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How do Monel 400 Bars perform against chemical acids in industrial plants

austenitic stainless steels corrosion resistance

Industries demand the corrosion resistant alloys that can offer longer life at an economical price. The nickel alloys are valuable in resisting corrosion in sea water and different salt solutions, hydrochloric, hydrobromic and hydrofluoric acids. Nickel alloy Monel 400 has good corrosion resistance, fabrication and welding characteristics. The applications of this super alloy in the chemical process industries are described in this article:

Sea Water: Various marine vessels, oil and coastal units deal with sea water. The sea water is a severely corrosive liquid that can induce pitting, crevice, stress corrosion cracking and uniform attack on the service materials. Biofouling is also a major problem found with sea water. Luckily, Monel 400 bars resist biofouling and other types of corrosion as the alloy contains higher content of chromium and molybdenum in addition of nickel.

Hydrobromic Acid: It is a very strong mineral acid that is used as a solvent for ore minerals for its high boiling point and reducing property. Hydrobromic acid is used in the development of inorganic bromides for the preparation of medicines, adhesives etc. The recommended alloy for use with hydrobromic and other halogen acids are those that consist of high molybdenum such as Hastelloy B-3 and Hastelloy C-2000. The nickel-chromium-molydenum alloys are oxidizing in nature and are suitable for use with these halogen acids.

Hydrochloric Acid: It is a very common chemical that is used in the diverse chemical industries. Hydrochloric acid is very harsh on stainless steels and other metallic materials. The Nickel-Chromium-Molybdenum alloys are the recommended materials for use with HCl acid , Inconel alloy 625 also offer significant resistance to hydrochloric acid. The Nickel-Chromium-Molybdenum materials like Alloy C-2000 and austenitic stainless steels offer considerably better performance than alloy 400.

Hydrofluoric Acid: It is a water soluble form of hydrogen fluoride that is used in diverse chemical applications such as in the development of adhesives, refrigerants and fluoropolymers. Hydrofluoric acid is vigorously severe to skin and if contaminated it causes trouble at the high temperatures. The recommended nickel alloys that offer considerable performance in hydrofluoric acid media are:

Monel 400 and C2000 alloy that offer the highest corrosion resistance. Alloy 400 is the best fit when completely plunged in the acid. In the hydrochloric acid lab experiments, the test time length is crucial that is related to the development of fluoride layers on the alloys.

The nickel alloys are prone to SCC in HF acid so operator should be careful to prevent residual stress in nickel alloy components subjected to the chemical. Stress corrosion cracking in hydrofluoric acid is an interesting concept as the cracks are not similar to those produced by chloride salts. Instead, craze-cracking is induced that increases in the broad-front manner. The alloys such as Inconel 625 do not attain stress corrosion cracking however it is attacked by uniform corrosion that grows more rapidly. C-2000 is found to be resistant to cracking. Nickel based super alloys are fit for different types of equipments required in the development and service of the acid.