Cuminum cyminum as green corrosion inhibitor for API 5 L X70 carbon steel in 0.5 M H2SO4 solution

Cuminum cyminum extract (CCE) has been studied as a corrosion inhibitor in controlling corrosion of C-steel corrosion in 0.5 M H₂SO₄, by weight loss (WL), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), energy-dispersive X-ray spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements. The findings demonstrated that inhibition efficiency (% IE) enhanced with increasing extract dosages, attaining 83.49% at 200 ppm and finishing at 91.83% at 400 ppm. However, inhibition efficiency was reduced by raising the temperature, decreasing from 91.83% at 298 K to 78.63% at 318 K (all at 400 ppm). CCE adhered to the C-steel surface by the Langmuir adsorption isotherm. EIS measurements exhibited increased transfer resistance (R_ct) as the extract dose increased. Polarization curves showed that CCE functions as a mixed-type inhibitor. Several thermodynamic parameters were computed and examined. The free energy of adsorption for the extract under study was calculated and was found 34.7-35.8 kJ mol^{- 1}. Chemical and electrochemical approaches yielded reliable and agreeable results.