Enhanced anti-corrosive capability of waterborne epoxy coating by ATT exfoliated boron nitride nanosheets composite fillers

In this work, 2-amino-5 mercapto-1, 3, 4-thiadiazole/boron nitride nanosheets (ATT/BNNS) nanofillers were prepared via using ATT as intercalating agent to exfoliate BNNS by a liquid-phase assisted ultrasound method. The FTIR and the XPS consequences testify that the corrosion inhibitor ATT is successfully grafted onto BNNS. TEM results indicate that BNNS is adequately exfoliated by ATT and the agglomeration phenomenon is alleviated. BNNS, ATT and ATT/BNNS nanofillers were processed into the waterborne epoxy (WEP) respectively, and WEP composite coatings were then fabricated by a spraying method on the copper electrode. The EIS measurements demonstrate that WEP ATT/BNNS coating displays the best protective performance in combination with optical morphology observation under saline immersion, compared with other three coatings. It is mainly attributed to the combined action of active protection from ATT inhibitor and physical barrier from BNNS. The two-dimensional BNNS nanofiller dispersed in the WEP coating plays the role of physical barrier, forms a "labyrinth effect", extends the invasion way of corrosive media, thus enhancing the physical barrier effect in the composite coating. Furthermore, ATT inhibitor can also diffuse through the coating to the copper substrate and build a safety shield to hold back further corrosion. Importantly, after 40 days immersion in 3.5 wt% NaCl solution, the value of impedance module at 0.01 Hz of WEP ATT/BNNS coating is about 2 orders of magnitude larger than that of pure WEP coating, revealing superior long-term anticorrosion performance.