Coil coating process is a method in which a liquid coating material is continuously applied on rolled metal strip via rotating rollers in a Continuous Coating Line (CCL). The strip is pretreated before coating and afterwards dried in curing ovens.
Coil Coating technology is over 50 years old and has been developing since. Its advantages are:
At OrelMetallPolymer we have a state-of-the-art Continuous Coating Line that allows us to apply any existing paint to CRS, galvanized steel, aluminized steel, stainless steel, aluminum and tinplate in coils.
The process of coil coating can be divided into three stages:
Pretreatment stage involves placing a metal coil on one of the Uncoilers (#1 and #2) and threading coil head into the line. Since in most cases coil heads have defects, they are normally cut off with the Entry Crop Shear. Then coil head is threaded into the Stitcher where it is joined with the tail of the previous coil.
Continuous strip enters Entry Accumulator which enables non-stop operation: it creates storage of material that is being fed into the line while coils are stitched.
Often incoming strip has flatness problems caused by previous technological processes or incurred during coil transportation. Flatness defects hamper coating process, damage the equipment and cause loss in coating integrity. This is why we have a Tension Roller Leveler in our CCL in order to improve strip flatness.
For the purpose of reaching proper coating adhesion to the metal substrate, the strip firstly must be cleaned of all impurities, oxides, preservation oil, passivation, remains of lubricants applied during previous technological stages. Secondly, the strip needs to be covered with conversion coating that improves adhesion of primer and topcoat to the metal substrate. These operations are performed in our efficient Brushing Unit and Chem-Coater.
After Pretreatment, the strip enters the Coating area. In our CCL, we have 3-roller coaters #1, #2a and #2b (see the schematics below) for primer and topcoats that allow us to apply double-layer polymer coatings on the front and back surfaces of the strip.
Coater #1 applies primer to the pretreated strip. Primer is responsible for adhesion of the entire coating system to the metal substrate. When leaving the Coater #1, strip enters Curing Oven #1 and subsequently cools down in the Water Cooler #1.
We have two topcoat coater installations (Coater #2a and Coater #2b) in our CCL that allow quick color and/or coating type changes without stopping the line: when we need to switch paints, rolls of the active coater open while rolls of the second coater close on the strip.
The open coater starts preparation for the next type of paint immediately. Topcoat is dried in the Curing Oven #2 and cooled down in the Water Cooler #2.
Coated strip is then subject to the finishing treatment:
Exit Crop Shear separates finished coil from the continuous strip, cuts out stitched parts of the strip and samples for quality check. As well as the Pretreatment area, the Finishing zone has Exit Accumulator to provide non-stop operation of the CCL by supplying the strip while the finished coil is being unloaded and the new coil head is being thread into the Recoiler.
Samples that have been cut out of the coil are passed to the workshop laboratory for testing and sent to the sample library for storage. In the lab, samples are tested for compliance with standard requrements and customer’s specifications. Obtained results are entered into the coil certificate.
Once unloaded from the Recoiler, finished coils are packed and labelled and moved to storage area.
Coil coating process in our facility fulfills all up-to-date requirements to equipment and consumables. In order to ensure consistently high quality of coatings, maintain stability and efficiency of production process, we picked the best available auxiliary equipment: low-molecular membrane water demineralization unit, sustainable regeneration system for waste heat, and chiller cold supply unit.
