Synthesis of 3-glycidoxypropyltrimethoxysilane modified hydrotalcite bearing molybdate as corrosion inhibitor for waterborne epoxy coating

Zinc aluminum hydrotalcite intercalated with molybdate (HTM) and modified by 3-glycidoxypropyltrimethoxysilane (HTM-GS) was prepared and incorporated into a waterborne epoxy coating. The synthesized HTM-GS was characterized by FTIR, XRD, SEM, and TEM. The inhibitive action of HTM-GS on carbon steel was evaluated using electrochemical measurement and SEM/EDX analysis. The corrosion protection of the waterborne epoxy coating containing HTM-GS was evaluated and compared to that of the pure waterborne epoxy coating and the waterborne epoxy coating containing HTM by salt spray test and adhesion measurement. It was shown that the molybdate was intercalated in the hydrotalcite structure and the molybdate contents in HTM and HTM-GS were 16.0 and 13.2 wt%, respectively. The polarization curves obtained on the carbon steel electrode showed that HTM and HTM-GS are anodic corrosion inhibitors, and their inhibition efficiencies at concentration of 3 g/l were 92.0 and 94.7%, respectively. Additionally, HTM and HTM-GS at concentration of 0.5 wt% improved corrosion resistance and adhesion of waterborne epoxy coatings. Surface modification by 3-glycidoxypropyltrimethoxysilane ameliorated the dispersion of HTM in epoxy matrix and the effect of HTM on protection properties of waterborne epoxy coating.