I'm on the 4th burning season with an EFM that was painted with the POR-15. It hasn't been affected by the corrosiveness of the coal ash. What has happened is that the nice silver finish turned amber where it was affected by the heat. The front door is still silver and the inside is still hard as nails. The floor of the base still is hard and all there. They make a POR-20 that is a higher temp but it needs to be cured with 475 degree heat. It stays soft and scratches real easy untill it is cured.