Adhesion Testing for Concrete Coatings: Significance, Methods, and Best Practices

Concrete coatings do more than just enhance surface appearance – they deliver essential protection against abrasions, moisture, chemicals, and daily wear. However, it is possible only when the coating creates a strong, reliable bond with the concrete substrate. 

Whether it is epoxy or polyurethane floor coating, to perform as intended, the bond with the concrete beneath should be consistent and compliant with industry standards. This is when adhesion testing plays a vital role. 

In this blog, we’ll walk you through its key standards, commonly used testing methods and best practices that ensure the coatings deliver long-term performance.

What is Adhesion Testing?

Adhesion testing is a reliable and effective method to determine the strength of the bond between the concrete substrate and the applied coating. Inspectors and maintenance professionals responsible for this job evaluate the interface between the layers. This provides them a valuable insight into the structural integrity and performance of the floor coating.

Why Adhesion Testing Matters?

Without strong adhesion, coatings are more susceptible to peeling, blistering, and delamination—issues that can lead to premature failure, costly repairs, and potential safety hazards. That’s why verifying adhesion is a critical step in any concrete coating application.

Whether you are applying epoxy or polyurethane coatings, testing the bond strength is essential. It helps ensure proper surface preparation, optimal product performance, and compliance with industry standards.  

Common Bond Strength Testing Methods

Several methods are there for conducting this test on bond strength between the concrete and the coating. A few of them are listed here. 

Pull-off test: This is the most widely preferred method where a metal dolly is attached to the coated surface with glue. Once the adhesive cures, a mechanical device is used to pull the dolly away at a perpendicular angle until failure occurs. This controlled tensile force used to detach the coating is measured, providing a quantitative assessment of adhesion strength. 

Standard Reference: ASTM D4541 / ISO 4624

Tape test: In this method, an adhesive tape is used over cross-hatched cuts made in the coating. The bond strength is evaluated by applying and removing this pressure-sensitive tape. The amount of coating removed by the tape is thus assessed and rated. 

Standard Reference: ASTM D3359

Scrape test: This test is perfectly suitable for soft or thick coatings. Here, the adhesion is determined by pushing the coated panels beneath a rounded stylus until the coating detaches from the substrate. The stylus is gradually loaded in increasing amounts to provide a comparative measure of the force required to remove the coating.

Standard Reference: ASTM D2197

Factors that may affect the testing result: Follow the Best Practices

No matter how perfectly a coating is applied on the concrete substrate, if the underlying surface isn’t properly prepared the result can be compromised. Poor surface preparation can weaken the bond, increasing the risk of adhesion failure and premature wear. 

Likewise, several other reasons are there that affect the result. Let’s have a look.

Curing time of the coating: Every coating requires sufficient curing time to develop and achieve a strong bond with the concrete substrate. Therefore, rushing the testing process before the coating is properly cured may show an artificial result.

Presence of moisture: High moisture content in the concrete can interfere with coating adhesion. This may generate failed test results.

Environmental conditions: If temperature and humidity during application and testing differ, it may affect the accuracy of the test. 

Coating thickness: Many of you consider applying a thick coating over the substrate for quality protection. Uneven or excessively thick coatings can also affect the test consistency, making it difficult to interpret the results.

Substrate conditions: If the concrete strength, porosity, or surface profile varies across the substrate, it may lead to inappropriate readings.

Final Thoughts

Adhesion testing isn’t just an option – it’s a necessity that ensures your concrete coatings deliver long-lasting performance and durability. Of course, partnering with experienced professionals will be a great help. 

Connect with our team and we can help you properly assess bond strength, interpret test results, and make informed decisions to optimize coating longevity and safety.

SEALWELL INC

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