Corrosion resistance of mild steel in sulphuric acid solution byCoreopsis tinctoriaextract: electrochemical and surface studies

Purpose The purpose of this paper is to investigate the inhibitive performance ofCoreopsis tinctoria(C. tinctoria) plant extract for the corrosion of mild steel in 0.5 M H2SO4. Design/methodology/approach The inhibition efficiency was studied by weight loss, electrochemical measurements and the surface analysis was done by Raman, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS) and atomic absorption spectroscopy (AAS) analysis. Findings Maximum inhibition efficiency ofC. tinctoriain 0.5 M H2SO4on mild steel is 80.62 per cent (500 ppm) at 303 ± 1K. The adsorption of theC. tinctoriaon the mild steel surface in 0.5 M H2SO4was found to obey Langmuir adsorption isotherm. Temperature studies were carried out and the significant parameters, such as change in enthalpy (ΔH°), change in entropy (ΔS°) and change in free energy (ΔG°ads) and heat of adsorption (Qads), were calculated. The productive layer formed on the mild steel surface in 0.5 M H2SO4were confirmed by the Raman spectral analysis. Originality/value This paper provides information on the inhibitive properties ofC. tinctoriaplant extract which is found to be a good corrosion inhibitor for mild steel in 0.5 M H2SO4.