GALVANISED FASTENERS

Galvanized nuts and bolts

Galvanised fasteners are produced by a process known as Hot Dipped Spun Galvanised, whereby the fasteners are placed inside a wire basket and dipped in a vat of molten zinc, the basket is then spun at high speed to remove any excess zinc by centrifugal force. This process protects the bolts from the external weather elements which defends the components against corrosion and rusting in the rain. This means that are ideal to use in the manufacture of products used outside. Ideal for both commercial and domestic markets for industries such as construction, engineering, automotive and marine, and outdoor homeware galvanised fasteners will sustain longevity and reliability.

As a general rule, nuts, bolts and washers down to 8mm diameter can be galvanized using the process decribed. To accommodate the thickness of zinc when galvanizing threaded components, extra clearance must be provided on the female threads. For ISO metric fasteners, the galvanizing of one thread either internal or external requires an extra clearance of four times the coating thickness.

Coating uniformity
Whilst there is some tendency for hot dip galvanizing to be thicker in thread roots, a near uniform coating can be obtained with modern equipment. Any thickening that does occur can be accommodated in the normal truncation on the thread of the nut.

Surface finish and appearance
Galvanized fasteners usually have a bright light grey appearance, but with certain grades of high yield and high tensile bolts, the coating may be matt grey because the higher silicon content of the steel makes them more reactive towards the molten zinc. Fasteners hot dip galvanized at high temperature (around 550°C) tend to take on a uniform, matt grey appearance due to the structure of the coating formed when the component is cooled.

Storage of galvanized bolts and nuts
Galvanized bolts and nuts should be stored under dry, well-ventilated conditions to minimise the occurrence of wet storage stain.

Relative costs
The initial cost of hot dip galvanizing threaded fasteners is generally a higher than zinc plating, however, in terms of cost per year of rust-free life, hot dip galvanizing is by far the most economical coating.

For more information on GALVANISED FASTENERS talk to Kayfast Ltd