Ni coatings were electrodeposited from 1:2 choline chloride (ChCl) - urea (U) deep eutectic solvents (DESs) on low carbon steel. We report on the inter-related influence of water content in the ...electrolyte and applied potential on the formation of Ni films and their chemical composition and morphology. This was investigated by cyclic voltammetry (CV) and chronoamperometry (CA) in combination with ex-situ characterization techniques (FE-SEM, EDS, XPS and Raman spectroscopy). Ni electrodeposition from DES is shown to be highly complex: Ni+2 reduction is followed by water reduction, which triggers electrolyte decomposition. A water content higher than 4.5%wt and/or performing electrodeposition at potentials more negative than E = −0.90V vs Ag quasi-reference electrode enhances the decomposition of the solvent. This breakdown appears via either an electrochemical reaction or triggered by water splitting. In both cases, it leads to the incorporation of DESs decomposition products, such as trimethylamine and acetaldehyde within the Ni film. Under these conditions, the films are composed of metallic Ni and NiOx(OH)2(1−x).
Deep Eutectic Solvents (DESs) are hygroscopic liquids composed of a hydrogen bond donor (HBD) and acceptor (HBA). Their physical, chemical and electrochemical properties can be tailored to use them ...as solvents for different applications,
i.e.
electrodeposition, catalysis, extraction,
etc.
This can be done by changing the HBD, as well by adding water. However, the interrelated influence of H
2
O and HBD on the structure of the electrolyte, and on the behavior of the active species is not fully understood. In this work, we select nickel electrodeposition as a case study and we combine electrochemical techniques (cyclic voltammetry, chronoamperometry) with UV-vis spectroscopy and molecular dynamics to understand the influence of water and HBD on the electrochemical behaviour of DESs. The unique combination of these different experimental and modelling techniques provides new insights into the field. The addition of H
2
O changes, not only the interactions between the constituents of the liquid, but also the coordination of metal cations, which is reflected in the electrochemical performance of different DESs. More importantly, we show that, in the presence of very little (between 0.1 wt% and 2.8 wt%) and high (>4.5 wt%) water contents, DESs behave differently, and the changes in their electrochemical behavior are caused by both the complexation of metal cations and the electrolyte transport properties.
Water concentration and hydrogen bond donor have both a big influence in the coordination of Ni cations in deep eutectic solvents, and will therefore affect their electroreduction.
Some three hundred mainly steel shipwrecks from both World Wars lie buried at shallow depths along the Belgian North Sea coast. They were examined recently to estimate corrosion rates over periods in ...excess of 100 years. The rate was estimated by comparing the measured in-situ steel plate thicknesses with archived ship information. The estimates show distinctly lower long-term corrosion rate compared to that predicted by the Melchers (Modeling of marine immersion corrosion for mild and low alloy steels - part 1: phenomenological model. Corrosion. 2003;59(4):319-334) corrosion model, when parameterised for local North Sea conditions. Concretion after 50 years has a multi-layer structure for which SEM-EDS and XRD measurements show the innermost layer, close to the metal surface, consisting of akaganeite, and the outer layer mostly of calcium carbonates, silicates, and some siderite. In between there is a considerable layer of hard magnetite. The latter is proposed as the reason for the low long-term corrosion rate (0.016 mm y
-1
) in an environment with calcium carbonate available in abundance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Deep Eutectic Solvents (DESs) are hygroscopic liquids composed of a hydrogen bond donor (HBD) and acceptor (HBA). Their physical, chemical and electrochemical properties can be tailored to use them ...as solvents for different applications,
i.e.
electrodeposition, catalysis, extraction,
etc.
This can be done by changing the HBD, as well by adding water. However, the interrelated influence of H
2
O and HBD on the structure of the electrolyte, and on the behavior of the active species is not fully understood. In this work, we select nickel electrodeposition as a case study and we combine electrochemical techniques (cyclic voltammetry, chronoamperometry) with UV-vis spectroscopy and molecular dynamics to understand the influence of water and HBD on the electrochemical behaviour of DESs. The unique combination of these different experimental and modelling techniques provides new insights into the field. The addition of H
2
O changes, not only the interactions between the constituents of the liquid, but also the coordination of metal cations, which is reflected in the electrochemical performance of different DESs. More importantly, we show that, in the presence of very little (between 0.1 wt% and 2.8 wt%) and high (>4.5 wt%) water contents, DESs behave differently, and the changes in their electrochemical behavior are caused by both the complexation of metal cations and the electrolyte transport properties.
Deep Eutectic Solvents (DESs) are hygroscopic liquids composed of a hydrogen bond donor (HBD) and acceptor (HBA). Their physical, chemical and electrochemical properties can be tailored to use them ...as solvents for different applications, i.e. electrodeposition, catalysis, extraction, etc. This can be done by changing the HBD, as well by adding water. However, the interrelated influence of H2O and HBD on the structure of the electrolyte, and on the behavior of the active species is not fully understood. In this work, we select nickel electrodeposition as a case study and we combine electrochemical techniques (cyclic voltammetry, chronoamperometry) with UV-vis spectroscopy and molecular dynamics to understand the influence of water and HBD on the electrochemical behaviour of DESs. The unique combination of these different experimental and modelling techniques provides new insights into the field. The addition of H2O changes, not only the interactions between the constituents of the liquid, but also the coordination of metal cations, which is reflected in the electrochemical performance of different DESs. More importantly, we show that, in the presence of very little (between 0.1 wt% and 2.8 wt%) and high (>4.5 wt%) water contents, DESs behave differently, and the changes in their electrochemical behavior are caused by both the complexation of metal cations and the electrolyte transport properties.
In this paper a mechanistic model is elaborated to simulate the corrosion behavior of aluminum–zinc–magnesium coatings on steel. The model is based on the mass transport and reactions of the ions in ...the electrolyte (MITReM). The finite element method has been used, which allows to perform time‐dependent simulations with micrometer scale to study local corrosion effects. The formation of corrosion products and the prediction of electrolyte concentration distributions are compared for different metallic coating compositions. The spatial and temporal simulation of complex precipitates provides an additional tool to validate the model through corrosion product characterization. The simulation results are compared to experimental observations, presented in part I of this paper. The MITReM simulations are limited to the micro‐scale and therefore to small geometries. A link is made with the potential model which can be applied on macro‐scale objects. A qualitative agreement is found between the simulations at both scales and the experiments. Further quantification of this model would optimize the simulations for material design and for predictive maintenance.
In this paper a mechanistic model is elaborated to simulate the corrosion behavior of aluminum–zinc–magnesium coatings on steel. The model is based on the mass transport and reactions of the ions in ...the electrolyte (MITReM). The finite element method has been used, which allows to perform time‐dependent simulations with micrometer scale to study local corrosion effects. The formation of corrosion products and the prediction of electrolyte concentration distributions are compared for different metallic coating compositions. The spatial and temporal simulation of complex precipitates provides an additional tool to validate the model through corrosion product characterization. The simulation results are compared to experimental observations, presented in part I of this paper. The MITReM simulations are limited to the micro‐scale and therefore to small geometries. A link is made with the potential model which can be applied on macro‐scale objects. A qualitative agreement is found between the simulations at both scales and the experiments. Further quantification of this model would optimize the simulations for material design and for predictive maintenance.
A mechanistic model for cut‐edge corrosion is developed and validated. The numerical experiments complement the experimental work (presented in part I of this work) and predict pH distribution, corrosion currents, ion distributions, and the precipitation of corrosion products. Both time dependent and spatially resolved results confirm the limited protection of the substrate by the formed corrosion products.
Corrosion of AlZnMg coated steel in chloride media is a complicated process, which progress is determined not only by the electrode reactions but also by the local pH and formation of soluble and ...insoluble corrosion products. In order to adequately describe and predict the corrosion behavior of steel/AlZnMg cut‐edge, a multi‐ion transport, and reaction model (MITReM) is built. Such model takes into account the transport of species in the solution together with their production/consumption in electrochemical and chemical reactions. The main aim of this work is the validation of a numerical model for describing and predicting corrosion of steel/AlZnMg cut‐edge in immersed conditions. This first part describes the experimental work done to obtain model input parameters and validation measurements. The metallic coatings are characterized experimentally with respect to their composition and microstructure, global and local electrochemical behavior (polarization curves, AESEC, and SVET). Local distribution of corrosion products and local pH are also characterized. No blocking effect of the precipitated corrosion products has been observed and dedicated measurements are performed to validate this observation. Based on the experimental input from this part, numerical models of cut‐edge corrosion with different levels of details are developed in Part II.
Corrosion of AlZnMg coated steel in chloride media is a complicated process, which progress is determined not only by the electrode reactions but also by the local pH and formation of soluble and ...insoluble corrosion products. In order to adequately describe and predict the corrosion behavior of steel/AlZnMg cut‐edge, a multi‐ion transport, and reaction model (MITReM) is built. Such model takes into account the transport of species in the solution together with their production/consumption in electrochemical and chemical reactions. The main aim of this work is the validation of a numerical model for describing and predicting corrosion of steel/AlZnMg cut‐edge in immersed conditions. This first part describes the experimental work done to obtain model input parameters and validation measurements. The metallic coatings are characterized experimentally with respect to their composition and microstructure, global and local electrochemical behavior (polarization curves, AESEC, and SVET). Local distribution of corrosion products and local pH are also characterized. No blocking effect of the precipitated corrosion products has been observed and dedicated measurements are performed to validate this observation. Based on the experimental input from this part, numerical models of cut‐edge corrosion with different levels of details are developed in Part II.
A combination of electrochemical and surface analytical techniques is applied to study the corrosion process of cut edges of aluminized steel with different coating alloy compositions. The outcome are qualitative (rate constants, pH distributions, ..) and quantitative (position and composition of corrosion products) insights. The result of this work is used as input for numerical corrosion modelling and validation of simulation results in part II.
This article links fundamental electrochemical research with its application in the steel industry. Sometimes, electrochemistry is for problem solving the ultimate technique to compete with the most ...powerful analytical techniques nowadays available.
Examples of potentiodynamic scans on steel surfaces and critical pitting temperature measurements on stainless steel surfaces will be shown. An evaluation of the electrochemical techniques is made compared to micro-analytical techniques.
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