Corrosion And Protection Of Aluminium In The Hydrochloric Acid

Aluminium material has some good characteristics, such as light weight,good diathermancy,good electric performance and so on. So aluminium and its alloy have replaced traditional iron material in some fields recently. In order to improve surface of aluminium or be easy to next process, acid washing is an important step. Aluminium erodes easily in this step, so it has important significance to study corrosion and protection of aluminium .A series of polarization curves were tested in the hydrochloric acid with different H+and Cl-, the relation between corrosive potential, corrosive current and the concentration of H+andCl- were analyzed and obtained two kinetic equation. It showed that the corrosion of aluminium included many steps in hydrochloric acid, H+ and Cl- took part in the process of anodic dissolution and cathodic reaction. The reaction progress of H+ equaled to that of Cl- in anodic process, H+ influence corrosive velocity more greatly than Cl- in cathodic process. Based on SEM, the corrosive shape of aluminium was pitting corrosion and become all-around corrosion gradually in hydrochloric acid.Some inhibitors were estimated by porlar resistance, decvlamine had best inhibitive efficiency. Inhibitive performance of decvlamine on aluminium was studied by electrochemical polarization curves. Experimental data was analyzed and discussed by using adsorption theory. The results show that decvlamine has some inhibitive effects on aluminium in hydrochloric acid and it is a kind of mixed and leant anodic reaction inhibitor by means of geometric blocking effect. The adsorption behavior of decvlamine obeys Flory-Huggins isotherm model.Some correlative thermodynamic functions were calculated by isotherm model, the adsorption of decvlamine on aluminium was characterized by means of FT-IR.It showed that decvlamine and Cl- adsorbed and formed a film on metal by competitive model and its driving force was entropy increment. The process included physical adsorption and chemical adsorption.The corrosion inhibition behaviors of decvlamine or/ and I- were studied by polarization curves and electrochemical impedance spectroscopy (EIS). The results showed that KI have some inhibitive effects on aluminium, but its efficiency was not good. The best concentration ratio is 1:4 when mixed with decvlamine and decvlamine was the main factor of inhibition in the synergistic system.The studies of synergistic effect of BTA and decvlamine showed that BTA was a kind of inhibitor by means of geometric blocking effect, it restrained corrosion with decvlamine by synergic manner. The best concentration ratio is 2.5:2.5 when mixed with decvlamine. Inhibitive efficiency improved gradually with the hoist of temperature and has good temperature performance.