The role of spray-primer formulation chemistry towards robustness of adhesion to an epoxy-based electrocoat was examined for a range of coatings representative of those used in automotive OEM applications. For coatings exhibiting degraded adhesion performance, high-resolution X-ray photoelectron spectroscopy (XPS) identified the presence of a surface-active polyether-based anti-cratering agent (ACA) formulated into the epoxy-based electrocoat at the primer/electrocoat interface. The adhesion performance of the better-performing systems was found to be related to the spray-primer’s ability to accommodate the ACA by either absorbing or displacing it from the electrocoat surface, thus diluting it to concentrations no longer adversely affecting adhesion.