of the Neodymium (III)-Benzimidazole hybrid complex in the epoxy coating/mild steel system

Abstract

The effectiveness of loading Neodymium (Nd)-Benzimidazole (Bi) complex pigment into the epoxy coating to achieve an effective active/barrier protective system has been studied. The Nd-Bi hybrid pigment chemical structure was analyzed by Fourier Transfer Infrared (FT-IR) analysis. The incorporation effect of Nd-Bi hybrid pigment on the physical properties and surface chemistry of epoxy coating films without and with Nd-Bi was examined by FT-IR, Thermogravimetric analysis (TGA/DTG) analysis, and contact angle measurements. From the results it was designated that the Nd-Bi incorporation into the epoxy coating has not negative influence on the coating stability under thermal condition, meaning that the curing process was kept unchanged. The influence of Nd-Bi pigment on the coating active/barrier inhibition mechanisms of the coating was evaluated by electrochemical impedance spectroscopy (EIS) analysis as well as salt spray test. The pigment impact on the coating interfacial adhesion in dry condition by pull-off test and the resistance against cathodic disbonding were studied. The obtained results from EIS, salt spray and cathodic delamination tests evidenced that the epoxy coating active/barrier inhibition performance in the presence of Nd-Bi pigment was significantly improved. The morphology and composition of the precipitated film in defect zone after 700 h exposure to salt spray test were studied by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analyses. The SEM and EDS analyses results confirmed the film formation in the artificial defect zone.