Green Corrosion Inhibition and Adsorption Behaviour of Cistus ladanifer Extract on 304L Stainless Steel in Hydrochloric Acid Solution

The use of Cistus ladanifer methanolic extract as a 304L stainless steel (304L SS) corrosion inhibitor in 1 M HCl solution was investigated using weight loss measurements and electrochemical tests. The data showed that C. ladanifer extract inhibited 304L SS corrosion, with an inhibition efficiency of 97.8%. The chemical composition of the extract was determined by Fourier-transform infrared spectroscopy. Results confirmed the presence of several functional groups in this extract. The effect of temperature on extract efficiency and thermodynamic parameters was studied. The adsorption of the extract on 304L SS surface obeyed Langmuir adsorption isotherm. Furthermore, the extract effects on 304L SS physicochemical properties, including hydrophobicity and acid–base properties, were investigated using contact angle measurements. The results showed that the treated coupon surfaces became hydrophilic and predominantly electron-donating. Finally, the surface morphologies of 304L SS coupons, in both the absence and presence of C. ladanifer extract, in HCl solution were observed using scanning electron microscopy.