In the aviation industry, enhancing the corrosion resistance of metal components is crucial. Nickel coatings are commonly used for their protective properties, but they often have defects like porosity and coarse grains. This study investigates the addition of cerium (Ce), a rare earth element, to improve nickel coatings’ performance. NiCoCe alloy layers were electroplated onto Q235 steel, a material used in aircraft structures. The coatings were then modified through heat treatment and evaluated for corrosion resistance using immersion tests and electrochemical experiments. Results showed that at a current density below 0.04 A/cm2, increasing the current density refined the coating’s grains, enhancing compactness and corrosion resistance. However, excessive current density led to coarser grains and more surface defects, reducing corrosion resistance. The addition of Ce improved corrosion resistance by refining the grains. Heat treatment at 300–500 °C decreased corrosion resistance due to grain growth and reduced stability of surface oxides. These findings are significant for developing advanced coatings for aviation materials, where superior corrosion resistance is essential for aircraft component longevity and safety.