(NOTE: Request for explanation and questions are highlighted in last paragraph. Please help if you can...thanks !)
treasure-SeekR..........I assume your coin is a plain 1943, without the "D" mint mark, otherwise my advice would have been to look at it closely under lighted magnification to see if the "D" has been double stamped. This is the most valuable variety, the F-12 lowest condition shown in the 59th Edition of the RED BOOK being valued at $6.00 retail. If that were the case, and you intended to sell the coin someday, I wouldn't clean it at all. Cleaning can reduce the value drastically !
My experience, so far, is with copper pennies only. I decided to share that in the next paragraph below, just FYI. But as far as the 1943 and '43D war time pennies, I can only offer references to what I have found on the web about the use of Molasses for cleaning rust from steel, beginning below at paragraph #4. Lastly, I attached a post from another forum, which I thought was interesting (note that this post recommends a 5:1 ratio, rather than the 9:1 indicated in the metalwebnews report at the web address address below.).
I am no expert on coin cleaning methods by a long shot. I have a little experience cleaning dug post-1982 low copper U.S. Lincoln clads and pre-1982 95% copper Lincoln's, using three methods, as follows: Hydrogen Peroxide Topical Solution full strength, CLR full strength and Distilled White Vinegar with salt added. Cleaning action can be speeded up by heating these chemicals in a micro wave oven until hot to the touch. I would use a glass vessel, just large enough so that the liquid covers the quantity of coins you intend to clean by about 1/2" over the coins. Add the salt to the vinegar after it has been heated, otherwise, you raise the viscosity/conductivity and take the chance of boiling-off the acid level in the solution. After heating the vinegar, stir in the salt and drop in the coins. As you know, when using a micro wave oven, NEVER, place any metal objects inside the oven, so always wait until the hot liquid has been removed from the oven, then add the coins. With any one of these methods, with the liquid hot, you should see bubbles start to rise within a few seconds after dropping in the coins. With post-'82 clad pennies, monitor the coins frequently when using the vinegar/salt, as it will eat through the thin copper cladding pretty quick, leaving pits. In my experience, the other two chemicals (HPTS or CLR) don't seem to be as severe with equal time-in-solution. Also, whenever using any solution containing acid, always remember to soak coins afterwards in a neutralizing solution, such as household baking soda and water, otherwise acid residue left on coins might continue to eat at the metal, especially if moisture is present. As far as what ratios to use for the vinegar/salt or baking soda/water solutions, I just guess at these, but perhaps other members can advise on this.
Paragraph #4 - This address: http://www.metalwebnews.com/howto/rust/rust.html takes you to a report that is very enlightening, but the subtitle Removing Rust and specifically paragraph #11, beginning with "I read of using a solution..." deals with the subject of using Molasses to clean rust from steel.
After reading a lot of material on the web, I ran across a term associated with the use of Molasses, called "chelation" and another statement that said molasses is a chelating agent. So, I went to the page dealing with this term on Wikipedia.......it was a bit too scientific for me to comprehend. I wish someone could give us an explanation in simple-to-understand language.
In addition, I discovered that molasses is made from different things, most commonly sugar cane and beets. When made from sugar cane, there are three grades, first molasses, second molasses and Black strap molasses, and these grades can be either sulfured as a preservative, or non-sulfured, according to the Wikipedia, tab titled Molasses at: http://en.wikipedia.org/wiki/Molasses. Click-on this address if you want to go there to review that information. I haven't found anything suggesting that any of these three grades are considered synonymic with "RAW" molasses, which is the general term used in suggestions for cleaning rusty steel. Can anyone clarify this ? Secondly, which one, i.e. first, second, Black strap or RAW, would be the most efficient for cleaning rusty steel ? Or would something like unsulfured Grandma's Molasses, available in grocery stores, work just as well ?