Here is the method I use to clean my J-38 keys. Some key collectors
believe that keys should be left exactly as they are found, but considering
the construction, materials, and ubiquity of J-38 keys, I think
that carefully and gently cleaning them is appropriate. Do not, under
any conditions use wire brushes or other highly abrasive methods.
1. Disassemble the key. Look carefully for, and set aside, the positioning pins in the binding posts (if they are loose) and all of the fiber washers. Put the bakelite and hard rubber parts in soapy water. Put the metal parts in ammonia. Let both soak overnight. Don't panic, because some of the metal parts will turn black.
2. Carefully wash off the bakelite/rubber parts. If the two knobs are very dull I sometimes us black shoe polish on them. The bakelite you can carefully clean with Flitz (see below) if it is still dirty or discolored.
3. The metal parts I clean first with "Nevr-dull". It is a "wadding polish" product that I get here in a hardware store, but I think it is also sold in boat stores, grocery stores, auto stores, etc. It is manufactured by The George Basch Co., Inc., Freeport, New York, 11520, USA.
4. Then I clean some of the larger metal parts with "Flitz", which is a metal/fiberglass cleaner made in West Germany and packaged in the USA by Flitz International, Ltd., WI 53185. It is available in boat stores, and I buy it from West Marine on the internet (www.westmarine.com). Just get a very small tube of it--it goes a long way. Flitz protects the metal from corrosion.
The most important step is #1. The soaking makes a big difference!