In this study, we focused on unraveling the intricate world of intermetallic compound formation at the interface of solid Fe and liquid Al–Mg–Si alloy. Our primary aim was to shed light on the phenomenon of Fe degradation in molten Al alloys. Our investigation led us to discover two distinct intermetallic phases, namely Fe2Al5 and Fe4Al13, each exhibiting unique growth dynamics influenced by the interplay of volume diffusion and interface reactions. Moreover, delving deeper into the mechanics of these processes, we meticulously analyzed the rate-controlling mechanisms governing layer growth, exploring both volume diffusion and interface reactions. Furthermore, we quantified the activation enthalpy associated with these phenomena, enriching our understanding of the energy barriers involved in atom or molecule diffusion across solid-liquid interfaces. The implications of our findings extend far beyond the confines of the laboratory, holding significant promise for real-world applications. These insights into Fe degradation prevention and the enhancement of Al alloy performance when in contact with Fe materials offer exciting prospects for materials design and process optimization across diverse engineering and industrial domains.