Steel is only stainless if it has a minimum Chromium content of 11-12%. An extremely thin, continuous and stable oxide film forms on the surface due to the Chromium, this makes the surface inert to chemical reaction, rendering it passive. This is Stainless Steel's natural built in corrosion resistance. Austenitic or Chromium - nickel Steel is the most commonly used for fasteners.
The two main grades of Stainless Steel used are as follows:
A2 (304) 18/8 - Most commonly used grade of Stainless Steel, with basic composition Chromium 18% + Nickel 8%. It has outstanding corrosion resistance under normal atmospheric conditions, wet surroundings, oxidizing and organic acids and many alkalic and salt solutions. Typical applications include Chemical and civil engineering projects, food Processing, Medical and Brewing equipment and many domestic appliances. Fasteners for Aluminium Alloy, Plastic and Plastic coated steel assemblies, , special purpose building, masonry fixings and cryogenic equipment.
A4 (316) - This grade has the highest level of corrosion resistance also called 'Acid Proof' with basic composition Chromium 18% + Nickel 8% and Molybdenum 3%. It has more resistance to aggressive climates such as seawater (chlorides) and industrial (sulphur dioxide) climate and oxidizing acids. Typical applications include fasteners for boat deck fittings, chemical plant, swimming baths and dye vats. , rayon and sewage treatment plant, Fertiliser, medical sterilising, equipment, dairy equipment, special purpose building and masonry fixings.
Other Materials - We can also supply fasteners in the following materials:
Aluminium, Titanium, Phos. Bronze, Brass, Aluminium and Bronze
Visit the A and D Fasteners website for more information on Specs