Bonded washers have a rubber-like gasket "fused" to the steel washer to provide a seal on the
surface area.
Fastening sheet metal, fiberglass or other manmade products or panels in exterior applications requires a gasket to prevent water from penetrating beneath the fastener head. The absence of a seal can result in rot, discoloration or corrosion. Fasten with sufficient force to flatten the washer without "dishing" it.
Bonded washers are both ozone and weather resistant.
Zinc plated fasteners have good corrosion resistant qualities and are a good choice for indoor, outdoor and industrial applications.