Corrosion inhibitive property of 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol for mild steel corrosion in 1·0M hydrochloric acid

Abstract

The efficiency of 4-Amino-5-phenyl-4H-1,2,4-triazole-3-thiol (APTT) as corrosion inhibitor for mild steel metal in 1·0M HCl has been investigated. Weight loss, direct current (potentiodynamic polarisation), alternating current (electrochemical impedance spectroscopy), change of open circuit potential (OCP) with immersion time and scanning electronic microscopy were used to study the effect of APTT on the corrosion inhibition of mild steel. Results obtained from weight loss, potentiodynamic polarisation, impedance measurements and change of OCP with immersion time are in good agreement and indicated that the inhibitive efficiency of the inhibitor increases with the rise of concentration. Polarisation curves show that APTT is a mixed type inhibitor. Results showed that APTT performed excellent inhibiting effect for the corrosion of mild steel in 1·0M HCl solution and inhibition efficiency is higher than 90% at 80 × 10^–5 M APTT. The high inhibition efficiency in terms of molecular adsorption and forming a protective film on the metal surface was discussed in this work. Adsorption of the inhibitor on the mild steel surface followed Langmuir adsorption isotherm and the value of the free energy of adsorption ΔG _ads indicated that the adsorption of APTT molecule was a spontaneous process and was typical of chemisorptions. Surface photographs showed a good surface coverage on the metal surface.