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Reynolds G.J.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | Barrett Z.S.,University of Swansea | McMurray H.N.,University of Swansea | Williams G.,University of Swansea
Corrosion Science | Year: 2013

A high-throughput method of investigating organic coating delamination from iron substrates incorporating interfacial thin metallic films of varying thickness is presented. Physical vapour deposited aluminium is demonstrated as a means of limiting underfilm oxygen reduction and slowing rates of corrosion-driven cathodic disbondment. A wedge of graded thickness is deposited on an iron surface and over-coated with a model organic layer. After initiating corrosion by applying corrosive electrolyte to a penetrative defect, rates of corrosion-driven delamination are determined by in situ scanning Kelvin probe measurements, enabling the influence of a range of Al thicknesses to be studied on a single sample. © 2013 Elsevier Ltd.


Geary S.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | McMurray H.N.,University of Swansea | De Vooys A.C.A.,Tata Steel
ECS Transactions | Year: 2012

E-SVET describes a novel, Environmentally controlled, Scanning Vibrating Electrode Technique which allows the measurement of localised corrosion current flux under conditions of low oxygen partial pressure. E-SVET replicates the low oxygen partial pressure conditions which occur inside a food can. SVET was utilized to investigate rapid detinning processes initiated in the presence of aerated fruit acid. In this investigation, two corrosion mechanisms were detected; de-tinning on the outer surface of the coating, followed by localised pitting on the iron-tin alloy layer. Corrosion pits were subsequently characterized using White Light Interferometry, a practical method for obtaining detailed information on the geometry of the corrosion pits. © The Electrochemical Society.


Mawali F.A.,Oman Oil Refineries and Petroleum Industries Company | Geary S.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | McMurray H.N.,University of Swansea | Williams G.,University of Swansea
EUROCORR 2013 - European Corrosion Congress | Year: 2013

The Scanning Vibrating Electrode Technique (SVET) was used to characterise localised pitting corrosion occurring on 11% Cr FV566 steam turbine blading steels. Calculations of theoretical pit depths were estimated by the volume of metal mass loss detected by SVET. Volume equations of different conical shapes were used to determine the pit geometries which are correlated with measurements obtained from optical instruments, namely; White Light Interferometry (WLI) and Laser Confocal Scanning Microscopy (LCSM). Initially, difficulties arose where the refractions from the pit to the instrument detector were insufficient, in order to circumvent this drawback, a contrast medium (aluminium flakes) were employed to introduce additional contrast prior to imaging. A quantitative comparison of theoretical pit depth detcted with SVET was conducted and results indicate a weak correlation with WLI whereas a strong correlation with LCSM is observed.


Eaves D.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | Williams G.,University of Swansea | McMurray H.N.,University of Swansea
Electrochimica Acta | Year: 2012

A volumetric measurement of evolved hydrogen is used to quantify rates of corrosion occurring on unpolarized samples of commercially "pure" magnesium immersed in 5% (w/v) aqueous sodium chloride electrolyte. This approach is used to compare rates of uninhibited corrosion with rates occurring in the presence of arsenate and phosphate corrosion inhibitor species dissolved in the experimental electrolyte at concentrations between 10 -4 and 10 -2 mol dm -3. The effective cathode in commercially pure magnesium comprises a population of micron and submicron size iron-rich particles widely dispersed in the magnesium matrix. It is shown that arsenate, but not phosphate, acts to poison the hydrogen atom recombination reaction as it occurs on the surface of these cathodic particles. It is shown that because hydrogen evolution is the predominant cathodic process the onset of H-atom recombination poisoning results in greatly reduced rates of magnesium corrosion. Additional mechanistic information regarding the effect of phosphate and arsenate corrosion inhibitors is obtained through systematically investigating the effect of solution pH on inhibitor efficiency. © 2012 Elsevier Ltd.


Wilson B.P.,University of Swansea | Searle J.R.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | Yliniemi K.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | Yliniemi K.,Aalto University | And 2 more authors.
Electrochimica Acta | Year: 2012

The paper outlines details of a mathematical model and a series of experiments performed to evaluate the extent to which SVET response artefacts are generated when scanning non-planar surfaces. This work establishes guidelines for SVET use and the potential issues that must be taken into account when using SVET to examine the corrosion behaviour of non-planar specimens. Results from the mathematical model indicates that response artefacts will be minimal until the probe/sample angle exceeds 30° off perpendicular; a finding validated by the experimental and literature data. © 2012 Elsevier Ltd. All rights reserved.


Searle J.R.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | Wilson B.P.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | Wilson B.P.,Aalto University | Yliniemi K.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | And 3 more authors.
ECS Transactions | Year: 2015

The three-dimensional Scanning Vibrating Electrode Technique (3D-SVET) has been used to investigate the effects of forming and UV irradiation on model plasticized PVC coatings and specifically the influence on the barrier properties of the coating. In addition, an industrially produced coating that had undergone outdoor exposure (for approximately seventeen years) was analyzed as a comparison. Results from the investigation show a significant correlation between the corrosion observed on the model samples when compared to the naturally weathered material. © The Electrochemical Society.


Geary S.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | McMurray H.N.,University of Swansea | De Vooys A.C.A.,Tata Steel | Williams G.,University of Swansea | Lammers K.,Tata Steel
ECS Transactions | Year: 2015

Isolated Open Circuit Potential (OCP) measurements are performed on pure tin and iron in aqueous malic acid solutions (1-2x10-3mol dm-3). In de-aerated aqueous malic acid solutions ≥1.56x10-2mol dm-3 tin was found to become sacrificial with respect to iron, reversing the polarity predictions on the basis of tabulated EOCP values. In the presence of oxygen polarity reversal is not established. Additions of Sn2+ >10-4 mol dm-3 to aerated 0.1 mol dm-3 aqueous malic acid influences iron to be cathodic with respect tin. However, in the absence of oxygen tin becomes cathodic with respect to iron in 0.1 mol dm-3 malic acid solutions containing Sn2+ >10-4 mol dm-3. Voltammetric measurements indicate a self-limiting displacement mechanism of Sn2+ on the iron surface. Ex-situ XPS surface measurements confirm tin oxide coverage on iron following short immersion times in 0.1 mol dm-3 malic acid containing Sn2+ = 10-3 mol dm-3. © The Electrochemical Society.


Williams G.,University of Swansea | Geary S.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | McMurray H.N.,University of Swansea
Corrosion Science | Year: 2012

Novel calcium(II) and zinc(II)-exchanged pigments based on cross-linked sulphonated polystyrene (CSP) are used in model polymer coatings to inhibit cathodic disbondment on galvanised steel surfaces. An in situ scanning Kelvin probe (SKP) technique is used to quantify coating delamination rates as a function of pigment volume concentration after applying aqueous sodium chloride to a penetrative coating defect. Both in-coating cation types significantly retard delamination rates compared with the un-pigmented case. The performance of CSP is compared with pigments prepared from inorganic cation exchangers and shown to be less effective when incorporating Zn(II) cations, but superior when Ca(II) is present. © 2011 Elsevier Ltd.


Williams G.,University of Swansea | Grace R.,University of Swansea | Woods R.M.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings
Corrosion | Year: 2015

A scanning vibrating electrode technique (SVET) is used to investigate the influence of a selection of potential inhibitor species, including rare earth cations, along with fluoride, chromate, and phosphate anions on the localized corrosion of unpolarized magnesium alloy AZ31 in 5% w/v aqueous sodium chloride electrolyte. Of the inhibitors studied, chromate and phosphate additions are shown to produce the most efficient inhibition of AZ31 localized corrosion. A study of the influence of varying phosphate concentrations showed that inhibition is less complete than that produced on pure Mg, but that the same cathodic inhibition mechanism remains in operation. In contrast, chromate inhibits by acting as a cathodic depolarizer, producing a profound inhibition at a 10-2 mol dm-3 concentration. In situ SVET analysis (with chromate) reveals intense, short lived local cathodes, which couple with a low intensity anode distributed over the majority of the exposed surface. It is proposed that the inhibition mechanism involves the replacement of cathodic hydrogen evolution by a self-limiting chromate reduction to Cr(iii) at cathodic sites, where elevated pH subsequently produces a solid Cr(iii) hydroxide film, thus blocking further electron transfer. © 2015, NACE International.


Searle J.R.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | Glover C.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | Khan K.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | Wilson B.P.,Sustainable Product Engineering Center for Innovative Functional Industrial Coatings | And 3 more authors.
ECS Transactions | Year: 2015

Scanning Kelvin Probe (SKP) and the 3D Scanning Vibrating Electrode Technique (3D-SVET) have been used to examine a selection of bi-metallic coins. The SKP has first been used to identify the electrochemical compatibility of the two alloys and inform a prediction of the anodic and cathodic regions observed in the 3D-SVET experimentation, performed in artificial sweat solution. This is compared to open circuit potential (OCP) measurements, also measured in artificial sweat. It was observed that the SKP in atmospheric conditions records larger potential differences between the alloys than that observed in OCP under immersion conditions, however the relative activity is consistent across all 3 techniques. The 3D-SVET clearly identifies galvanic corrosion as a result of the differences in the galvanic activity between the two alloys. The anodic activity is predominantly on the nickel brass section of the coin, while the cathodic activity remains on the cupronickel portion. © The Electrochemical Society.

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