[article]
| Titre : |
Evaluation of organic coatings with electrochemical impedance spectroscopy : Part 3 : Protocols for testing coatings with EIS |
| Type de document : |
texte imprimé |
| Auteurs : |
David Loveday, Auteur ; Bob Rodgers, Auteur ; Pete Peterson, Auteur |
| Année de publication : |
2005 |
| Article en page(s) : |
p. 22-27 |
| Note générale : |
Bibliogr. |
| Langues : |
Américain (ame) |
| Index. décimale : |
667.9 Revêtements et enduits |
| Résumé : |
In Parts 1 and 2 of this Series, we discussed the technology of applying electrochemical impedance spectroscopy (EIS) to organic coatings on a metallic substrate such as aircraft, marine, or industrial maintenance coatings. This article describes several experimental protocols to evaluate these coatings with EIS. These experimental protocols differ primarily in the process used to stress the coating and accelerate the degradation of the coating.
There is no standard recipe for an EIS-based evaluation program that is guaranteed to work for every coating in every environment. This may come in time and, indeed, a standard for EIS evaluation of coatings is under development at ASTM and ISO.3 However, EIS can be employed in a variety of ways to evaluate virtually any coating.
It may be useful to think of EIS as a very sensitive detector that provides a snapshot of coating status. However, a single EIS measurement of an organic coating tells you nothing. To measure coating lifetime or performance, the coating must be stressed to bring about its failure. By making periodic EIS measurements during the stress process, a rate of coating failure can be estimated and a series of coatings may be ranked.
Even though some publications discuss the determination of the time-to-failure of a coating, this may be an unrealistic goal. There are too many variables that separate us from this "Holy Grail", most of which are not related to EIS. A more achievable objective is to use EIS in an experimental program that results in a performance ranking of a series of coatings for use in a specific environment.
The nature of the stress applied to the coating is, of course, very important in several aspects. The experimental design to prompt the failure of the coating must (1) simulate the service environment the coating will encounter and it must not change the failure mechanism.
To use EIS to evaluate a specific coating system, place the coated sample in an environment designed to accelerate the degradation of the coating, measure the EIS curves over time, and identify an "index" that tracks coating quality. The index could be the Coatings Capacitance or the Pore Resistance, for example. The index can be very simple or more complex and we will look at several examples in this article. Unfortunately, all coatings do not fail in the same way, so there is no universal index for assessing coating quality with EIS.
This complex nature of coatings is no surprise to coatings scientists. A coating system may consist of the metal substrate, surface pretreatment, a primer, and one or more topcoats. Results can vary depending on types of coatings, thickness, number of layers, surface treatment, and the nature of the metal substrate. |
| En ligne : |
https://drive.google.com/file/d/18hKXfc0o18eO395PEjMtMddkEoCmfc9W/view?usp=drive [...] |
| Format de la ressource électronique : |
Pdf |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5527 |
in COATINGS TECH > Vol. 2, N° 13 (02/2005) . - p. 22-27
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Evaluation of organic coatings with electrochemical impedance spectroscopy in COATINGS TECH, Vol. 2, N° 13 (02/2005)
