Adsorption and Corrosion Inhibition of Cactus cladode Extract and Effect of KI Addition on Mild Steel in 0.5 M H2SO4

Adsorption and corrosion inhibitionof Cactus cladode(CC) extract collectedin eastern Algeria from areas of Chetaibi in Annaba on mild steel (MS) in 0.5 MH2SO4 solution were studied with potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) measurements. The electrochemical stability of surface inhibitor film was investigated by chronoamperometry (CA) technique. The MS surface exposed to thecorrosive medium in the absence and presence of CC extract was examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques. The potential of zero charge(E-pzc) of MS in the presence of CC extract was determined by EIS methodand excess surface scharge of the metal surface was determined. It was found that CC extract has a high inhibition effeciency on the corrosion of MS. The thermodynamic examinations indicated that K-ads was 20.88 L g(-1) and G(ads)(0) was -24.64 kJ mol(-1).Thevalue of E-pzc confirmed excess positive charge atthe MS surface. The adsorption of extract molecules obeys to Langmuir isotherm. The inhibition efficiency was 91.8 % at 1000 ppm CC extract concentration, while it iscreased to 97.7 % when 1000 ppm KI was added to this solution.The inhibitor film formed over the metal surface has a hydrophobic character.The addition of KI to the inhibited solution stabilizes the surface film and enhances inhibition efficiency.