As a screw is tightened, these metric washers flatten to add tension to the joint, counteracting fatigue around the joint from small amounts of vibration. This makes them a common choice to prevent fasteners from loosening. However, they resist the least amount of vibration compared to other locking washers. They meet a DIN or ASME standard for split lock washer dimensions.

Standard split lock washers have a left-hand helix that have right-hand threads to prevent loosening. They have uneven split ends that bite into fasteners for a tight grip but won’t work with hardened surfaces. They hold better than curved or wave washers. These washers are not reusable after tightening.

Stainless steel washers resist corrosion better than steel and are nearly as strong. 18-8 stainless steel washers withstand humid, damp, and washdown environments but will corrode when exposed to salt water and other chlorine solutions. 316 stainless steel washers resist corrosion from wet environments as well as salt water, chlorine solutions, and chemicals.

Stronger and more durable than stainless steel, steel washers plated with zinc or galvanized withstand varying degrees of corrosion. Zinc-plated steel and zinc yellow-chromate plated steel washers withstand wet environments. However, they will corrode in salt water and chlorine solutions. The zinc plating temporarily protects against rust, but once it wears off, the steel will rust. Zinc-flake coated steel washers resist corrosion from chemicals and have passed a 1,000-hour salt-spray test. They’re also known as armor coat and ultra coat. Galvanized steel washers are 10 times more corrosion resistant than zinc-plated steel washers.

Steel washers are stronger and resist wear better than zinc-plated steel and stainless steel washers. Use them in dry environments. Blue-dyed steel washers are easy to spot. Black-oxide steel washers have a black residue that forms from being heat treated; the color will wear away over time.

Silicon Bronze washers are corrosion resistant in wet environments, nonmagnetic, and electrically conductive.

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