An impedance spectroscopy study of the degradation mechanism for a model epoxy coating on mild steel

Geenen, F.M.; Wit, J.H.W. de; Westing, E.P.M. van

doi:10.1016/0033-0655(90)80007-l

Cited by 73 publications

(13 citation statements)

References 5 publications

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“…After 432 h, the EOC abruptly decreases to -0.6 V/(Ag/AgCl/KClsat), very close to that EOC of the substrate, suggesting that the electrolyte may have reached the coating/substrate interface. Other coatings showed at initial immersion times EOC values close to -0.4 V/(Ag/AgCl/KClsat), and at times less than 200 h the EOC values were almost the same of the substrate, indicating electrolyte uptake by the coating and coating degradation as verified by other studies 25 . Fig.…”

Section: Electrochemical Measurementssupporting

confidence: 81%

“…6B), indicating a high degree of degradation. This can be attributed both to a low degree of polycondensation and to the hydrolysis of the siloxane bonds due to electrolyte uptake, generating these preferential pathways for the onset of the corrosion process at the substrate surface 25,37 as also detected in the EIS experiments. The EDS microanalysis of this sample after 240 h of test (Fig.…”

Section: Electrochemical Measurementsmentioning

confidence: 63%

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Influence of Ce(IV) ions amount on the electrochemical behavior of hybrid films in 0.1 mol L-1 NaCl solution

et al. 2019

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In this work, the influence of ceric ions (Ce(SO4)2) addition to the hydrolysis solution on the corrosion protection afforded by organic-inorganic hybrid coating obtained from tetraethoxysilane (TEOS) and 3-methacryloxy-propyl-trimethoxysilane (MPTS) to a carbon steel substrate in 0.1 mol L-1 NaCl solution was studied. Open circuit potential (EOC) and electrochemical impedance spectroscopy (EIS) experiments were carried out and showed that the protection afforded by the organic-inorganic hybrid coating was extremely dependent on the Ce4+ ions amount. These results were in close agreement with optical microscopy observation of the degrading surfaces, both procedures showing that more protective coating was produced when 500 ppm of Ce4+ ions were added to the organic-inorganic hybrid solution. The chemical state of the organic-inorganic hybrid coating investigated by X-ray photoelectron spectroscopy (XPS) indicated that the addition of Ce4+ ions enhances the polycondensation degree of the organic-inorganic hybrid coating leading to a denser siloxane (Si-O-Si) network. A strategy using laser-induced breakdown spectroscopy (LIBS) and UV-Vis spectrometry was set up in order to verify, respectively, the presence of Ce ions within the coating structure and its oxidation state. LIBS results confirmed the incorporation of Ce ions in the coating, which, according to UV-Vis measurements, are mainly in the (IV)-oxidation state.

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Section: Electrochemical Measurementssupporting

confidence: 81%

Section: Electrochemical Measurementsmentioning

confidence: 63%

Influence of Ce(IV) ions amount on the electrochemical behavior of hybrid films in 0.1 mol L-1 NaCl solution

et al. 2019

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“…In both cases, the impedance spectra of specimens with defects have the form of two semicircles (Fig. 1), as was observed earlier [7,8]. One may attribute the first semicircle to the dielectric properties of the polymer layer, and the second to the properties of the electric double layer at the interface "galvanized steel-corrosive solution."…”

Section: Resultsmentioning

confidence: 72%

The effect of chromate pigment on the protective properties of an epoxy prime coat

Zin¹

1999

Mater Sci

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Sheet steels with combined protective coating are widely used in world practice [1 ]. During forge-rolling, one first applies a zinc layer onto a steel sheet by the method of hot-dip galvanizing and, later on, a polymer coating consisting of an epoxy prime coat and an upper polyester layer. An important role is played by the prime coat, which is a promoter of adhesion between the hot-galvanized steel, on the one hand, and the upper polymer layer and anticorrosive modifier, on the other hand. The prime coat must preserve the metal from corrosion even in the case of through damages of the main layer and at the unprotected edges of the sheet. Epoxy prime coats are used for already protected galvanized steels before the spraying of the main polymer coating. The epoxy composition for anticorrosive coatings and prime coats contains epoxy-dianic resin, a plasticizer, a structurizing agent, and a solvent. After curing, such compositions adhere well with the metal and have a high corrosion and chemical resistance [2,3].Thickness of the layer of an epoxy prime coat (-20 ~tm) cannot guarantee a barrier protection of the metal. However, one introduces anticorrosive pigments into the prime coat which protect the metal electrochemically. One of the most generally used anticorrosive pigments for epoxy prime coats are chromate pigments [4]. They are rather efficient in neutral and weak acid media; nevertheless, producers of sheets with polymer coatings try to decrease the content of chromate pigments to 2% because of ecological requirements. At the same time, numerous investigators in the world are searching for less deleterious pigments which can replace chromates. This is possible on the basis of a detailed study of the mechanism of protective action of a chromate pigment dispersed in the volume of an epoxy prime coat.The aim of our investigation is to study the protective properties of an epoxy prime coat with a low content of strontium chromate in the presence of through defects. ExperimentalWe manufactured coatings based on the two-component epoxy composition Epilife of the H. Marcel Guest Ltd. firm (Manchester, England). It consisted of epoxy-dianic resin and polyamide curing agent. The anticorrosive pigment (strontium chromate) with a concentration of 2 mass % was additionally introduced into the composition.Using a special applicator (Sheen instrumentation draw-bar), we obtained a coating of thickness 20-30 ~tm after complete curing. We made a through defect 1 cm in length and 0.1 mm in width in a specimen with area of 3.14.10 -4 m 2 by a sharp scalpel. We structurized the obtained polymer coatings for 24 h at 20~ and additionally subjected them to heat treatment in a thermostat for 6 h at 60~We estimated the protective properties of the prime coats by the method of impedance spectroscopy in a corrosive solution (Table 1) imitating acid atmospheric precipitations in the industrially developed countries of Europe [5] by using a three-electrode electrochemical cell. We used a calomel reference electrode and an additional p...

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“…Alternative fitting procedure of curves, constant phase element [27,45], and most probable equivalent circuit concept have been developed and used for accurate determination of impedance parameters which was used for predicting long-term performance taking into account the complex nature of impedance curves involved in different systems. In this study, impedance parameters could be determined using typical equivalent circuit as in Figure 2 for different stages of degradation.…”

Section: Break Point Frequencymentioning

confidence: 99%

“…The pigments used were mostly quartz to study its effect on the deterioration of coating using Bode plots, open-circuit potential, and lowfrequency impedance. The anticorrosion behavior of different inorganic pigments in epoxy-polyamide [3], degradation of epoxy coating with artificial defect [27,28], and chemical degradation of novolac coatings [29] has been analyzed by EIS to obtain information on the corrosion protection. Epoxies represent perhaps the best combination of corrosion resistance and mechanical properties, when they are crosslinked notably with suitable amines or polyamides [1,6].…”

Section: Introductionmentioning

confidence: 99%

Chemical Degradation of Epoxy-Polyamide Primer by Electrochemical Impedance Spectroscopy

2012

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The degradation of organic-inorganic hybrid materials based on epoxy resin was characterized electrochemically in aggressive chemical electrolyte. In the present study, the hybrid material as primer was prepared from epoxy resin pigmented by zinc phosphate cured with polyamide (EPZ). The hybrid material was coated on mild steel substrate, and the corrosion behavior was studied by electrode-potential time measurements and mainly by electrochemical impedance spectroscopy (EIS) in 5% NaCl solution. The impedance parameters, namely, coating capacitance (C c ), pore resistance (R po ), charge transfer resistance (R t ), double layer capacitance (C d1 ), and break point frequency ( f b ), corresponding to 45• phase angle as a function of time of exposure were estimated. The observed impedance behavior were compared with the established equivalent electrical circuit represents the coated metal/electrolyte interface. Changes in the values of the circuit components given the information on the stages of degradation and physical phenomenon occurring throughout the degradation of primer coating were also been predicted. In addition, information related to the porous nature of the primer, limited passivation effect, and delamination of coating with longer exposure that resulted in the diffusion controlled corrosion of metal are also recognized. Thus, results indicate that the EPZ coating had good corrosion resistance. This could be a nonpolluting alternative to the traditional chromate like environmentally harmful coatings.

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An impedance spectroscopy study of the degradation mechanism for a model epoxy coating on mild steel

Cited by 73 publications

References 5 publications

Influence of Ce(IV) ions amount on the electrochemical behavior of hybrid films in 0.1 mol L-1 NaCl solution

Influence of Ce(IV) ions amount on the electrochemical behavior of hybrid films in 0.1 mol L-1 NaCl solution

The effect of chromate pigment on the protective properties of an epoxy prime coat

Chemical Degradation of Epoxy-Polyamide Primer by Electrochemical Impedance Spectroscopy

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