3 Reasons Epoxy Coatings Can Turn Yellow

Published on March 29, 2023

As a concrete coating company that only installs polyurea coatings we often get questions regarding how polyurea differs to other forms of concrete coatings. One of these questions that we get the most is just why epoxy coatings turn yellow over time. For those who got an epoxy coating installed this is a risk that you will have to account for. Our polyurea coatings on the other hand do not yellow but remain pristine for their lifetime.

Epoxy coatings typically turn yellow due to how 3 environmental stimuli interact with the carbon element in the epoxy layer. First, UV light will slowly turn a new epoxy concrete coating yellow due to bleaching within the carbon layer. Second, the epoxy top coat often degrades faster than the carbon epoxy element due to oxidation. Third, extreme amounts of water and heat can cause an epoxy floor to slowly discolor over time and create a yellow appearance.

Here at Xano521, we pride ourselves in providing the industries leading concrete coating; we only install polyurea coatings. This is because a polyurea coating will withstand the test of time while providing unparalleled protection for your concrete. If you’re interested in our services then I highly suggest you check out either our gallery page for inspiration from the latest jobs or reach out to us by clicking here to discuss exactly what your project needs.

Epoxy Coatings Yellow Due To UV Light

One of the main reasons why epoxy coatings turn yellow over time is due to near-constant exposure to UV light. Any sunlight that hits the epoxy coating will slowly turn yellow over time.

Epoxy coatings can fade and discolor when exposed to UV light. This is because UV radiation can break down the chemical bonds within the epoxy resin, causing it to degrade and lose its structural integrity. This process, known as photodegradation, can cause the epoxy coating to become brittle, crack, and ultimately fade in color.

The UV radiation initiates a chain reaction within the epoxy resin, causing it to break down into smaller, unstable molecules. These molecules then react with oxygen in the air, leading to the formation of free radicals, which can further degrade the coating. Over time, this process can lead to a loss of color and gloss in the epoxy coating, as well as a decrease in its mechanical properties.

Simply put, an epoxy coating will start to fade as soon as the sunlight hits it. This will over time turn it from a desired color into a faded yellow color that we here in the industry call ‘yellowing.’ This can cause problems if the potential client is not aware of this yellowing process.

Epoxy Coatings Turn Yellow Due To Oxidation Of The Top Coat

Another reason why epoxy coatings turn yellow is because of oxidation of the top coat. This is due to the resin compound reacting to either moisture or chemicals in the air that slowly begin to degrade the layer and change the color.

Epoxy coatings can turn yellow due to a process known as oxidation, which occurs when the epoxy molecules react with oxygen in the air. This process can be accelerated by exposure to UV radiation or high temperatures, causing the epoxy to yellow and become discolored.

The yellowing of epoxy coatings is primarily caused by the oxidation of the epoxy resin’s aromatic rings. Aromatic rings are a type of chemical structure found in epoxy resin that is susceptible to oxidation, especially in the presence of UV radiation. As these aromatic rings oxidize, they produce a yellow-brown color, which can become more pronounced over time.

In addition to the oxidation of the epoxy resin, other factors can contribute to the yellowing of epoxy coatings. For example, exposure to high temperatures or certain chemicals can cause the epoxy to break down, leading to discoloration. Furthermore, improper mixing of the epoxy components or inadequate curing can also lead to yellowing.

Because of this most people often find that epoxy coatings turn yellow overtime as the top layer is oxidized. This part of the yellowing process can be maintained but will require new top coats to be applied in order to prevent the yellowing process.

Extreme Heat or Water Can Cause An Epoxy Concrete Coating To Yellow

The third and final reason why epoxy coatings can yellow over time is due to large amounts of heat and water changing the chemical makeup of the epoxy coat itself. In high humidity and heat environments such as Central Florida, this can cause major problems with your epoxy coatings over time.

Water and heat can cause an epoxy coating to yellow through a process called hydrolysis. Hydrolysis occurs when water molecules react with the chemical bonds in the epoxy resin, causing it to break down into smaller molecules. This process can be accelerated by high temperatures, which increase the rate of chemical reactions.

During hydrolysis, water molecules react with the epoxy resin’s ether bonds, which hold the epoxy molecules together. As the ether bonds break down, the epoxy resin becomes less stable and more susceptible to oxidation, which can cause yellowing. The reaction between water and epoxy can also produce acidic byproducts, which can further contribute to discoloration.

In addition to hydrolysis, exposure to high temperatures can cause the epoxy coating to yellow through a process known as thermal degradation. High temperatures can cause the epoxy molecules to break down and release volatile organic compounds (VOCs), which can react with oxygen in the air and cause yellowing.

Because of this most people will experience their epoxy coating yellowing in Central Florida over time. You can prevent against this form of yellowing so long as you constantly repair the epoxy coating but that can be a costly measure.


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