Environment-dependent corrosion of base, anodized, and welded Aluminum 3000 for food applications.

: This study investigated the corrosion behavior of 3000 series aluminum alloys exposed to simulated food and biological environments (3.5% NaCl, 1% lactic acid, and 1% whey protein) under three different metallurgical conditions (base metal, anodizing, and TIG welding). Using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and long-term gravimetric analysis, the synergistic effects of surface heterogeneity and electrolyte chemistry on the corrosion mechanism were elucidated. For the base metal, the corrosion resistance order was as follows: whey protein > lactic acid ≈ NaCl. Anodizing, by forming a strong oxide layer, changed the corrosion resistance order to: whey protein > lactic acid > NaCl. Notably, TIG welding fundamentally changed the environmental sensitivity of the alloy and changed its corrosion resistance order to: whey protein > NaCl ≈ lactic acid. In the welded samples immersed in whey protein, a unique dual corrosion potential behavior (-0.65 V and -0.44 V) was observed, which was attributed to the electrochemical dichotomy between the fine-grained weld zone and the heterogeneous heat-affected zone (HAZ). The chloride environment primarily causes localized pitting corrosion, while lactic acid causes general chemical dissolution, a process accelerated by the microstructural defects caused by welding. In contrast, whey protein, through selective protein self-assembly, facilitates adsorption-mediated deactivation and significantly suppresses ion release over a 30-day exposure period. These findings emphasize the urgent need for environmental-specific surface engineering in food and pharmaceutical applications and highlight the necessity of careful monitoring to reduce aluminum migration and its associated public health risks.