FOCUS ON COIL PROCESSING conditions or terrible weather . Coil coatings can be utilised to cover building walls and roofs , add decorative accents and produce lighting fixtures . Transport applications include container sheets and panels ; the sides and interiors of caravans and mobile homes ; the bodies of vans and trailers , insulated boxes and both road and rail coaches . They are also utilised in a variety of appliances including refrigerators ; washing machines ; dishwashers ; microwaves and heating , ventilation and air conditioning ( HVAC ) equipment ,” outlined the analyst .
The analyst confirmed that urbanisation is a primary factor in market expansion . The number of new government programmes and tax breaks that stimulate large-scale manufacturing and use of coil coating is also a major factor driving market expansion .
“ Businesses are investing significantly more in research and development , with the primary objective of creating a new generation of eco-friendly and non-polluting coil coatings . The new generation of products manufactured in this manner can be utilised in a variety of ways ,” it added .
A sustainable choice
Coated coil can be slit for narrow widths , cut to required lengths , bent , profiled or deep drawn without damaging the organic coating . It can be processed into any number of shapes , depending upon the end use .
The continuous coil-coating process provides high standards of quality assurance through coil-to-coil consistency and has significantly lower environmental emissions than batch or post-painting processes . This reduces the need for re-work and lowers non-conformance levels and associated costs .
The coated surface can have a wide range of colours , gloss levels and surface textures . The end use of the finished product generally dictates the choice of coating . The user may require non-stick properties , great flexibility or high chemical resistance . Many new coating types are available to meet the increasing demands of users .
By utilising pre-painted metal in their process , manufacturers can also eliminate their paint lines which are usually the major bottleneck in their operation . Capacity constraints are minimised , potentially improving ROCE .
“ Although the organic coatings used in coil coating are generally thinner than post-applied powders and films , they still give better inservice performance . So , you use less paint which minimises resource consumption and enables you to cut down or even eliminate maintenance and re-painting ,” commented ECCA ( The European Coil Coating Association ).
“ The cost of complying with environmental regulations is significantly reduced , or even eliminated . The cost of the disposal of hazardous waste associated with the painting operation is also eliminated , Scheduling problems and the costs associated with batchtype processing are minimised or removed altogether . Since input material is more directly related to output , the processing time is reduced and stocks are minimised ,” it added .
Coil coating ( image : Cooper Coated Coil .)
The coil coating process
The coil-coating process , which is used to produce pre-painted metal , is continuously evolving . According to ECCA ( The European Coil Coating Association ), some of the major innovations in recent years have been :
■ Roller coating : The basic technique of applying paint by roller coating is at the heart of pre-painted metal and continuous innovation is used to make this faster , more consistent and more efficient .
■ No-rinse pre-treatment : The adoption firstly of reverse-cascade rinsing and then of no-rinse pre-treatment on many coilcoating lines has dramatically reduced water usage in the initial stages of the process .
■ Curing ovens : The most energy-intensive part of the coil-coating process has seen major development to provide more efficient ovens , able to cure paint in seconds , using both traditional gas-fired techniques but also innovative induction , IR and NIR curing techniques .
■ VOC elimination : The coil-coating process allows for very efficient collection of VOCs from the solvents used in paints . The latest oxidisers ensure that over 99 % of these are destroyed without polluting the atmosphere .
“ The metal substrate ( steel or aluminium ) is delivered in coil form from the rolling mills . Coil weight varies from 5-6 tonnes for aluminium and up to 20 tonnes for steel . The coil is positioned at the beginning of the line and then unwound at a constant speed , passing through the various pre-treatment and coating processes before being recoiled ,” said ECCA .
Two strip accumulators found at the beginning and end of the line enable the work to be continuous , allowing new coils to be added ( and finished coils removed ) by a metal stitching process without having to slow down or stop the line ,” it continued . The steps on a modern coating line are : -
■ Mechanical stitching of the strip to its predecessor .
■ Cleaning the strip .
■ Power brushing .
■ Surface treatment by chemical conversion .
■ Drying the strip .
■ Application of primer on one or both sides .
■ Passage through the first curing oven ( between 15 to 60 seconds ).
■ Cooling down the strip .
■ Coating the finish on one or both sides .
■ Passage through the second curing oven ( between 15 to 60 seconds ).
■ Cooling down to room temperature .
■ Rewinding of the coated coil .
Additional functionality for coatings
Pre-painted metals are available with additional functionality included in the organic coating . This includes anti-bacterial ; antifingerprint ; anti-dirt ; easy-clean ; non-stick and heat-reflective capability .
“ This added functionality gives added value in many applications , but the coatings of tomorrow may include even more such as self-healing coatings or the ability to convert sunlight into energy or capture carbon dioxide from the atmosphere ,” explained ECCA .
In February 2023 , Beckers developed its first commercial paint formulations for dual ultraviolet and electron-beam curing in the coil coating market . The technologies can significantly reduce VOC and CO₂ emissions and enhance efficiency by reportedly providing up to twice the surface coverage per kilogram of paint .
“ The finished coil-coated steel has the same material , protection and corrosion-resistance properties as conventional coil coated steel or aluminium , but with much less embodied environmental impact . UV / EB coil coating significantly reduces CO₂ emissions and enhances resource efficiency . Being solvent-free , it also significantly reduces Volatile Organic Compounds ( VOCs ) as well as reducing the quantity of paint required to achieve a defined coverage on the metal ,” concluded Beckers . n
A coated coil ( NLMK ).
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