GMW GMW3179 PDF

This specification covers the basic requirements for corrosion resistant finishes for iron and steel substrates whose basic characteristic is zinc phosphate treatment and subsequent protective compound. Parts coated with this coating are typically used internally for engines and transmissions or in areas where minimum corrosion protection is required.

Finishes with oil coatings are not recommended to be used against plastic surfaces.

Material Description. The material approved to this specification covers zinc phosphate treatments plus subsequent protective compounds. This coating system must be free of hexavalent chromium with no hexavalent chromium in final product per the requirements of GMW3059. GMW3034 shall be used as a referee test. This coating process does not generate hydrogen, however, pretreatment processes i.e. acid pickling could cause hydrogen absorption. This coating has high permeability, which allows effusion of hydrogen during curing which might have been absorbed during acid pickling.

A grade with zinc phosphate only may be designated or may be followed by a supplemental coating. A code system is provided in the Table in Appendix A for designating certain limitations on compounds.

Cross-Reference of Replaced Specifications.

Typical Application. This coating is suitable for internally threaded parts, parts with internal drive recess, externally threaded and non-threaded ferrous parts where minimum corrosion protection and freedom from hydrogen embrittlement are required.

Remarks. Use of this coating on threaded surfaces and/or bearing surfaces 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.