Understand the different types of coated steel

Main product groups

The most common coated steel products are metal coated steels. Its manufacture typically uses cold-rolled steel (although a small percentage is made from hot-rolled coil or plate) which is then plated with zinc or tin. An additional coating is often added to zinc-coated steel in a later process step to produce color-coated steels.

Zinc coated steels

There are several different types of zinc (or galvanized) coating. These are

• Continuous Hot-Dip Galvanizing – In this process, a cold-rolled coil or sheet is dipped into a pot of molten zinc. A common manufacturing technique for hot-dip galvanized steel is the Sendzimir process (which uses a small amount of aluminum in the coating). Continuous hot dip galvanizing is currently the most popular method of producing coated steels. Typical applications for these steels include construction (roofs, walls, often as sandwich panels), auto body components (exposed panels), manufacturing (metal cabinet frames and walls), agriculture (latrines, livestock buildings, silos), heating and ventilation (enclosures). ), air ducts); and it is very common for galvanized steel to be further coated (see below) for many of these uses.
• Hot-Batch Galvanized – Used for small batches in a non-continuous batch process. Typical products may include lighting poles, antenna poles, radio towers, road barriers, power transmission lines, camera poles, highway crash barriers, pedestrian bridge systems, garden frames, galvanized wire or mesh, street furniture, advertising poles, boilers, ducts, tubes and other profiles, etc. The usual production process involves immersing the cast steel fabrication in a molten bath, which can be up to 12 meters long.
• Electro-galvanizing – a somewhat popular coating technique that produces a zinc coated steel with a coating of 25-100 g/m2 per side, although capital costs, operating costs and market preferences have driven demand away from electrogalvanizing to continuous hot-dip galvanizing in recent years. .
• Galvalume, which involves the application of an alloy of 45% zinc and 55% aluminum. Galvalume is especially suitable for highly corrosive environments [e.g. sea air] and is suitable for roofs, exposed panels, non-exposed auto parts, etc. [Galvalume is a registered trademark of BIEC International Inc].
• Galvanneal: Here, a zinc coating application is followed by a heat treatment to form a Zn-Fe alloy coating (8-15% Fe and 100-120 g/m2 total) of very high surface quality. The product is ideal for paint coatings and is easily weldable. Steel grades can range from soft deep drawing to high strength low alloys.

color coated steel

Organic-coated steel (also known as “color-coated steel”) is a product made from zinc-coated steel, typically made from hot-dip galvanized steel. Here, the galvanized coil or sheet is painted with an organic coating such as PVC or polyester resin, which imparts greater durability to the surface. As a result, the useful life of the steel can be extended for another 20 years or more, as the added protection of the extra organic coating inhibits corrosion.

tin plate

Tinplate is popularly used in beverage cans, for food packaging, as well as in the chemical industry. [aerosols, paint, oil cans etc]. Despite the name, tinplate actually takes one of two forms:

• One form is thin-gauge cold-rolled steel that is electrolytically plated with tin.
• The other form is called tin-free steel and uses a chrome plating instead of a tin plating. By producing a less bright finished product, tin-free steel was introduced a few years ago in an attempt to reduce packaging costs when the price of tin rose to high levels. However, most tin-plated steel today is still produced as tinplate rather than tin-free steel.

There are a number of other coatings on the market for steel, and these include nickel-zinc coating [favoured by some automotive producers] and matte-coated steel [which uses lead – often for applications such as petrol tanks]. Therefore, this is a fairly fragmented market and it is likely that additional coatings will continue to emerge for new applications over time.