Synergistic Inhibition Effect of 3-Carboxypyridine and Potassium Iodide on Mild Steel Corrosion in H2SO4: Electrochemical and Surface Analyses

The effective inhibition of MS corrosion in H2SO4 by CP and CP + KI was assessed by EIS. SM of MS was studied using SEM and AFM. The rise in Rct and decrease in Cdl, with higher C of CP and CP + KI, confirmed MS CI. IE(%) increased with higher C of CP only and CP + KI (from 10-3 to 10-1 M). CP maximum IE(%) was 93.9%, at 10-1 M. CP + KI, due to I- ions synergistic effect, showed an IE(%) of about 98.8%, at 10-1 M. CP only and CP + KI adsorption mechanism followed Langmuir's isotherm. SM studies suggested that a barrier film of CP only and CP + KI, mitigated MS surface corrosion. CP + KI is an efficient inhibitor in H2SO4.