Pirate sword painting So, I've thought of using glue to stick pieces of cardboard together into a sword and then putting aluminum foil on it and painting it to look like it has rusted. Turns out, for paint to stick to aluminum you need to make sure there is no aluminum oxide and treat the aluminum. Paint won't stick to bare aluminum but acrylic paint is the best type of paint to use on aluminum. Is there any inexpensive metal foil for which I could just paint it on and not have to worry about treating the metal? 

I want to get this type of color on the sword blade:



So you can see, there are some areas where I would be using black paint and others where I would be using orange paint and I think I might want to like do a whole layer of black paint and then after drying, put the orange paint on in another layer. But I don't want to go through the expensive process of getting rid of the aluminum oxide and treating the aluminum so is there an inexpensive metal foil that paint will actually stick to without treating the metal?
Do you mean paint won’t stick to aluminum foil? Because any two-component epoxy based paint will stick to aluminum and aluminum foil. But I think your approach is flawed from the get go. You should look into the way cosplayers build swords. They have a skeleton-like frame (sometimes a solid wood dowel) underneath the sheathing which is very often a type of foam matt like you would find at a camping store for underneath a sleeping bag or a type like that which is used for yoga. They cut shapes and glue them together, perhaps even screwing them to the dowel, paint them, apply decals from model kits etc. The videos can be quite entertaining.