From paint to coating: Evaluating colour coated steel and traditional painted steel
Product25 Jul 2023
Steel, a material that has withstood the test of time, continues to be the backbone of construction and manufacturing industries, propelling human achievements to new heights. Its unique properties and adaptability have made it an indispensable element in the modern world. From the majestic frameworks of architectural marvels that define city skylines to the intricate components that power our cutting-edge technologies, steel's significance remains undeniable.
Exploring steel colour coating
- The process starts by uncoiling the coil and joining the head end of the strip to the tail end of the previous coil for continuous operation.
- Pre-treatment is done to ensure a uniform and clean substrate surface, crucial for better adhesion and formability of the coated steel sheets.
- Chemical pre-treatment involves strip surface washing and adding a passivation layer in four phases to improve corrosion resistance and adhesion.
- A uniform primer with controlled thickness is applied on the pre-treated surface to provide flexibility and corrosion resistance.
- Different types of primers are available like epoxy, polyester, polyurethane, and PVC based on resins. Epoxy primers are preferred for roofing due to their better corrosion resistance.
- The colour coating line typically has two coaters: one for the primer and another for the top coat and backing coat.
- After coating, convection ovens cure the colour coatings with precise temperature controls.
- Multi-layer coating can be applied for higher quality demands, with a finish coat on top of the prime coating.
- The top coat contains colour pigments and additives for required colour and performance properties.
- After curing, the painted strip is quenched in water, though for it to be laminated an adhesive is applied first followed by the laminate film being pressed onto the strip.
- A protective film may also be applied to safeguard the coating during subsequent processing by the customer. Visual inspection and quality control are performed before coiling the strip.
Different types of coats used in colour coated steel
Colour-coated steel is achieved through various coating processes, each offering a specific benefit.
Epoxy coatings are used in colour coated steel for specific applications that require exceptional chemical resistance and adhesion. They are commonly used in industrial settings where chemical exposure is a concern.
Silicone modified polyester (SMP) coatings are blended with polyester coating to provide weather resistance and durability.
Polyvinylidene fluoride (PVDF) coatings, known for exceptional weather resistance and colour retention, are also applied through the coil coating process using high-quality fluorocarbon and acrylic resin. SMP being a harder paint system than PVDF makes a SMP-coated material more difficult to scratch
On the other hand, plastisol coatings create a textured finish through dip-coating or rotary gravure methods. Polyurethane coatings offer flexibility and abrasion resistance through the coil-coating process.
Exploring traditional painted steel
The painting process involves applying paint to a prepared surface using a specific sequence of steps. It starts with selecting the appropriate paint resin, which determines the type of paint (e.g, acrylic, oil). Resin also helps the paint particles adhere to the surface and holds the particles together.
Additives can be included to modify paint properties, like thickness and smoothness. Pigments are added to give the paint its desired colour.
Solvents are used to adjust paint's consistency and drying time. Once mixed, the paint is tested before application. It can be applied with brushes, rollers, or spray equipment. After application, the paint dries, forming a solid film on the surface. Multiple coats may be required for full coverage. Proper cleanup is essential for painting tools and equipment.
Thickness comparison
Industrial painting:
Industrial painting typically involves the application of multiple layers of paint to achieve the desired thickness. The thickness may vary based on the application method, surface preparation, and the type of paint used.
Colour-coated steel:
Colour-coated steel is a pre-finished product where a specific colour-coating is applied to the steel substrate during the manufacturing process. The colour-coating is typically applied in a controlled and automated process, ensuring uniform thickness and coverage.
Performance comparison
Durability: Both industrial painting and colour coated steel are designed to provide durability and protection against environmental factors. However, colour-coated steel often benefits from controlled application processes, leading to better adhesion and uniformity, which can contribute to enhanced durability.
Colour retention: Colour-coated steel tends to have better colour retention over time compared to industrial painting. The colour coating is factory-applied and specially formulated to resist fading, chipping, and uv degradation.
Corrosion resistance: Colour-coated steel is engineered to provide excellent corrosion resistance due to the combination of the steel substrate and the protective colour coating. Industrial painting can also offer corrosion protection but may require additional layers or specialised coatings for optimal performance.
Maintenance: Colour-coated steel generally requires less maintenance over its lifespan compared to industrial painting. The pre-finished surface helps reduce the need for periodic repainting, saving time and costs.
Application speed: Colour-coated steel offers faster installation times since the coating is applied during manufacturing, eliminating the need for on-site painting.
Why should you opt for colour coated steel?
Colour-coated steel offers a multitude of advantages that address the challenges posed by corrosion in various applications. The material's ability to withstand intense forming operations even in low temperatures makes it ideal for industrial use and renovation purposes alike.
Beyond its practical benefits, colour-coated steel offers aesthetic enhancement, providing architects and designers with a vast array of colour, shapes, and textures to choose from. Whether for urban buildings or traditional projects, the versatility of finishes, ranging from gloss to matt and smooth to rough, allows for creative expression in architectural design.
Additionally, the environmentally conscious aspect of colour-coated steel is noteworthy. It stands as a sustainable choice, being recyclable, and contributing to building practices that prioritise sustainability. As it protects and beautifies structures for a lifetime, its end-of-life phase involves recycling, converting worn-out sheets into new steel products. This not only aligns with environmental principles but also makes colour-coated steel an affordable and economical solution, further enhancing its appeal as a material with a cause. With its remarkable advantages, colour-coated steel emerges as a solution that addresses corrosion concerns while promoting environmental responsibility and design versatility.