Electrochemical impedance spectroscopy (EIS) modelling of different behaviours of Ni and Ni oxide thin films for corrosion prevention in sour media

摘要

Purpose - The purpose of this paper is a theoretical modeling use of electrochemical impedance spectroscopy (EIS) technique for different cases that could describe the possible electrochemical behaviour on steel coated with metallic and oxide thin films(of nickel) deposited by magnetron sputtering, and compare them to know if the theoretical analysis resembles the real case. It is extremely important to clarify that such simulations do not consider the use of the constant phase element (CPE) for the analysis. Therefore, the goal for the theoretical models should be to gain acceptance in electrochemical research. Design/methodology/approach - In order to obtain the equivalent circuits to explain the different possible behaviours of the films and their protective properties in sour media, EIS experimental data were correlated with data from the simulation software. The different nickel and nickel oxide thin films were tested after their deposition by magnetron sputtering on low-carbon steel and after they had then been exposed to the sour media electrolyte of NaCl 3 wt% + H_2S (saturated). Findings - The EIS simulation starts from the laboratory evaluation of nickel and nickel oxide thin films as anticorrosive protection for low-carbon steel exposed to sour media. From these results, it is found that the nickel and nickel oxide films could adopt seven different behaviours, and all are possible to occur. Practical implications - The equivalent circuits proposed will give an insight into the corrosion phenomena for different metals coated with thin films and exposed to sour media, because all of the simulations are made on the basis of real EIS results. Originality/value - The electrical analysis in the simulation diagram did not consider the use of the CPE to adjust the plots. In consequence, the values of all parameters for the seven different adjustments obtained through the simulations establish a reference for the explanation of the corrosion phenomena. They are also a tool with which to predict the possible behaviour of a thin film deposited on metal and exposed to electrolytes that are as aggressive as sour media.