The interfacial morphologies and erosion-corrosion behavior of directional Fe-3.5wt.% B steel in flowing liquid Zn-0.30wt.% Al were investigated. Adding 0.30wt.% Al to liquid zinc significantly improved the erosion-corrosion resistance of directional Fe-3.5wt.% B steel, which possesses greater erosion-corrosion resistance when the [002] orientation of Fe2B is perpendicular to the erosion-corrosion interface. The erosion-corrosion interface consisted of an inhibition layer, determined by 0.30wt.% Al, liquid zinc temperature and Fe2B orientation. This interface inhibited the diffusion, controlled Fe2B failure mode, resisted micromechanical scouring, and suppressed erosion-corrosion. Deterioration of the inhibition layer at the erosion-corrosion interface resulted in severe erosion-corrosion damage.