Effects of primer and annealing treatments on the shear strength between anodized Ti6Al4V and epoxy

Abstract

The effects of primer and annealing treatments on the shear strength between anodized Ti6Al4V and epoxy were investigated. Primer coating improved the shear strength between anodized Ti alloy and epoxy by up to 81.3% using concurrent curing compared with that of control specimens. After annealing of anodized Ti alloy and applying primer, the shear strength of the specimen was further increased by 6.4% due to the formation of stable TiO2 transferred from TiO in the anodization process. SEM analysis revealed the specimen without primer and annealing treatments showed adhesive failure between epoxy–alloy interface and discontinuous cohesive failure of epoxy. Primer coating initiated a new interfacial failure mode between the oxide layer and alloy due to the improved bonding strength between epoxy and oxide layer. In addition, annealing and primer treatments generated large tracts of epoxy continuous cohesive failure, showing good agreement with its higher shear strength and work of fracture.