Civil War-era military arms would certainly rust and soldiers took great pains to prevent this from happening. Pvt Edward Wightman of the 9th NY Volunteers noted:
"Our spare time is generally spent scrubbing up the equipment. Rifles are atomized, screw drivers, emery paper, buckskin, oil, etc. brought into requisition as a mass got up on short notice comparable with house cleaning. Daubs of rust and dust get in your nose, and your hands become coal-colored when there is no water to wash. In some circumstances, one feels as if he had been dipped in cobwebs." (Longacre, ed., From Antietam to Fort Fisher, p. 58)
The US Government (Rules for the Management and Cleaning of the Rifle Musket, Model 1855, 1862, p. 24) recommended the following for cleaning the piece in the field:
"It is not essential for the musket to be dismounted every time that it is cleaned . . . it can be perfectly cleaned as follows: Put a piece of rag or soft leather on the top of the cone, let the hammer down upon it: pour a gill [four ounces] of water into the muzzle carefully, so that it does not run down the outside: put a plug of wood into the muzzle, and shake the gun up and down, changing the water repeatedly until it runs clear. Then withdraw the leather and stand the musket on the muzzle a few moments, then wipe out the barrel by screwing the wiper, sometimes erroneously referred to as the "worm," onto the end of the ramrod and putting a piece of dry cloth or tow around it, sufficient to prevent it from chafing the grooves of the barrel: wipe the barrel quite dry, changing . . . the cloth two or three times, and also wiper the exterior of the lock and the outside of the barrel around the cone and cone-seat, first with a damp rag, then with a dry one, and lastly with a rag that has been lightly oiled. In this way, all the dirt from firing may be removed without taking out a screw. If, however, the hammer works stiffly or grates upon the tumbler, the lock must be immediately taken off and the parts cleaned and touched with oil."
My favorite account is from Leander Stillwell, 61st Illinois, who while camping at Bolivar, Tennessee, mid-July, 1862 noted in his memoirs (p. 90):
"We were required to keep all the metal parts (except the butt-plate) as bright and shining as silver dollars. I have put in many an hour working on my gun [an Austrian rifle-musket] with an old rag and powdered dirt, and a corn cob, or pine stick, polishing the barrel, the bands, lockplate and trigger-guard until they were fit to pass inspection. The inside of the barrel we would keep clean by the use of a greased wiper and plenty of hot water. In doing this, we would ordinarily, with our screwdrivers, take the gun to pieces, and remove from the stock all metal pieces. . . . We soon learned to take care of our pieces in a rain by thoroughly greasing them with a piece of bacon, which would largely prevent rust from striking in."
Stillwell was issued the Austrian Rifle model of 1854, which he calls "a wicked good shooter." He is one of the few to comment favorable on what we call the M-54 Lorenz today.