Basic knowledge of color steel and common coatings

Color coated steel plate, commonly known as color steel plate, is a cold-rolled steel plate coated with other metals, non-metals or alloys (zinc, aluminum, magnesium, manganese, silicon, etc.) as the substrate, after surface treatment and transformation (degreasing, phosphating, chromate) ), coated with organic coating and baked, it has the characteristics of light weight, high strength, bright color and good durability. It is widely used in construction, home appliances, decoration, automobile and other fields.

The strength of the color steel plate depends on the substrate material and thickness, and the durability depends on the coating, surface coating and processing technology. The coatings include polyester coating (PE), fluorocarbon coating (PVDF), and silicon modified coating (SMP). ), High Weather Resistance Coating (HDP), Acrylic Coating, Polyurethane Coating (PU), Plastisol Coating (PVC), etc. The coating structure has two coatings and one baking, two coatings and two baking, etc. The maintenance-free service life can be 10-30 years depending on the environment and atmosphere.

Coating structure

Upper surface lower surface

One time coating, no coating 1/0

One time coating One time coating 1/1

Secondary coating No coating 2/0

Secondary coating Primary coating 2/1

Secondary coating Secondary coating 2/2

1. Polyester (PE, Polyester)

     PE coating has good adhesion to the material, the color-coated steel plate is easy to process and shape, the price is low, the product is large, and the choice of color and gloss is large. Polyester coatings are not ideal for UV resistance and chalking resistance of the coating film. Therefore, the use of PE coatings still needs to be subject to some restrictions. It is generally used in areas with less air pollution or products that require multiple molding processes.

2. Silicone Mobified Polyester (SMP, Silicone Mobified Polyester)

      Because polyester contains reactive groups -OH/-COOH, it is easy to react with other polymer compounds. In order to improve the sunlight resistance and chalking properties of PE, the color retention and heat resistance of Silicone resin is used as a denaturation reaction. , And the denaturation ratio of PE can be between 5%-50%. SMP provides better durability of steel plate, and its anti-corrosion period can be as long as 10-12 years. Of course, its price is also higher than that of PE, but because of Silicone resin Adhesion to materials and processing and formability are not ideal, so SMP color-coated steel sheets are not suitable for occasions that require multiple forming and processing. Most of them are used for building roofs and exterior walls.

3. High weather resistant polyester (HDP, High durable Polyster)

      Regarding the shortcomings of PE and SMP, British HYDRO company (now acquired by BASF), Sweden's BECKER, etc. in early 2000 developed HDP polyester coatings that can reach 60-80% weather resistance of PVDF coatings, which are better than ordinary silicon modified coatings. Polyester paint, its outdoor weather resistance can reach 15 years. The high weather resistance polyester resin uses monomers containing cyclohexane structure during synthesis to achieve the balance of flexibility, weather resistance and cost of the resin, and uses non-aromatic polyols and polyacids to reduce the resin’s absorption of UV light. , To achieve the high weather resistance of the coating. Adding UV absorbers and sterically hindered amines (HALS) to the coating formulation can improve the weather resistance of the paint film. High weather-resistant polyester coil coatings have been recognized by the market abroad, and the cost-effectiveness of the coatings is very outstanding.

4. PVC Plastisol (PVC Plastisol)

      PVC resin has good water resistance and chemical resistance. It is generally coated with high solid content, and its coating thickness is between 100-300μm. It can provide smooth PVC coating or light embossing treatment as embossing coating. ; Since the PVC coating film is a thermoplastic resin, it has a high film thickness and can provide good protection for the steel plate. But the heat resistance of PVC is weak. In the early days, it was used more in Europe. Due to its relatively poor environmental protection properties, it is currently used less and less.

5. PVDF

      Due to the strong bond energy between the chemical bond and the chemical bond of PVDF, the coating has very good corrosion resistance and color retention. Among the color-coated steel plate coatings for the construction industry, it is the most advanced product with a large molecular weight. Straight bond structure, so in addition to chemical resistance, mechanical properties, UV resistance and heat resistance are also outstanding. Under normal circumstances, its anti-corrosion period can be as long as 20-25 years. In recent years, fluorine-containing resins copolymerized with chlorotrifluoroethylene and vinyl ester monomers have become popular in China, and they are widely used in building exterior walls and metal panels. Due to the use of easily hydrolyzed vinyl ester monomers and the content of fluorine is 30% lower than that of PVDF %, so there is a certain gap between its weather resistance and PVDF. For the fluorocarbon coating produced by Baosteel, the PVDF content of the coating is not less than 70% (others are acrylic resin).

6. Polyurethane

A new type of topcoat developed in recent years, with excellent comprehensive performance and high price, is being promoted.

7. Acrylic resin

The comprehensive performance is good, the price is expensive, and it is only used in specific fields (such as containers).

Resin category	hardness	Bend	Corrosion resistance	Weather resistance	cost	Film thickness requirement/um
Polyester	excellent	good	good	good	excellent	20
Acrylic	excellent	Can	good	good	inferior	20
Silicon modified polyester	good	Can	good	excellent	good	20
PVC sol	Can	excellent	excellent	good	inferior	200
PVDF resin	Can	excellent	excellent	excellent	inferior	25
High weather resistance polyester	good	excellent	good	excellent	good	20

Color Classification:

In addition to the non-ferrous colors of major factories, the main color standard of the color steel industry is to adopt the German European standard color card (1927), which is translated into Chinese: Raul color card (RAL K5, RAL K7,... )

Part of the color series:

Ranking of the world's top ten paint brands

AKZONOBEL (N.L.) AkzoNobel (Netherlands)

Akzo Nobel is a global Fortune 500 company, the world's leading large industrial company, and one of the world's largest decorative paint companies. Its business covers Europe, America and all over the world. Its products involve industrial coatings, powder coatings, marine and protective coatings, and packaging coatings. , Pulp and paper chemicals, basic chemicals and polymer chemicals, etc., a wide range of production and supply of various oils, coatings and professional chemicals, including Dulux, Laiwei paint, Dulux professional, Mi Shili and other worlds Well-known architectural decoration paint brand.

PPG Industries (U.S.) PPG Industries (U.S.)

PPG Industries was founded in 1883 and is headquartered in Pittsburgh, USA. It is a global manufacturing company that produces and sells coatings, glass, glass fiber and chemicals, and is a leader in the industry in the world. PPG Industries was founded in 1883 and is headquartered in Pittsburgh, USA. It is a Fortune 500 company in the United States. It has production bases and affiliates in nearly 70 countries around the world. It has more than 30,800 employees and has been ranked in the Fortune 500 for 51 consecutive years. Among them, it is the world's leading manufacturer of paints for transportation, industrial, aerospace and packaging.

Nippon Paint (J.P.) Nippon Paint (Japan)

NipponPaint is the world's earliest paint company, and it is also the world's top ten brands of paint|paint|latex paint.