What Are the Types of Coil Coating?

In the mid to late 1930s, Joseph Hunter, the founder of Hunter Engineering, installed the first coil painting line. He used this method to paint the shutters as part of a continuous strip. Later, Hunter Engineering went on to design and build more coil coating lines. It was eventually acquired by the Italian global engineering company FATA Spa, which is known for building coating lines all over the world.

 

Today, the coil coating process offers a wide range of opportunities for the world's coating companies. The coil coating process is like one of those giant printing presses that produce evening newspapers. The process does not stop, it runs at a constant speed and the metal coils are constantly spliced together so that the moving web can be infinitely long.

Aluminum Coil

 

What is the coil coating process?

According to EN-10169:2012-06, the coil coating process is a method of applying a continuous coating of organic coating material to a rolled metal strip substrate. The process consists of

 

Unrolling and cleaning of the coil, if necessary

Chemical pre-treatment of the metal surface (one or both sides), and

Single or multiple applications of (liquid) paint or coating powder, followed by curing or lamination with plastic film.

Cooling and rewinding of the same coils for transport to the cutter, slitter or manufacturer.

Aluminum Coils for 3D

From the oldest and most basic lines to the newest and most modern, all web coating lines have many steps or processes in common.

 

A basic principle of web coating materials is that the material passes through the various process sections in a continuous manner without stopping or changing speed!

 

As a result, the material being coated has extremely consistent properties.

 

In addition to the obvious labour efficiency, environmental benefits and energy savings; coil-coated materials are inherently more consistent than those produced part by part.

Aluminium Coils for Can-end & Tab Application

 

Key coating types used in the coil coating process

The two main types of coatings used for coil coating include

 

Liquid coatings

Powder coatings

 

Litong offers different types of coil coating and meets different aesthetic requirements.

 

In addition, films are used instead of lacquers or additional lacquers where a very high aesthetic quality is required. Films are available in a wide range of film thicknesses, colours and finishes (smooth, structured or printed).

Aluminum Ceiling

Liquid coatings

Liquid coatings must meet a number of basic requirements to be successfully applied. Easy application even on the fastest production lines (up to 220m/min) to provide a homogeneous appearance and a defect-free film.

 

Very short curing times for pigment colours to remain stable - the time spent in the oven can vary between 6 and 60 seconds depending on the production line, while the substrate temperature varies between 210ºC and 250ºC depending on the paint used

 

Flexibility to bend the coated metal without cracking or loss of adhesion of the paint film.

 

Dry film thicknesses are typically between 5 and 35 microns for primers and between 15 and 200 microns for topcoats. The thickness depends on the quality of the chosen paint and the final requirements of the pre-painted metal product.

PVDF / FEVE - Coated Aluminum Coil

Powder Coatings

Powder coatings can be described as "solid coatings" which melt to form a continuous film on the substrate.

 

These coatings can easily be applied by electrostatic or frictional electrostatic spraying to cover the item being painted. As the thickness of the coating increases, the coating is self-limiting and therefore a uniform film thickness can be achieved. The powder coated article then cures as the powder melts and flows out to form a continuous film of paint followed by a chemical reaction to form a solid inert coating.

 

What is the best paint to use for color coated aluminum coils?

Colour coated aluminium coils are one of the most popular decorative materials due to their stable performance and corrosion resistance. Its superior performance is attributed to the coloured coating.

 

There are four main types of paint used for aluminium at home and abroad: PVDF, acrylic paint, epoxy paint and PE. what is the best paint for colour-coated aluminium rolls? Let's find out one by one.

PVDF / FEVE - Coated Aluminum Coil

PVPD coating is a coating with fluorine resin as the main film-forming substance. Of these four coatings, PVDF coating has the best anti-ageing properties and the strongest UV resistance. It also has excellent weather resistance, heat resistance, low temperature resistance, chemical resistance, unique non-stick properties and low friction properties. Its drawback is the limited choice of colours.

 

PE coatings

PE, or polyester, is another type of paint that we are familiar with. Polyester paint is mainly made from polyester resins. It offers good adhesion, rich colours, excellent outdoor durability and moderate chemical resistance. It is relatively less expensive than PVDF paints.

 

There are two improved polyesters, HDP and SMP. HDP has excellent colour retention, UV resistance and is cost effective. SMP has good hardness, abrasion resistance and heat resistance, but is moderately flexible and moderately cost effective.

PE Coating Coils

Acrylic pigments

It is a self-drying weather resistant anti-corrosion coating based on traditional acrylic resin with polyethylene rubber and weathering fillers and additives. It is easy to apply and cure at room temperature.

 

Epoxy resin paint

Its main components are epoxy resin and curing agent. Epoxy paint film has good adhesion, corrosion resistance and wear resistance, but is brittle. It is generally used as a backing paint for aluminium coils.

 

The choice of different paints for coated aluminium coils also means that the price will vary. So it is important to choose the right paint for the application and occasion of the aluminium coil. This will be the best paint for aluminium colour coated coils.

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