GMW GMW4700 PDF

This specification covers the basic requirements for barrel or rack electrodeposited zinc alloy plating over a ferrous substrate. Various alloy platings are covered by this specification with supplementary treatments. Table 1 lists the zinc alloy finishes covered by this specification.

Note: This finish is not recommended for applications where white corrosion is a cosmetic concern.

Material Description. To distinguish between alloys, the chemical symbol of the alloying element must be added as a suffix to the specification number to designate the alloy desired. This coating system must be free of hexavalent chromium with no hexavalent chromium per the requirements of GMW3059.

Plating Composition. The percentage of alloying element present in the zinc alloy electrodeposit differs for each of the zinc alloys. The concentration limits for the various alloys are shown in Table 1.

Accurate control of alloy composition and alloy ratios within the limits given in Table 1 are essential for optimum corrosion resistance and plating performance.

Cross-Reference of Replaced Specifications.

Typical Application. Zinc alloy plating is especially suitable for small to medium ferrous parts such as castings, stampings, clips, fasteners and other ferrous parts where levels of corrosion protection exceeding pure zinc are required. A suffix code G is to be used when specified on fasteners. Use of this finish on fasteners could affect the torque-tension relationship. It is recommended that a torque-tension study of the fastener joint be performed before use of this finish on fasteners.

Zinc Alloy plated parts or their corrosion products must not come in contact with stressed Polyamides 6 or 66.