Synergistic effect p-phenylenediamine and n,n diphenylthiourea on the electrochemical corrosion behaviour of mild steel in dilute acid media

Roland Tolulope Loto,Abimbola Patricia Popoola,Akanji Lukman Olaitan

doi:10.1007/s40090-015-0063-7

Abstract

Electrochemical studies of the synergistic effect of p-phenylenediamine and n,n diphenylthiourea (TPD) as corrosion inhibitor of mild steel in dilute sulphuric and hydrochloric acid through weight loss and potentiodynamic polarization at ambient temperature were performed. Experimental results showed the excellent performance of TPD with an optimal inhibition efficiency of 88.18 and 93.88 % in sulphuric and 87.42 and 87.15 % in hydrochloric acid from both tests at all concentration studied. Polarization studies show the compound to be a mixed-type inhibitor. Adsorption of deanol on the steel surface was observed to obey the Langmuir and Frumkin isotherm models. X-ray diffractometry confirmed the absence of corrosion products and complexes. Optical microscopy confirmed the selective inhibition property of TPD to be through chemical adsorption on the steel surface.

Highlights

Carbon steel is extensively utilized in petrochemical plants, chemical processing plants, extractive industries, and construction and automobile industries due to its goodInt J Ind Chem (2016) 7:143–155 as inhibitors decelerate the electrochemical processes responsible for corrosion
Experimental results showed the excellent performance of TPD with an optimal inhibition efficiency of 88.18 and 93.88 % in sulphuric and 87.42 and 87.15 % in hydrochloric acid from both tests at all concentration studied
Inhibitors consisting of double or triple bonds facilitate the adsorption of the organic compounds onto metal surfaces, forming an impenetrable protective barrier through chemisorption reactions [9,10,11,12,13,14,15,16,17]

Summary

Introduction

Carbon steel is extensively utilized in petrochemical plants, chemical processing plants, extractive industries, and construction and automobile industries due to its goodInt J Ind Chem (2016) 7:143–155 as inhibitors decelerate the electrochemical processes responsible for corrosion. Inhibitors consisting of double or triple bonds facilitate the adsorption of the organic compounds onto metal surfaces, forming an impenetrable protective barrier through chemisorption reactions [9,10,11,12,13,14,15,16,17]. The chemical bond is formed between the electron pair and/or the pi-electron of the protonated species and the valence metal ions at the surface, thereby reducing corrosive attack in an acidic medium. Thiourea derivatives and p-phenylenediamine have been studied individually in previous research for corrosion inhibition properties with mixed results [19,20,21,22,23]; this research aims to study the synergistic effect of n,n diphenylthiourea and p-phenylenediamine as corrosion inhibitor for low carbon steel in 1 M sulphuric and 0.5 M hydrochloric acid

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Results