There are many professional terms for valve materials, such as fluorine alloy, 304316, etc. Today we are going to introduce one of the valve materials, which we call "nickel molybdenum alloy".
When the mass fraction of molybdenum in nickel molybdenum alloy exceeds 16%, the corrosion resistance in hydrochloric acid is significantly improved, which is due to the influence of molybdenum content in nickel molybdenum alloy on the corrosion resistance (in hydrochloric acid). And their modified alloys have high molybdenum content and good corrosion resistance in hydrochloric acid, especially Hastelloy B, which has good corrosion resistance to all concentrations of boiling hydrochloric acid. Because stainless steel and most other metals and alloys have poor corrosion resistance in hydrochloric acid, nickel molybdenum alloys have poor corrosion resistance to hydrochloric acid, so nickel molybdenum alloys have more valuable corrosion resistance to hydrochloric acid.
In addition to hydrochloric acid, nickel molybdenum alloy can resist the corrosion of non oxidizing acids such as sulfuric acid, phosphoric acid, hydrofluoric acid, bromic acid, formic acid, acetic acid and other organic acids. It also has good corrosion resistance in non oxidizing salt solutions such as aluminum chloride, magnesium chloride, copper chloride, antimony chloride, and wet hydrogen chloride. However, the corrosion resistance of Ni Mo alloy is not good in solutions containing oxidizing ions and oxidizing acids such as nitric acid. When hydrochloric acid and sulfuric acid contain oxidizing salts (including ferric oxide, ferric sulfate, copper chloride, etc.), even with the concentration of ppm, the corrosion rate of nickel molybdenum alloy can be significantly increased. The corrosion of nickel molybdenum alloy will be aggravated when trace nitric acid is mixed in hydrochloric acid. Dissolved oxygen in hydrochloric acid will also increase the corrosion of nickel molybdenum alloy. For example, the hydrochloric acid valve made of nickel molybdenum alloy will intensify the corrosion at the inlet due to the contact between the valve body and the air.
Nickel molybdenum alloy has high nickel content, so it has good chloride stress corrosion resistance. Due to the high content of molybdenum, it has good corrosion resistance to most halogen media. It is commonly used in halogen media containing reducing acids (sulfuric acid, hydrochloric acid, hydrofluoric acid, bromic acid, etc.). It also has good corrosion resistance in the halide catalyst system for manufacturing ethylene glycol.
Nickel molybdenum alloy is called nickel molybdenum alloy because chromium is added in nickel molybdenum alloy in a similar amount to acid resistant steel. SteeloyC, HastellC-4, Hastelloy-276, etc. belong to this category. Because they contain chromium, they can resist the corrosion of oxidizing acids, such as the mixed acid of nitric acid and sulfuric acid, and the mixed acid of chromic acid and sulfuric acid. It can also resist the corrosion of oxidizing salts, such as ferric salt, bivalent copper salt or media containing other oxidants, such as hypochlorite solution with temperature higher than normal temperature. It has good corrosion resistance in seawater, formic acid, acetic acid and wet chlorine, and can also be used in media containing chlorine and chloride.
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