Effectively Improving the Anti-corrosive Properties of Triazine-based Mixed Corrosion Inhibitors by the Adjustment of Bridge Heteroatoms: a Combined DFT and MD Simulation Study

In this study, to develop new advanced corrosion inhibitors with high corrosion inhibition efficiency at low concentration, a simple but effective strategy that is the adjustment of bridge heteroatoms in a mixed corrosion inhibitor named 2-(n-hexylamino)-4-(3-N,N-dimethylaminopropyl)amino-6-(2-aminobenzimidazol)-1,3,5-s-triazine (BDCT) was used to improve the anti-corrosive properties. Two series of new compounds were designed by adjusting three bridge N atoms in BDCT by different number of O and S atoms at three different positions. The molecular structures and different kinds of anti-corrosive properties of 14 designed compounds were investigated by the DFT and MD methods. The results showed that when compared to BDCT, the molecular area, electrophilicity, electronegativity, strength of feed-back bonding, softness, chemical reactivity and binding energy on the Fe(110) surface were improved obviously by the introduced bridge O and S atoms, leading to higher corrosion inhibition efficiency. This effect could be further enhanced with the increased number of them, and S atoms were found to better than O atoms obviously. The introduction positions of O and S atoms also made effects on anti-corrosive properties, introducing them at the R1 position was more helpful for improving anti-corrosive properties than R2 than R3. As a result, the compound with three bridge S atoms (B7) has the best anti-corrosive properties. The adsorption sites, type of bonding with metals and corrosion inhibition mechanism of BDCT were also changed completely by O and S atoms.