Copper corrosion inhibition by Azadirachta indica leaves extract in 0.5 M sulphuric acid

Azadirachta indica leaves extract (AI) was investigated as a copper corrosion inhibitor in 0.5 M sulphuric acid. Inhibition efficiency of AI was compared to that of the already proven good inhibitors 2-acetamino-5-mercapto-1,3,4-thiadiazole (AAMTDA) and 1,2,3-benzotriazole (BTAH). The inhibition properties were studied using electrochemical polarization and weight loss techniques. In the region of active copper dissolution, the highest inhibition efficiency was exhibited by AAMTDA (92.7%). AI exhibited somewhat higher efficiency (86.4%) than the widely used BTAH (85.5%), showing that the extract could serve as a effective substitute for currently preferred copper corrosion inhibitors in sulphuric acid. The weight loss results were interpreted by means of the Frumkin isotherm of adsorption on the metal surface. The values of ΔGads equal to − 41.96 kJ mol− 1 for AAMTDA and − 35.22 kJ mol− 1 for BTAH indicate strong spontaneous adsorption while the surface coverage dependence on the log c following the Frumkin isotherm is suggestive of chemisorption in case of all three tested inhibitors.