The Electrochemical Behavior of Al Alloys in NaCl Solution in the Presence of Pyrazole Derivative

This paper studies the corrosion inhibition of Al-Mg alloy system in 0.5 mol/dm3 NaCl solution in the presence of pyrazole derivative using potentiodynamic polarization and linear polarization method. The inhibition efficiency as a function of concentration and temperature was investigated. From the polarization curves, it can be concluded that the pyrazole derivative behaves like a mixed inhibitor. It has been shown that the efficiency of the inhibitor increases with increasing concentration and with increasing temperature and it indicates a chemisorption process. It was concluded that the pyrazole derivative adsorbed on the electrode blocks the active surface sites and reduces the corrosion rate. The kinetic and thermodynamic parameters of the adsorption process were determined. The relatively low efficiency of the inhibitor at room temperature could be an indicator of increased desorption in the adsorption-desorption equilibrium process. With increasing temperature the equilibrium is shifted in the direction of adsorption, causing an increasing inefficiency. Also, the positive values of equilibrium adsorption constant Kads indicate chemisorption of the pyrazole derivative on the alloy surface. The values of the activation energy in the presence of inhibitor were lower than in the uninhibited solution, which also indicates the chemical adsorption. Negative values of adsorption free energy ΔGads show that the adsorption process is spontaneous.