Thanks - googled treadmaster and there's a treadmaster forum - I'm thinking scouring pad on a angle grinder or sander and some acetone as well - they say to avoid white spirit. I'm sure 3m do a scourer for a grinder and sander.
Once you have sanded the Treadmaster and Epoxy away, you will be left with a fair amount of cleaning up to do! The sanding dust should be swept up, and the deck surface will need to be cleaned prior to replacing the decking; we recommend using Acetone or Propanol to clean the surface of the deck, it is essential that you do not use White Spirit, this will leave a greasey residue that will affect the future bond. If you have a metal deck, the surface should be lightly abraded and then cleaned before applying new Treadmaster. The cleaning is essential to ensure that any dirt or sanding residue is fully removed before starting again.
Although I've found it brilliant for some jobs, take care with acetone.
It takes the oils out of your skin and eventually mealts some 'rubber' gloves and it's not good to use in a confined unventilated space.