Abstract
The inhibitive effect of Launaea nudicaulis methanolic (MLN) and aqueous acidic (ALN) extracts on the corrosion of mild steel in 1.0 M HCl solution was investigated by using weight loss, Tafel plots, linear polarization, electrochemical impedance spectroscopy (EIS) as well as SEM and EDS techniques. It was found that both extracts (MLN and ALN) inhibit remarkably the corrosion of mild steel in acidic solution and inhibition efficiencies increased with the increase of extracts concentration. The results revealed that MLN and ALN behaved as mixed type corrosion inhibitors with predominant anodic effectiveness. Inhibition efficiencies obtained from weight loss and electrochemical experiments were in good agreement and they were up to 92.5 % for MLN and 87.2 % for ALN. The effect of temperature on the corrosion behavior of mild steel was studied in the range of 298K-328 +/- 1K. Adsorption behavior of both green inhibitors on the MS surface followed the Langmuir adsorption isotherm and they inhibited the corrosion of mild steel by adsorption mechanism where the adsorption process involved was spontaneous, exothermic and physically adsorbed (physisorption). Surface morphology study through scanning electron microscope (SEM) and energy dispersive X-ray spectrometry (EDS) analysis showed a significant improvement on the surface morphology of the mild steel plate in the presence of MLN as well as ALN in 1.0 M HCl media. However, MLN was found to be more potent than ALN. The results showed that L. nudicaulis extracts could serve as efficient corrosion inhibitor for mild steel in hydrochloric acid environment.