Steel is a compound metal that contains iron. Iron is highly prone to oxidization – the formation of rust. If steel is allowed to rust, it can become weaker, more prone to warping, more prone to material corruption and generally far less fit for purpose. Rusting occurs when the element iron is exposed to water and oxygen. This forms hydrated iron oxide – which we see as red rust.
For obvious reasons, engineers have devised many methods for preventing oxidization. Galvanizing steel in zinc is one of the most effective methods of stopping rust and increasing the service life of steel components. A layer of zinc is bonded to the steel. This provides a barrier that prevents water and oxygen from coming into contact with it. Below is a rundown of how steel is typically galvanized.
Pre Treatment
When a heavy-duty steel component, like the 14 gauge stem wire at Baling Wire Direct, needs to be galvanized, there are several pre-treatment processes that need to be completed before any zinc is applied. Firstly, all surfaces are checked for contamination that may impact the effectiveness of the galvanization processes: grease, oil and paint on metal all prevent galvanization.
Steel is immersed in a degreasing solution and then ‘pickled’ in acid to make sure that no contaminants are present. It is then coated in flux. The flux used in galvanization is usually zinc chloride.
Dipping
Once the pre-treatment processes have been completed, the dipping can begin! A bath of molten zinc is heated up to a temperature of around 450 degrees Celsius. This is an immensely dangerous task due to the heat involved and must be completed in a controlled environment. The ‘bath’ is more like a large tray in appearance. Once the zinc is at the correct temperature, the cleaned and fluxed steel component is lowered into the bath.
Once the steel heats up to the same temperature as the zinc, a chemical reaction takes place. This reaction creates thin layers of zinc/iron alloys. As the component is removed from the bath these alloys will quickly solidify. They are blasted with air or water in order to prevent alloys from solidifying in such a way that they might change the shape of the component. This is important, as customers may be ordering parts for engineering projects that need extremely tight parameters.
The galvanized component is then lowered into a cooling tray containing water. This is known as a quench tank, and is essential in speeding up the galvanization process. Without quench tanks, each component would have to be left to cool for a very long time indeed.
Inspection
Once the galvanized product is cool enough to be handled safely, it is inspected thoroughly. Inspectors check for any discoloration, gaps in the iron/zinc coating and lumpen shapes. Components are sometimes picked at random to undergo non-destructive testing. Customers often expect a certain percentage of components to have been tested in order to confirm their durability.