B-2/N10665, B-3/N10675... The B series is mainly used in reducing acid environments such as hydrochloric acid evaporators and hydrofluoric acid reaction kettles.
Hastelloy B-2 (UNS N10665) is a nickel-molybdenum alloy that takes an extreme 'specialization' approach in the field of corrosion resistance—focusing exclusively on reducing acids but absolutely avoiding oxidizing environments.
📊 Core Properties
The core design philosophy of B-2 is to achieve ultra-strong corrosion resistance through high molybdenum (26-30%) and extremely low carbon (≤0.02%).
· Excellent resistance to reducing acids: It performs exceptionally well in hydrochloric acid (full concentration range) and medium-concentration sulfuric acid. It also exhibits outstanding resistance to organic acids such as phosphoric acid and acetic acid.
· Good resistance to localized corrosion: It offers good resistance to stress corrosion cracking (SCC) and pitting caused by chloride ions.
· Excellent weldability: The extremely low carbon and low silicon design significantly reduces intergranular precipitates in the welding heat-affected zone, meaning corrosion resistance can be maintained in the welded condition.
· ⚠️ Critical Limitation: It must never be used in media containing oxidizing ions (such as Fe³⁺, Cu²⁺), e.g., nitric acid. Otherwise, it will rapidly undergo intergranular corrosion, leading to premature equipment failure. It is also not suitable for long-term service at high temperatures (>650°C) as brittle phases may precipitate.
🏭 Main Application Industries
Its applications are almost entirely concentrated in the chemical industry where handling of strong reducing acids is required:
· Production and transportation equipment for hydrochloric acid, sulfuric acid, phosphoric acid, and acetic acid.
· Chemical process systems containing hydrogen chloride gas.
· Reactors and components for strongly reducing chemical environments such as those involving aluminum chloride catalysts.
In summary: The only reason to choose B-2 is to handle reducing acids, especially hydrochloric acid. If there is even a slight risk of oxidation in the operating conditions, it must be avoided, and more 'versatile' alloys like C-276 should be considered instead.
