Metal Coatings 101

What is a Coating?

Coatings are made up of four ingredients: pigments, resins, solvents and additives. The amount of each ingredient can vary based on the desired outcome for the coating. Let’s take a closer look at what each ingredient does.

• Pigments are tiny particles of powdered color that are blended to create the desired coating color. Pigments boost the aesthetics of a coating, provide hiding and help with chemical and corrosion resistance.

• Resins provide the physical performance properties of a coating. They act as a binding agent by holding everything together and give coatings their durability, hardness, flexibility and adhesion.

• Solvents help with the overall application process and are the vehicles that transport solids to the substrate. Solvents also provide viscosity, leveling and flow stability.

• Additives are any number of chemicals supplementing the coating to produce special effects. Additives enhance coating formulas by adding texture, hardness, flexibility and more.

Pigments are a key ingredient that can make or break a coating. They provide the coating’s color and function, but also help with a coating’s resistance to corrosion and water. Depending on which type of pigment you choose, pigments can enhance or degrade the overall performance of a protective color coating. There are four high-performance pigments that can go into a coating:

• Organic Pigments
• Inorganic Pigments
• Specialty Pigments
• Solar Reflective Pigments

Organic Pigments

Organic pigments are natural, carbon-based pigments that are often made from petroleum compounds. They’re bright in color but have less hiding power and weathering resistance compared to inorganic pigments.

Inorganic Pigments

Inorganic pigments, also known as ceramic pigments, are made of metal oxides and mixed metal oxides. They are typically seen in neutral and earth-toned colors, but offer superior stability, hiding power and weather resistance.

Specialty Pigments (Effects)

Add depth to any color with specialty pigments. From shimmering metallics to color-shifting finishes, specialty pigments can help coatings take on a new dimension. There are three types of specialty pigments you can use to achieve a specific look:

• Mica/Metallic
  Using mica-based pigmentation, these pigments reflect light in a unique way and take on a pearlescent or metallic look, all without the need for a clear coat.

• Intense Sparkle
  Add rich, eye-catching color to any coating with intense sparkle. Our proprietary pigmentation system offers varying levels of intense sparkle in silver, gold and copper to complete your vision.

• Color-Shifting
  Experience stunning color that shifts when viewed from different angles. Color-shifting pigments use pearlescent mica or aluminum flakes. With our process, we can control and customize the degree of color shifting through formulation.

Solar reflective pigments have been altered both physically and chemically to reflect infrared radiation while still absorbing the same amount of visual light. These types of pigments help:

• Cool roof coatings
• Reduce energy use
• Reduce air pollution and greenhouse gas emissions

With solar reflective pigments, sunlight hits the surface and is reflected away from the structure. Some heat is still absorbed and transferred to the building below, but less so than in structures without solar-reflective pigments.

Resins are the binding agent that holds all the components in a coating system together. They make up the physical performance properties of a coating and boost its durability, physical strength and chemical resistance. There are four types of resins you can use in a coating:

Coil Resins:
Fluoropolymer Resins (PVDF / FEVE)
Siliconized Modified Polyester Resins
Polyester Resins

Extrusion Resins:
Fluoropolymer Resins (PVDF / FEVE)
Acrylic Resins
Polyester Resins

Solvents adjust the application properties and act as a carrier of resin and pigments. They dissolve or disperse the resin and allow it to “flow out” on the substrate. Solvents provide:

• Viscosity
• Leveling
• Flow stability

Additives enhance the formula which affects the overall product performance and appearance. Additives also:

• Add texture (crinkle)
• Increase hardness
• Help with flexibility
• Assist with curing and more

Coil Coatings Process

Coil coatings are applied in an efficient, highly controlled process. During the coil coatings process, coil coatings are applied to coil formed metal sheets by a continuous automated process that can happen at up to 700 feet per minute. Coil is unwound, cleaned, treated, primed, painted and baked before being recoiled for shipment.

What would otherwise be wasted is turned into useful energy by the coil coating process. As the coil coating metal is paneling, the solvents in the coating are captured and become fuel for the curing process.

Extrusion Coating Process

While coil coatings are applied to metal before it’s formed, extrusion coatings are spray applied after the metal has been formed. Shop-applied coatings are specially formulated to adhere to metal substrate and resist wear and tear through the manufacturing process.

Extrusion coatings are applied in a manufacturing process that consists of cleaning and pretreating aluminum preformed extrusions, going through a spray process and then thermally curing the metal coating system for it to set.

Coatings have many enemies that can lead to the breakdown of color over time. Exposure to UV rays, moisture, humidity, high temperatures and temperature fluctuations can affect the look and performance of a color.

When a coating starts to fail, you’ll see:

• Chalking
• Fading
• Blistering

To prevent coating failure, every Sherwin-Williams Coil Coating system is subjected to the harshest testing environments at our test fence facility in Fort Myers, Florida.

Chalking

After the coating is exposed to UV rays, the system begins to degrade and leads to chalking. As the resin system breaks down, particles take on a powdery appearance and embedded pigment particles lose their adhesion to the film. This makes the color look faded or white.

Fading

Fading is caused by the UV and hydrolytic degradation of the resin system. Organic pigments may also deteriorate if they are present in color. Fading is calculated by using Delta E values, a single number that represents the distance between two colors.

Blistering

When a coating is exposed to heat, moisture or a combination of both, you may see a localized loss of adhesion and the coating lifting from the underlying surface. Over time, blistering leads to peeling and corrosion. While moisture and heat are often to blame, blistering can sometimes be the result of improper drying or curing of the coated material.