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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. Source


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. Source


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. Source


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. Source


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. Source

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