Preventing coating problems and failures on bolted bridge connections / James D. Machen in JOURNAL OF PROTECTIVE COATINGS & LININGS (JPCL), Vol. 33, N° 12 (12/2016)  

[article]  inJOURNAL OF PROTECTIVE COATINGS & LININGS (JPCL) > Vol. 33, N° 12 (12/2016) . - p. 12-19 Titre : Preventing coating problems and failures on bolted bridge connections Type de document : texte imprimé Auteurs : James D. Machen, Auteur Année de publication : 2017 Article en page(s) : p. 12-19 Langues : Américain (ame) Catégories : Anticorrosifs Anticorrosion Assemblages à boulons Métaux -- Revêtements:Métaux -- Peinture Ponts -- entretien et réparations Ponts métalliques -- Revêtements protecteurs Index. décimale : 667.9 Revêtements et enduits Résumé : Rather than describe a failure that has already occurred, this article addresses key steps to follow when painting bolted connections in order to prevent failures from occurring by focusing on surface preparation and painting practices that have been used successfully on bolted bridge connections such as splice plates and gusset connections for new construction projects or new steel additions to existing bridges. Larger connection surfaces are typically shop blast-cleaned and shop primed only with an inorganic or organic zinc-rich primer and then bolted together in the field using hot-dipped-galvanized (HDG) or mechanically galvanized bolt assemblies consisting of a nut, bolt and washer. Smaller shop-primed connections are sometimes bolted in the shop prior to shipping. Field finish painting of bolted connections is typically accomplished using an epoxy intermediate coat followed by a urethane finish coat. However, some bridge owners specify the application of an organic zinc-rich primer on mechanically galvanized bolt assemblies prior to the epoxy intermediate and urethane finish. Because galvanized bolt assemblies (as opposed to plain black bolts) are typically used in conjunction with steel connections primed with zinc-rich primer in the shop, that is our focus here. While the paintable surface area of bolted bridge connections is small compared to the whole structure, on larger structures, individual connections can contain dozens or even hundreds of closely spaced bolt assemblies. Because the bolt assemblies have a more complex configuration and are spaced so closely, cleaning and painting these surfaces presents challenges that require more time, effort and expense to properly complete, versus other bridge surfaces. Proper painting of bridge connections is critical because these are the surfaces where premature coating problems often begin. Standard practices used by various bridge owners and recommended by paint manufacturers are addressed in this article. Note de contenu : - Surface preparation of galvanized bolt assemblies - Preparing rust and damaged galvinizing on bolt assemblies - Removal of nut lubricants from bolt assemblies - Additional nut lubricant options - Paint application on bolt assemblies - FIGURES : 1. The two bottom rows of bolts show damage to the galvanizing caused by tightening with too large of a socket - 2. This photo shows nut lubricant on hot-dipped-galvanized bolt assemblies (green, left) and mechanically galvanized bolt assemblies (blue, right) - 3. This photo depicts both the pre-cleaning and post-cleaning conditions of bolt assemblies. For this test, solvent cleaning with MEK was most effective for removing the blue-colored nut lubricant En ligne : http://www.paintsquare.com/archive/?fuseaction=view&articleid=5971 Format de la ressource électronique : Web Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28378 [article]

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