Corrosion protection
Spring steel with a zinc flake coating
The zinc-lamella-coated spring steel version combines high mechanical performance with a defined spring function and proven corrosion protection.
It achieves salt spray resistance of up to 840 hours according to DIN EN ISO 9227. The zinc-lamella coating system not only provides high corrosion protection but also ensures low coefficient of friction variation and minimizes the risk of hydrogen embrittlement. This version is available in two defined coefficient-of-friction classes, thereby enabling fixed coefficient-of-friction ranges and reproducible tightening torques.
However, according to DIN EN ISO 10683, zinc lamella coatings must not be used on electrically conductive components that carry current, as they exhibit limited electrical conductivity or insulating properties.
A4 Stainless Steel / NIRO
The A4 stainless steel version, made from grade 1.4401, is designed for demanding corrosion conditions—particularly in the presence of moisture, exposure to media, or chloride-containing atmospheres.
Its corrosion resistance is tested on the finished fastener, rather than being derived solely from the material designation. This ensures that factors such as forming, surface finish, and component geometry are also taken into account.
NSK washers are additionally tested for over 4,200 hours in a salt spray test in accordance with DIN EN ISO 9227—based on DIN EN ISO 12944.
Zinc-Nickel
The zinc-nickel-coated version is specifically designed for electrically conductive and dynamically loaded screw connections. It minimizes variations in the coefficient of friction, thereby ensuring reproducible tightening torques.
In addition, it offers corrosion resistance of up to 720 hours in a salt spray test according to DIN EN ISO 9227, as well as high temperature resistance. This version is used in particular for electrically conductive fasteners designed to carry pure electrical current and meets the requirements of DIN 25201-3.
Corrosion tests
The corrosion resistance of our NSK discs made of material A4 / 1.4401 has been verified through independent component testing conducted by the Institute for Corrosion Protection in Dresden, and no signs of corrosion were observed during the visual inspection without the use of any tools after the testing was completed.
| Test Area | Standard / Method |
| Pitting and Crevice Corrosion | DIN EN ISO 15158 |
| Intergranular Corrosion | ASTM A262 |
| Salt spray test / NSS test | DIN EN ISO 9227, 4,200 h, based on DIN EN ISO 12944 |