aluminum pitting

In short, not likely, even if you tried to coat it and fill in the pits with a plastic. As soon as you have pitting, it probably can't be assuredly cleaned to be made food-safe. Also, all coatings have holes. (That's the normal assumption for coatings. Someone will argue with that, though.) If a hole and a pit coincide, you have a reservoir for microorganisms.
If cost is no object and the vessel is big enough, you may find some imaginative ideas on how to refurbish it, but I've never encountered a case where cost is no object. Cost always objects!
Buy replacment(s) or re-design to work with whatever parts you CAN get.
My $0.02. (non-inflation adjusted)

Liam:
The problem is likely galvanic corrosion. Go take a look at the Alubook. The solution would not be to coat the aluminum (anode), but rather the cathode, since it is the cathode (other more noble metal) whose area would be controlling the corrosion rate. See: and also see the advice on: How to avoid or minimize galvanic corrosion at: may have the electrolytic problem deposition mentioned if you have copper tubing upstream of the aluminum boiler. This is a special form of galvanic corrosion. Also see the comments on design at: It's hard to fix a lousy design.
Pittsburgh Pete
DISCLAIMER
We do not believe what we write, and neither should you. Information furnished to you is for topical (external) use only. This information may not be worth any more than either a groundhog turd, or what you paid for it (nothing). The author may not even have been either sane or sober when he wrote it down. Do not worry, be happy.

i like that disclaimer.
FWIW, if you zincate the interior, and then tin plate it, then polish it out, you very well could save it.
expense?
hoo boy....