As new processes are developed and cleaning procedures become increasingly harsh, demands on materials are greater than ever. To compound the problem, for several years steel producers have been employing a method known as “alloy shaving.” This technique limits the concentrations of the steel alloying elements to the low end of the allowed ASTM range. The resulting steel meets the ASTM specification, but the overall mean corrosion resistance is lower than that of steels produced to the same specification 25 to 30 years ago.

Austenitic stainless steels are made using up to 80% scrap iron. Not only is stainless steel an alloy of iron, but depending on the fabrication process, it can be loaded with tramp elements and inclusions detrimental to finishing requirements and corrosion resistance. Austenitic stainless steels have been the workhorse of the sanitary food and pharmaceutical industry for years. However, for reasons mentioned above, processors are beginning to use more corrosion resistant alloys to achieve the required life-cycles for their systems. One such material is Hastelloy^® C-22^®.

C-22 alloy is one of the most versatile nickel-chromium-molybdenum-tungsten alloys available today. This alloy demonstrates improved corrosion resistance to both uniform and localized corrosion and will exceed the performance of C-276, C-4 and alloy 625 in a variety of corrosive environments.

C-22 Nominal Chemical Composition, wt%

Ni	Co	Cr	Mo	W	Fe	Si	Mn	C	V
56	2.5	22	13	3	3	0.08	0.50	0.01	0.35

The high chromium (Cr) content contributes to the alloy's outstanding resistance to pitting, crevice corrosion and stress corrosion cracking. C-22 has excellent resistance to oxidizing aqueous media, including wet chlorine and nitric acid mixtures or oxidizing acids with chloride ions. Molybdenum (Mo) and tungsten (W) supply the resistance to wet reducing media (e.g. hydrochloric and sulfuric acids). The high level of nickel (Ni) is responsible for the alloy's resistance to attack by chlorides, fluorides and other halide compounds at ambient and elevated temperatures.

Because of such versatility, it can be used in applications where “upset” conditions are likely to occur. Contact CSI to discuss your application with one of our specialists.

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