Structural adhesive bonding of galvanized steel and aluminum is widely used in automotive industries. It has been widely noted that surface preparation of steel and aluminum surfaces prior to adhesive bonding plays a significant role in improving the strength of the adhesive bond. In this study, we have employed nanosecond pulsed laser to fabricate two kinds of textures (grid pattern, sinusoidal pattern) on the metal substrate. Superhydrophobic nanosilica coating and silane coating were sprayed on the laser textured substrate, respectively. We have studied effect of the hybrid pretreatment on the adhesive bonding characteristics. A bi-component epoxy adhesive was used to join the treated surfaces and the bond strengths were evaluated via single lap shear (SLS) tests in pristine as well as degraded conditions. Surface morphology, chemistry and wettability of laser textured surface with and without coating were characterized using various surface analytical tools such as scanning electron microscopy and energy dispersive X-ray analysis, optical profilometry and contact angle goniometry. The interfacial characterization and corrosion performance was analyzed by electrochemical impedance spectroscopy (EIS). The effectiveness of the pretreatment process was also confirmed by durability assessment of epoxy-bonded single lap-shear joints after environment exposure to 70°C, 100% R.H. for 4 weeks. Excellent adhesion characteristics with complete cohesive failure of the adhesive were encountered on the hybrid treated surfaces. The hybrid treatment reported in this work is a simple method with the use of laser pretreatment and silane coating being sufficient to produce durable joints.
