Investigation of the inhibitory effect of some nut shell extracts on mild steel corrosion

In this study, the inhibitory effect of walnut, hazelnut and peanut shell extracts containing phenolic compounds for mild steel was investigated in acidic (0.2 M HCl solution), chloride (5% NaCl solution) and basic (0.2 M NaOH solution) mediums. The external skin of hazelnuts, peanut and walnuts were pre-treated by cleaning, drying, grinding and sieving at certain particle size before extraction prosedure. After the extraction process, the extracts were separated from the solid by centrifugation. In order to find the appropriate solvent, the total phenolic substance (TPC) in the extracts was determined by the Folin-Ciocalteu method. As a result of this analysis, it was determined that the solvent used to obtain the extract with the highest TPC value was 75/25 acetone/water by volume. Corrosion behavior of mild steel in corrosive environments such as 0.2 M HCl, 5% NaCl and 0.2 M NaOH containing different concentrations of nut extracts (500, 1000 and 2000 ppm) obtained by using acetone and water mixture as solvent was examined by using cyclic voltammetry and Tafel polarization curves. As a result of the experiments, it was determined that the efficiency of inhibition enhanced with the increment in the concentrations of all extracts. The best efficiency of inhibition has been found about 80.6% in alkaline medium (0.2 M NaOH) with walnut extract, 88.6% in acidic medium (0.2 M HCl) with hazelnut extract and 49.2% in chloride medium (5% NaCl) with hazelnut extract.