Industrial coating is a process that paints a layer of organic materials on the substrate of steel. It makes the steel attractive and corrosion-resistant. There are four commonly-used coating types including polyester (PE), silicone modified polyester (SMP), high durability polyester (HDP) and polyvinylidene fluoride (PVDF). Different coatings have different durability and resistance to UV. Below are features and applications of the coatings.
PE sheets are easy to process and have good adhesion. There are various colors to choose from. Besides, it’s the most cost-effective coating among other coating types. But its resistance to UV is poor. Therefore, the use of PE coating is limited. Its service life is 7-8 years.
Polyester contains active groups -OH/-COOH, which can easily react with other polymers to improve the sunlight resistance and chalking properties of PE. Therefore, SMP has good color retention and heat resistance.Also, the corrosion resistance of SMP reaches 10-12 years. But its price is higher than that of PE. Because the adhesion and formability of silicone resin are not good, SMP color-coated steel sheets are not suitable for products that require multiple forming processes. Most of them are used for building roofs and exterior walls.
The outdoor weather resistance of HDP polyester coating is better than that of PE and SMP coatings, and its service life is up to 15 years. The high-durability polyester resin uses monomers containing cyclohexane structure during synthesis, which achieves a balance between the flexibility, weather resistance of the resin, and cost. At the same time, UV absorbers and hindered amines (HALS) are added to the paint formulation to improve the weather resistance of the film. Durable HDP coatings have been recognized by the market for high cost performance.
Due to the strong chemical bonding ability, PVDF coating has strong corrosiveness and color retention. Besides, its large molecular weight and linear structure offer great chemical resistance, and strong UV and heat resistance. Even in a typical environment, its service life can reach 20-25 years.
Below is a table to compare the performance.
| Coating Types | Hardness | Strength | Weather Resistance | Corrosion Resistance | Cost |
| PE | Excellent | Good | Good | Good | Low |
| SMP | Good | Common | Excellent | Good | Medium |
| HDP | Good | Excellent | Excellent | Excellent | Medium |
| PVDF | Common | Excellent | Excellent | Good | High |
