1 Scope
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:
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a) the local coating thickness for six grades of coating;
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b) possible types of post treatment;
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c) the assessment of corrosion resistance of unused coated parts when subjected to neutral salt spray testing (see BS EN ISO 9227:2006).