Washer DIN 9021 M4(4,3) 200HV zinc-nickel black

Enlarged washer is a fastener having the form of a flat disk with a smooth cylindrical hole in the middle, the diameter of which is larger than the diameter of the metric product with which it is used. Materials from which they are made: steel 140, 200.

Scope of use DIN 9021 is effectively used when joining materials with soft structure, such as wood, plastic and the like. Popularly also has the name "washer under the rivet", which indicates its appropriate use. It is also often used with DIN 571 self-tapping screws and DIN 975 threaded rods when installing wooden structures.  A characteristic feature of this washer is that the outer diameter is equal to 3 inner diameters, which helps to take into account these parameters in calculations and installation.

The material of manufacture is high-strength structural alloy steel. 

Coating: Zinc-nickel black. Zinc-nickel coating is an innovative anti-corrosion solution for fasteners that combines high protective ability, mechanical strength and environmental safety.

The key advantages of zinc-nickel coating are:

• Excellent corrosion resistance - more than three times higher than that of ordinary zinc;
• Low risk of hydrogen embrittlement;
• Compatibility with aluminum - does not form galvanic couples and does not cause corrosion in combination with aluminum parts;
• Increased heat resistance - retains its protective properties at changing temperatures and during prolonged operation in high-temperature conditions;
• Mechanical strength - harder than pure zinc, has better resistance to scratches and wear;
• Environmental friendliness - less formation of oxidation products, which means lower zinc emissions into the environment throughout the product's life cycle.
• Aesthetics and invisibility - the coating has a deep black color, which makes it hardly noticeable.

Analogues GOST 6958-78, ISO 7093-1. ISO 7093-2.