The information below describes and shows the process of gently cleaning rusted gun metal without harming any original aged finish. The gun used for this demonstration is an L. Pomeroy Model 1816 Musket dated 1833. Over the years it was by contract converted from Flintlock to Percussion and then altered to Shotgun. From 1831 browning of barrels was discontinued in favor of the old bright finish. This gun is from Zane Wilson's Collection.
This gun is an excellent demonstration example because it has all three major forms of rust, that is, powdery rust, scaled rust, and pitted rust. It also has the remaining portion of the original brass flashpan and much, apparently, original finish on the lock plate. The photos below show the Model 1816 before cleaning:
The image below is from the book "Rare Selections From Old Gun Catalogs 1880-1920":
The gun used for Cob Blasting and WD-40 soaking for one year and three months is a Miquilet shotgun that had been convreted from Flint to Percussion
The gun metal is gently cleaned using high pressure water, boiling water, WD-40 (Water Displacement - 40th attempt), and a short bristled nylon brush (e.g. toothbrush). To prevent damaging the original aged finish, water and WD-40 are the only two solutions used to remove contaminants. High pressure water aids in removing rust scale. Boiling water is used to remove any corrosive salts that may remain from corrosive primers or black powder ammunition. Boiling water also aids in removing rust scale because the rust scale expands and contracts at a different rate than the metal. WD-40 is used to penetrate into, loosen, and flush away rust and other contaminants as well as displace any remaining water. No form of rust remover, abrasives, scrapers, electrolysis, etc. is used to prevent damaging the original aged finish.
The brushing process is performed thoroughly and efficiently by bolting a nylon brush to a Palm Sander as shown in the photo below. Two brushes may be used. A firm bristle (0.009" diameter) brush is primarily for removing rust scale. A soft bristle (0.006" diameter) brush is primarily for removing rust from pits.
Note that a brush may be extended to clean difficult to reach areas such as inside the barrel of a Blunderbuss.
For cleaning the inside of smoothbore barrels, a cleaning rod may be attached to a Drill as shown in the photo below:
The cleaning rod may be attached to a Reciprocating Saw as shown in the photo below:
Rifled barrels need the cleaning rod to be pushed and pulled in and out of the barrel to prevent harming the rifling.
The cleaning procedure follows:
1. Wash in hot rise cycle using high pressure car wash wand concentrating on rust scale and pits. 2. Spray with WD-40 and brush with firm bristled nylon brush. 3. Freeze for 12 hours or longer. 4. Place in boiling water for 10 minutes. 5. Remove from boiling water and immediately dry and spray or soak in WD-40 till cool. The boiling water is then poured down the barrel(s) and the bore(s) scrubbed with a cleaning rod. 6. Soak in WD-40 for 24 hours or longer. 7. Brush with FIRM nylon brush. 8. Soak in WD-40 for 24 hours or longer. 9. Brush with SOFT nylon brush. 10. Repeating the above steps will remove slightly more rust. 11. The WD-40 that had been used to soak parts in is then poured down the barrel(s) and the bore(s) scrubbed with a cleaning rod.
Optional Additional Cleaning
Optionally soak in WD-40 for 24 hours or longer and then carefully brush with fine bristled brass brush for removing excessive rust scale that is not removed by above steps. The brass brush may be attached to a Palm Sander as shown in the photo below:
Optionally soak in WD-40 for 24 hours or longer and then carefully brush with fine bristled stainless steel brush for removing excessive rust scale that is not removed by above steps. The stainless steel brush may be attached to a Palm Sander as shown in the photo below:
The sections that follow give the results after each major cleaning step in the procedure. The photos given will be as follows:1. Outside of lock plate.It should be noted that to reveal rust remaining on the parts in the photos, the parts had been washed with detergent, rinsed in very hot water, and thoroughly dried before photographing.
2. Inside of lock plate.
3. Top of lock plate.
4. Main Spring (left) and underside of hammer (right).
High Pressure Water
The photos below show the results after spraying with high pressure car wash wand:
Notice the green oxidation on the portion of the original brass flashpan.
Freeze, Boil, WD-40, Nylon Brushing
The photos below show the results after freezing for 12 hours, boiling for 10 minutes, soaking in WD-40 for 24 hours and then brushing with firm and soft nylon brushes:
Notice that some of the green oxidation on the brass flashpan has been removed after brushing with a nylon brush.
WD-40, Brass Brushing
The photos below show the results after soaking in WD-40 for 24 hours and then brushing with brass brush:
Brass residue from the brass brush remains on surfaces after brushing. This residue may be removed using Cleaner-Degreaser.
Notice that most of the green oxidation on the brass flashpan has been removed after brushing with a brass brush. This removes some brass and is not recommended. Instead, brass metal may be gently cleaned as described at: Gun Brass Metal Cleaning.
WD-40, Stainless Steel Brushing
The photos below show the results after soaking in WD-40 for 24 hours and then brushing with stainless steel brush:
Notice that all of the green oxidation on the brass flashpan has been removed after brushing with a stainless steel brush. This obviously removes some brass and is not recommended. Instead, brass metal may be gently cleaned as described at: Gun Brass Metal Cleaning.
The photos below show the striking portion of the hammer. The first two photos show the results after partially then thoroughly sandblasting to give an indication of the amount of rust remaining. The last photo show the result after blueing.
Indication Of Rust Remaining
After soaking for 1 year and 3 months with rear portion of trigger guard submerged half way.
After brushing with stainless steel brush:
After washing in Dawn and drying: