[ILLusion]

If it's the original frame, it will be impossible to get any type of surface treatment applied to it. If you attempted it, you'll end up pulling maybe a small remaining sliver of metal out of the acid bath (if anything were left at all.)

The original frame is NOT machined material. It is die-casted. Being "CNC Machined" says very little about the quality/composition/durability of the material. It is simply a process to create a shaped object in a controlled production. Generally, CNC machining is used for batch produced items to keep per unit costs low. All it is, is computer controlled machining. Hand machining isn't far off.

Die-casting is a completely different process altogether, utilizing injection moulding that doesn't give you the sharp, smooth and crisp machining lines that full milling is capable of. On a per unit cost, it gives a very cheap product, and is why it's generally used in toys. The disadvantage is a lower wear cycle (versus billet aluminum), a porous material (breaks easier), and is extremely susceptible to the environment (wear, erosion, etc.)

If you want to protect the surface from oxidation, then spray an acrylic enamel on it to protect it, but be aware that it will leave behind a sheen AND will wear off over time. You'll have to re-apply the coating after several cycles of use. Be sure to protect all areas that must maintain a dimensional tolerance, such as all areas where the slide contacts.

It's been said many times on this forum: Polishing your TM die-cast metal will give you all the "oohs" and "ahs" the moment it's completed, but the days and months following, with dull grey surfaces caused by the pitting of oxidation will undeniably leave a regrettable taste in your mouth. In the end, the same thing happens to every single part that gets this treatment of bling-destruction... it ends up in the trash or gets sold for incredibly low prices just so you can get rid of it put the funds towards a new (and silver from the factory) part.

If you want silver, buy it as silver.