Corrosion is a subject of interest to interdisciplinary research communities, combining fields of materials science, chemistry, physics, metallurgy and chemical engineering. In order to understand mechanisms of corrosion and the function of corrosion inhibitors, the reactions at the interfaces between the corrosive electrolyte and a steel surface, particularly at the initial stages of the corrosion process, need to be described. Naturally, these reactions are strongly affected by the nature and properties of the steel surfaces. It is however seen that the majority of recent corrosion and corrosion-inhibition investigations are limited to electrochemical testing, with ex situ analysis of the treated steels (post-exposure analysis). The characterization of materials and their surface properties, such as texture and morphology, are not being considered in most studies. Similarly, in situ investigations of the initial stages of the corrosion reactions using advanced surface characterization techniques are scarce. In this review, attention is brought to the importance of surface features of carbon steels, such as texture and surface energy, along with defects dislocation related to mechanical processing of carbon steels. This work is extended to a critical review of surface analytical techniques used for characterization of carbon steels in corrosive media with particular focus on examining steel surfaces treated with corrosion inhibitors. Further, emerging surface analysis techniques and their applicability to analyse carbon steels in corrosive media are discussed. The importance of surface properties is commonly addressed by surface scientists as well as researchers in other chemistry fields such as nanotechnology, fuel cells, and catalysis. This article is expected to appeal to a broad scientific community, including but not limited to corrosion scientists, material chemists, analytical chemists, metal physicists, corrosion and materials engineers.

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Carbon steel corrosion: a review of key surface properties and characterization methods

An investigation of benzimidazole derivative as corrosion inhibitor for mild steel in different concentration HCl solutions

This review summarizes recent progress in the development and application of potentiometric sensors with limits of detection (LODs) in the range 10−8–10−11 M. These LODs relate to total sample concentrations and are defined according to a definition unique to potentiometric sensors. LODs calculated according to traditional protocols (three times the standard deviation of the noise) yield values that are two orders of magnitude lower. We are targeting this article at analytical chemists who are non-specialists in the development of such sensors so that this technology may be adopted by a growing number of research groups to solve real-world analytical problems.

We discuss the unique response features of potentiometric sensors and compare them to other analytical techniques, emphasizing that the choice of the method must depend on the problem of interest. We discuss recent directions in sensor design and development and present a list of 23 sensors with low LODs, with references. We give recent examples where potentiometric sensors have been used to solve trace-level analytical problems, including the speciation of lead and copper ions in drinking water, the measurement of free copper in sea water, and the uptake of cadmium ions by plant roots as a function of their speciation.

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Potentiometric sensors for trace-level analysis

Evolution of dissolution processes at the interface of carbon steel corroding in a CO2 environment studied by EIS

An iron(III) ion-selective sensor based on a μ-bis(tridentate) ligand

This paper presents a fundamental study of the influence of carbon steel microstructure on the corrosion rate Subsequently, the corrosion performance of various grades of carbon steels were evaluated in stirred autoclaves under elevated carbon dioxide and temperature conditions Corrosion and penetration rates were determined via mass loss and optical microscopy, respectively It was found that the corrosion rate of carbon steel line pipe is influenced by microstructure More specifically, a relationship between localized corrosion susceptibility and the presence of pearlite bands in the steel microstructure was found However, no correlation was evident between minor elemental concentrations (ie, Ni, Cr, Mo) and corrosion resistance It has been proposed that the corrosion stability of the various microstructures may arise from variations in the distribution of carbon bearing phases within the steel In the banded ferrite/pearlite structure, the carbon-bearing phase (pearlite) is distributed in layers whereas in the other structures the carbon-bearing phases are much more evenly distributed This study reports on the corrosion resistance of carbon steels in relation to their chemical and physical properties

The influence of microstructure on the corrosion rate of various carbon steels

Corrosion rate data for several commercial carbon dioxide corrosion inhibitors have been fitted to the Temkin adsorption isotherm and van't Hoff equation, enabling a determination of the enthalpy of adsorption (ΔHad∘). It has been found that experimentally determined ΔHad∘ values for commercial inhibitor formulations can provide valuable insights into the behaviour of the inherent active components. The temperature sensitivities along with the mechanism of adsorption (physi- or chemisorption) and the minimum concentration required for activity of inhibitors is determinable by this approach. Additionally, FTIR has been used to identify those inhibitors that are tenaciously adsorbed to steel, and suitable for use in batch treatment applications.

A study of the adsorption properties of commercial carbon dioxide corrosion inhibitor formulations

Calibration of a chalcogenide glass membrane ion-selective electrode for the determination of free Fe3+ in seawater: I. Measurements in UV photooxidised seawater

The response mechanism of the iron(III) chalcogenide glass membrane ion-selective electrode (ISE) in saline media has been studied using electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). EIS equivalent circuits and XPS surface compositions for the FeIII ISE are consistent with the presence of two surface films probably comprising a outer surface layer (OSL) and an Fe-deficient modified surface layer (MSL), along with a low-frequency charge-transfer impedance that is attributable to the reduction of Fe3+. In accordance with literature data for the conductivity of low-bearing iron(III) chalcogenide glasses, a high-impedance MSL is internally consistent with XPS data for an Fe-deficient MSL. It is evident that the impedance of the MSL diminishes on exposure to solutions containing Fe3+, and this finding is consistent with the ion exchange of Fe3+ within the MSL. Likewise, the charge-transfer impedance also decreases at elevated levels of Fe3+, demonstrating that Fe3+ is a participant in the reversible charge-transfer reaction occurring at the electrolyte/electrode interface. The kinetics of charge transfer are facilitated by Fe chelating agents (e.g., citrate, salicylate, EDTA, etc.) due presumably to the complexation of the products of the charge transfer process (possibly Fe2+). It is shown unequivocally that the response of the FeIII ISE in saline buffers is independent of pH, demonstrating that the ISE is responding directly to Fe3+, not H+. A mechanism involving a combination of charge transfer and ion exchange of FeIII, at the electrode diffusion layer, has been proposed to explain the 30 mV/decade slope of the FeIII ISE.

Electrochemical Impedance Spectroscopy and X-ray Photoelectron Spectroscopy Study of the Response Mechanism of the Chalcogenide Glass Membrane Iron(III) Ion-Selective Electrode in Saline Media

This paper presents a fundamental study of the influence of various chemical inhibitors on the corrosion rate of mild steel in brine electrolyte under carbon dioxide conditions. The corrosion inhibitors were fitted to a Temkin adsorption isotherm, and various fundamental constants of adsorption (i.e., adsorption equilibrium constants and molecular interaction constants) have been obtained. The inhibitor adsorption mechanism has been discussed in terms of thermodynamics (i.e., AH, AG, and ΔS), and this revealed that some compounds chemisorb onto the steel electrode. In addition, molecular modeling was undertaken using PCS-SPARTAN Plus and HyperChem Professional, and the various molecular parameters have been correlated with the thermodynamic adsorption properties of the inhibitors. Three-parameter and four-parameter fits for both negative and positive models are discussed. Multiple linear regression was performed on various combinations of molecular descriptors to describe the enthalpies and entropies of adsorption. Similarly, principal component analysis (PCA) was employed to corroborate the scientifically based selection of molecular descriptors used in the multivariate regression models.

R. De Marco

Papers

The influence of microstructure on the corrosion rate of various carbon steels

A study of the adsorption properties of commercial carbon dioxide corrosion inhibitor formulations

Calibration of a chalcogenide glass membrane ion-selective electrode for the determination of free Fe3+ in seawater: I. Measurements in UV photooxidised seawater

Electrochemical Impedance Spectroscopy and X-ray Photoelectron Spectroscopy Study of the Response Mechanism of the Chalcogenide Glass Membrane Iron(III) Ion-Selective Electrode in Saline Media

Predicting the Adsorption Properties of Carbon Dioxide Corrosion Inhibitors Using a Structure-Activity Relationship