Hastelloy C-22 is a nickel-chromium-molybdenum-tungsten austenitic alloy. It has high nickel content and low carbon content. This alloy is used in various applications to resist oxidizing and reducing media. It is welded using gas tungsten-arc welding and submerged arc welding methods. Hastelloy C22 Pipe Fittings resist reducing media, acid environments, and pitting corrosion. The material is also resistant to high temperatures. These fittings are available in different types, including 45-degree elbows and two-joint pipe fittings.
Types of Hastelloy C22 Pipe Fittings
Buttweld Pipe Fittings: Hastelloy C22 Buttweld Fittings are made of nickel alloys such as nickel and molybdenum. It has excellent weldability, resistance to boundary precipitates, and excellent tensile strength. However, the production costs of heat-resistant stainless steel are high because of the high nickel content. Hastelloy pipe fittings are used in chemical, beverage, and pharmaceutical processing. They have good resistance to stress-related corrosion cracking. These fittings are also resistant to crevice corrosion, pitting, and oxidizing media. Moreover, Hastelloy C22 Buttweld Fittings are not sensitive to heating processes. They also resist the formation of grain boundaries in the heat-affected zone. Hastelloy C22 Buttweld Fittings are available in different sizes and shapes. The dimensions are specified according to the ASME B16.9 standard. They are available in different grades, depending on the applications. The prices of Hastelloy c22 Buttweld Pipe Fittings are directly related to the cost of the raw materials.
Seamless Pipe Fittings: Generally, Seamless Hastelloy C22 Pipe Fittings are made up of Nickel-chromium-molybdenum alloy. This material is known for its good resistance to oxidizing media, acid environments, and crevice corrosion. It also has the benefit of being resistant to stress-related corrosion cracking. This material is used in chemical and pulp, and paper industries and in nuclear power plants. Seamless Hastelloy C22 pipe fittings can be fabricated using various welding methods. They are supplied with a phosphate finish, Electro Zinc finishes, or a self-color coating. They are also supplied with a capped end. These are useful in areas with limited clearance.
Resistance Properties of Hastelloy C22 Pipe Fittings to oxidizing media
Compared to other nickel-chromium-molybdenum-tungsten alloys, Hastelloy C-22 has outstanding oxidizing and reducing media resistance. This alloy has also been shown to resist stress-corrosion cracking. Hastelloy C-22 can be machined using conventional machining methods. It has a high resistance to chloride ions-containing oxidizing acids and chloride-ion-containing reducing media. However, it is not suitable for service at high temperatures. Its excellent resistance to oxidizing media makes it a good choice for many applications. Its high nickel content gives it high resistance to corrosion, stress corrosion, and pitting. This alloy is also suitable for chlorinated systems, including waste incineration.
Resistance to High-Temperature attack by Halides
Despite its high corrosion resistance, Hastelloy C-22 alloy is not recommended for service temperatures above 1250 deg F. This is because it can form detrimental phases with temperatures above this range. In addition to its good corrosion resistance, Hastelloy C-22 also exhibits good resistance to oxidizing and non-oxidizing acids. This good resistance happens because a bilayer structure characterizes the passive film of this alloy. This property is accompanied by an inner barrier layer that provides a stable passive behavior.
Interestingly, the corrosion rate of C22 alloy at 50 degC is initially low, but it increases to a maximum after 48-64 hours. This activity is due to the sequential formation of a productive passive film. This process is attributed to the penetration of small-radius halide ions into the base metal. At 70 deg, the corrosion rate increases due to the attack of the grain boundary. The variation in the corrosion rate of C22 alloy is mainly due to two behaviors: accelerated electrochemical reaction and penetration of smaller-radius halide ions. The synergistic effect of these behaviors explains the corrosion behavior variation.
Applications of Hastelloy C22 Pipe Fittings
These pipe fittings are widely used in chemical processing, pickling components, and sulfur oxide cooling towers. This Hastelloy is highly useful for a variety of applications. This Hastelloy C22 Pipe Fitting is used in many industries, such as chlorination systems, chloride-ion-containing oxidizing acids, cellophane manufacturing, and pesticide production. It is also used in nuclear fuel reprocessing, chemical/petrochemical processing, and flue gas desulfurization.