The „traditional“ materials A 2 and A 4 (and to some extent A 1 and A 5) are quite sufficient for most of the application cases in which fasteners made from stainless steel are used on grounds of their material properties.
Special materials, however, are often required for use in particularly aggressive environments or where they come into contact with reducing media such as acids and temperature. Thanks to their chemical composition, these offer greater resistance and anticorrosive properties.
Both normed and standardized articles and special parts are available in different materials. This includes:
Hastelloy B-2 (2.4617)
Nickel-molybdenum alloy (NiMo28) with a good level of resistance to reducing media, particularly hydrochloric acid in all concentrations up to boiling point.
Hastelloy C-276 (2.4819)
One of the most corrosion-resistant nickel-molybdenum alloys (NiMo16Cr15W), especially resistant to oxidizing influences. Is used predominantly for bleaching solutions that contain free chlorine and for chlorides, hypochlorides, sulphuric and phosphoric acid, organic acids such as vinegar and formic acid, solutions from nitrates, sulphates, chlorides (e.g. largely insensitive to crevice corrosion by Cu and Fe chloride) and chlorates, chromates and cyanic compounds.
Incolloy 825 (2.4858)
Titanium-stabilized chromium-nickel-iron alloy (NiCr21Mo) for particularly high levels of corrosion stress. Resistant to substances including oxidizing and reducing hot acids such as sulphuric acid, phosphoric acid and nitric acid.
Inconel 600 (2.4816)
Chromium nickel alloy (NiCr15Fe) with a good level of oxidation stability at temperatures up to 1150°C; at the same time the high nickel content provides excellent resistance to stress corrosion.
Monel 400 (2.4360)
Nickel copper alloy (NiCu30Fe) distinguished by a good level of firmness and toughness. High resistance to salt water and sulphuric, hydrochloric and phosphoric acid.
Monel K 500 (2.4375)
Precipitation-hardening nickel copper alloy (NiCu30AIF62) that combines the good corrosion stability of Monel 400 and increased hardness and toughness.
Suitable for weight-saving structures that are subjected to high stress levels. Relatively good fatigue strength, high corrosion resistance for the reagents commonly used in the chemicals industry, beneficial against oxidizing media, resistant to salt water.