Chemistry Corner: Ultraviolet Radiation and Industrial Paint Reply

Most people who aren’t professional painters think discolored paint is an eyesore. Whether it be on an old car driving by or a warehouse they pass on the way to work, cracked and faded paint often leads to people wondering, “Why don’t they repaint that building?” or “That car sure could use a fresh coat of paint.” Most people don’t stop to think about it beyond the noticeable appearance of the item, but professional painters know better. They realize that while aesthetic appearance is important, faded paint is actually an indicator of a bigger problem: the surface below is being irreparably damaged by harmful ultraviolet rays.

UV paint damage on a building

Paint that has been discolored by ultraviolet rays.
Image courtesy of Vivilon.

When thinking about the protective properties of paint, we most obviously think about protecting the substrate from elements like wind and rain, heat and dirt. But perhaps the most significant and powerful catalyst for damage on many outdoor structures and surfaces comes from above: the sun. Just like it’s a bad idea to spend the day at the park or an afternoon on the beach without sunscreen, it is also a bad idea to not consider proper UV protection for the substrate when painting.

Ultraviolet radiation effects paint in two different ways. UV-A radiation will dry out the resin in a paint leading to cracking as the paint begins to dry up on itself.  UV-B radiation leads to a change in the color of the paint, most often fading or outright discoloration. However, for any ultraviolet radiation to effect paint color or stability, it must be absorbed by the paint itself. Certain paints, like acrylics and polyurethane paints, are slow to absorb ultraviolet rays and are thus much slower to dry up and lose their color. Conversely, items like plastics, rubber, or vinyl will much more quickly absorb UV radiation, which leads to much faster color degradation and cracking.

Faded garage doors

An example of an exterior treated with a clear coat to protect against UV rays.
Image courtesy of Newglass.

Ultraviolet radiation breaks down organic compounds like binders, which leads to the effects detailed above.  These breakdowns mean the paint is no longer retaining the chemical and physical properties with which it was designed. This is significant because as the paint breaks down further, the level of damage actually accelerates. Fortunately, breakthroughs in paint chemistry have enabled manufacturers to create paint products that protect surfaces from damage using inorganic compounds. Companies like BYK utilize cerium oxide and zinc oxide to absorb ultraviolet radiation as a way to protect substrates. In many instances, a clear coat containing one of these materials can be applied on top of a surface to offer enhanced protection.

UV damage car

A car with paint damage caused by UV rays.
Image courtesy of Meguiarsonline.com

Most professional painters are aware that sunlight will eventually cause some sort of damage to the paint on an architectural structure, automobile, or building. It is important that you educate your clients, so they know that while the most obvious result of painting these things is an improved appearance, the most important purpose is to protect the substrate from the damage that comes not just from things we can see like rain, but from more dangerous, unseen things like sunlight and ultraviolet radiation. Click here to learn how BYK can help protect what you are painting from ultraviolet radiation!

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