Coil coating process is a steel industrial process in which large metal coils go through a series of fully automated production steps to be painted continuously. It is a very efficient way to produce uniform, high quality, coated finish over metal. Today an estimated of 80 % of metal are painted by coil coating. Color coated steel coils of Wanzhi Group also adopt this method.
The typical coil coating line is composed of decoiler, inlet looper, cleaning, chemical pretreatment, primer coat, curing, finish coat, curing, outlet looper, and recoiler. Below are the detailed steps.
-Mechanical stitching of the steel strip and being delivered in coil form
-Cleaning and chemical pre-treatment the metal surface
-Application of primer on one or both sides, then be dried and cooled down
-Coating the finish on one or both sides, and then be dried and cooled down
-Rolling up into coils after quality control system
1. Cold rolled steel (CR) without any zinc coating
2. Hot dip galvanized steel (HDG)
3. Electro-galvanised (EG) coated steel
4. Hot-Dip Al-Zn coated steel sheet (GL)
The key to coil coating process is to maintain a constant speed of the strip through the process. The accumulators allow this by letting the middle of the line to continue running at the prescribed rate while new material is added at the decoil end. The modern coil lines can run at speeds as high as 700 feet per minute and cure the applied paint in 15-45 seconds.
In the past times, steel and other metals arrived at a factory in an untreated state. Companies would fabricate and paint or treat the metal components of their product before assembly. This unsafe and environmentally harmful process ends until the coil coating method first developed in the 1930s. The procedure of coil coating pretreat the metal before it is cut and formed, and this invention sharply improved the efficiency of iron company at that time. But the whole process was not a high speed or continuous operation like we have today. In 1970s and 1980s, with the development of the accumulator towers, some lines can run up to 1000 feet per minute and coil coating has become a very cost-efficient way to paint metals.
The coating can keep the base metal from rusting and corrosion to prolong the service life of metal. Also, it makes the metal good-looking. That’s why color coated steel is used widely. For example, the market for pre-painted steel is in household appliances (refrigerators, freezers, microwave ovens, etc.), buildings (roofing, wall panels, doors, etc.), office furniture (desks, shelves, cabinets, etc.), transport industries (panels, bumpers, signal boards), etc. Compared to powder painting line, it is more cost-effective and the layers are thinner and more uniform. So the list continues to grow. It means it is promising to invest in pre-painted steel. If you are interested in the business, please contact us for details!
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