If the coating is an anodised finish, then you can strip this easily in caustic soda and hot water.
When I stripped the finish from our Steyrs I found 1 dessert spoon of soda to each litre of hot water.
Using a wallpaper tray with 4 litres of water was about right.
It will only need about 30 seconds in the caustic - if left too long (only a few minutes)any threads with be damaged as the caustic will eat the ally.
Take it out the caustic and rinse well with running water.
WEAR RUBBER GLOVES AND GOGGLES
ALWAYS ADD THE CAUSTIC SODA TO THE WATER A LITTLE AT A TIME - AND BEST DONE OUTSIDE
DON'T BREATH IN THE FUMES - THEY ARE NOT GOOD FOR YOU.