The role of stress and topcoat properties in blistering of coil-coated materials

• Published in: Progress in organic coatings Vol. 68; no. 4; pp. 328 - 333
• Main Authors: Prosek, Tomas, Nazarov, Andrej, Olivier, Marie-Georges, Vandermiers, Catherine, Koberg, Dorothe, Thierry, Dominique
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2010
• Subjects: Accelerated testing; Atmospheric humidity; Blistering; Blisters; Coating thickness; Condensation; Curvature; Curvature method; Elevated temperature; Film preparation; Galvanized metal; Galvanizing; Glass transition; Glass transition temperature; Hot-dip galvanized steel; Interfacial bonds; Mechanism; Organic coatings; Paint; Paint films; Painted; Paints; Photoresists; Protective coatings; Stress; Stress development; Stress relief; Stresses; Temperature and relative humidity; Tensile stress; Thermal expansion; Thermal expansion properties; Thickness measurement; Accelerated testing; Blistering; Organic coatings; Mechanism; Stress
• ISSN: 0300-9440; 1873-331X; 1873-331X
• DOI: 10.1016/j.porgcoat.2010.03.003

The effect of topcoat properties on the tendency of painted materials to blistering was studied. Six topcoats were applied on identical panels of hot-dip galvanized steel painted with a polyester primer. The tendency to blistering was assessed under the conditions of permanent condensation in a Q-panel condensation test at 60 °C. Internal tensile stress and stress development in organic coatings during temperature and relative humidity cycling were investigated by the cantilever curvature method. Although blisters originated from the metal/polymer interface, the extent of blistering was strongly influenced by the topcoat. Available data suggest that it may increase with the coating thickness, glass transition temperature ( T g) and thermal expansion properties. Connection was found between the internal tensile stress formed in topcoats during the paint film preparation and the extent of blistering. A hypothesis that stress-assisted interfacial bond hydrolysis was responsible for blister initiation is proposed. Other experiments suggested that local paint buckling over non-adherent sites can be caused by plastic deformation of the paint due to relief of compressive stress generated at elevated temperature or by ingress of water.