Corrosion inhibition of copper alloys by organic compounds

Abstract

Copper and copper alloys have been used widely in different applications, such as electric power transmissions and heat exchanges. However, they are susceptible to corrosion in different environments leading to damages and catastrophic failures. Different corrosion-inhibition strategies are used to retard corrosion of copper and copper alloys. Among them, corrosion inhibitors are successfully used to inhibit their corrosion. This thesis focuses on the corrosion inhibition of brasses (the copper-zinc binary alloys) using two kinds of organic inhibitors, namely 2-mercapto-1-methyl-benzimidazole (1H-HB-2T) and 2-mercapto-benzimidazole (MBI). Corrosion inhibition of the substrates using the inhibitors were screened using linear polarization resistance (LPR) measurements. Subsequently, electrochemical impedance spectroscopy (EIS) was used to study the detailed corrosion inhibition processes and mechanisms. Finally, two modes (RAS and ATR) of Fourier transform infrared spectroscopy (FTIR) were adopted for in-situ and ex-situ tests to study the adsorption mechanisms of inhibitor molecules on the surfaces. The research results showed that: (1) the composition (phase type) of the brass controls the interaction of inhibitor on surfaces; (2) an increased Zn content of brass leads to a decreased corrosion resistance; (3) 2-mercapto-1-methyl-benzimidazole (1H-HB-2T) exhibits better corrosion efficiency than 2-mercapto-benzimidazole (MBI) indicating the importance of the methyl functional group to increase the inhibitor’s efficiency; (4) 1HHB-2T exhibits a spontaneous structure transformation from thiol to thione and (5) within a maximum 5-hour exposure, the adsorption of the inhibitors to the metal surface is complete.