The Effect of Capsulated Linseed Oil-Nano Zirconia on the Tribological Properties and Corrosion Resistance of the Epoxy Coatings

Abstract

Utilizing self-healing polymer coatings to prevent the corrosion and degradation of steel surfaces is crucial. These coatings can repair the damage by releasing healing agents. This research focuses on the self-healing and self-lubricating behaviors of these smart polymers. To do so, different contents of ZrO2 nanoparticles (0, 1, 3, and 5 wt%) were dispersed in the linseed oil as healing and lubricant agents. Then, these agents were capsulated by a polyurea-formaldehyde shell through an in situ polymerization method. In the following, a uniform 5 wt% of microcapsules containing these agents were dispersed in the epoxy coating for application on steel surfaces. The tribological (pin-on-disk) and corrosion (polarization method) tests were used for characterizing the lubrication behavior and assessing the healing features of these coatings. Results revealed that higher amounts of ZrO2 nanoparticles in linseed oil led to an increase in the size of the microcapsules during the synthesis. Notably, coatings with microcapsules containing a lower concentration of ZrO2 nanoparticles exhibited significant improvements in wear and corrosion resistance, with the best enhancement observed at a concentration of 1 wt%. This optimal concentration resulted in an 80% reduction in the friction coefficient and an 88% decline in wear rate. The coatings demonstrated effective self-healing properties, successfully addressing microcracks and boosting corrosion resistance. Specifically, microcapsules with 1 and 3 wt% of ZrO2 nanoparticles markedly enhanced corrosion resistance. So that, the polarization test indicated a nearly 96% reduction in corrosion current density when the microcapsules with linseed oil and 1 wt% ZrO2 were used. In contrast, a concentration of 5 wt% ZrO2 nanoparticles proved to be less effective due to challenges related to uneven distribution and increased viscosity of the linseed oil.