Corrosion inhibition of amino acids for 316L stainless steel and synergistic effect of I− ions: Experimental and theoretical studies

The inhibition effect of amino acids l‐lysine (Lys) and l‐arginine (Arg), which serve as inhibition films for corrosion of 316L stainless steel in 0.5 M NaCl solution, is studied by electrochemical measurements. The adsorption of the inhibitor molecules on the steel surface is studied by Fourier transformed infrared spectroscopy (FTIR) and surface‐enhanced Raman spectroscopy (SERS), accompanied by the characterization of the metal surface by scanning electron microscopy (SEM). All in all, Lys or Arg can obviously restrain the corrosion of 316L steel, while the inhibition efficiency is even higher with the assistance of I− ions. Arg always has better inhibition performance than Lys regardless of the addition of I− ions. FTIR and SERS confirm the adsorption of amino acids on the metal surface; at the same time, the morphology and protection effect of the inhibition films is clearly illustrated via SEM images. Thanks to all experimental measurements as mentioned above and theoretical calculations, a mechanism model is proposed to simulate the corrosion inhibition process of amino acids and the synergistic effect of I− ions on 316L steel.