Corrosion product film (CPF) formation and its beneficial effect on corrosion protection of a Ni advanced weathering steel (WS), 3Ni WS, was investigated under the harsh marine environment in Maldives. The influence of Ni on the structure and the corrosion resistance mechanism of CPF was in detail studied. The CPF of 3Ni WS exhibits superiority in physical structure, phase composition, elemental distribution, and electrochemical properties over that of the conventional WS studied. These advantages are attributed to the formation and aggregation of NiFe₂O₄ in the inner layer of the CPF, which refines the crystal phases, transforms γ-FeOOH to fine-grained α-FeOOH, and forms an electronegative inner layer to resist Cl.