The importance of getting it right

KTA-Tator are a North American company specialising in the testing of steel and concrete structures to ensure that they not only meet mandatory requirements but they are fit for purpose and suitable to inhabit. With over 70 years' experience they have amassed a sizable body of knowledge, making them one of the leaders in third-party testing in the USA.

One of their consultants, Jay Helsel, recently posted a case study, reporting on the findings of their investigations into the failure of intumescent coatings applied to a project in a north-eastern, coastal location in continental USA.

Construction was only partially complete when application commenced of a one-component, solvent-based intumescent at up to a 25mils dry film thickness per coat. Multiple layers were required with appropriate curing time allowed between each coat - a process that was likely to span several days.

As the project was only partially complete, the building was not weatherproof and parts of the structure were exposed to weather exposure. Intumescent coatings are designed primarily for interior use, though they can succesfully be used in exterior applications with suitable top-coats, when they are applied correctly. They are also not suitable for indoor use where they are exposed to freeze/thaw conditions.

In this case the layers of intumescent coating were not adequately protected from the elements during application and, as a result, several areas of the coating failed, resulting in cracking, bubbling and lifting from the substrate surface, leaving the substrate exposed - even after a top-coat had been applied.

In other areas the fireproofing layer was found to be soft and pliable, as opposed to hard and brittle as in other areas.

After comprehensive testing it was found that the failures were due to exposure of the intumescent coating layers to weather - in fact it took several months after application of the intumescent coating for the building to be  enclosed. In addition several openings (doors and windows) remained open, allowing for freezing and thawing to occur, further compromising the intumescent coating and allowing water and/or solvent to remain in the intumescent system.

It was also discovered that proper intervals between the application of layers of the intumescent system were not observed and, whereas discernable layers of coatings were evident in some parts of the structure, the total thickness of the intumescent coating appeared as one single layer in several parts.

As a result the layers essentially "melted" together and, ultimately, resulted in the soft, pliable regions that were discovered.

This case study emphasises the importance of not just specifying intumescent coating systems correctly, but also applying them as per the manufacturer's instructions to ensure they perform as intended.

Swart & Sons have many years' experience in the specification and application of intumescent coating systems. Our approach is "do it once, and do it right".

For further details on this interesting insight into the correct use of intumescent coating systems, visit the publisher's website to read the whole story - https://kta.com/kta-university/intumescent-coatings or click the button below to download the artical as a PDF.