Nickel is located in the fourth period of the periodic table, group viii, and its outer electron configuration is 3D84S2. Nickel has remarkable chemical stability and excellent corrosion resistance. Under atmospheric conditions, pure nickel products are not only extremely difficult to rust, but also in strong alkali corrosion liquid, pure nickel corrosion rate is extremely slow. Some studies have found that the higher the purity of pure nickel products, the more significant the corrosion resistance. Such as atmospheric experimental results show that: purity of 99% nickel in 20 years without rust mark, in aqueous solution, or molten salt, pure nickel can show a very good corrosion resistance, such as in the concentration of 50% boiling caustic soda solution nickel corrosion rate does not exceed 25μ m every year. Moreover, nickel does not react with oxidizing solution, including nitric acid. Like caustic solution, nickel hydrochloric acid, sulfuric acid and organic acid have little effect on its corrosion. Dilute nitric acid has almost no corrosion effect on pure nickel, while the surface of pure nickel will be passivated in concentrated nitric acid, which effectively resist the corrosion of strong acid. In humid air at room temperature, the surface of nickel is oxidized to form a dense NiO film, which isolates the atmosphere and prevents further oxidation of the metal matrix.
