Galvanizing is a process of coating a metal with a layer of zinc to protect it from corrosion. Zinc is a highly reactive metal that readily oxidizes, which means that it will corrode before the metal underneath it. This makes it an ideal material for protecting other metals from rust and corrosion.
Not all metals should be hot-dipped galvanized, though. This post will look at what needs to be considered when deciding whether or not to use hot-dipped galvanizing.
- Most ferrous materials are suitable to be hot dip galvanized, including sound stress-free castings.
- Most hot rolled or cold formed steels, including structural angles, UB’s, UC’s, welded beams, channels, welded CHS, RHS & SHS, reinforcement steels and fastener grade steels can be galvanized. In general, the mechanical properties of structural steels are not affected by the galvanizing process.
- High strength steel up to 340HV are also able to be galvanized when acid pickling is not used in the pre-treatment of the steel.
- Grey cast iron and malleable cast iron can be galvanized, but special considerations need to be met. (For more information, refer to Clauses 2 and 9 of AS/NZS 2312.2.)
- Steel composition (particularly silicon and phosphorus content) can affect the characteristics of the hot dip galvanized coating.
- Combinations of ferrous materials or surface conditions
– Fabrications containing a combination of castings and steels, or rusted and mill scaled surfaces may be abrasive blast cleaned before galvanizing to provide a more consistent initial surface finish.
– Weld slags must be removed, which can be done via chipping, grinding, or using a pneumatic needle gun.
- Brazed assemblies may be galvanized, but check first with your galvanizer.
- Non-ferrous materials such as brass, aluminium and copper are not suited to the hot dip galvanizing process.
- It is not recommended to galvanize stainless steels.
- Sulphur-containing free-cutting steels (for example S1214) are normally unsuitable for hot dip galvanizing.
- Soft soldered assemblies cannot be galvanized.