The difference between NI201 and NI200 alloy
Pure nickel materials such as Ni 200/201 (UNS N02200/UNS N02201) are commercially pure nickel (>99.0%). It has good mechanical properties and excellent corrosion resistance, as well as other useful physical properties, including its magnetic properties, magnetostrictive properties, high thermal and electrical conductivity, etc. The corrosion resistance of Ni 200 makes it particularly useful in applications such as food, man-made fibers and caustic alkalis where product purity is required. It is also widely used in structural applications when corrosion resistance is a major consideration. Other uses include spacecraft and missile parts.
Nickel-based corrosion-resistant alloys include Hastelloy and Ni-Cu alloys. The main alloy elements are Cr, Mo, Cu, etc. They have good comprehensive properties and can resist various acid corrosion and stress corrosion. Monel was the first to use Ni-Cu composition; in addition, there are Ni-Cr alloy (ie nickel-based heat-resistant alloy, heat-resistant corrosion-resistant alloy among corrosion-resistant alloys), Ni-Mo alloy, Ni-Cr-Mo alloy (ie Hastelloy Alloy C series) etc. In terms of corrosion resistance properties, the corrosion resistance of Ni-Cu alloy is better than that of Ni in reducing media, and the corrosion resistance of Ni-Cu alloy is better than that of Cu in oxidizing media. Under conditions without oxygen and oxidants, it is a high-temperature fluorine-resistant alloy. The best material for gas, hydrogen fluoride and hydrofluoric acid; Ni-Cr alloy is mainly used under oxidizing media conditions. It can resist high-temperature oxidation and corrosion from gases containing sulfur, vanadium and other gases. Effective corrosion resistance can only be achieved when the Cr content in the alloy is greater than 13%. The higher the Cr content, the better the corrosion resistance. However, in the case of non-oxidizing In media such as hydrochloric acid, the corrosion resistance is poor. This is because non-oxidizing acids cannot easily form an oxide film on the alloy and also dissolve the oxide film.
Adding elements such as Mo and Cu to the nickel-based alloy can improve the corrosion resistance of the protective layer against reducing acids. For example, Ni-Mo alloy is mainly used under the conditions of reducing medium corrosion and is the best resistant to hydrochloric acid corrosion. An alloy whose corrosion resistance is significantly reduced in the presence of oxygen and oxidizing agents. Ni-Cr-Mo (-W) alloy has the properties of the above-mentioned Ni-Cr and Ni-Mo alloys, and is mainly used under mixed medium conditions of oxidation and reduction. This type of alloy is in high-temperature hydrogen fluoride gas, containing oxygen and oxidants. It has good corrosion resistance in hydrochloric acid, hydrofluoric acid solutions and wet chlorine gas at room temperature. The importance of Mo-containing nickel-based corrosion-resistant alloys is that they can resist both oxidizing and reducing acids. Titanium and stainless steel are only resistant to oxidizing acids. For example, Hastelloy C-276 or C-2000 alloy is a Ni-Cr containing W. -Mo.
Containing extremely low silicon and carbon, it is generally considered a universal anti-corrosion alloy. It has excellent corrosion resistance to most corrosive media in both oxidizing and reducing atmospheres, as well as excellent resistance to pitting corrosion, crevice corrosion and Stress cracking corrosion performance. This type of alloy reduces C and Si, so it can control the precipitation of carbides and improve its corrosion resistance. Because of its characteristics, it is widely used as an application material in harsh environments such as chemical equipment. In addition, Ni-Cr-Mo-Cu alloy is resistant to both nitric acid and sulfuric acid corrosion, and also has good corrosion resistance in some oxidation-reduction mixed acids.
