About the knowledge of the color-coated board, one article will make you an expert!
Many people do not know the specific difference between a really good color-coated panel and a poor color-coated panel when they buy color-coated panels,
because the surfaces are the same, and there will be no problems if they are not used for a period of time.
There are many factors to consider for the choice of coating, which mainly include the type of coating, the thickness of the coating, the color of the coating, and the gloss of the coating.
In addition, sometimes the requirements of primer and backside coating of the coating are also considered.
The types of coatings currently used for color coated steel plates include a polyester coating (PE), fluorocarbon coating (PVDF), silicon modified coating (SMP),
high weather resistance coating (HDP), acrylic coating, Polyurethane coating (PU), plastisol coating (PVC), etc.
Common coating types
Coating–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 many, and the color and gloss are 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 restricted. It generally uses in areas with less air pollution or products that require multiple molding processes.
Ordinary industrial plants and warehouses do not corrode the color panels themselves and do not have high requirements for the corrosion resistance and aging resistance of the color panels.
More consideration is given to the practicality and cost-effectiveness of plant construction.
Coating–Silicone Modified Polyester (SMP, Silicone Modified Polyester)
Since polyester contains active 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 are 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 higher than that of PE.
However, because Silicone resin has unsatisfactory adhesion to materials and processing and formability,
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.
Coating–High weather-resistant polyester (HDP, High durable Polyester)
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 achieve 60-80% weather resistance of PVDF coatings,
which are better than ordinary silicon modified Polyester paint, its outdoor weather resistance reaches 15 years.
The high weather resistance polyester resin uses monomers containing cyclohexane structure during synthesis to achieve the balance of flexibility,
weather resistance, and the cost of the resin, and uses non-aromatic polyols and polyacids to reduce the resin’s absorption of UV light.
To achieve high weather resistance of the coating.
UV absorbers and hindered amines (HALS) add to the coating formulation to improve the weather resistance of the paint film.
High weather-resistant polyester coil coatings have been recognized by the market abroad, and the coatings are very cost-effective.
Non-ferrous metal smelters (copper, zinc, aluminum, lead, etc.) in the metallurgy and power industries are the most challenging color plates for their service life.
Steel plants, power plants, etc. will also produce corrosive media, which require high corrosion resistance for color plates.
Coating–PVC Plastisol (PVC Plastisol)
PVC resin has good water resistance and chemical resistance.
It generally coats with high solid content, and its coating thickness is between 100-300μm. It can provide a smooth PVC coating or light embossing treatment as embossing coating.
Since the PVC coating film is a thermoplastic resin with high film thickness, it can provide good protection for the steel plate.
But PVC is weak in heat resistance.
In the early days, it uses more in Europe.
Due to its relatively poor environmental protection properties, it currently uses less and less.
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.
It the most advanced product among the color coated steel plate coatings for the construction industry.
It has a large molecular weight and a direct bond structure, so in addition to chemical resistance, mechanical properties, UV resistance, and heat resistance are also outstanding.
Under the general environment, its anti-corrosion period can reach 20-25 years.
In recent years, fluorine-containing resins copolymerized with chlorotrifluoroethylene and vinyl ester monomers have become popular in China,
and they have widespread use in building exterior walls and metal panels.
Since the content of easily hydrolyzed vinyl ester monomer and fluorine is about 30% lower than that of PVDF, there is a certain gap between its weather resistance and PVDF.
The PVDF content of the fluorocarbon coating produced by Baosteel is not less than 70% (others are acrylic resin).
Products in the chemical industry have the characteristics of volatility and are prone to produce more corrosive volatile substances such as acid or alkali.
When exposed to water, they are easy to form dewdrops and adhere to the surface of the color plate. Which will corrode the coating of the color plate and may further corrode.
To the zinc layer or even the steel plate.