Investigation of Coating Delamination Failure from Factory-Primed Galvanized Decking

Abstract A waterborne topcoat had been spray-applied to the underside of a factory-primed galvanized steel deck at an exterior, sheltered location of a shipment station. After nine months, extensive intercoat delamination failure occurred. The root cause of the poor intercoat adhesion was investigated by onsite inspections, review of project documents, and laboratory testing. Infrared spectroscopical analyses were additionally employed to characterize the factory-applied deck primer and to understand its role in the delamination failures. As part of the investigation, five different topcoat products were applied to samples of factory-primed decking. The coating adhesion of these trial specimens was measured and evaluated. The investigation ultimately revealed the use of a topcoat incompatible with the factory-applied deck primer. The results of the investigation were utilized to develop an approach for successful future painting of the factory-applied deck primer.