First-principles and experimental study on the inhibition efficiency of BTA for 20SiMn steel in chloride-containing solutions.

• There is an inhibition efficiency limitation of BTA towards 20SiMn steel in 3.5 wt% NaCl with the increasing concentration. • The chemisorption of BTA through N-Fe bond on the surface of 20SiMn steel is responsible for the inhibition effect of BTA. • The limitation of inhibition efficiency is the result of the unchanged DOS of Fe atom and Fe(1 1 0) surface. The inhibition effect of benzotriazole (BTA) with the increase of concentration for 20SiMn steel in 3.5 wt% NaCl solutions was investigated by electrochemical methods, Scanning Electron Microscope (SEM), X-ray Photoelectron Spectroscopy (XPS) and Density Functional Theories(DFT). Results indicate that BTA could suppress the corrosion of 20SiMn steel through chemisorption but with a limited inhibition efficiency (around 60%). DFT calculated results show that the chemisorption of BTA has noticeable effects on the charge distribution of the whole BTA molecule, as well as that of N atom which bonds with Fe atom, but has little influence on those of Fe atom in N-Fe bond and Fe(1 1 0) surface where BTA molecules adsorb. The DFT calculated Density of States (DOS) peaks of N atom in N-Fe and those of BTA molecule become lower after the adsorption, and the location of DOS peaks move far away from the Femi surface, implying a more stable structure. As to Fe atom in N-Fe bond and Fe(1 1 0) surface, neither height nor locations of the DOS peaks change,which is crucial for losing electrons of metallic matrix and thus responsible for the limitation of BTA inhibition effect. [ABSTRACT FROM AUTHOR]