Simplified Chemical Treatments for Improved Adhesive Bonding Durability and Corrosion Protection of High-Pressure Die-Cast Aluminum Alloy AlSi10MnMg

The adhesive bonding of high-pressure die-cast (HPDC) aluminum alloy AlSi10MnMg is extensively applied in the aerospace and automotive sectors. Surface pretreatment of HPDC aluminum prior to bonding is crucial for enhancing bonding strength and durability, as it regulates surface roughness, and chemical properties. Traditional multi-step surface treatments including chromic acid anodizing for HPDC AlSi10MnMg are hazardous, complex, and often fail to balance adhesive bonding durability and corrosion protection, limiting their industrial applicability. This study examined the impact of various chemical treatments on the adhesive bonding performance of an AlSi10MnMg aluminum alloy. The treated surfaces were bonded using a structural adhesive, and bonding performance was evaluated via wedge tests under pristine conditions and after accelerated aging. A scanning electron microscope (SEM) was used to study the surface morphology, chemical composition, and corrosion characteristics of the treated surfaces. Energy dispersive spectroscopy (EDS), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization measurements were employed. Excellent adhesion characteristics, dominated by the cohesive failure of the adhesive, were observed in H2O2-treated samples. The H2O2-treated samples exhibited the shortest initial crack length, indicating a superior baseline bonding quality, and showed minimal crack propagation (only slight extension) after aging under extreme environmental conditions (70 °C and 100% relative humidity for 4 weeks). Electrochemical measurements revealed that the SG200-treated sample achieved the lowest corrosion current density (0.25 ± 0.03 μA/cm2) with an excellent corrosion resistance, while sol–gel-treated samples generally suffered from a poor adhesion, with interfacial failure. This study proposes a simplified, single-step chemical treatment using an H2O2 solution that effectively achieves both a strong adhesive bonding and an excellent corrosion resistance, without the drawbacks of conventional methods. It offers a viable alternative to conventional multi-step hazardous surface treatments.