As the most common element on the planet, iron has made its way into nearly all aspects of human life, and has done so for thousands of years. This has never been more the case than it is today, as even when we are not using iron in its base form, we still usually end up using one of its many alloys, the most common of which is steel; in fact iron is its main ingredient.
Iron is what is known as a ferrous metal; or rather metals which contain iron are referred to as Ferrous. The word is derived from the word ‘Ferrum’, the Latin name for iron, which is the reason why the chemical symbol for Iron is ‘FE’. Regardless, it is common knowledge that iron, when in contact with oxygen, will tarnish and rust. This has a devastating impact on the material’s load bearing strength and its general aesthetics.
As a matter of fact, if given enough time rust will eventually eat through any amount of iron, essentially causing it to disintegrate; and the same goes for any material that contains it. There are exceptions to the rusting rule of course, for example stainless steel, which contains relatively high levels of chromium, but for those alloys that do not contain chromium, other means of protection have to be used.
WHAT IS GALVANISATION?
Galvanisation is one of the means by which we can protect ferrous metals from rusting, and it is done by taking advantage of the resilience and corrosion resistance of zinc. A zinc coating is applied to the ferrous material, steel for example, preventing air from getting to it and effectively halting any oxidisation that may have already occurred.
It is important to point out though that unless any and all rust present is removed first, galvanising the material will be ineffective.
Can You Weld Galvanised Steel?
Welding galvanised steel is possible, but unlike welding steel normally, when you weld galvanised steel it is important to use silicon bronze electrodes or aluminium bronze ones. If you use a standard stainless steel welding electrode you will cause the zinc coating to move toward the centre of the weld, which will result in centreline cracking as it starts to cool down and solidify. Proper fume extraction is imperative when welding galvanised steel.
Can You Paint Galvanised Steel?
There are paints available which can be applied directly on top of Galvanised surfaces, but otherwise paining on top of the zinc coating can be rather challenging. Some paints may seem to adhere to the surface at first, but the layer of galvanisation will soon cause the paint to shed and peel, creating an unsightly aesthetic.
To apply normal paint you need to use a primer on the surface. First however the surface must be properly cleaned before a diluted mixture of water and ammonia is applied and left to dry. Then the surface should be sanded down with sandpaper and wiped clean again; only then can the primer be applied and painted over.
If you have any questions regarding galvanisation, do not hesitate to leave a comment on this post or on our Facebook, Twitter or Google+. Alternatively if you have had experience with welding or painting galvanised steel and would like to share your story or some photos with us, we would be more than happy to hear from you.