Oxidation is a treatment that produces a thin protective layer of black iron oxide (Fe3O4), designed to provide nominal protection against rust from a metal weapon. Over time, however, this layer can wear out and needs to be renewed in order for the weapon's appearance to be restored. Depending on the weapon's age, monetary value, and sentimental value, you can either restore the weapon yourself or ask a professional for help.
Part 1 of 4: Deciding How to Reoxidize
Step 1. Analyze how much the old oxidation has worn away
If most of the original oxidation still exists, you can touch it up yourself with a cold oxidation kit; however, if most of the original oxidation has worn away, you may want to consider removing the rest of the old layer and hot oxidizing the weapon.
Step 2. Analyze the weapon's age
Old weapons, dating back to the 19th century, were oxidized using acid or evaporation. Currently, these processes are not used commercially due to the time required. There are products available on the market that will allow you to carry out acid oxidation, or you may find someone to do it for you.
Old weapons that have silver solder or brazing cannot be hot oxidized, as the caustic salts used in the process will corrode the silver. Double-barreled firearms typically used this type of soldering or brazing to keep the barrels properly aligned
Step 3. Analyze the weapon's value
Hot oxidation is significantly more costly than cold oxidation; therefore, first of all, you must consider the cost of the reoxidation process you plan versus what you spent on acquiring the gun, as well as its resale value if you want to sell it.
The intrinsic value of the weapon must also be analyzed, or what it means to you, as well as its actual monetary value. If the weapon is a family heirloom, you may want to spend more on its reoxidation, even if its monetary value is the same as a weapon purchased at a sporting goods store
Step 4. Analyze the potential cost of the oxidation process
In addition to the monetary and intrinsic value of the weapon, you must also take into account the costs of the oxidation process you want to perform.
- Cold oxidation, described in Part Two of this article, is the simplest of the processes, and therefore the cheapest, but it is also the least durable. If you plan to handle the gun a lot after the process, you should expect the oxidation to wear out reasonably quickly.
- Hot oxidation, described in Part Three of this article, is more durable than cold oxidation and acid oxidation, but it requires more labor and equipment to perform. If you think the gun deserves to be hot oxidized, but you're discouraged from getting the job done, you can hire someone to do it.
- Acid oxidation, described in Part Four of this article, requires less work than hot oxidation, but more work than cold oxidation. It is also the most time-consuming of the oxidation processes, as the weapon must rest for a while in order to reach the desired level of coloration. If you again find yourself discouraged from doing the work, you should hire someone to do it.
Part 2 of 4: Cold Oxidation
Step 1. Remove old oxidation if desired
Depending on the degree of wear from the old oxidation, it can be completely removed before reoxidizing the weapon. The following chemical agents can be used:
- Automotive rust remover based on phosphoric acid, such as Naval Jelly (naval jelly).
- White vinegar, which contains acetic acid.
Step 2. Jump the metal gun
Polishing removes surface rust and any scratches or marks the gun may have suffered over the years. You can use 000 steel wool or 600-1200 grit sandpaper.
Step 3. Clean the gun
How you choose to clean the weapon depends on your desire, which can be to oxidize the entire weapon or touch up the existing oxidation.
- If you plan to oxidize the entire weapon, immerse the weapon in a cleaning solution. Cleaning solutions that can be used include sodium triphosphate (commercial detergent), denatured alcohol, or naphtha. (If you choose to use naphtha, wash the gun in a mild detergent and then rinse it with hot water.)
- If you plan to immerse the gun parts to clean them, use a wire basket to place the small parts and insert a thin wire into the barrel so you can dip it in the cleaning solution, removing it later.
- If you only plan on touching up the existing oxidation, apply cleaning oil where you want to remove the old oxidation; then apply soaked acetone to cotton balls to remove the oil (such oil, a mixture of vegetable and mineral oils, alcohol, benzyl acetate and alkaline salts, is sold commercially under the name Ballistol.) As you remove the oil. old oxidation, some marks may be found that will need to be sanded or polished.
Step 4. Heat the metal carefully
Although this process is called cold oxidation, carefully heating the weapon before performing it provides better absorption and finish. The gun can be heated by being left in the sun for several hours, with a heat gun or hair dryer, or in a conventional oven at its lowest temperature.
Step 5. Apply the oxidation solution
Slowly apply the solution over the area to be oxidized as evenly as possible using a clean applicator. Apply the solution in one go, covering small areas, or in sections no larger than 5 to 7, 5cm; then skim the surface using a steel wool. This process will prevent the oxidation from staining.
- To apply oxidation to larger areas, old cotton shirts or new toothbrushes are recommended. For smaller areas, use a cotton ball, cotton swab, or toothpick that is no larger than the area to be covered.
- You can dip small parts, such as screws, or hard-to-cover parts into the solution. If you don't have enough solution to cover a recessed area, place the product in a spray bottle and generously spray the area in question onto a glass container or plastic tray. Once the region is completely covered, the solution left in the container or tray can be returned to the spray bottle and reused.
Step 6. Apply the solution several times until you have the desired oxidation level
Apply each coat with a new applicator, and use a fresh piece of steel wool to polish each new coat.
- The more layers applied, the darker the oxidation will be; however, each new layer is progressively less effective than the previous layer. In most cases, seven coats should be enough to achieve a bluish-black finish.
- If there are spots that do not darken, restart the process by sanding these places with a 320 to 400 grit sandpaper before applying the solution again. Try not to sand more areas than spots that have not been oxidized.
Step 7. Once you get the desired oxidation level, coat the gun with gun oil
Apply a coat of oil every few hours, using a cotton ball to remove the previous coat before applying the new coat. (In essence, you are removing the oxidation solution with oil rather than removing it with water.).
Do not use cleaning oil in this process as it will remove the oxidation that has been done with your hard work
Part 3 of 4: Hot Oxidation
Step 1. Skip the parts of the weapon to be oxidized
Again, you can use 000 steel wool or 600-1200 grit sandpaper to polish the metal.
Step 2. Prepare the parts to be immersed in the cleaning and oxidation solutions
Although the cleaning solution used may not require it, the chemical agents used in the hot oxidation process, typically potassium nitrate and sodium hydroxide, are highly caustic. It will be easier to immerse the gun barrel if you introduce wire into the piece, and smaller pieces should be placed in a wire basket to facilitate immersion.
Assembling the parts before cleaning will facilitate their transfer from the cleaning tank to the oxidation tank; also clean the used wire and basket in order to avoid contamination of the gun parts in the oxidation tank
Step 3. Dip the gun parts in the cleaning solution
The parts must remain immersed for 10 to 15 minutes and be rubbed while immersed, in order to remove all oil, dirt or grease that could hinder the oxidation process. You can use any chemical cleaner listed in the cleaning step for cold oxidation as long as you follow all instructions for using, handling, and disposing of the remover.
Step 4. Rinse the cleaning solution in cold water
The rinse time should not exceed more than 2 to 3 minutes..
If you are using detergent to remove chemical cleaning agents, you may need to use hot water for rinsing
Step 5. Dip the gun parts in the oxidation solution
The hot oxidation solution, known as “Traditional Black Oxidation”, must be heated to a temperature of 135 to 155 degrees centigrade.
- Before heating the solution, shake it thoroughly to dissolve any clumps of salt that may occur on the surface or bottom of the container where the product is.
- When dipping gun barrels in oxidation solution, dip them at an angle that allows any bubbles that have formed to be eliminated. Be sure to immerse the pipe completely.
- Shake the metal basket containing the smaller parts of the weapon in the solution to ensure they are completely covered by the product.
- Leave the parts in the solution for 15 to 30 minutes. Pay attention and check when the metal reaches the desired shade of oxidation and then remove them from the solution.
- If your weapon has stainless steel parts, they must be immersed in a different chemical solution, which is a mixture of nitrates and chromates, and heated to temperatures similar to those of a mixture of hydroxide and nitrate.
Step 6. Rinse the oxidation solution in cold water
Shake the parts in cold water to eliminate the oxidation salts.
Step 7. Soak the gun parts in boiling water
This process will eliminate any remaining residue from the solution. Simple parts need to be immersed for 5-10 minutes, while complex or decorated parts may need to be immersed for up to 30 minutes.
If the weapon has welded parts, use a cotton swab and apply a chemical agent over them, which will color the welds, making them the same color as the rest of the metal
Step 8. Soak the treated parts in a container of anti-moisture oil
This will protect the finish from rust, sweat, and body oils. Leave the parts in the container with oil for 45 to 60 minutes, until they have cooled down.
Part 4 of 4: Acid Oxidation
Step 1. Skip the parts that will be oxidized
Use a steel wool or 600-1200 grit sandpaper to remove rust, scratches and marks from the metal.
Step 2. Chemically clean any remaining dirt, oil or grease
You can use any of the removers listed in the cleaning step under the cold oxidation process, unless the manufacturer of the oxidation solution being used has different instructions. After using the cleaning solution, rinse the product.
Step 3. Cover the metal parts with the solution
This solution is usually a mixture of hydrochloric and nitric acids, and causes the metal to oxidize evenly.
- Instead of covering the parts with the acid solution, you can place an open container with the acid solution and the gun parts in a closed cabinet and leave it in place for 12 hours. The acid evaporates and condenses around the weapon; this method is called evaporative oxidation.
- Another variation is to cover the gun parts with the acid solution and then place them in an exhaust hood (or, in this case, a steam cabinet) for the same 12 hours. Often the first coat is applied as a preparation before covering the parts a second time and then placing them in the steam cabinet.
Step 4. Soak the metal parts in boiling distilled water
This removes the acidic solution, stopping the oxidation process.
Step 5. Scrub the red oxide that has formed, leaving the black oxide layer below
The rusty surface is usually removed with a drum carder or carder brush, which has very fine, soft wire bristles.
Step 6. Repeat the acid treatment, boiling and rubbing until you get the desired level of oxidation
In some cases, the metal can develop the deepest possible coloration, making other attempts at oxidation counterproductive.
Step 7. Coat the gun parts with oil
The oil inhibits the formation of rust and protects the finish from dirt, sweat, body oil and wear. Once you've applied the oil, let the parts sit overnight before assembling them.
- Before carrying out any oxidation process described above, make sure the weapon is unloaded! Also remove the handle or stock from the weapon.
- With all oxidation processes, work in a well-ventilated area as caustic salts are especially harmful.
- Do not carry out the hot oxidation process on aluminum; it reacts violently to caustic salts, which can cause severe burns.