Small articles may be galvanized by a variation on the standard hot dip galvanizing process and is known as ‘Spin Galvanizing’ or Centrifuge Galvanizing.
In centrifuge galvanizing (or spin galvanizing) the work follows the same process route as for larger articles except the items are loaded into a basket which is spun at high speed immediately after removal from the molten zinc.
- Parameters of the Process
- Appearance and Surface Quality
- High Strength Friction Grip Bolts
- British Standards for protective coatings on threaded fasteners
- Other Fabricated Small Components
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Parameters of the Process
Centrifuge galvanizing may be conducted by the conventional process at about 450°C or by the high temperature process at about 550°C. In the conventional process a series of zinc-iron alloy layers which are metallurgically bonded to the base steel are formed during immersion in the molten zinc, these being covered by an outer layer of soft pure zinc.
Appearance and Surface Quality
The action of centrifuging removes some of the pure zinc layer and so small components which have been centrifuged usually have thinner coatings than those which have not been centrifuged. As a result, the zinc coating on components which have been centrifuged may not have a shiny silver appearance which is associated with articles which have been galvanized.
High Strength Friction Grip Bolts
General grade high strength friction grip bolts (ISO 8.8) can be galvanized without difficulty while higher strength fasteners (ISO 10.9) are galvanized in the UK following prior blast cleaning.
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