A seven-element Modified Embedded Atom Method (MEAM) potential comprising Fe, Mn, Si, C, Al, Zn, and O is developed by employing a hierarchical multiscale modeling paradigm to simulate low-alloy steels, inhibition layer, and galvanized coatings. Experimental information alongside first-principles calculations based on Density Functional Theory served as calibration data to upscale and develop the MEAM potential. For calibrating the single element potentials, the cohesive energy, lattice parameters, elastic constants, and vacancy and interstitial formation energies are used as target data. The heat of formation and elastic constants of binary compounds along with substitutional and interstitial formation energies serve as binary potential calibration data, while substitutional and interstitial pair binding energies aid in developing the ternary potential. Molecular dynamics simulations employing the developed potentials predict the thermal expansion coefficient, heat capacity, self-diffusion coefficients, thermomechanical stress-strain behavior, and solid-solution strengthening mechanisms for steel alloys comparable to those reported in the literature. Interfacial energies between the steel substrate, inhibition layer, and surface oxides shed light on the interfacial nanostructures observed in the galvanizing process.