**1.3 Aim of this study**

Although many interesting topics have been explored for AlxCoCrFeNi alloys [10,11], investigation on their corrosion property is still lacking. Therefore, this study elucidates how Al affects their corrosion behaviour. The electrochemical properties of the alloys in sulfuric acids are investigated using the potentiodynamic polarization curve and a weight loss measurement method. Additionally, these alloys are compared with SS 304, especially with respect to the effect of temperature. Moreover, based on use of electrochemical impedance spectroscopy (EIS), the effect of Al on corrosion behaviour is analyzed. Furthermore, the relationship of stability of oxide film with Al content is examined by varying the chloride concentration in a sulfuric solution. Additionally, this study, which extends [17], also attempts to investigate the mechanism of the passive layers influenced by Al content x at various temperatures in detail.
