The Effect of Immersion on the Breaking Force and Failure Locus in an Epoxy/Mild Steel System

This paper presents the effects of immersion on the adhesion behavior in a polyamide-cured epoxy system immersed in sodium chloride electrolyte adjusted to three different pH values. The strength of lap shear joints was measured before and after exposure and after redrying. The failure locus was determined on a macroscopic and microscopic level. It was found that a large adhesion loss occurred upon immersion. Most of that loss was recovered upon redrying. All of the breaking force was recovered when the immersion fluid was distilled water. The locus of failure was primarily through the bulk of the adhesive before immersion. After immersion the failure was interfacial with a thin residue of polymer remaining on the metal surface. These results are discussed with respect to earlier work on the water absorption properties of the system.