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Electrolysis - Rust Removal

 

Many guns, knives and other metal objects we recover underwater are covered with rust which slowly destroys the item as well as hides identifying information which could help identify the item. Information such as serial numbers, manufacturer name, the caliber of the weapon and other important information can be hidden or even removed. In order to begin to preserve the item and to obtain the needed information that will help identify the item recovered, we must first remove the rust.

 

But like always, if this is a recovered item of importance, I contact my laboratory to check to see what they prefer I do with the weapon. Sometimes, they prefer to do the processing.

Just as a reminder, rust, which is also known as oxidation is a chemical union of iron, water and oxygen, which produces iron oxides.  Iron oxides is the rust buildup we see on many metal items that have been allowed to get  wet. Rust has a tendency to pit and scar the surface of the metal item recovered and the longer the rust is allowed to stay on the item, the more damage it does.

The electrolytic method of rust removal

 

The electrolysis method involves immersing the rusty object in an electrically conducting solution of washing soda (sodium carbonate). The negative lead (black) from a battery charger or jumper cable (the jumper cables are attached to a car battery) is attached to the object, and the positive (red) lead is attached to a steel electrode (rebar) placed in the solution. When the current is turned on, electrochemical reduction reactions occur at the metal/oxide interface on the object's surface. These reductions loosen the rust layer, allowing it to be easily brushed off by using a metal brush and rag. Once the item is cleaned, you want to give it a good cleaning and light oiling to prevent the item from rusting again.

 

How electrolysis works is not exactly known. However, it is clear that a major reaction at the negative electrode occurs which produces thousands of tiny bubbles of hydrogen from the electrochemical reduction of water. The hydrogen may in turn react chemically with the iron oxides, or it may simply act to physically dislodge the rust layer. Whatever is happening, the process does not appear to cause further damage to the recovered item and once you remove the rust, you can see what the final condition is.

 

Safety Precautions

 

Before we begin, you must first understand that electrolysis can be dangerous if you are not careful and take some safety precautions like:

  1. Always wear eye protection and gloves because the cleaning solution we submerged the rusted item in is alkaline and will irritate the skin and your eyes. If you do happen to get some of the solution in your eyes or on your skin you should immediately rinse the effected area with fresh cold water and seek medial attention if needed.

  2. To generate an electrical current, we either use a battery charger or a car battery. Both of which can shock you if you put your hand in the solution or touch both electrodes while the current is turned on. Keep the battery charger or battery away from the solution and protected. 

  3. One of the side effects of the electrolysis is that the water will break down into its components, hydrogen and oxygen. For this reason you should work in a well ventilated area and avoid any sources of ignition, ie. cigarettes, or sparks from shorting out the battery leads.

 

What do you need to start?

  1. A plastic tub slightly larger than the item recovered.

  2. Fresh water

  3. Washing soda (sodium carbonate). You can find this at Walmart in the pool section. They sell  "ph Add" by Aqua Chem. It's used to raises the ph level in pools. It's also 100% sodium carbonate.

  4. A 6 or 12-volt battery charger that can produce a few amps (two amps at 12 volts is typical) of direct (DC) current is needed or a car battery will work. I perfer a car battery. I bought several battery chargers but shorted them out.

  5. Steel or iron electrode such as rebar. I prefer rebar because its cheap and easy to come by.

 

The Procedure

  1. Poor enough water in the tub to cover the item to be cleaned so that the item is submerged a few inches underwater. Dissolve approximately 1 tablespoon per gallon of washing soda in the water and make sure all the crystals dissolve.

  2. Attach the positive lead (red) from the battery charger or jumper cables (that are attached to a car battery) to the rebar. I bent the rebar in the picture to give the gun a lot of submerged surface area on the electrode. Submerge the rebar in the cleaning solution and make sure the clamp from the battery lead isn't submerged because it will be eaten away with this process. The rebar will also be eaten away but very slowly. If you are cleaning a large piece like a rifle, the best thing to do is break it down into smaller parts. The way this works is the rebar has to be facing the area you want cleaned. Usually, the area facing the metal anode will be cleaned and the area on the back side will not get as much of a cleaning.

  3. Attach the negative lead from the battery charger or jumper cables to the item that you want cleaned and submerge it keeping it and the rebar away from each other by several inches. It does not matter if the clamp gets submerged a little because it will not be effected by the electrical current. Make sure the rebar and the recovered item do not come into contact with each other. It could short out the process.

 

Once it is set up and working you should see small bubbles of hydrogen and oxygen coming from the electrodes. Now you just have to wait. The time required to clean a part will depend on many variables:

  • Size of the part

  • Current used

  • How rusted the item is

 

You can leave the operation on overnight if needed as long as you have ventilation and you are not cleaning the item in an enclosed space. You will have to keep checking on the process as well as reposition the item to ensure the item is being cleaned completely. I usually have a bucket of clean water I can dip the item in to get a good look. You can also use a plastic and/or metal brush to help remove the rust and sludge. If the item is still a little rusty place it back in the water. If a certain area is rusty, point that area directly at your rebar and let it sit for a while longer to remove the rust. Once you are done the item will have a gray finish which is a oxide coating. You can leave it if you like the look or take a metal brush and brush it off. And again, after you have finished cleaning the item from rust, give it a good oiling.

 

NOTE:

  • You might want to remove the gun handles and other coated surfaces before submerging because the cleaning solution may remove paint and other finishes on wood and other surfaces, so be careful.

  • If you have several parts and piece, each one needs to have a good electrical contact for cleaning to take place.