A regular question from both DIY’ers and flooring professionals is whether they can coat new epoxy over older coatings of epoxy. Logics tells us that it is possible as we basically want to bond two identical materials. However it is advisable to take some care so as to ensure the best possible result.
The following problems are likely to occur when coating over an older epoxy floor surface:
Cratering: Now this one is a common problem. What happens here is that the differences in surface tension between the fresh coating and the old coating may lead to craters resulting in the uneven leveling of the material. To help avoid this, ensure that you properly clean the old epoxy coating and you will minimize the risk.
Poor Adhesion: Whilst it is not often that you will see one epoxy layer detaching itself from the other. On occasion it will occur. This may happen if the bottom epoxy layer is dirty or humid – again, ensure the old surface is thoroughly cleaned before laying the new epoxy over top.
Cracking: This is a frustrating scenario that is quite likely not to occur straight away, but could suddenly appear a few months after the project has been completed. Cracks will start forming along the surface for no apparent reason. What this is due to is a unsatisfactory bonding between the two layers which then leads to cracks when the floor undergoes contractions for variances in daily temperatures.
What to do to prevent these problems from occurring?
Firstly, as already partially mentioned, proper surface preparation is the key.
Every epoxy substrate that is at least 3-4 days old needs to undergo surface preparation. This means the floors should be properly ground down or sanded. Remember, the purpose in this preparation process is to lightly ‘scrape’ the floor without causing damage. Method options are using a diamond grinder or a rotating sanding disc machine the once the dust has been cleaned thoroughly, you can then proceed to priming the surface using a quality high viscosity epoxy primer.
Make sure your primer is not too thick (low viscosity) as you need to ensure penetration of the primer in the scratched surface. Give you primer sufficient time to dry properly giving consideration to air temperatures and moisture elements then you can proceed to recoat your floor.