Galvanised steel can be found just about everywhere. It is used to make buckets, rubbish bins, railings, roofing, hinges and much, much more. We know that it is more resistant to corrosion than untreated steel, making it perfect for use outdoors or in marine environments, but what exactly is galvanised steel and how is it made?
Galvanising is a chemical process which leaves steel more durable and more suitable for demanding applications. Unlike painting which simply coats and seals the metal, galvanising makes the inert material – in this case zinc – a permanent part of the steel which is far longer lasting than a painted layer.
One of the most common methods of galvanising steel is the hot dipping method, in which steel is submerged in molten zinc. This leaves the outer layer of the material purely zinc, with a gradient mixture of zinc and iron and a core of pure steel. The degree of galvanising usually refers to the weight of zinc per surface area rather than the outer layer’s thickness, and this gives a far more accurate representation of how much of the zinc has been applied.
Steel is protected by zinc in two ways. First, the physical layer of zinc prevents oxygen and moisture from reaching the steel. This layer is extremely resistant to scratches and other damage, and will reliably protect the ferrous material for years. Furthermore, the zinc acts as a sacrificial layer. This is particularly useful in very demanding environments – such as those where the steel may come into contact with sea water – as the zinc will begin to corrode long before the steel will. Even where the galvanising layer is scratched, the surrounding zinc will corrode before the steel does.
Should a damaged area be discovered, it is possible to repair it with a galvanising spray. Since this is a paint which is applied to the surface of the metal it will not have the same lifespan as the hot dipped galvanising, but it is a perfectly adequate preventative measure which will stand up in most outdoor environments.
