Everything You Need to Know About Corrugated Galvanised Iron
While you might be familiar with galvanised corrugated sheets as building materials that are commonly used as roofing sheets, it may surprise you to know that these sheets, although referred to as ‘iron’ especially in the UK, are actually made of steel (iron alloyed with carbon for strength). In fact, only the vintage sheets that survive might actually be composed of 100% iron. These sheets are composed of hot-dip galvanised mild steel, which has to be cold-rolled. This is done to produce a linear corrugated pattern in them. Corrugations increase the ability of the sheet to bend in the direction perpendicular to the corrugations, because of which each sheet is manufactured so that it is longer in its ‘strong’ direction.
The popularity of corrugated galvanised iron stems from the fact that it is lightweight and easily transported. This is one of the reasons that it was so prevalent in military buildings such as sheds and water tanks and also came to be used in rural areas. They are beneficial in the sense that they have proved helpful for developing countries.
The process of corrugation is done by a technique called roll forming, in which a long strip of sheet is continuously bent into a desired cross-section. This process is modernised and highly automated, which allows high productivity with low labour costs. First, the sheet metal is pulled of the large rolls and put through rolling dies that create the corrugations, after which the sheets are automatically sheared off at a desired length. A variety of shapes and sizes are available, such as the conventional round wavy style, or the trapezoid sheet metal, often seen on industrial buildings.
Today, not only steel, but other materials such as ferrous alloys like stainless steels, aluminium and copper undergo the corrugation process. The most common materials are regular ferrous alloys, due to their affordability and abundance. The sizes of these materials range from very thin (30 gauge- 0.30 mm) to a relatively thick 6 gauge (4.94 mm). They can be produced in thinner or thicker variations according to the requirements of the consumer by reputed manufacturers such as Jindal Vijayanagar steel limited.
Plastic and fiberglass have also been roped in and given the corrugated look. These are especially useful, as they can be used to provide transparency for light to penetrate when used with metal sheets.
The corrugations have grooves, or the distance between two crusts, known as the pitch. They also have a depth, or the height from the top of a crest to the bottom of a trough. It is important for these to be uniform in order to allow easy stacking and overlapping.