Corrosion Resistant Alloys

Alloy 22 is a fully austenitic, nickel-chromium-molybdenum-tungsten alloy with better overall corrosion resistance compared to other nickel-chromium-molybdenum alloys, including alloy C-276, alloy C4 and alloy 625. The high chromium content provides good resistance to oxidizing media while the molybdenum and tungsten content gives good resistance to reducing media. This combination of corrosion resistance makes alloy 22 particularly useful in applications where mixed acids are present.

Alloy B-2 is a solid solution strengthened, nickel-molybdenum alloy typically used in extreme reducing conditions. Alloy B-2 has significantly lower carbon, silicon and iron compared to the predecessor, alloy B (UNS N10001). Compared to alloy B, alloy B-2 is less susceptible to weld zone corrosion in the as-welded condition.

B-3® Alloy is an additional member of the nickel-molybdenum family of alloys with excellent resistance to hydrochloric acid at all concentrations and temperatures. It also withstands sulfuric, acetic, formic and phosphoric acids, and other non-oxidizing media. B-3® alloy has a special chemistry designed to achieve a level of thermal stability greatly superior to that of it predecessors, e.g. B-2 alloy.

Nickel 200 and Nickel 201 are solid solution strengthened, commercially pure wrought alloys. The elemental restrictions of both alloys are combined into one, dual-certified chemistry, resulting in a single alloy with the desired characteristics of both alloys. When operating temperatures are expected to exceed 600°F, carbon content becomes critical. The lower carbon content of Nickel 201 makes the material resistant to graphitization and therefore less subject to embrittlement.

Alloy 400 is a single phase, solid-solution nickel-copper alloy that offers superior resistance to many corrosive environments over temperatures ranging from sub-zero to 800°F. This alloy is only hardenable through cold working, rather than heat treatment. The Curie Temperature of this alloy lies in the ambient temperature range and is affected by variations in the alloy’s chemical composition. Caution is advised in applications where strong nonmagnetic characteristics are desired. The ratio of copper to nickel in alloy 400 is almost identical to that found in the ore the metal is derived from.

Alloy 405 is a nickel-copper alloy that is an enhanced machining version of alloy 400. A controlled amount of sulfur is added to improve machinability. Corrosion resistance characteristics and physical properties are similar to alloy 400, but the mechanical property ranges differ slightly. Alloy 405 can be slightly magnetic at room temperature, like alloy 400.

Alloy K-500, commonly referred to as “K-MONEL®”, is a precipitation hardenable, nickel-copper alloy. It has similar corrosion resistance to that of alloy 400, with the additional advantage of greater strength and hardness. The additions of aluminum and titanium to the nickel-copper base allow for subsequent heat treat that increases the mechanical properties. Alloy K-500 also has low magnetic permeability and strong non-magnetic characteristics over a wide range of temperatures, including subzero.

Alloy 625 is a nickel-chromium-molybdenum alloy that is used for its high strength, high toughness and excellent corrosion resistance. The strength of alloy 625 is derived from the stiffening effect of molybdenum and niobium on its nickel-chromium matrix. Although the alloy was developed for high temperature strength, its highly alloyed composition also provides a significant level of general corrosion resistance.

Alloy 600 is a nickel-chromium-iron, solid solution strengthened alloy used for applications that require corrosion and elevated temperature resistance. Service temperatures for alloy 600 can be from cryogenic to 2000°F. This alloy also has good workability, weldability and high strength.

Alloy 800H/800HT® are two individual solid solution strengthened, iron-nickel-chromium alloys. They are typically offered as one, dual certified alloy, meeting the chemical composition requirements of both alloys. The principle difference between alloys 800H and 800HT® is the restricted aluminum and titanium content in 800HT®, which results in higher creep and stress rupture properties.

Alloy 20 is a nickel-iron-chromium based, austenitic alloy with excellent corrosion resistance in chemical environments containing sulfuric acid and many other aggressive media. This alloy is stabilized with niobium to resist intergranular corrosion. Alloy 20 may provide potential cost savings when carefully compared to higher nickel-based alloys, while out performing standard stainless steels.

Alloy F255 is a highly alloyed, super duplex (ferrite-austenite) solid solution strengthened alloy, which provides high strength and wear resistance while offering superior corrosion resistance compared to 316 stainless steel. This alloy also offers better resistance to stress corrosion cracking as well as crevice and pitting corrosion than lower alloyed materials.

Alloy 6B is a cobalt-based alloy with great wear, erosion and abrasion resistance. The wear resistance of alloy 6B is due to the chemical composition and is not a product of heat treatment or other hardening mechanisms. The low coefficient of friction of alloy 6B allows it to resist seizing and galling; proving useful in areas and applications where lubrication is difficult or impractical.

Titanium Grades 1, 2, 3 and 4 are commercially pure (99% minimum titanium). Each grade has slight variations in chemical composition that affect mechanical properties and design capability. The corrosion resistance is similar across all four grades. Titanium is light weight, exceptionally corrosion resistant and often exceeds the corrosion resistance of stainless steels in most environments. Of the four commercially pure (C.P.) titanium grades, Grade 2 is the alloy of choice for most industrial applications that require good ductility and corrosion resistance.