Corrosion inhibition of mild steel in acidic media by amino-pentadecylphenols derived from cashew nut shell liquid

This study involved the synthesis of amino-pentadecylphenols and a study of corrosion inhibiting properties in 1.0 M HCl solutions. The formation of a mixture of 2,4-diamino-5-pentadecylphenol and 2,4,6-triamino-3-pentadecylphenol from anacardic acid (AnAc) isolated from Cashew Nut Shell Liquid (CNSL) was confirmed using FT-IR and 1H-NMR analyses. A mixture of these amino-pentadecylphenols was observed to be potential corrosion inhibitor for mild steel in 1.0 M HCl solutions. The inhibition efficiency was observed to increase with increase in the concentration of the inhibitor up to 600 ppm showing up to 98.50 % at 30 °C. The effect of temperature was also studied and it was found to accelerate corrosion rate of inhibited systems. The inhibitor performance decreased with increasing temperature, suggesting that as temperature increases, the inhibitive properties of the amino-pentadecylphenols were hindered. The adsorption of the inhibitor on mild steel under stationary condition at 30 oC was found to obey Temkin’s adsorption isotherm. The presence of the inhibitor in the test solution increased the activation energy of the corrosion reaction. In addition, the inhibitor was found to exhibit poor performance in rotating system compared to stationary system. Based on these results, it can be concluded that the inhibitor molecules undergo physical adsorption on the metal surface.