Corrosion Resistant Alloy
Corrosion Resistant Alloy
The main alloying elements are copper, chromium and molybdenum. It has good comprehensive properties and is resistant to various acid corrosion and stress corrosion. The earliest application (produced in the United States in 1905) is nickel-copper (Ni-Cu) alloy, also known as Monel alloy (Monel alloy Ni 70 Cu30); in addition, nickel-chromium (Ni-Cr) alloy (that is, nickel-based heat-resistant alloy) , heat-resistant corrosion-resistant alloys in corrosion-resistant alloys), nickel-molybdenum (Ni-Mo) alloys (mainly refers to Hastelloy B series), nickel-chromium-molybdenum (Ni-Cr-Mo) alloys (mainly refers to Hastelloy C series), etc.
At the same time, pure nickel is also a typical representative of nickel-based corrosion-resistant alloys. These nickel-based corrosion-resistant alloys are mainly used in the manufacture of components for various corrosion-resistant environments such as petroleum, chemical, and electric power.
Nickel-based corrosion-resistant alloys mostly have austenite structure. In the state of solid solution and aging treatment, there are also intermetallic phases and metal carbonitrides on the austenite matrix and grain boundaries of the alloy. Various corrosion-resistant alloys are classified according to their components and their characteristics are as follows:
The corrosion resistance of Ni-Cu alloy is better than that of nickel in reducing medium, and its corrosion resistance is better than that of copper in oxidizing medium. The best material for acids (see Metal Corrosion).
Ni-Cr alloy is also a nickel-based heat-resistant alloy; it is mainly used in oxidizing medium conditions. It is resistant to high temperature oxidation and corrosion of gases containing sulfur and vanadium, and its corrosion resistance inases with the inase of chromium content. These alloys also have good resistance to hydroxide (such as NaOH, KOH) corrosion and stress corrosion resistance.
Ni-Mo alloys are mainly used under the conditions of reducing medium corrosion. It is one of the best alloys for corrosion resistance to hydrochloric acid, but in the presence of oxygen and oxidants, corrosion resistance deases significantly.
The Ni-Cr-Mo(W) alloy has the properties of the above-mentioned Ni-Cr alloy and Ni-Mo alloy. Mainly used under the condition of oxidation-reduction mixed medium. Such alloys have good corrosion resistance in high temperature hydrogen fluoride, in hydrochloric acid and hydrofluoric acid solutions containing oxygen and oxidants, and in wet chlorine gas at room temperature. Ni-Cr-Mo-Cu alloy has the ability to resist both nitric acid and sulfuric acid corrosion, and also has good corrosion resistance in some oxidative-reductive mixed acids
