An intelligent coating based on pH-sensitive hybrid hydrogel for corrosion protection of mild steel

Abstract

• A novel hybrid hydrogel of BTA@PHVA/PEI was synthesized by one-pot synthesis method. • The releasing rate of BTA@PHVA/PEI rises upon external pH values due to its pH-sensitivity. • The smart coating based on BTA@PHVA/PEI can provide strong corrosion protection. In the present study, we developed an intelligent coating for the corrosion protection of mild steel. A novel hybrid hydrogel of BTA@PHVA/PEI was synthesized through free radical polymerization. The morphology and composition of BTA@PHVA/PEI were characterized by SEM, FTIR and TGA/DSC. The as-prepared BTA@PHVA/PEI presents high thermal stability and the weight percentage of the loaded BTA is about 10.12 wt%. The self-releasing property of BTA@PHVA/PEI was evaluated by UV–vis spectroscopy, which indicates that the releasing rate rises with increasing the external environment pH values. Furthermore, an intelligent coating was fabricated on mild steel by using an alkyd primer doped with various contents of BTA@PHVA/PEI. The corrosion protection of the intelligent coating was evaluated by electrochemical measurements and neutral/acid salt spray tests. The results demonstrate that the anti-corrosion capability of the intelligent coating increases with the content of BTA@PHVA/PEI doped into the coating. The corrosion of mild steel was prohibited by forming a layer of inhibitor-adsorptive film from the released BTA inhibitors, which was detected on the steel surface after 30 days immersion in the corrosive medium by EDS and FTIR. The as-prepared intelligent coating in this work shows remarkable corrosion protection for mild steel, which also sheds light on corrosion protection of other metals and alloys.