As sheet metal machine experts, we love exploring different aspects of sheet metal fabrication. One aspect that we’ve never discussed before is metal that’s been specially treated or coated – such as galvanised steel or iron. But what is galvanisation? Galvanisation is the process of treating metal to be anti-corrosive. This widely used method is achieved by applying a light zinc coat to the metal which helps shield it from the elements.
Why galvanise metal?
To protect it. The zinc coating acts as a line of defence against corrosive substances and essentially sacrifices itself by corroding first. This ensures the metal lasts longer without rusting or corroding. Only when the zinc coating completely corrodes will the base metal begin to be affected by the elements.
Galvanisation also offers a more cost-effective alternative to materials such as stainless steel. By galvanising normal steel or iron you’re extending its life and bolstering it against the elements. Without a zinc coating, they would be sure to oxidise and corrode at a much faster rate. Have you ever noticed how street signs have a silver, shimmery effect at night when light is shined upon them? That’s the zinc coating.
How does galvanisation work?
The protective layer offered by the zinc is a lot more than just a shield. Whilst it will protect elements such as moisture and other substances from coming in contact with the base metal – it can also protect in a more complex way. This is through a process called galvanic corrosion which relates to one metal corroding faster than another when they’re in electrical contact with each other and near an electrolyte.
When this electrochemical process occurs, the zinc coating tends to turn into an anode – which means it will deteriorate faster – but it means that the base metal will be the cathode – resulting in a much slower corrosion rate.
For example, if this process was to occur without the zinc coating, then one of the metals would be the cathode and the other the anode. The zinc coating can protect the metal it’s on by acting as the anode – forcing it to become the cathode.
What are the different methods of galvanisation?
Hot dipping – The most popular and widely used method of galvanising steel and iron is hot dipping. For starters, the metal needs to be clean so the zinc coating can be applied without any issues. This can be done by submerging the metal in an alkaline solution – removing any grease or rust – or mechanically. Once the metal is clean, it can be submerged in molten zinc where it must remain until a series of alloy layers are formed with the base steel. The amount of time this will take depends on the thickness of the metal.
Pre-galvanising – This method is very similar to the hot dipping one but is usually performed on rolls of continuous sheet metal rather than metal that has already been shaped. The metal is first cleaned and then submerged into molten zinc like hot dipping. One of the disadvantages with this method, though, is that if the sheet metal is cut, then the newly cut area will not be galvanised.
Electrogalvanising – This process is quite different from the other two and involves transferring zinc ions onto the base metal via an electrical current in an electrolyte solution. This method is typically applied to rolls of sheet metal like the pre-galvanising method. Whilst an even thickness of the coating is often achieved through this method – the coating tends to be thinner compared to molten zinc submersing methods, which can result in less protection.
Do you need to purchase a sheet metal machine?
ACRA Machinery is home to a plethora of fantastic new and used sheet metal machines such as slitter foldersand laser cutters. Not sure what machine will best suit your needs? Have a chat to our experts and they can help you break down the features of each machine to ensure you find the best fit. We also offer on-site repair and maintenance solutions to make sure your machines are kept in optimal condition regularly.
If you’d like to get in touch with our sheet metal machine experts, then please don’t hesitate to fill out the contact form on our website or call 03 9794 6675.