Why Isn’t My Polyurea or Hybrid Coating Adhering to the Surface?

If you notice your polyurea or hybrid coating isn’t adhering to the surface, several factors could be the cause. Surface preparation, the environment, the application process, and recoating can all be reasons for adhesion failures.

Knowing how to work with these coatings is important for optimal performance and adhesion. Due to rapid cure times and the use of high-pressure equipment for most applications, it’s easy to make mistakes. Read the material technical data sheet (TDS) before you begin working to avoid issues.

Reasons Adhesion Failures Occur in Coatings

One of polyurea and hybrid coatings’ most desirable traits is their ability to create a strong, long-lasting bond. When they adhere, they provide long-term protection to the surface underneath. When they don’t adhere, they will peel off prematurely from the surface, negating any effect you should have gotten.

1. Poor Surface Preparation

The most common reason for adhesion issues is failure to prepare the surface before application. If you have a lot of ground to cover, it might seem easier to skip surface preparation and go right to applying the coating. A good application is completely reliant on the surface preparation that was done in advance.

If you don’t ensure that the surface is clean and free of contaminants, you may see bubbling and blistering in those areas. These defects will cause bonding issues and delamination.

Some surfaces have extra preparation requirements, which include sanding, grinding, shot blasting, making repairs, etc. Failure to properly prepare the surface will result in adhesion failure.

Also, not all surfaces are compatible with polyurea and hybrid coatings. Some require the use of a primer as a bonding agent to promote adhesion. Porous surfaces that contain moisture and aren’t primed can also cause adhesion issues through bubbling and blistering.

2. Environmental Extremes

While many manufacturers boast about polyurea’s moisture insensitivity, it is sensitive for adhesion. Just because it can cure over a block of ice does not mean that it can stick to the block of ice. And because polyurea hybrids are partly composed of polyurethane, they are even more sensitive. Most coatings require a dry surface to adhere effectively. Excessive moisture on the surface can cause blisters, pinholes, and peeling, which weaken the coating.

This is why it’s essential to make sure the environment and application surface have low or no moisture content. Moisture compromises the integrity of the coating and will cause adhesion issues.

Another environmental factor that can cause adhesion issues is temperature. It plays a big part in the coating’s ability to cure. If the surface, environment, and material temperatures are not in line with the manufacturer’s guidelines, issues will arise. The coating might not cure correctly in extreme hot or cold temperatures. Curing issues lead to bubbling, pinholes, peeling, and delamination.

3. Application Issues

Some coatings are fast-setting and harder to apply consistently without training. Coating speed is directly related to how long a coating has to bond to the surface to provide adhesion. The faster the coating the less time for adhesion to occur. To combat this issue, you can use a slower version with low-pressure or cartridge-based equipment that grants higher adhesion. Additionally, the thicker you spray or apply a coating the faster it will cure reducing your adhesion.

As two-component materials, polyurea and hybrid coatings have to be mixed at a specific ratio to cure. If the incorrect mix ratio is used, it will affect their strength and physical properties. A weakened coating will lead to poor adhesion. Inadequate mixing can also cause curing and adhesion issues. These are problems with the spray equipment that need to be corrected.

4. Missed Recoat Window

Apart from surface adhesion failure, there is also intercoat adhesion failure. Intercoat adhesion failure can occur when adding another coat to the surface. Failure typically occurs because the applicator has missed the recoat window. Once the window closes, you must apply a primer to promote adhesion between coats; otherwise, failure will occur.

Solutions

If your coating isn’t adhering to the surface, you will have to restart the application process. Always read the manufacturer’s instructions before working with polyurea or hybrid coatings. Ensure temperature and humidity levels are suitable for application, which is dependent upon your product. We typically recommend working between 50-90°F. If you’re working with a porous surface, it should be free of moisture or have a low moisture content.

Use a compatible cleaning agent or detergent to remove dirt, dust, oil, films, and more. Sometimes, a degreaser or pressure washer is used to make the process easier.

Specific surface preparation is going to depend on what surface you are applying the coating to. Some metal and wood surfaces might need to be sanded or scuffed. 40-grit sandpaper or a wire cup brush sander are recommended for applications like truck beds. For harsher surfaces, roughly sanding or sandblasting to SP6-SP10 to remove rust, mill scale, dirt, and more is essential. Repair damaged or cracked areas to ensure a smooth surface for coating.

For increased adhesion, use an approved primer. VFI’s recommended primers are VFI-#11 9:1 Epoxy Primer, VFI-1016 Steel Primer, and VFI-1017 Porous Surface Primer. Which one you use will depend on the surface type. They will form a bond between the surface and coating to ensure a strong and durable finish.

Optimize your adhesion based on your application. There are specific instances where speed is not as critical, and you are able to use a slower coating. Anytime you can go slower you will gain more adhesion. VFI does have formulas that are optimized for adhesion, and they will usually be slower than a 10 second gel time.

When spraying the material, ensure that your equipment is calibrated to the correct mix ratio. Also, ensure that it can get up to the recommended temperature and pressure outputs. This will ensure a smooth application and promote better adhesion.

It should then be applied in a continuous, even layer. Stay within the recoat window if you are applying layers to build thickness. If you miss the recoat window, prime or prep the surface to ensure adhesion based on recoat instructions.

Contact VFI if you are experiencing other issues with polyurea and hybrid coatings.