Hi @imkp,
A warm welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Do you have a photo you can upload? This would help our members offer their best advice.
Intumescent paint can be incredibly difficult to remove as it is designed to resist extreme conditions. Considering it is an epoxy coating; it could be even more difficult as solvents will not affect it.
Have you had any luck at all with the scraping and sanding?
Unfortunately, I think abrasive action is the only way you're going to be able to remove it.
You could maybe try using a more aggressive grit sandpaper with a belt sander or even an abrasive flap disk with an angle grinder. Alternatively, planing the timber to remove the top layer should work.
Let me know what you think.
Jacob
