Epoxy Troubleshooting – hot tyre (tire) pickup.
Have you ever seen a floor coating lift right where a car was parked?
That is hot tyre/tire pickup!
You might not see it on all tyres, perhaps just the front tyres. You might only see it where one tyre rests. You might not even see it the first time the car parks on the floor coating. It is the same problem with different degrees of severity.
If you are going to do a floor coating in a garage then you have to be aware of this problem so that you don’t find yourself trying to fix it down the track.
So why does hot tyre/tire pickup happen and how can I prevent it happening?…
There are lots of reasons why the coating can lift under a car tyre. Here is a summary of reasons I have come across -
- The preparation of the concrete was poor and laitance was not removed properly before overcoating. It takes very little effort to fail a coating on a poorly prepared substrate.
- The floor coating was applied onto a used slab where the owner had previously sprayed a “tyre shine” and there was overspray that had soaked into the concrete. If there was oil or silicone spray on the concrete then it is likely you would have seen noticeable crawling when the basecoat was applied.
- The basecoat was a single pack product with poor crosslink density, hence when heat was applied to the coating it softened. Once softened it is more prone to peel off.
- The basecoat may have been a two pack water based product but it did not crosslink well. This can happen if the product starts to crosslink before the water has evaporated out of the system – the crosslinking takes place and once the water has evaporated it leaves an open, porous structure that is relatively weak.
I have hinted at some of the reasons of failure and you can now gather what commonly takes place. The car, while driving, heats up the tyres (the front tyres heat up more than the back when engines are on the front), the owner drives the car home and parks on the coating, heat is transferred into the coating and if the Tg (glass transition temperature) is too low then it will soften. Softening a coating changes the stresses within the film – if the coating is hard and rigid then it is more subject to tensile or lap shear stresses whereas once the coating softens it is subject to more peel stresses.
So there is the problem! The list of reasons why the problem occurs naturally illustrates how to overcome it -
- Ensure you prepare the slab properly by removing the contamination first and then any laitance before commencing.
- Do water bead tests to establish if there is any contamination left on the surface before commencing your coating process.
- I favour two pack epoxy products as the basecoat because the number of failures appears to be significantly less than with other basecoats. In addition, I favour two pack solventless epoxy products because I do not like solvents inside a building and if I choose a solventless epoxy that is not as susceptible to moisture/humidity then I minimise my risk of curing problems.
- And finally, use the products as recommended by the manufacturer, paying particular attention to the curing conditions.
The best example I ever heard of hot tyre pickup was a water based epoxy product used in a garage. The coating was well adhered in all other places except where the car was parked. The coating did not come up in a large chunk, it only peeled the tyre tread pattern. I hope to get a photo of the failure as it would illustrate the point perfectly.
What other classic problems have you come across in garage floor coatings?
Take care and talk to you later,