Experimental, quantum chemical calculations and molecular dynamics (MD) simulation studies of methionine and valine as corrosion inhibitors on carbon steel in phase change materials (PCMs) solution

Corrosion inhibition of methionine (Met) and valine (Val) molecules on carbon steel was investigated in phase change materials solution. Electrochemical measurements showed that these inhibitors can protect steel against corrosion, with a maximal protection efficiency up to 96.85% by the molar ratio of Met/Val is 1/1 and the concentration of Met is 0.05 mol·L−1. All inhibitors acted as anode type inhibitors. The analysis result of scanning electron microscope (SEM) showed that the surface morphology of the carbon steel sample immersed in the phase change materials solution in the presence of the Met/Val inhibitor was significantly better than that of the uninhibited sample. The inhibition mechanism was theoretically investigated through the quantum chemical calculation and molecular dynamic simulation, that showed the Methionine and valine molecules could adsorb on Fe (110) surface, N atoms, S atoms, and COOH group were the main adsorption active sites. Finally, the migration rate of Cl− ions in the film of three corrosion inhibitors (concentration: 0.05 mol·L−1) was studied.