Folic acid as a green inhibitor for corrosion protection of Q235 carbon steel in 3.5 wt% NaCl solution

This study combines experimental and theoretical explorations. The corrosion inhibition performance of different concentrations (50, 100, 250, and 500 ppm) of folic acid in 3.5 wt% NaCl solution on Q235 steel was tested by weight loss and electrochemical test. The corrosion inhibition efficiency increased with the gradual increase of folic acid concentration and reached a maximum of 87% at 500 ppm folic acid. The experimental results for electrochemistry and weight loss are in good agreement with the simulation calculations. The adsorption of folic acid on the steel surface obeyed the Langmuir isotherm, and the adsorption process was a combination of chemisorption and physisorption. The contact angle test also yielded the maximum increase in hydrophobicity of the specimen surface at the added folic acid concentration of 500 ppm. The corrosion morphology after the addition of corrosion inhibitor was relatively flat. The adsorption orientation of folic acid molecules on the steel surface in an aqueous environment was investigated using density functional theory (DFT)/molecular dynamics (MD) simulations. The microscopic mechanism of action of folic acid corrosion inhibitors is clarified.