<p>In the process of protecting ferrous materials, aluminum coating usually forms a dense oxide film on the surface of the iron-based alloy. However, the capacity of the sacrificial anode is rather insufficient. In order to solve this problem, the microstructure and electrochemical corrosion properties of Al-8Si-3Fe-xIn alloy under low chlorine conditions were studied. The results show that indium (In) dissolves to form In³⁺ and In⁺ reverse plating on the surface of the bare substrate to form a passivation film defect. When the In content is high, the segregated In forms an activation point in the form of a cathode phase. In activates <i>τ</i>₆ phase to form a micro-couple, which improves the non-uniform corrosion. The In-containing corrosion products at the phase boundary hinder the diffusion of Cl⁻. With an increase of In content, the self-corrosion potential (<i>E</i>_corr) of the alloy shifts negatively, and the self-corrosion current density (<i>J</i>_corr) decreases from 6.477 µA/cm² to 1.352 µA/cm², and then increases gradually. However, when the In content is 0.1%, the <i>E</i>_corr of the alloy changes from −0.824 V to −0.932 V, and the <i>J</i>_corr decreases from 6.477 µA/cm² to 4.699 µA/cm², suggesting that the use of sacrificial anode will give the best effect.</p>