Adding molybdenum can increase the corrosion resistance of nickel in reducing acids, especially hydrochloric acid. With the increase of molybdenum content, the self-corrosion potential of nickel-molybdenum alloy in hydrochloric acid and sulfuric acid gradually moves forward. Generally, the corrosion resistance of the alloy can be significantly improved when the Mo content is ≧ 15%, and when the Mo content reaches 30% , The best effect. Nickel-molybdenum alloys have poor corrosion resistance in oxidizing acid solutions.
The early development of nickel-molybdenum alloy is 0Mo20Ni60Fe20, and its trade name is Hastelloy A, which is resistant to hydrochloric acid corrosion below 70 ° C. Later, alloys such as 0Mo28Ni65Fe5 (HastelloyB), 00Mo28Ni68 (Hastelloy B2), and 00Mo28Ni65Fe5V (Corronel 220), which have higher corrosion resistance and heat resistance, have been successively developed.
HY-Industry is a typical nickel-molybdenum alloy Hastelloy B alloy with a composition code of 0Mo28Ni65Fe5V, which is equivalent to the domestic brand NS321. Its significant advantage is that it is particularly resistant to corrosion in hydrochloric acid. It is resistant to corrosion in any concentration of hydrochloric acid at normal temperature without being filled with air. At present, only Mo, Zr, W, Ta and other metals have better resistance to hydrochloric acid than Ni-Mo alloys. Because Ni-Mo alloys are less resistant to corrosion by oxidizing media, the corrosion rate of Hastelloy B alloy will increase significantly when air is present in hydrochloric acid.
Hastelloy B alloy can withstand the corrosion of hydrofluoric acid below 100 ℃ without air, and the corrosion rate is generally less than 0.150mm / a. In pure phosphoric acid, the corrosion resistance of the alloy is also good when it is not filled with air, and the corrosion rate at any concentration and below 120 ° C is 0.15 mm / a or less. This alloy has good corrosion resistance in acetic acid, glacial acetic acid, or acetic acid containing Cl.
Hastelloy B alloy has good corrosion resistance in alkaline solutions. Under the conditions of concentration ≦ 70% NaOH and temperature ≦ 120 ° C, the corrosion rate is only 0.050mm / a. In 165 ° C, 60% and 191 ° C, 70% NaOH solutions, the corrosion rate is ≦ 0.50 mm / a.
Among high and low temperature neutral and alkaline non-oxidizing salts, Hastelloy B alloy has good corrosion resistance, and the corrosion rate does not exceed 0.1mm / a. However, it is severely corroded in oxidizing acid salts such as ferric chloride, copper chloride, iron sulfate, and copper sulfate. For example, corrosion rates in 2% CuCl2 and 2% FeCl3 solutions are as high as 3.825 and 5.850 mm / a, respectively.
Hastelloy B alloy has good corrosion resistance in the solid solution state, but once welded, it will have a severe tendency of intergranular corrosion in hydrochloric acid and sulfuric acid, knife-shaped corrosion at the weld, and intergranular corrosion in the heat affected zone The two sensitization temperature zones are: a high temperature sensitization zone of 1200 to 1300 ° C and a medium temperature sensitization zone of 600 to 900 ° C. Such an intergranular corrosion tendency cannot be prevented even by a rapid cooling solution treatment.
HY-industry is qualified Nickelalloy&cobalt alloy materials supplier.
We have more than twenty years experience in kind of High temperature alloy production.
Inconel 718, Monel 400，Stellite 6，Stellite 12，Incoloy 800ht，Incoloy 901，Nimonic 80A，Kovar，Invar 36，Inconel 625，Hastelloy C276， Incoloy 825 are mature productes of us.
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