Service life prediction of organic coatings: electrochemical impedance spectroscopy vs actual service life / Subrahmanya Shreepathi in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 8, N° 2 (03/2011)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 8, N° 2 (03/2011) . - p. 191-200 Titre : Service life prediction of organic coatings: electrochemical impedance spectroscopy vs actual service life Type de document : texte imprimé Auteurs : Subrahmanya Shreepathi, Auteur ; Akshay Kumar Guin, Auteur ; Shrikant M. Naik, Auteur ; Mohan Rao Vattipalli, Auteur Année de publication : 2011 Article en page(s) : p. 191-200 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Durée de vie (Ingénierie) Electrochimie Essais accélérés (technologie) Essais de brouillard salin Spectroscopie d'impédance électrochimique Index. décimale : 667.9 Revêtements et enduits Résumé : Electrochemical impedance spectroscopy (EIS) is used to derive an expression for predicting the service life of organic coating in a C4-type environment (industrial and costal areas with moderate salinity) as defined in ISO 12944 standard for paints and varnishes—corrosion protection of steel structures by protective paint systems. Three coating systems with a record of 2, 5, and 10 years of durability were selected for the study. The selection was also based on proven composition and dry film thickness (DFT) of the coatings as per ISO 12944. Electrochemical impedance measurements of the paint-coated panels were carried out by exposing the coated mild steel panels without scribe in different corrosive environments such as immersion in NaCl solution, neutral salt spray, etc. Neutral salt spray exposure was found to be the most severe corrosive environment among all the three coating systems. In most of the cases, EIS gave early indication of coating failure when compared to visual defects such as blistering and over-film corrosion. Note de contenu : - EXPERIMENTAL : System 1 : Low durable system for normal inland System 2 : Mdium durable system for coastal environment - RESULTS AND DISCUSSION : Exposure to immersion in 3.5 % NaCl Exposure to ASTM B117 (neutral salt spray) ASTM G85 (Prohesion cabinet test) ASTM D5894 (cyclic corrosion test) Immersionin 10 % HS2O4 and NaOH Service life prediction DOI : 10.1007/s11998-010-9299-5 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-010-9299-5.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=11361 [article]

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Water transportation through organic coatings : correlation between electrochemical impedance measurements, gravimetry, and water vapor permeability / Subrahmanya Shreepathi in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 9, N° 4 (07/2012)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 9, N° 4 (07/2012) . - p. 411-422 Titre : Water transportation through organic coatings : correlation between electrochemical impedance measurements, gravimetry, and water vapor permeability Type de document : texte imprimé Auteurs : Subrahmanya Shreepathi, Auteur ; Shrikant M. Naik, Auteur ; Mohan Rao Vattipalli, Auteur Année de publication : 2012 Article en page(s) : p. 411-422 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Humidité -- Absorption Infiltration Perméabilité Revêtements -- Effets de l'humidité Revêtements organiques Spectroscopie d'impédance électrochimique Vapeur d'eau Index. décimale : 667.9 Revêtements et enduits Résumé : A primary cause of coating failure is diffusion of water through organic coatings during which many corrosive species are transported to the metal-coating interface. However, water vapor permeability through the coating improves blister resistance to a certain extent. The present work describes the influence of chemical nature of the polymer on the above two properties. Attempts were also made to establish a correlation between these two properties for pigmented organic coating. Six paints were formulated and processed using six different types of binders at a constant pigment volume concentration (PVC) and specific gravity. Water ingress, water vapor permeability, and water absorption of these coatings were estimated using electrochemical impedance measurements (EIS), permeability cup method, and gravimetric method, respectively. There exists a good linear correlation between water uptake measured by EIS and water absorption measured by gravimetry. Similarly, a correlation was also noticed between water uptake by EIS and water vapor permeability. However, polyurethane type polymers did not fit into this linear correlation. Furthermore, influence of the resin chemistry on anticorrosive properties of these coatings was also studied using EIS and salt spray exposure test. Among all polymers under investigation, acrylic polyol-based polyurethane has shown the lowest water uptake, higher impedance, better salt spray resistance but higher water vapor transmission rate. Note de contenu : - EXPERIMENTAL : Materials and reagents - Processing of paints - Characterization - RESULTS AND DISCUSSION : Water uptake by EIS - Water vapor permeability - Water absorption measurements - Role of resin on corrosion protection performance - Salt spray exposure studies DOI : 10.1007/s11998-011-9376-4 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-011-9376-4.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15992 [article]

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