C.R. Magaña‐Zavala, M.E. Angeles‐San Martín, F.J. Rodríguez‐Gómez, D.R. Acosta, R. Ávila‐Godoy and B. Hidalgo‐Prada
The purpose of this paper is a theoretical modeling use of electrochemical impedance spectroscopy (EIS) technique for different cases that could describe the possible…
Abstract
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% + H2S (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.
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Keywords
Atefeh Bahrami Mousavi, Pouria Baghery, Mahmoud Peikari and Gholam‐Reza Rashed
The purpose of this paper is to investigate the effect of TiO2 nanoparticle content on the corrosion behavior of Ni‐Cr/TiO2 nanocomposite coatings applied by pulse‐reverse…
Abstract
Purpose
The purpose of this paper is to investigate the effect of TiO2 nanoparticle content on the corrosion behavior of Ni‐Cr/TiO2 nanocomposite coatings applied by pulse‐reverse electroplating.
Design/methodology/approach
Ni‐Cr/TiO2 nanocomposite coatings with various contents of TiO2 nanoparticles were electrodeposited by pulse‐reverse method from a bath containing TiO2 nanoparticles to be codeposited and citric acid as the complexing agent. The surface morphology and the composition of coatings were studied by scanning electron microscopy (SEM) equipped by energy dispersive X‐ray system (EDS). The corrosion performance of coatings in the 0.5 M NaCl as a corrosive solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods.
Findings
It was found that the surface of Ni‐Cr/TiO2 nanocomposite coatings showed a finer structure that was more uniform and compact in appearance than was that of Ni‐Cr coatings. The incorporation of TiO2 nanoparticles in the alloy coating matrix improved the corrosion performance of the coatings and the higher content of nanoparticles gave better corrosion resistance.
Originality/value
Applying the Ni‐Cr coatings by the pulse‐reverse plating method eliminated cracks that were a problem in the Ni‐Cr alloy coating structure. Furthermore, the corrosion resistance was improved by the addition of TiO2 nanoparticles to the alloy matrix. This paper reports the optimum plating conditions that gave the better corrosion performance.
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Ximing Li and Homero Castaneda
The purpose of this paper is to study the damage evolution (DE) of coated API5L-X52 steel pipe with cathodic protection (CP) in nature soil. Also, different coating conditions…
Abstract
Purpose
The purpose of this paper is to study the damage evolution (DE) of coated API5L-X52 steel pipe with cathodic protection (CP) in nature soil. Also, different coating conditions, intact coating and coating with artificial holiday defect are considered to study the electrochemical behavior combined with soil properties and CP potential. An approach of electrochemical impedance spectroscopy (EIS) analysis is also developed.
Design/methodology/approach
This work developed a laboratory experimental set-up of coated pipeline under CP in nature soil. The electrochemical behavior has been investigated using EIS. The CP potential provided by a DC power supplier has been adjusted and recorded to maintain the protective potential of pipe at −850 mV vs Cu/CuSO4.
Findings
Various parameters were derived from the EIS fitting data by equivalent circuit models to illustrate the three DE stages of coated carbon steel in soil. Each stage changes faster for the artificial defect coating system compared to intact coating, especially at the initial water uptake and ion transport stage. The CP potential has been proved to be correlated to the soil properties, coating conditions and DE stages of pipeline samples.
Originality/value
This work is the first one to study DE of coated pipeline system under CP in soil. It introduces an electrochemical method to study coating defects which can promote to design the deterministic model to detect coating defects of buried pipe using AC impedance technique.