The influence of mechanical and chemical treatments on the environmental resistance of epoxy adhesive bonds to titanium

In this investigation, the effect of mechanical and chemical treatments on titanium for bonding to a rubber toughened epoxy adhesive has been examined. Titanium alloy was roughened using either abrasion or grit-blasting techniques. An air-plasma treatment of the titanium prior to organosilane treatment also improved uniformity of the resultant thin film as determined by AFM and XPS. Grit-blasting significantly increased the titanium surface roughness and increased the alumina character of the surface layers. The fracture toughness of the epoxy-titanium bonds, as measured by the wedge test, was affected by the degree of surface roughness at short humid-exposure times. Further, the addition of a thin organosilane film to the titanium slowed degradation rates and led to higher fracture toughness at longer humid-exposure times.