Corrosion resistance of mild steel in sulphuric acid solution by Coreopsis tinctoria extract: electrochemical and surface studies

Purpose The purpose of this paper is to investigate the inhibitive performance of Coreopsis 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 of C. tinctoria in 0.5 M H2SO4 on mild steel is 80.62 per cent (500 ppm) at 303 1K. The adsorption of the C. tinctoria on the mild steel surface in 0.5 M H2SO4 was found to obey Langmuir adsorption isotherm. Temperature studies were carried out and the significant parameters, such as change in enthalpy (H-degrees), change in entropy (S-degrees) and change in free energy (G degrees(ads)) and heat of adsorption (Qads), were calculated. The productive layer formed on the mild steel surface in 0.5 M H2SO4 were confirmed by the Raman spectral analysis. Originality/value This paper provides information on the inhibitive properties of C. tinctoria plant extract which is found to be a good corrosion inhibitor for mild steel in 0.5 M H2SO4.