Abstract
The effect of isatin on the corrosion of Cu-20%Zn-2%Al (alloy I) and Cu-31% Zn (alloy II) in NaCl solution has been studied using different electrochemical techniques [open circuit, potentiodynamic, and impedance spectroscopy (EIS)]. The two copper alloys were used in condenser tubes of heat exchanger for power station plant in Egyptian financial and industrial company Assiut factories. The steady state potential E-s.s values increase to more negative values by increasing NaCl concentration which indicated that the destruction of pre-immersion passive film formed on the Cu-Zn surfaces. The corrosion rate of the two alloys decreased by increasing concentration of isatin, which indicated the effect of isatin as a corrosion inhibitor. The inhibition efficiency of isatin in 0.1M NaCl solution was 88.5 % in alloy I and 73.9 % in alloy II at a concentration 0.01M of isatin. The significant inhibition processes due to the adsorption characteristics of isatin on the two alloys surface. The chemical composition of alloy I was more resist to corrosion in NaCl solution than the chemical composition alloy II due to presence of Al.