Electroysis | ucidiver

Electrolysis - Rust Removal

Many guns, knives, and other metal objects we recover underwater are covered with rust, which slowly destroys them and hides identifying information that could help identify them. Information such as serial numbers, manufacturer name, caliber, and other important details can be hidden or even removed. To begin preserving the item and obtaining the information needed to identify it, we must first remove the rust.

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

Just a reminder: rust, also known as oxidation, is the chemical reaction of iron, water, and oxygen that produces iron oxides. Iron oxides are 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 recovered metal, and the longer it is allowed to remain on the item, the more damage it causes.

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 it from rusting again.

How electrolysis works is not exactly known. However, it is clear that a major reaction occurs at the negative electrode, producing thousands of tiny hydrogen bubbles 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, such as:

Always wear eye protection and gloves, as the cleaning solution we submerged the rusted item in is alkaline and can irritate your skin and eyes. If you do happen to get some of the solution in your eyes or on your skin, you should immediately rinse the affected area with fresh cold water and seek medical attention if needed.
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.
One side effect of electrolysis is that water breaks 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, cigarettes, sparks from shorting out the battery leads.

What do you need to start?

A plastic tub slightly larger than the item recovered.
Fresh water
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 raise the pH level in pools. It's also 100% sodium carbonate.
A 6- or 12-volt battery charger that can deliver a few amps (two amps at 12 volts is typical) of direct current (DC) is needed, or a car battery will work. I prefer a car battery. I bought several battery chargers but shorted them out.
Steel or iron electrode, such as rebar. I prefer rebar because it's cheap and easy to come by.

The Procedure

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, making sure all the crystals dissolve.
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 on the battery lead isn't submerged, as it will be eaten away during 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 that the rebar has to be facing the area you want cleaned. Usually, the area facing the metal anode is cleaned, while the back side receives less cleaning.
Attach the negative lead from the battery charger or jumper cables to the item you want cleaned, then submerge it, keeping it and the rebar several inches apart. It does not matter if the clamp gets submerged a little because it will not be affected 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 the process and reposition the item to ensure it is 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 specific area is rusty, point it 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 an 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 rust off the item, give it a good oiling.

NOTE:

You might want to remove the gun handles and other coated surfaces before submerging, as the cleaning solution may remove paint and other finishes on wood and other surfaces. Be careful.
If you have several parts and pieces, each one needs good electrical contact for cleaning to take place.