<p>Hard alloys are indispensable in modern manufacturing fields such as aerospace, metallurgy, and electronic communication due to their high hardness, excellent wear resistance, and red hardness. However, the cobalt binder in WC–Co alloys is prone to corrosion, leading to selective dissolution, depletion of the binder, and loosening of the hard phase, thereby limiting service life. This article reviews the latest progress in the corrosion protection of hard alloys. Firstly, the article traces the development of hard alloys and emphasizes key innovations: protective coatings, gradient structures, and nanocrystalline treatment. Secondly, the article summarizes the main types of corrosion, including galvanic corrosion, fatigue corrosion, high-temperature corrosion, and friction corrosion. It explains how each type of corrosion damages the microstructure (e.g., grain coarsening, binder loss) and the mechanical properties (e.g., hardness, strength). Thirdly, the article outlines three core mitigation strategies: (i) adding chromium or nickel as the binder; (ii) using surface coatings such as CrN or TiB₂; (iii) optimizing cleaning and treatment to reduce corrosion triggers. This review provides a concise and practical basis for designing hard alloys with high strength and long-lasting corrosion resistance.</p>