Nickel base alloy has excellent corrosion resistance, and has high corrosion resistance in many substances and even strong corrosive substances. Nickel base alloys have excellent physical and technological properties, but they are generally not used casually because of their high price. However, due to the development trend of high main parameters (temperature, working pressure, material concentration) in the whole process of chemical plants, there are more and more places with strong corrosivity, and the corrosion standards are becoming more and more strict. Therefore, the common machinery and equipment are not only required to be resistant to overall corrosion but also more and more resistant to pitting, stress corrosion, gap corrosion, etc. When selecting raw materials, we should not only consider the one-time project investment cost but also consider the maintenance, depreciation, shutdown loss, and other costs and their safety factors. Therefore, we pay more attention to the stability of the long-term operation of machinery and equipment. This element promotes the use of nickel-based alloys with high corrosion resistance.
At present, most of the nickel base alloys commonly used in the processing and manufacturing industry adopt the models of international standards. Therefore, the following is dominated by the American nickel base wrought aluminum alloy, and a brief and detailed introduction to pure nickel is given.
Pure nickel has good corrosion resistance in hot concentrated alkaline solution, does not cause alkali ductile stress corrosion cracking, and has good corrosion resistance to water, seawater, high- temperature dry fluoride, but is not corroded by oxidizing acid, aqueous solution with reducing agent and most of its molten metal materials. It can corrode and become brittle in gas with high-temperature sulfur content. With the increase of nickel content in stainless steel and nickel base alloy, the corrosion resistance in dilute hydrochloric acid, sulfuric acid, and ammonium sulfate is significantly enhanced, and the stress corrosion resistance in sodium hydroxide solution is also significantly enhanced. The corrosion resistance in caustic soda solution is basically positive correlation with nickel content.
For a pure nickel, the market generally includes NICKEL200 and NICKEL201
Carbon C ≤ 0.15
Silicon Si ≤ 0.35
Manganese Mn ≤ 0.35
Sulfur S ≤ 0.01
Nickel Ni+Cobalt Co greater than or equal to 99
Copper Cu ≤ 0.25
Fe ≤ 0.4
NICKEL200 is mainly used to solve the problem of oxidizing halogen system vapor, alkali solution, non-reducing acid salt, organic acid, and other machinery, equipment, and components. In the application, the temperature should be less than 315 ℃ in the natural environment. NICKEL200 corrosion resistance: corrosion is relatively slow in the air, and HCl has excellent corrosion resistance in various sulfuric acids in the sea. However, it should be used cautiously in HIC acid with high water flow. It is not easy to use in H3PO4 and HNO3. It has very good corrosion resistance in H2SO4, which is only used to block gas, in HF without water at high temperature, in chlorine and HCl at high temperature, and in chlorine and fluorine.