Effect of Thyme extract as an ecofriendly inhibitor for corrosion of mild steel in acidic media

Abstract Natural extracts have been widely used to protect metal materials from corrosion. Mild steel (MS) corrosion inhibition in 0.5 M sulfuric acid was investigated in the absence and presence of Thyme leaf extracts as an economical corrosion inhibitor. The effects of various concentrations and different temperatures on inhibitor efficacy were investigated. Using electrochemical impedance spectroscopy and polarization curves, the corrosion resistance of the alloy was also estimated. The polarization technique indicated that the Thyme extract is a mixed‐type inhibitor for MS in 0.5 M H 2 SO 4 . The obtained results revealed an excellent inhibition efficiency of 98% at 200 ppm of Thyme concentration. The thermodynamic parameters calculated, the effects of temperature, and the adsorption mechanism were also investigated, that suggested formation of monolayer inhibitor molecules (i.e. the Langmuir adsorption isotherm) on the metal surface. The value calculated from the Langmuir adsorption isotherm plots for inhibitor indicated that it was adsorbed on the alloy surface via a physisorption mechanism. Additional studies on plant extracts as corrosion inhibitors on metals are needed to produce solutions for industrial purposes.