BS 7371-8:2011

• 21.060.01 Fasteners in general
• 25.220.40 Metallic coatings

This part of BS 7371 specifies requirements for sherardized coatings on iron and steel fasteners and accessories applied by thermal diffusion of zinc powder onto a component’s surface.

NOTE Hydrogen embrittlement is not induced as a result of this coating process.

The coating consists of zinc/iron alloys, which are subsequently treated using either a zinc phosphate treatment (see BS 7371-9:1996, Type 2) or a suitable substitute treatment similar to those used in electroplating zinc (see BS 7371-3:2009) and mechanical plating (see BS 7371-7:2010). This results in a dust free surface, which, when required, can be lubricated to give controlled torque/clamping force properties (see BS 7371-2:1993).

In addition to the requirements in this part of BS 7371, the requirements in BS 7371-1:2009 that are applicable to sherardized coatings apply.

This part of BS 7371 also specifies requirements for:

1. the local coating thickness for six grades of coating;

2. possible types of post treatment;

3. the assessment of corrosion resistance of unused coated parts when subjected to neutral salt spray testing (see BS EN ISO 9227:2006).