Investigation on imidazoline amide adsorption and electrochemical behaviour of coupled steels

Abstract

The adsorption behaviour of imidazoline derivative as a cationic inhibitor on the galvanic electrode has been investigated by electrochemical methods, Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). The galvanic electrode was prepared by coupling N80 carbon steel and S31803 stainless steel, and all experiments were performed in NaCl solution in the presence or absence of the inhibitor. Electrochemical experiments reveal stainless steel and carbon steel carry positive and negative excess charges in NaCl solution. For the galvanic electrode, positive and negative charges are carried on the carbon steel side and stainless steel side respectively, and the inhibitor is a type of cathodic inhibitor for galvanic corrosion. Fourier transform infrared spectroscopy and AFM were used to analyse the protective layer formed on the electrodes, a weaker adsorbability of the inhibitor on the anode (carbon steel side) of the galvanic electrode was measured. Results show the protective layer formed on the single carbon steel electrode is compact. In the case of coupling carbon steel and stainless steel, the adsorption film on the anode (carbon steel side) of galvanic electrode (GE) is not intact but defective. A major cause of failure of inhibiting galvanic corrosion is proposed based on the results obtained from electrochemical methods, FTIR and AFM.