What is Galvanised Steel?
Galvanised steel is a type of steel that has been coated with a layer of zinc to protect it from rust and corrosion. This coating significantly increases its lifespan compared to untreated steel, particularly in outdoor environments like gardens or garages. Because the zinc acts as a barrier, galvanised steel products require less frequent maintenance than standard steel – typically just occasional cleaning. It’s also heavier than non-treated steel, which can be an important factor when considering installation and weight limits. The zinc coating adds to the overall cost of the product.
Galvanised steel’s protective coating isn't just a simple layer; it’s a sophisticated process involving hot-dip galvanisation. The steel is submerged in a bath of molten zinc, creating a metallurgical bond between the two metals – this is far stronger than simply painting or powder coating. This zinc coating protects against rust and corrosion through a phenomenon called ‘sacrificial protection’; if the galvanised layer is scratched or damaged, exposing the bare steel to the elements, the zinc will corrode preferentially, acting as a shield for the underlying steel. The thickness of this protective zinc layer varies considerably depending on the product – heavier garden furniture might have a 250-350 micron coating, while smaller items could be just 100 microns thick. You can sometimes visually assess the galvanisation by looking for a uniform, silvery-grey surface; however, a proper measurement requires specialised equipment to determine the zinc thickness, which manufacturers often provide in their technical specifications. A common mistake UK shoppers make is assuming all galvanised steel is equal – cheaper items may have thinner coatings and therefore require more frequent upkeep, particularly after exposure to harsh weather.
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FAQ
What does ‘zinc coating weight’ refer to?
Zinc coating weight, usually expressed in microns (µm), indicates the thickness of the zinc applied during galvanisation. A higher micron rating generally provides greater protection and longer lifespan, with 250-350µm being common for outdoor furniture and 100-150µm often found on smaller garden tools.
How does galvanised steel compare to powder coating?
Powder coatings offer a durable aesthetic finish but don't provide the same level of corrosion protection as galvanisation. While powder coatings can resist scratches, they are susceptible to rust if the underlying metal is exposed; galvanised steel’s zinc layer actively inhibits this process.
Can I clean galvanised steel with harsh chemicals?
Avoid using strong acids or abrasive cleaners on galvanised steel as they can damage the zinc coating. Gentle cleaning with soapy water and a soft brush is recommended, followed by rinsing thoroughly to prevent residue build-up.
What if the galvanisation starts to peel?
Minor surface peeling is normal due to weathering but significant loss of the zinc layer indicates inadequate protection. Addressing this promptly – usually by applying a specialist zinc treatment or carefully repairing the damage – can extend the product’s lifespan.
Is all steel used for garden furniture galvanised?
No, not all steel is galvanised. Some manufacturers use hot-dip galvanisation on specific components or use coated steels like polyester powder coating, which provides a similar level of corrosion resistance though doesn't offer the sacrificial protection of galvanisation.
How does galvanisation affect the weight of garden furniture?
Galvanised steel is significantly heavier than untreated steel due to the added zinc. This increased weight needs to be considered when planning installation, especially if you’re installing heavy items on a balcony or patio – ensure adequate support structures are in place.
What's the difference between galvanised and ‘zinc-plated’ steel?
‘Zinc-plated’ often refers to a surface treatment where zinc is applied through electroplating, which typically results in a thinner and less durable layer compared to hot-dip galvanisation. Hot-dip galvanisation creates a far stronger metallurgical bond.
How does weather affect galvanised steel?
Prolonged exposure to salt spray (common near the coast) or acidic rain can accelerate corrosion, even with a good zinc coating. Regular cleaning and applying protective waxes specifically designed for galvanised surfaces can mitigate this risk.
What should I look for in product specifications regarding galvanisation?
Manufacturers should state the zinc coating weight (in microns) and ideally, the method used (hot-dip galvanisation is preferable). Checking these details allows you to compare products and select those with a higher level of corrosion protection.
Can I repair damage to a galvanised steel product myself?
Minor scratches can often be buffed out. However, deeper damage may require specialist repair kits containing zinc filler or patching compounds designed for galvanised metal – consult the manufacturer’s instructions before attempting any repairs.