Corrosion inhibition effect of ethylene glycol on aluminium 7075 alloy in 3.5 NaCl medium

摘要

Ethylene glycol is commonly used in chilled water air conditioning system that places either the chiller or air handlers outside as well as a system that must be cold below the freezing temperature of water. Nowadays, especially in automotive industry, Al alloys have been broadly integrated into vehicular heat exchange systems, replacing more traditional materials like stainless steels and copper alloy. Corrosion of engine components by coolant is an important issue in the automotive industry. Inhibiting effect of ethylene glycol on aluminium 7075 alloy corrosion in %3.5 NaCl has been studied by using dynamic electrochemical impedance spectroscopy (DEIS) and potentiodynamic polarization (PDP) methods supported with surface morphological assessment via scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). Results gotten indicate that, in the presence of ethylene glycol, the corrosion resistance of aluminium 7075 in the studied environment improves and the extent of improvement is found to be concentration dependent. The optimum inhibiting ability (68%) is afforded by 40% ethylene glycol. The PDP results portray ethylene glycol as a mixed type corrosion inhibitor. Inhibition of aluminium 7075 corrosion by ethylene glycol molecules is by formation of a protective film on the metal surface as indicated by SEM, AFM, and EDS results. The adsorption of the inhibitor molecules can be approximated by Temkin adsorption isotherm.