Bryant Wells
B Chem Sc, MBA, Certified NACE 3
Technical Manager
Application Issues for Epoxy, Polyurethane and Polyaspartic Coatings
1. Moisture Issues
A high moisture level in the concrete will interfere with the first application to concrete. An epoxy coating will see adhesion issues, and in isocyanate-cured coatings (Polyurethane and Polyaspartic), foaming will occur as the isocyanate reacts with water to create carbon dioxide. The moisture content on the concrete can be checked in three different ways.
| Liquimix concrete moisture Requirements | ||
| Standard | Description | Pass / Fail |
| ASTM D4263-05
ASTM F2659-10(2015) ASTM F2170-11 |
Plastic Sheet Method Electronic
Moisture Meter Relative Humidity using probes |
Moisture Presence
< 7% < 75% |
2. Outgassing Issues
As the concrete heats up during the day, moisture vapour will leave the concrete. As the coating is curing, this can lead to pinholing or bubbles. The sealer coat is the first coating application to concrete; its goal is to penetrate deeply and seal the concrete. The only way to stop outgassing is to reapply when the concrete is cooling down rather than heating up.
3. Opacity Issues
Applying Polyaspartic, Epoxy and Polyurethane white flooring products over dark primers and concrete, will require multiple applications. The poor hiding power of white flooring products over dark colours means that many coats must be applied to get a consistent white colour. 
4. Delamination (Recoat Window Exceeded)
All flooring products have a recoat window that must be adhered to. A recoat window is the minimum and maximum time after application that will allow another application without requiring surface preparation. Polyaspartics are a faster curing floor coating that generally exhibits shorter recoat windows. Applying a second coating application after the recoat window without sanding, will lead to delamination of the newly applied coating, or in simpler words, the topcoat will peel off.
5. Rejection Issues
Rejection is when a floor coating pulls back from the substrate or previous coat. Rejection on coated floors is commonly caused by contaminants (oil, grease, silicon and other foreign materials). It is not possible to predict when this will occur. Be cautious of using different products from different suppliers together, as the combined system needs to be tested before use. Rejection is more common when mixing up different chemistries as the material will naturally be less compatible. 
