Synergic Effect of Nano‐SiO 2 and 3,5‐dinitrobenzoic Acid on the Mechanical Properties and Corrosion Properties of Epoxy Coatings

ABSTRACT In advanced organic coatings, nano‐SiO 2 can serve not only as the reinforcers/nanofillers, but also as the nanocontainers for self‐healing agents. This study aims to explore how SiO 2 nanocontainers with 3,5‐dinitrobenzoic acid (SiO 2 ‐DNBA) can enhance both mechanical and anticorrosion properties of epoxy coating on a steel substrate. IR, UV‐vis spectroscopy and TGA analysis indicated that SiO 2 nanocontainers adsorbed with 3,5‐dinitrobenzoic acid (SiO 2 ‐DNBA) were successfully synthesized at various SiO 2 :DNBA ratio of 9:1, 4:1, 3:1, and 3:2. FESEM images indicated that when 2.5% of SiO 2 ‐DNBA nanocontainers (at SiO 2 : DNBA ratios of 9:1 and 4:1) were added, the nanocontainers were relatively uniformly dispersed within the epoxy matrix. Whereas, significantly larger agglomerations appeared at higher SiO 2 ‐DNBA ratios (3:1 and 3:2). Mechanical tests showed that the presence of SiO 2 ‐DNBA nanocontainers increases the abrasion resistance and impact resistance of the epoxy coating, with the 9:1 ratio being the highest. The salt spray test indicates that SiO 2 ‐DNBA nanocontainers not only enhance the barrier effect of the epoxy coating, but also inhibit the delamination of the coating and corrosion of steel up to 30 days of exposure, with a SiO2:DNBA ratio of 9:1 being the best. EIS fitting data indicated that adding SiO 2 ‐DNBA nanocontainer into the epoxy coating increases both coating resistances and charge transfer resistance resistances, with SiO 2 : DNBA of 9:1 ratio being the largest. The EP/SiO 2 ‐DNBA coatings exhibit self‐healing capabilities via releasing the DNBA inhibitor from SiO 2 nanocontainer.