Stefan Krakowiak

Cyclic analysis of thermal impedance of a passive layer of aluminium in a neutral borate buffer solution

Purpose – The purpose of this paper is to examine the passive layer on 1050A aluminium alloy in non‐stationary conditions of linearly raised and lowered temperatures by means of dynamic electrochemistry impedance spectroscopy (DEIS).Design/methodology/approach – The oxide passive layer on aluminium was examined using DEIS under non‐stationary conditions of linearly raised and lowered temperatures. In total, five heating‐cooling cycles were performed.Findings – A significant change of impedance was observed only during the first cycle, which was called the forming one. During the subsequent cycles, the impedance of the system changed in a reversible manner.Originality/value – The analysis using a equivalent circuit allowed us to determine a change of electric parameters of the circuit in the temperature function. Obtained changes of the electric parameters were correlated with layer structure.

Corrosion resistance evaluation of Al‐based alloys by means of dynamic electrochemical impedance spectroscopy

Purpose – The purpose of this paper is to present the investigation of aluminum alloy by means of dynamic electrochemical impedance spectroscopy (DEIS), which is simultaneous method of AC impedance and DC polarization measurements.Design/methodology/approach – A method of DEIS has been applied. Changes in equivalent circuit (EC) parameters versus potential for both investigated aluminium alloys are evaluated.Findings – On the basis of obtained results, it is unambiguously demonstrated that the addition of 4.5 percent magnesium degraded the anticorrosive properties of the test alloys. It is difficult to define unequivocally the range of passive state and a moment of passive layer breakdown on the basis of current/voltage dependencies. However, application of the DEIS method and analysis of the evolution of particular elements of an electrical EC allowed identification of the instant of corrosion process initiation.Practical implications – The presented method is only suitable for laboratory evaluation of m...