These washers with serrations are designed to bite into the bearing surface. These are especially effective when used with soft materials such as aluminium or plastic.
Stainless steel does not readily corrode, rust or stain with water as ordinary steel does. However, it is not fully stain-proof in low-oxygen, high salinity, or poor air-circulation environments. There are different grades and surface finishes of stainless steel to suit the environment the alloy must endure. Stainless steel is used where both the properties or steel and corrosion resistance are required.