Degradation of modified carbon black/epoxy nanocomposite coatings under ultraviolet exposure

Abstract

Degradation of epoxy coatings with and without Carbon Black (CB) nanoparticles under ultraviolet (UV) radiation were investigated using electrochemical impedance spectroscopy (EIS). Sodium dodecyl sulfate (SDS) was used to obtain a good dispersion of CB nanoparticles in a polymer matrix. TEM analysis proved a uniform dispersion of modified CB nanoparticles in epoxy coating. The coatings were subjected to UV radiation to study the degradation behavior and then immersed in 3.5wt% NaCl. The results showed that the electrochemical behavior of neat epoxy coating was related to the formation and development of microcracks on the surface. The occurrence of microcracks on the surface of the coatings and consequently the penetration of ionic species reduced by adding CB nanoparticles into the formulation of the coatings. CB nanoparticles decreased degradation of CB coatings by absorbing UV irradiation. The ATR-FTIR results showed that decrease in the intensity of methyl group as main peak in presence of 2.5wt% CB was lower than neat epoxy. In addition, the reduction in impedance of neat epoxy coating under corrosive environment was larger than CB coatings. The CB coating with 2.5wt% nanoparticles had the highest impedance to corrosive media after 2000h UV irradiation and 24h immersion in 3.5wt% NaCl.