Galvanised steel is a term many people have heard of, but only some understand. It is a type of steel coated with a layer of zinc, which helps to protect it from rust and corrosion. But what makes galvanised steel unique, and why is it used in many applications?
Let’s explore the world of galvanised steel, from its origins and manufacturing process to its unique properties and benefits. Whether you're a builder, engineer, or just curious about this versatile material, you'll find everything you need to know and more at Steel Builders.
What is Galvanised Steel?
Galvanising, often known as galvanisation, is an industrial process in which a zinc coating is applied to steel or iron to protect and prevent rusting. Zinc is an excellent choice for this purpose, as it is highly resistant to corrosion and can last for decades without deteriorating.
There are two main types of galvanised steel: hot-dip galvanised and electro-galvanised.
- Hot-dip galvanisation involves dipping the steel into a bath of molten zinc;
- Electro-galvanisation uses an electric current to bond the zinc to the steel.
Both methods produce a strong, durable coating that helps extend the steel's life, though hot-dip galvanising is the most common technique.
The zinc coating on galvanised steel provides many benefits. For instance, it is highly resistant to rust and corrosion, making it ideal for harsh environments. The zinc coating also helps protect the steel from damage and extends its lifespan, even in challenging conditions. Furthermore, galvanised steel is versatile in various applications, from construction and manufacturing to automotive and marine industries.
Overall, galvanised steel is an excellent choice for those looking for a robust, durable material that can withstand harsh conditions and provide long-lasting performance.
The Galvanising Process
The first step in the galvanising process is cleaning. Any oil, grease, or dirt from the surface of the steel is removed using a degreasing solution, which can be either an alkaline or acidic cleaner, depending on the type of contaminants present on the steel surface.
After degreasing, the steel is rinsed with water to remove residual cleaner or contaminants.
After cleaning, the steel is pickled to remove any impurities, rust, and scale from the metal surface. The purpose of pickling steel is to remove any surface contaminants that could interfere with the subsequent galvanising process.
The galvanising process requires a clean surface for the zinc coating to bond effectively to the steel. Pickling also helps to remove any rust or scale that may have formed on the steel surface, which can be a common issue in steel manufacturing and storage.
The pickling process involves submerging the steel in the acidic solution for several minutes. After pickling, the steel is thoroughly rinsed with water to neutralise the acidic solution and remove any remaining contaminants before the next processing stage.
The purpose of fluxing is to remove any oxide film that may have formed on the steel surface after pickling, which could interfere with the adhesion of the zinc coating.
The flux used in the galvanising process is typically a liquid solution of zinc ammonium chloride, which is applied to the steel surface by dipping the steel into the solution or spraying it onto the surface. The flux solution helps remove any remaining surface impurities and promotes the formation of a clean surface for the zinc coating to bond with.
The zinc ammonium chloride solution acts by dissolving any oxides that may have formed on the steel surface, which is essential for ensuring good adhesion of the zinc coating. The solution also helps to activate the steel surface by promoting the formation of zinc-iron intermetallics, which further improve the adhesion of the zinc coating.
After fluxing, the steel is then immersed in a bath of molten zinc, which is usually maintained at a temperature of around 450°C. The molten zinc reacts with the clean steel surface to form a series of zinc-iron alloy layers, which provide a highly effective barrier against corrosion.
The final step is to test the quality of the coating to ensure that it is uniform and fully covers the steel surface to achieve the desired level of protection against corrosion.
There are several methods used to test the quality of the galvanised coating. One common method is visual inspection, where the coated steel is visually examined for any signs of defects, such as bare spots, rough surfaces or excessive drip marks. Visual examination is best done using bright lighting to highlight areas where the coating may be incomplete or uneven.
Another method used to test the coating quality is the "pencil hardness" test, where a graded set of pencils are used to scratch the surface of the coating. This test helps to determine the coating's resistance to scratching and abrasion.
A third method is the "thickness gauge" test, which measures the thickness of the coating to ensure that it meets the desired specification. Too thin, and the coating may not provide adequate protection against corrosion. Too thick, and it may have a higher risk of cracking and peeling.
In addition to these tests, you may use other quality control measures to ensure that the galvanised steel meets the desired specifications. These may include testing for adherence, ductility, and impact resistance, among other factors.
Overall, the final step in the galvanising process involves careful testing and inspection of the coated steel to ensure it meets the desired quality standards, provides adequate protection against corrosion, and has a long-lasting service life.
What Are the Benefits of Galvanised Steel?
There are many benefits to using galvanised steel, which is why it is such a popular material in a wide range of industries. Some key advantages include the following:
- Corrosion resistance: Galvanised steel is highly resistant to rust and corrosion, making it ideal for harsh environments.
- Durability: The zinc coating helps to protect the steel from damage and extends its lifespan, even in challenging conditions.
- Versatility: Galvanised steel can be used in various applications, from construction and manufacturing to automotive and marine industries.
- Cost-effective: While the initial cost of galvanised steel may be slightly higher than other materials, it's durability and low maintenance requirements make it a cost-effective choice in the long run.
- Sustainability: Galvanised steel is a sustainable material that is fully recyclable and can be reused indefinitely.
How is Galvanised Steel Used?
Thanks to its unique properties and benefits, galvanised steel has many applications. Some of the most common uses include:
- Construction: Galvanised steel is a popular choice for building materials, including roofing, fencing, and structural components.
- Automotive: Galvanised steel is used in producing cars and trucks, providing excellent corrosion resistance and durability.
- Manufacturing: Galvanised steel is critical in many manufacturing processes, from appliances and electronics to machinery and equipment.
- Marine: Galvanised steel is often used in the marine industry, as it is highly resistant to corrosion from saltwater and other harsh conditions.
- Agriculture: Galvanised steel is used extensively in agriculture, from farm equipment and storage tanks to barns and livestock enclosures.
Galvanised Steel vs Stainless Steel
There are numerous stainless steel grades, each with various quantities of alloys—these steel grades balance malleability, hardness, and anti-corrosive characteristics.
Stainless steel, like galvanised steel, has an anti-corrosive ingredient added to it, typically 10% chromium. Stainless steel, unlike galvanised steel, is an alloy containing a non-oxidizing element added during the smelting process. The chromium alloy reacts with oxygen in the air to generate a coating of chromium oxide on the surface of the steel.
While galvanised and stainless steel prevents oxidation, each metal has different applications. Galvanised steel is a less expensive technique than stainless steel production, making it more common as machine parts and tools in the construction and automotive industries.
On the other hand, stainless steel is often used for culinary utensils, tools, and railway tracks.
Australian-Made Galvanised Steel
Galvanised steel is a unique and versatile material that offers many benefits over traditional steel. Its corrosion resistance, durability, and sustainability make it an excellent choice for various applications, from construction and manufacturing to automotive and marine industries.
Contact Steel Builders today to learn more about our structural steel products and how they can meet your needs. We offer next-day dispatch across the Sydney metropolitan area and free pick-up from our St Mary's or Belmore warehouse for your convenience.
Galvanised Steel FAQs
Q: Is galvanised steel better than regular steel?
A: Galvanised steel is more durable and corrosion-resistant than regular steel, thanks to the galvanising process.
Q: How long does galvanised steel last?
A: Galvanised steel can last for decades, even in harsh environments.
Q: Can galvanised steel be painted?
A: Galvanised steel can be painted, but preparing the surface is crucial to ensure good adhesion.
Q: How is galvanised steel made?
A: Galvanised steel is made by coating steel with a layer of zinc through galvanisation.
Q: Is galvanised steel environmentally friendly?
A: Galvanised steel is considered an environmentally friendly material, as it is fully recyclable and can be reused indefinitely.
Q: Is galvanised steel more expensive than regular steel?
A: Yes, galvanised steel is typically more expensive than regular steel due to the cost of the zinc coating process.
Q: Can galvanised steel rust?A: While galvanised steel is highly resistant to rust and corrosion, it can still rust over time if the zinc coating is damaged or worn away.