First, to identify the cause of failure for both the coated and uncoated material. Second, to identify and provide the necessary guidelines to assure excellent field performance of the applied material. Third, to develop a quality control field testing procedure that will identify whether the primer is in a condition for exterior exposure and/or topcoating.

The study has been completed, and the results published in Adhesion Criteria Between Water-Based Inorganic Zinc Coatings and Their Topcoats for Steel (FHWA-RD-98-170 - 3/99, PDF). The report presents the more practical results of the study. It demonstrates that environmental conditions may be a contributing cause of the failures but are not the primary cause. Substrate salt contamination and improper mixing of the coating were shown to cause freckle rusting. Acrylic topcoat delamination was related to residual alkaline compounds on the primer surface. The surface pH was reduced by applying a dilute acid solution or by weathering for 2 weeks in a northeastern marine atmosphere. Additional ways of reducing the surface pH (weathering or otherwise) should be investigated.