low alloyed steel	according to DIN EN 10263-2 (for fasteners without heat treatment, e.g. C10C)
case-hardend steel	e.g. SAE 1018, tempered
heat-treated steel	e.g. SAE 1022, 23MnB4, heat-treated on e.g. Rm min. 1040 N/mm2 Standard for EJOT PT®, DELTA PT®, Duro-PT®, ALtracs®
austenitic stainless steel A2 1.4303	X4CrNi 18-12 (preferred material for thread-rolling screws Ø >= 3,0 mm)
austenitic stainless steel A2 1.4301	X5CrNi 18-8
austenitic stainless steel A2 1.4567	X3CrNiCu 18-9-4 (preferred material for very small-sized screws Ø <= 2,5 mm
austenitic stainless steel A4 1.4401	X5CrNiMo 17-12-2 (on request)
ferritic stainless steel F1 1.4016	X6Cr17 ferritic chrome steel
alloy material	(on request)

Please note when placing an order of stainless steel fasteners:

 The term "stainless steel" describes steel, which has an oxide layer high in chrome at the surface. Amongst these are the austenitic steels (A2 and A4).

This oxide layer is also called a passivated layer and is responsible for the corrosion protection. Even if this passivated layer is damaged, it always re-generates under the influence of oxygen.

The generation of the passivated layer can be accelerated through additional chemical passivation (e.g. according to ISO 16048). This passivation cannot be compared to the artificial passivation on zinc. If not agreed otherwise, the fasteners have to be delivered according to DIN EN ISO 3506-4, in a clean and metallic blanc state. To reach the highest possible corrosion resistance a passivation is recommended. If a passivation is requested, it has to be carried out according to ISO 16048.

The corrosion resistance of austenitic steel cannot be defined through salt spray tests. The salt spray test is only intended to show weak spots in coated systems (e.g. galvanic coatings or organic/inorganic coatings).

If fasteners made of austenitic steel are out through a salt spray test, they are definitely going to rust. The reason is the destruction of the oxide layer by the salt spray and because of the constant spray no new oxide layer can be generated. Due to this, the corrosion resistance auf stainless steel screws cannot be compared to galvanic or organic/inorganic coated screws by means of a salt spray test.

We do not know of any standards either where stainless steel fasteners are put through a salt spray test. Under the condition that a fastener made from austenitic steel comes into contact with oxygen and thus shows the corresponding oxide layer, this element will be superior to a fastener made from conventional low alloyed steel (with a galvanic or organic/inorganic surface).

Contact:

EJOT GmbH & Co. KG
Industrial Fasteners
Engineering Services
phone +49 2751 529-123
e-mail: hotline@ejot.de