The results indicate that a ferric sulphate etch or the use of a silane/gritblast/oxygen plasma pretreatment are both suitable as alternative procedures to the chromic acid etch currently used. Plasma pretreatments were found to improve both surface cleanliness and wettability of the aluminium but resulted in lower bond strengths than the chemical pretreatments or gritblasting. The 3-aminopropyltriethoxysilane primer was found to provide adequate bond strengths provided the surface was prepared by gritblasting first. The use of an oxygen plasma etch on a gritblasted surface coated with the 3-aminopropyltriethoxysilane was found to produce strongest initial bond strengths with values exceeding those obtained by chromic acid etching. Possible mechanisms of surface modification were identified using water contact angles, optically stimulated electron emission surface quality measurements and x-ray photoelectron spectroscopy.
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