CATHODIC DISBONDMENT RESISTANT EPOXY POWDER COATING COMPOSITION AND REINFORCING STEEL BAR COATED THEREWITH

摘要

A thermosetting epoxy resin powder coating composition is provided thatcomprisesan epoxy resin composed of a diglycidyl ether of bisphenol A, a curing agentcomposed of abisphenol A endcapped diglycidyl ether of bisphenol A, and a cure catalystcomposed of animidazole adducted to a diglycidyl ether of bisphenol A, in which the ratio ofcuring agent toepoxy resin is below 70 % stoichiometry, and preferably between about 10% and60%stoichiometry. The thermosetting epoxy resin powder coating composition notonly exhibitsthe desired flexibility and fast cure speeds, but also exhibits superioradhesion and superiorresistance to delamination and cathodic disbondment, preferably havingcathodic disbondmentvalues typically less than 4 mm radial disbondment, and preferably less than 2mm radialdisbondment. Such properties are highly advantageous for protective powdercoatings usedon rebars and pipelines. The marked improvement in adhesion combined with goodflow outbehavior provide the thermosetting epoxy resin powder coating composition withthe abilityto effectively adhere to steel strappings and other dirty, oily and scalymetallic substrates. Thethermosetting epoxy resin powder coating composition also begins to cure atvery lowtemperatures for acceptable oven bake times. This property is highlyadvantageous forprotective and decorative powder coatings used on wood and other heatsensitive substrates.