Red tetrazolium as an effective inhibitor for the corrosion of cold rolled steel in 7.0 mol·L? 1 H2SO4 solution

Red tetrazolium as an effective inhibitor for the corrosion of cold rolled steel in 7.0 mol·L-1 H2SO4 solution

The corrosion inhibition of cold rolled steel (CRS) in 7.0 mol·L^-1 H₂SO₄ solution by red tetrazolium (RTZ) was carefully investigated using both experimental procedures and theoretical techniques. The results show that RTZ acts as an effective inhibitor for the corrosion of CRS in 7.0 mol·L^-1 H₂SO₄, and the maximum inhibition efficiency is higher than 95% with a RTZ concentration of 2.0 mmol·L^-1. The adsorption of RTZ on CRS surface follows Langmuir isotherm. RTZ effectively retards both cathodic and anodic reactions, and acts as a mixed-type inhibitor. EIS exhibits two capacitive loops, and their resistances increase drastically in the presence of RTZ. SEM and AFM confirm that the addition of RTZ could significantly retard the corrosion of CRS surface. A series of characterizations like FTIR, RS, XRD and XPS reveal that the corrosion CRS surface is composed of the corrosion products of iron sulfates, iron oxides and iron hydroxide, as well as inhibitor. Theoretical results of quantum chemical calculation and molecular dynamics (MD) indicate that the adsorption center of RTZ⁺ (organic cationic part of RTZ) mainly relies on its tetrazole ring, and the adsorption of RTZ⁺ on Fe (001) surface is in a nearly flat orientation mode.