A-Z of Galvanizing
Welcome to our A-Z of Galvanizing – everything you’ve ever wanted to know about galvanizing if you work with steel.
Pre-treating steel to ensure it is free from surface contaminants is a fundamental part of the hot dip galvanizing process, as zinc will not react to unclean metal. As part of the pre-treatment stage, steel is pickled in acid to remove mill scale and rust, producing a chemically clean surface for galvanizing.
Different bath sizes suit varied steel fabrications. No matter how large your steel, we can help. Across all Joseph Ash Group plants, we have a range of bath sizes to suit the smallest to the largest of jobs. Visit our bath dipping sizes page for more information.
A circular economy encourages materials to be made, remade and recycled. Hot dip galvanizing fits perfectly into a circular economy because it optimises the durability of steel (enabling it to be used again) and facilitates the ease of reuse. It can also be recycled if there’s no immediate need to repurpose it. Read The sustainability of galvanized steel for more detailed information.
When designing steel for construction, also design it for galvanization, as a good design will prevent any processing problems at the galvanizing plant and ensure the best steel coating possible. For design advice, talk to our Technical Team. They’d love to help. You can also download Safe Design for Hot Dip Galvanizing.
At Joseph Ash Galvanizing we are committed to preventing pollution and minimising environmental impacts. For every process of our operations, we take a proactive approach to controlling emissions and ensuring the highest protection for the environment. Follow how we do this in Our Green Future – a fun, interactive graphic showing all our service steps, from collecting steelwork from a customer to its delivery at the end destination and all our environmental processes along the way. See it on our website
Once steel has been hot dip galvanized, a small amount of surface finishing may be required to smooth, clean or condition the metal. This is known as fettling.
The Galvanizers Association provides free authoritative advice on hot dip galvanizing since 1949. Visit their website for a wealth of steel and coatings information.
Health and safety at a galvanizing plant are of the utmost importance. At Joseph Ash Galvanizing, we are committed to ensuring our plants are safe environments to work and visit.
ISO standards dictate ways of doing things, whether making a product or providing a service. They are the distilled wisdom of people with expertise in their subject matter. There are many different standards that Joseph Ash Galvanizing complies with to ensure we provide the best service and product for our customers. Examples are the Coatings Requirements of BS EN ISO 1461:2022, the Quality Management System of ISO 9001, and the Environmental Management System of ISO 14001.
A jig holds steel in place in the correct orientation throughout the galvanizing process to facilitate ease of handling.
Galvanizing baths are also known as galvanizing kettles. They are large rectangular structures made from steel plates welded together. They come in many sizes. (We have a range of sizes across the Joseph Ash Group.) Galvanizing kettles are filled with zinc, which becomes a liquid state when heated to 438-460C. Steel that needs to be galvanized is lowered into a kettle at an angle so that the zinc can coat the steel.
Steel is a tough, durable metal; it can last for decades when appropriately treated. In the UK, galvanized steel (with a typical thickness of 85 microns) can last about 85 years before it needs maintenance. The lifespan does depend on the environment, however. For example, the lifespan might be slightly less in damp coastal areas or places with high levels of Sulphur Dioxide. For more information, view the Galvanizers Association corrosion map. It’s an excellent resource for calculating the levels of corrosion in atmospheric conditions across the UK.
A micron signifies one thousandth of a milimetre. In the steel and galvanizing industry, in order to be standards compliant, >6mm thick steel requires an average coating of 85 microns. This can last for a century in many UL settings.
As stated by the Galvanizer’s Association: “It is astonishing to think that a coating, just thicker than a sheet of A4 paper, can protect a steel structure for the better part of 100 years.”
At Joseph Ash Galvanizing, we mainly galvanize large items such as lampposts and motorway barriers for our clients. What about the small steel parts that hold the bigger pieces together, though? The nuts and bolts? Yes, we galvanize those in a spin bath at our Telford plant. When nuts and bolts are used to hold parts of a bridge in place, it’s just as vital that they are rust resistant too.
Hot dip galvanizing is a chemical process, carried out by highly skilled operatives. At Joseph Ash Galvanizing, many of our valued team have been honing their skills over periods of 20, 30 and 40 years, which means your steel is in safe hands.
Powder coating is a paint mainly applied to metals to provide a harder finish than a normal paint. The paint is applied as a powder electrostatically from a spray gun and is cured in an oven under high heat to form a tough, durable skin. Powder coating paints come in many colours and can be used to create different finishes, such as textured or metallic.
Quenching is the process where steel is rapidly cooled after it has been lifted from the galvanizing bath by immersion in water and/or a dilute chromate or phosphate solution.
Steel is made from iron, which rusts when exposed to water and oxygen. Rust is the result of a chemical reaction called corrosion. To prevent rust from forming, hot dip galvanizing coats steel in zinc. The zinc reacts with oxygen and carbon dioxide to form zinc carbonate. This becomes a protective barrier, stopping water and oxygen from reaching the steel.
Small items such as nails, chains and screws need to be as rust resistant as the steel structures they support. However, they are too small to galvanize in a hot dip galvanizing bath. With spin galvanizing, small items can be placed in a perforated basket and immersed in molten zinc. Once the zinc/alloy layers form, the basket is centrifuged at high speed so that the spinning action removes the excess zinc and creates a clean profile.
Wherever you are, or wherever the end destination for your fabrications is, Joseph Ash can transport them for you using our large fleet of specially equipped lorries, including articulated, rigid, and Hi-ab craned vehicles.
The ability to collect and deliver steel is vital as we like to make life as easy as possible for customers.
Galvanizing baths protect steel against rust, enhancing its lifetime. But galvanizing baths need protection, too, so they can continue to galvanize. Non-destructive testing is used for this purpose. The testing involves ultrasounds which determine the thickness of a bath over time. If the bath becomes too thin, it could crack. Not only would this put the bath out of action for many months, but it would also be perilous for our team if molten zinc leaked onto the floor of the plant.
To achieve the best quality zinc coating, it is important to ensure that the molten zinc can flow freely over all surfaces, externally and internally. So, where there are sealed hollow sections or cavities, vent and drain holes are essential. Please download Venting Tips for Hot Dip Galvanizing.
Our galvanizing plants are self-contained – with steel going in at one end and the final product coming out at the other. This means we can control the amount of waste we produce. At Joseph Ash Galvanizing, we minimise waste by recycling it at almost every stage of our operations. For example, Zinc that oxidises on the surface of our baths is removed as ash and recycled, and waste heat is used to warm pre-treatment tanks. Any wastewater generated can also be treated and reused, with only small volumes of stable solids requiring external disposal. See our ‘Green Plan’ for further examples.
At Joseph Ash, we want to make our customers’ lives easier. We do this by providing a range of additional services which include: Collection and delivery, Additional paperwork if requested, bundling, packing and labelling of all steelwork, passivation post-galvanizing, on-site storage, full technical support, a one stop-shop service.
At Joseph Ash Galvanizing, the essential part of our process is you – our customers. We hear your requests and treat your steel according to your needs. Whether you need hot dip galvanizing at a certain level of microns, or a duplex coating with a particular colour and finish, we will help. We’ve been in business since 1857 because you have trusted and kept us here.
Zinc is a chemical element with the symbol Zn and atomic number 30. It is found in mineral deposits along with other base metals, such as copper and lead.
The galvanizing process coats steel in zinc, which acts as a protective barrier against water, the leading cause of rust. The zinc in a galvanizing bath is molten at 450°C. Once the steel has reached this temperature, it is ready to be lifted from the bath.