GB/T 19350-2012Metallic and other inorganic coatings -- Post-coating treatments of iron or steel to reduce the risk of hydrogen embrittlement (English PDF)

1 Scope

This Standard specifies procedures for reducing susceptibility, or degree of susceptibility, to hydrogen embrittlement that can arise in surface finishing processes.

The heat-treatment procedures for iron or steel specified in this Standard have been shown to be effective in reducing the susceptibility to hydrogen embrittlement. These heat-treatment procedures are used after surface finishing, but prior to any secondary conversion-coating operation.

Stress-relief heat-treatment procedures applied after fabrication, but prior to surface finishing, are specified in ISO 9587.

This Standard does not apply to fasteners.

NOTE The heat treatment does not guarantee complete freedom from the adverse effects of hydrogen embrittlement.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 2080, Metallic and other inorganic coatings - Surface treatment, metallic and other inorganic coatings - Vocabulary

ISO 9587, Metallic and other inorganic coatings - Pretreatment of iron or steel to reduce the risk of hydrogen embrittlement

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO

2080 and the following apply.

5 Embrittlement-relief treatment classes

6 Heat treatment after processing

6.1 The heat treatment shall commence as soon as possible, preferably within 1 h but not later than 3 h after surface finishing, and before commencement of any grinding or other mechanical operation. For cadmium, tin, zinc, their alloys or any other coating receiving a chromate treatment, heat treatment shall be carried out before chromate treatment, with the exception of electrodeposited zinc-cobalt alloys that should be passivated prior to hydrogen-embrittlement-relief heat treatment.

NOTE 1: Chromate coatings undergo change at temperatures above 66°C. The coating changes from an amorphous structure to a crystalline structure and no longer exhibits

“self-healing” properties. Although the crystallized chromate coating will provide satisfactory corrosion protection under most natural environments, the chromate coating will no longer pass accelerated corrosion tests.

NOTE 2: The time period referred to in this Clause is the time between the end of the plating operation and the loading of the article concerned into the heat-treatment processor.