Silanisation of adhesively bonded aluminium alloy AA6060 with γ-glycidoxypropyltrimethoxysilane. I. Durability investigation

The wedge test was used to determine the durability of adhesively bonded joints of pretreated aluminium alloy AA6060 in a hydrothermal environment. Testing of joints bonded with the one-component epoxy adhesive XD4600 showed that the durability was higher for surfaces that were grit-blasted with alumina than for alkaline etched, FPL-etched, and sulphuric acid anodised surfaces. All these surfaces performed much better than those abraded with ScotchBrite®. It was discovered that increased surface roughness improved the durability, while increased surface contamination reduced the durability of the bonded joints. On a very rough surface such as the grit-blasted, the effects of surface contamination were more than outweighed by the effects of surface roughness. Treatment of some of the pretreated surfaces with a 1% aqueous solution of γ-glycidoxypropyltrimethoxysilane significantly improved the durability, but the ranking between the pretreatments was the same as before the silane treatment. The silane treatment also reduced the initial crack lengths of the wedge test specimens. The best performance was seen by the grit-blasting plus silane treatment, which performed much better than the well-established FPL-etch.