Since you are going to keep the pump outside, as I have done for 2 of my pumps, I recommend that you have the exterior sandblasted, if budget allows and then use two part epoxy primer to keep the rust from forming. I tried to power sand with discs and wire brush to remove the rust and could never remove 100% like the sand blasting does. I was able to get the exterior blasted for $50. Boat shops carry two part epoxy for boat hulls. It is expensive, but I believe it creates a barrier to rust better than traditional primers.

Try Brasso or equivalent and steel wool on the tags and then seal with polyurethane asap or a sealer made for brass. I purchased a small can of polyurethane at a hobby shop. The spray size is a very fine mist.