I used to have a lot of stuff powdercoated- a grand or two a month, for almost 10 years. And so, I spent a lot of time at high quality powdercoating shops- guys who had ovens that were 20 feet by 10 feet by 10 feet. The pros do just as several people here suggested- burn it first, then sandblast.
The big shop in Paramount Ca. that I used to use had an oven that went to 1500 degrees, not any measly 540, for "burn out" of mistakes. It had a little railroad track going into it, and a very hefty cart that the work sat on. And a monthly visit from the Southern California Air Quality Management district, to make sure its scrubbers were working right. Not Cheap. Then, when the powder was crispy, you could sandblast it off. But it wasnt easy- it was still stuck on there pretty good.
Without heating it, sandblasting is almost useless- it can be done, but it takes forever. I also used to frequent a huge industrial sandblaster in LA- 30,000 sq ft, bridge cranes, a whole loft full of ancient 200 hp compressors- single piston models from before the second world war. Their air holding tank was 2 stories tall, and if filled with water could have supplied a small town. These guys were pros, set up to do anything. And they had a policy- NO SANDBLASTING POWDER COAT. People would come in with 10 dollar import metal lawn chairs, and try to get them sandblasted. White powdercoat. Little grid of 1/8" wire. And they would laugh, and tell them that if they were foolish enough to take the job, they would have to charge $150 or $200 each, because it took so long.
Powder coat is great for indoor uses. It sucks for exterior, because it always starts to peel and rust eventually, but never over the whole thing- only in spots, making it look ugly, but still making it near impossible to remove.
Its usually cheaper to make a whole new part than to remove powdercoating.