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Unicoil production facility.
Three years after commissioning of its coil coating line, Unicoil of Saudi Arabia has reached a milestone of having completed painting 100 million sq m of steel and aluminium coils.
The state-of-the-art coil coating line is a joint venture between the Zamil and Rashid groups of Saudi Arabia and BHP of Australia.
In the past three years, Unicoil has established itself as a reliable supplier of prepainted steel and aluminium in the GCC region. The prepainted steel is predominantly used in the building sector for making rollformed roofing and walling.
The other applications of Unicoil's painted products are in the fabrication of garage doors, sandwich panels, outer covers for appliances such as refrigerators, deep freezers and washing machines.
The selection of metal substrates and the type of applied paint coatings, depends on the end use of the painted products.
The building sector uses commercial and structural steel grades. The cold-rolled steel is either aluminium-zinc alloy coated or hot-dipped galvanised. Aluminium-zinc alloy-coated steel is marketed as Zincalume. The coating consists of 55 per cent aluminium, 1.5 per cent silicon and the balance is zinc. These metal coatings offer galvanic protection to steel. The corrosion resistance of Zincalume steel coatings is higher compared to the life of galvanised coating of equal thickness under the same exposure conditions
Various type of metallic coating are used on steel.
Unicoil imports the galvanised and zinc-aluminium alloy-coated coils from southeast Asia, Australia and Europe.
After the commissioning of Hadeed's cold rolling and galvanising facilities in Jubail, it is expected that Hadeed will be a major supplier of galvanised steel to Unicoil. Initial trail runs have indicated that Hadeed can produce galvanised steel suitable for painting.
Painting process
The painting process consists of following sequences:
Paints used
Unicoil uses a variety of paints suitable for various end applications. All paints used are of the thermoset type, which need curing at specific temperatures to achieve the required properties. The coil coating paints are manufactured locally by Dammam-based paint manufacturers - International Paints and Sipco, both companies use Akzo Nobel's paint technology.
Primers: Epoxy and polyester primers are generally used. These primers have excellent corrosion resistance properties and provide good adhesion to the second layer of paints. When substrate flexibility is very important in any application, flexible polyurethane-based primers can be provided.
Topcoats: The majority of the top coats are polyester-based. Besides providing a good finish to the steel, these coatings have excellent resistance to UV (ultra-violet) degradation and chalking. For severe environments, fluorocarbon-based topcoats are also available.
Unicoil has few standard colours in white, beige, blue and green shades. Beside these standard colours, other colours can also be painted. The current list of paints has 80 shades, the most popular being white. Film thickness of the topcoats ranges from 15 microns to 30 microns.
Backer: The back side of the coil - which is the non-exposed side - has a primer and a backing coat . Generally, the film thickness on the back is less than the top side. These backers are compatible for applying polyurethane or polystyrene insulation material.
The painted steel of Unicoil is marketed under the house brand, Colorite and Molawan, as well as BHP's Colorbond painted steel.
Paint performance
Unicoil offers warranties against weathering on its Colorite and Colorbond brands.
Further details on Unicoil and its product range are available on its web site (www.Unicoil.net)
