Ultra‐Improved Interfacial Strength Between Metallic Surface and Polyurethane via Cost‐Effective Anodizing Process

ABSTRACT Interfacial strength at the metal‐adhesive joint is a pivotal parameter to define adhesive bond reliability and its overall mechanical performance. This study systematically investigates and optimizes sulfuric acid anodizing (SAA) parameters to promote the interfacial strength between aluminum Al2024 (Al) alloy and polyurethane (PU). Response surface methodology (RSM) was employed for the design of experiments by altering acid concentration, anodizing current, and time. Surface roughness and contact angle were measured to assess the effect of these parameters, while scanning electron and atomic force microscopies were employed to elucidate structure‐property relationships. SAA exceptionally enhanced the interfacial strength by increasing the contact area by creating a micro‐ and nano‐porous oxide layer, resulting in a 920% and 15 100% improvement in the single lap shear strength (SLSS) and fracture energy, respectively, after 45 min anodizing. By maximizing SLSS and minimizing cost through time, electric current, and concentration, RSM defined the optimum SAA conditions at 0.4144 M concentration, 1.0907A current, and 5.505 min; experimental measurements validated the optimized outcomes, showing respective increases of 600% and 6700% in SLSS and fracture energy. Also, the failure mode shifted from adhesive to predominantly cohesive mode. Additionally, different machine learning (ML) algorithms were trained using various combinations of anodizing and surface topography features; the most influential parameters were identified while mitigating overfitting despite the limited dataset. Among all tested ML models, support vector regression showed the highest accuracy, achieving a remarkable mean absolute percentage error of ≈11%. The study highlights the effectiveness of SAA to enhance Al/PU interface strength.