Possibilities for Life Time Prediction of Organic Coatings with Electrochemical Impedance Measurements

Wit, J.H.W. de; Lenderink, H.J.W.; Weijde, D.H. van der; Westing, E.P.M. van

doi:10.4028/www.scientific.net/msf.192-194.253

Cited by 9 publications

(6 citation statements)

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“…8, that is, the delaminated area induces a higher capacitance in accordance with de Wit's results. 30 As expected, R f is high in the mercury cell, but is not infinite, therefore the ionic conduction through the polymer film takes place even with mercury cell.…”

Section: Table I Results Of Regression Calculation On the Basis Of Tmentioning

confidence: 70%

Electrochemical Impedance Spectroscopy of Epoxy-Vinyl Coating in Aqueous Medium Analyzed by Dipolar Relaxation of Polymer

Duval

Keddam²,

Sfaira

et al. 2002

J. Electrochem. Soc.

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The performance of electrochemical devices, namely, the potentiostat, has increased considerably lately, and some commercial devices determine impedance on the order of teraohms (10 12 ⍀). At the same time, the protective effectiveness of paint films has also improved markedly, and the paint films exhibit capacitance behavior only in the millihertz range. Up to now, electrochemical impedance spectroscopy ͑EIS͒ spectra of polymer-coated specimens were interpreted with a mechanism involving only the film resistance due to flaws through the polymer layer and the film capacitance. However, since almost no flaw should be present at huge impedance, a new insight in the modeling of EIS data for polymer coated metal electrode is needed. Therefore, the concept of dipolar relaxation developed in polymer science is introduced to interpret EIS data. To compare the dipolar relaxation and the electrode impedance, the Cole-Cole capacitance determined straightforwardly from impedance spectra was found to be a very powerful tool. It is shown that the water uptake of a paint film could be evaluated from the Cole-Cole capacitance at infinite frequency C(ϱ), because the plasticizing effect induced by absorbed water in lower frequencies may lead to an overestimation of water uptake.Organic polymer coatings are widely used to reduce the corrosion of metallic structures exposed to aggressive media. Generally, it is considered that the paint film acts as a barrier layer that isolates the substrate metal from aggressive agents. 1,2 Therefore, the water uptake and ion migration inside the coating are determining factors of protective performance. [3][4][5] Electrochemical impedance spectroscopy ͑EIS͒ constitutes a powerful tool to evaluate these parameters. The EIS technique was applied for the first time in the early 1970s to the corrosion study for evaluating the protective effectiveness of paint film. 3 In early work, the measured impedance was low, and the resistance of organic coating was associated with the ionic conductance of electrolyte due to coating film breakdown, such as pores or crevasses. Electrolyte is then directly in contact with substrate metal, and the corrosion process takes place at delaminated areas of coating. This model is largely applied even in these days, and describes many corrosion circumstances. 6-8 In the last decade, the performance of electronic devices is considerably improved, which allows the measurements of higher and higher impedances. Nowadays, the measured modulus is huge, on the order of teraohms. 9 EIS becomes then sensitive to the intrinsic film conductance, due to ionic impurities in the film. The mobility of macromolecular chains and that of ions inside polymer layer becomes the determining factor of the film properties. Consequently, it becomes necessary to associate the EIS spectra to the relaxation of organic macromolecules and intrinsic ionic conduction. 10 A coating of epoxy-vinyl paint often protects pumping stations and tubing with mild steel structures in agricultural irrigation system...

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Section: Table I Results Of Regression Calculation On the Basis Of Tmentioning

confidence: 70%

Electrochemical Impedance Spectroscopy of Epoxy-Vinyl Coating in Aqueous Medium Analyzed by Dipolar Relaxation of Polymer

Duval

Keddam²,

Sfaira

et al. 2002

J. Electrochem. Soc.

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“…Blister formation can occur as a consequence of underpaint corrosion by anodic undercutting, 4,29,40,41 corrosion product wedging, 30 cathodic delamination, 2,3,29,30 or by chemically induced loss of adhesion, 42,43 as well as osmotic effects. 28,44,45 In the mechanisms that involve underpaint corrosion processes, generally galvanic coupling between heterogeneous sites such as IMC and the matrix is involved.…”

Section: Discussionmentioning

confidence: 99%

“…15 Blister formation and filiform corrosion are important modes of coating failure on aluminum alloys like AA2024-T3. [21][22][23][24][25][26][27][28][29] Filiform corrosion occurs in humid air in the presence of chloride, whereas blister formation dominates in full immersion. 30 Upon immersion in NaCl solutions, solution-filled blisters form on polyurethane-and epoxy-coated AA2024-T3.…”

mentioning

confidence: 99%

In Situ Confocal Laser Scanning Microscopy of AA2024-T3 Corrosion Metrology

Schneider

Ilevbare

Kelly

et al. 2007

J. Electrochem. Soc.

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Epoxy-coated AA2024-T3 samples were exposed to solutions of specific chloride concentration and pH. Underfilm corrosion processes were monitored in situ with confocal laser scanning microscopy. In near-neutral solutions, pitting at both intermetallic compounds and within the alloy matrix was observed during coating blister formation and growth. Evidence for anodic undermining/corrosion product wedging was obtained. In addition, general corrosion of the matrix led to a strong roughening of the surface. In acidic NaCl solutions, localized corrosion was observed at the original blister site. Thereafter, general attack on the Al-matrix near the original blister was more important than intermetallic particle corrosion. In acidic sulfate solutions, the coating started to fail at many locations on the sample at the same time due to attack of the coating and loss of adhesion at the interface. This more global failure is in agreement with electrochemical impedance measurements and the observation of numerous blisters on large-area panels.

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“…Application of EIS to coatings is not being considered in this section. References [58,60] and [68][69][70][71][72][73] are provided as places to start for information on coating evaluation.…”

Section: E Corrosion Prediction Using Electrochemical Impedance Specmentioning

confidence: 99%

Practical Corrosion Prediction Using Electrochemical Techniques

Silverman¹

2011

Uhlig's Corrosion Handbook

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Possibilities for Life Time Prediction of Organic Coatings with Electrochemical Impedance Measurements

Cited by 9 publications

References 0 publications

Electrochemical Impedance Spectroscopy of Epoxy-Vinyl Coating in Aqueous Medium Analyzed by Dipolar Relaxation of Polymer

Electrochemical Impedance Spectroscopy of Epoxy-Vinyl Coating in Aqueous Medium Analyzed by Dipolar Relaxation of Polymer

In Situ Confocal Laser Scanning Microscopy of AA2024-T3 Corrosion Metrology

Practical Corrosion Prediction Using Electrochemical Techniques

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