Aluminium is soft making it very easy to scratch. It is a horrible material to work with because it is so soft it clogs up all your saw blades, files and abrasives like treacle tart. Most timpani chassis are made aluminium castings because it is also lightweight.
Commonly timpani use 3 points of contact with the floor (so they don’t wobble), with two wheels at the back and the pedal at the front, with the aluminium casting under the pedal sitting on the floor. As the drums are moved around, the aluminium foot at the front suffers from abrasion until they are completely worn away. This is a problem that I often have to resolve, but the biggest “problem” is reversing the shit solutions that other people have created to repair them!