Electropolishing of steel in presence of some amines

Abstract

Abstract Electropolishing of Steel in phosphoric acid is considered as corrosion rate of Steel and due to the economic importance of Steel, there are several researches deals with acceleration and inhibition of this process. This paper threw some light on the effect of adding some organic amines on the electropolishing of steel. Different concentration were used from 10−5mol.L-1 to 10-2 mol.l-1 and different organic amines derivatives (methyl amine, dimethyl amine, diethyl amine, triethyl amine, diethanol amine and triethanol amine) were used. Electropolishing process of steel inhibited by different ratio. The results show that organic amines have strongest inhibiting effect ranging from 5% to 59.7% and the thermodynamic parameters as ΔS*, ΔH* and ΔG* were studied. The values of ΔGads are given in negative values in all cases means that spontaneous adsorption of inhibitor on steel surface and strong interaction between the inhibitor molecules and metal surface. It lies in the range of (32–38) kJmol-1 for Flory - Huggins and (15–17) KJ mol-1 for kinetic isotherm. It s found that (ΔGads) values are more positive than -40 Kjmol-1 indicating that the inhibitors are physically adsorbed on the metal surface and the adsorption isotherm were given. The effect of amines compounds with nitrogen free, on the corrosion process is revealed by adsorption curves. The efficiency in inhibition decreases in the order: triethanol amine\u2009>\u2009diethanol amine\u2009>\u2009triethyl amine\u2009>\u2009diethyl amine\u2009>\u2009dimethyl amine\u2009>\u2009methyl amine.