Main Steps of Metal Coil Coating

Coil coating line is an automated and efficient method of coating metals. It is a continuous process that requires a roll of metal for each finishing step from cleaning to curing before packaging for shipping. Coil coating provides a consistently high quality product that is durable, corrosion resistant, cost effective, recyclable and more environmentally friendly than other alternatives.
In this article, we will learn about the coil coating process, the different coating technologies used for coil coating.

Main steps

The coil coating process starts with a coil of untreated sheet metal that is unrolled, treated, coated, cured, rewound and packaged for shipping at a rate of 100-200 meters per minute. This process can be used on one or both sides of the sheet metal and up to three layers of paint can be applied and cured. Sheet metal is most commonly aluminum, steel or galvanized steel, with varying coil sizes. The coil coating process is shown below.
Stitching the strip to the previous coil
Cleaning the strip
Power brushing
Chemical pretreatment
Drying the strip
Apply primer on one or both sides
First curing oven
Cool the strip
Topcoat on one or both sides
Second curing oven
Cooling to room temperature
Rewinding of wrapped coils

Benefits of Coil Coating

Companies in the building and construction, HVAC, electrical, automotive, transportation and furniture industries are increasingly using pre-painted or coil-coated materials in their manufacturing and construction. The top five reasons for this are

Environmental protection

The closed loop of coil coating systems eliminates the large amount of waste associated with the painting process. Coating application efficiency exceeds 90%, excess metal can be recycled, and emissions and disposal are low and controlled.

Cost Reduction

Coil coating significantly reduces or eliminates paint waste, material handling costs, energy consumption, hazardous waste disposal, insurance premiums, capacity constraints and compliance costs.

High Quality Finishes

Applying a smooth flat metal provides a smooth and consistent finish while eliminating the risk of corners and gaps that can cause adhesion problems and hide defects. A uniform layer of coating also allows for strict color consistency.

Corrosion Resistance

Studies have shown that coil-coated metals consistently provide better corrosion resistance than post-painted surfaces. The consistency and accuracy of the coating process also ensures the best protection and finish.

Different coating chemistries

For such a finely tuned process, the coating technology offers remarkable flexibility. Metal sheets can be coated to suit your specific end use.

Polyester Coatings

Polyester is an extremely hard and tough coating that can be used on a variety of heavy-duty surfaces. Polyester can be used in a range of formulations that enhance certain properties. Combining versatility with low cost, it is clear why polyester is a common choice for warehouses and industrial or storage buildings. Polyester is also used for appliances due to its excellent scratch resistance, outstanding flexibility and formability, and stain and dirt resistance.

PVDF

Also known as 70% PVDF (from the percentage of PVDF in the resin), polyvinylidene fluoride is a high-performance fluoropolymer coating that is particularly well suited for architectural applications. Although known for its non-stick properties, the fluoropolymer also offers stability, chemical resistance, corrosion and temperature resistance, and excellent color and light retention due to its UV stability.

SMP Coatings

Silicone modified polyester is made by adding silicone resin to a polyester resin coating. SMPs are more scratch and abrasion resistant than PVDF, which means they can withstand harsher handling conditions. They can be modified to have a life expectancy of up to 20 years.
 

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