Harry:

You could probably save yourself some money here.

Oren's recommendation of Loctite's Naval Jelly Rust Dissolver utilizes a well known chemical reaction between rust and phosphoric acid that converts the rust into a black compound called Ferric Phosphate or FePO4.

Here's what Wikipedia says about using Phosphoric acid to convert rust to Ferric Phosphate:
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Phosphoric acid - Wikipedia, the free encyclopedia

Rust removal:
Phosphoric acid may be used as a "rust converter", by direct application to rusted iron, steel tools, or surfaces. The phosphoric acid converts reddish-brown iron(III) oxide, Fe2O3 (rust) to black ferric phosphate, FePO4.

"Rust converter" is sometimes a greenish liquid suitable for dipping (in the same sort of acid bath as is used for pickling metal), but it is more often formulated as a gel, commonly called "naval jelly". It is sometimes sold under other names, such as "rust remover" or "rust killer". As a thick gel, it may be applied to sloping, vertical, or even overhead surfaces.

After treatment, the black ferric-phosphate coating can be scrubbed off, leaving a fresh metal surface. Multiple applications of phosphoric acid may be required to remove all rust. The black phosphate coating can also be left in place, where it will provide moderate further corrosion resistance (such protection is also provided by the superficially similar Parkerizing and blued electrochemical conversion coating processes).
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So, I took a look at the MSDS for Loctite Naval Jelly Rust Dissolver, and sure enough it's mostly phosphoric acid. It's got 10 to 30 percent phosphoric acid in it. It's got some other stuff in it too, but those other things are to gel it so that it can be applied to vertical surfaces and overhead:

Household Products Database - Health and Safety Information on Household Products

Now, phosphoric acid is commonly used as the active ingredient in toilet bowl cleaners. If you just go down to your local home center or hardware store and look at the toilet bowl cleaners they sell, many of them will give a phosphoric acid content, or have a warning saying that it contains phosphoric acid.

Here's a phosphoric acid based toilet bowl cleaner being marketed by a company called "Iowa Prison Industries":
http://www.iaprisonind.com/downloads...osAcidBowl.pdf

If Loctite Naval Jelly Rust Dissolver has a phosphoric acid content of 10 to 30 percent, you can use any phosphoric acid toilet bowl cleaner with a phosphoric acid content between 10 and 30 percent to get identical results as you'd get with the Loctite product.

Many toilet bowl cleaners will contain hydrochloric acid, but you want to use phosphoric acid for converting rust into that stable black compound, ferric phosphate.

Also, EVERY janitorial supply store listed under "Janitorial Equipment & Supplies" will, in all certainty, sell a phosphoric acid toilet bowl cleaner you can use on your tools.

Phosphoric acid is a mild acid. It's about the same strength as CLR. It won't harm your tools if you leave it on too long, but doing that won't remove any more rust. Once the rust turns black, just wash the remaining phosphoric acid off your tools with water and dry immediately with a rag or paper towels.

Rubbing oil over the ferric phosphate won't do anything, and it'll only make dirt stick to your tools. I would leave out the business about applying oil to anything because as soon as you use that tool, the oil film will get wiped/rubbed off anyway. Just keep your tools dry.