GMW GMW4205 PDF

This specification covers requirements for a corrosion resistant black finish over an electrolytically deposited zinc-iron alloy, nickel alloy and/or zinc-nickel alloy substrate.

Material Description. This coating system shall be free of hexavalent chromate in final product per GMW3059 requirements. The plating shall be called out on the part drawing per example shown in paragraph 7.

Typical Application. This coating is intended primarily for bulk processed small steel parts such as bolts, screws and nuts used on exterior and interior visible parts (cosmetic applications). This coating is especially suitable for internal drive (cross recess, 6 lobed socket etc.) threaded fasteners and self drilling and tapping screws.

Remarks. Use of this coating system on threaded surface and/or bearing surface of joints could affect the torque-tension relationship. It is recommended that a torque-tension study of the fastener joint be performed before releasing this finish on any new application.