Full Description

This specification covers the basic requirements for Sn-Znelectroplate on steel substrates matingto aluminum, steel and cast iron with provisions for supplementarytreatments and corrosionresistance. This plating is intended for grounding purposes. Alloycomposition shall be a range of75 ± 10% Sn and the remainder Zn. Minimum recommended platingthickness shall be 8 µm.Higher or lower plating thickness may be specified at the discretionof the user.

Note: Verification of alloy composition shall be by XRF (X-rayFluorescence) or AA (AtomicAbsorption) using standards and procedure approved by the chemicalsupplier or equipmentmanufacturer.

Material Description. The material approved to this specificationcovers Sn-Zn electroplate plus asubsequent protective treatment. This coating system must be free ofhexavalent chromium with nohexavalent chromium in final product per the requirements of GMW3059.GMW3034 shall be used as areferee test.

Symbols. Not applicable.

Typical Applications. This coating is suitable for fastenersdesignated for grounding purposes. Inaddition this coating may be used for fasteners M5 or smaller. Thiscoating shall not be used forapplications exceeding 195°C during manufacture or in service.

Remarks. Use of this coating on threaded surfaces and/or bearingsurfaces of joints could affectthe torque-tension relationship. It is recommended that atorque-tension study of the fastenerjoint be performed before releasing this finish on any newapplication.