A Guide to Steel Coating Technologies
- 4 years ago
There are many different types of steel coating technologies available today and all are there to help protect the steel from corrosion and degradation. Let’s take a look at some of the different methods along with the pros and cons with regard to their usage in differing environments.
- Galvalume – Galvalume is an extremely popular coating process which uses 55% aluminium to 45% zinc alloy. Used widely in roofing across North America, Galvalume is a great coating due to its excellent anti-corrosive properties. Its strength also means that it doesn’t dimple as easily as other coatings in hailstorms. Galvalume is easy to work with, looks good and last for a long time. The added aluminium helps in heavy salt environments such as seaside properties. Corrosion can increase if ponding is allowed to happen.
- Continuous hot dip galvanising – A very common technique in the manufacture of coated steel. This process is where a steel sheet is immersed into a vat of molten zinc to form the coating. Used in everything from car body panels to air ducts. The zinc coating offers good resistance to corrosion and works well in low temperatures. However, there are disadvantages with the process such as its usage in pipework. Often after galvanising there are rough spots on the inside of the pipework that can cause obstruction and there have also been reports of leeching, where lead can enter the water system. It is for this reason that copper piping is so often used inside homes. Usage near salt water should also be avoided.
- Hot dip batch galvanising – This method is popular for small amounts of large bulky items. The preformed items are dipped into a bath of molten zinc to coat the steel frame. Similar pros and cons to that of continuous hot dip galvanising apply.
- Electrolytic galvanizing – A method that produces a 25-100 g/m² zinc coating on each side. Higher costs have made this a less popular technique than hot dip galvanising these days. Pros are that the amount of coating layered onto the steel can be very closely controlled and offers a much better finish than hot dip galvanising. The fine layer of zinc doesn’t offer the same protection as other methods so the majority of electrolytic galvanised parts are for indoor usage only.
- Colour coated steel – Also referred to as Organic Coated Steel. This is a product that is produced by taking zinc coated steel, and then applying a painted layer, such as polyester resin or PVC, over it. Doing so adds far greater durability to the surface area and can extend the life of the product by 20 years or more. Commonly used in building projects worldwide because of its superior anti-corrosive properties.
Choosing the correct steel coating depends on many factors, such as what the end product will be and where it will be used. Hopefully the brief descriptions above will help you make the correct choice.