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Peeling is Not Appealing: How Chemechanics Can Put an End to Adhesion Failure

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Nothing ruins a final project quicker than experiencing paint adhesion failure due to the wrong coating being used.

Luckily, we’ve seen this a lot with our customers and we know exactly how to solve this problem — Application Specific Advanced Coatings™ (ASAC™)!

Did you know that Van Technologies, Inc. manufactures Application Specific Advanced Coatings™ (ASAC™) under the GreenLight Coatings brand name? 

It’s true! This coating meets individualized customer demands by integrating the proper chemistry. In order to avoid a poor finish and reach the perfect coating, the details in the chemistry and mechanics have to be just right.

Over the years, we have had a lot of practice with this process and are considered to be one of the best in the industry. We have even coined the term “Chemechanics” to describe the specific process of applying the coating.

Waterborne-UV Curable Paint and Adhesion Failure 

Our client came to us for help when they started experiencing paint adhesion failure (i. e. cracking and flaking) from the recesses and transition areas of pre-primed door casing profiles.  This cracking and flaking was observed upon installation in two housing complexes. 

The coating that had been applied was a waterborne-UV curable paint that was applied by a reciprocating flatline spray process.  The finishing line operators assumed that the paint was the cause of the adhesion failure since the problem went away upon change over to an alternative paint material. 

In our review of the project, we came to the conclusion that the finishers must have noticed this failure before the changeover but shipped the defective profiles regardless, rather than correcting the problem from the beginning.

To determine the true cause of the problem, we focused on the properties and performance of the waterborne-UV curable paint.

Diagnosing the Problem

To know how to solve our client’s problem, we had to review the adhesion failure in person. For our quality review, we started by pulling the liquid retain (the “control”) from the corresponding batch during manufacture and re-qualified it in the quality lab. Detailed chemical analysis was then conducted of the suspect waterborne-UV curable paint returned from the finisher vs. control batch materials.

We also performed an on-site review by visiting the two housing construction sites to perform on-site adhesion checks. A complete review of the finishing line operation and interviews with the line operators were also performed. During finish line visitation, the suspect waterborne-UV curable paint was sampled and provided to the quality lab referenced above.

Key Results

Linear Profile Section

After our review and analysis, we were able to confirm the paint adhesion failure but only in discrete locations along the linear profile.  No loss of paint adhesion was observed in any other location.   

The changeover to an alternative paint material did result in elimination of the adhesion issue.  The reason why became a focus of study.

Microscopic inspection showed that excessive paint thickness (73% more) was present in the locations associated with paint adhesion failure.  Additionally, it was seen that there was a layer of primer present on the underside surface of isolated paint flakes.

The re-qualification of the control quality retain and the returned suspect waterborne-UV curable paint resulted in no deviation from specification.  Performance testing also indicated compliance to all criteria.

Detailed chemical analysis of the suspect waterborne-UV curable paint vs. the control quality retain, and 2 other lots used by the finisher resulted in no discernable difference in chemical composition.

Job side inspections confirmed paint adhesion failure at discrete locations that appeared to be at an interval between 8” to 9” apart along the profile length. 

Job Site photo Job Site photo

Job Site photo

Prior to tape adhesion testing, locations along the profiles were observed to exhibit what appeared to be “mud cracking”.  Those locations directly coincided with the locations exhibiting paint removal upon tape adhesion testing.

Our Conclusions

The results indicate that the paint adhesion failure was not caused by defective waterborne-UV curable paint but was caused by a mechanical malfunction in the finishing process.  If it was indeed that the waterborne-UV curable paint was defective, the problem should occur over all surfaces of the profile and not as seen in regular intervals along the length of the profile.

A key to identifying the nature of the problem was provided by the repeat pattern associated with the paint adhesion failure and the changeover to an alternative paint topcoat.  This was caused by a faulty air cap and/or fluid tip in the reciprocating spray process.  Stripes of excess coating were applied and should have been attended to in process.  The 8” to 9” interval distance is consistent with the conveyor speed and reciprocating action of the gun carriage.

The change to an alternative paint topcoat required a cleaning of the spray system to avoid potential cross contamination of the paint to be used.  It was evident that the faulty air cap and/or tip was corrected during cleaning.

The excess waterborne-UV paint applied in the repetitive strips set up ideal conditions for “mud cracking” to appear.  The stress imposed on the underlying primer layer, as the applied topcoat paint dried, caused the primer layer to split leaving a partial layer on the underside of removed paint flakes.

Chemechanical: Combining Chemistry with Mechanics

This finishing experience serves well to illustrate the importance of “Chemechanical” balance in the finishing process. The performance of the “Chemistry” is only as good as the “Mechanics” used to apply it.   

It also serves to highlight the need for finish line operators to recognize the proper actions to take to avoid compounding the problem.  Knowing of an issue and ignoring it resulted in a significant amount of work needed to correct it both for the finisher and the home builder involved.  Attention to the “Chemechanics” would have identified the need to clean air caps and tips long before any defective parts made it to the end customer.  

All’s well that ends well as they say and the finisher became more Chemechanically educated.  Unfortunately, education does not come cheap!

If you would like to learn more about how our Chemechanical knowledge can benefit your next job, give us a call at 218-525-9424. We would love to see how we can help you avoid costly mistakes!

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