Pretty cool base texture.

Right now, the corrosion doesn't seem to be realistic, in that the first places to get corroded, usually, is in the crevasses such as around the protruding rings and around the cap especially.

As you mentioned, fluid stains would help out.

As for thepuddle, I'm not 100% certain, but I would think fluid effects would not be the way to go. From what I understand, fluid effects are generally for simulating moving fluid, not a stationary puddle on the ground. I think your best bet would be to create it with geometry and texture it. The texturing would be mostly in the amount of reflectivity, the base color of the liquid, and the reflectivity map you use.