Cleaning Parts By Electrolysis

Decided to try cleaning the prop shaft flange from the diff by electrolysis. Found a guide on the internet and gave it a go with good results. Would have been great to use this method for refurbing parts during my build.

The chemistry bit....

Electrolysis involves passing an electric current through an electrolyte; the result is a movement of charged ions from one electrode to the other. In this process, the rust (Fe2O3) is chemically converted to iron, releasing oxygen and hydrogen. Electrolysis works best with iron, but can work with any metal that can conduct electricity. It should be noted that some metals, like aluminium, will disintegrate faster than others.

CAUTION: This project can be dangerous; take all precautions to ensure your safety.

If the item has rubber parts, then this process may harden the rubber or leave the surface rather sticky.

Things You'll Need:

• Plastic bucket or similar plastic container.
• Battery charger (with 'Boost' mode) 
• Sodium Carbonate / Washing Soda / Soda Ash
• White vinegar 
• Safety glasses
• Safety gloves
• Scrap Copper
• Wire Brush
• Paper Towel

Step 1.

Add 1/3 cup Sodium Carbonate to 100ml White vinegar (Lemon Juice also works) in a cup. Mix into a paste, adding warm water as necessary. 

Caution: this mixture will froth so wear safety glasses and gloves. 

It is the current that cleans, not the solution, so making a more concentrated solution does nothing.

Step 2.

Using a wire brush, remove any loose rust from the item to be cleaned.

Step 3.

Put on the rubber gloves and goggles; as this paste is toxic and really irritates the skin. Using a paper towel, cover the item in the paste from Step 1 and leave to stand for 15 minutes.

Step 4.

Fill a bucket or similar plastic container with 4.5litres of water (warm is better - it helps the paste dissolve more quickly).

Step 5.

Connect a piece of clean scrap copper (rebar) to positive lead (anode) from a 12v battery charger (The red lead from the battery charger is the positive node.) Clamp it into place ensuring that it does not touch the side or bottom of the bucket. The rebar is a sacrificial anode will corrode away. Therefore ensure the charger's clamp does not come into contact with the water. 

A Stainless Steel rebar may produce better results, but it will release a highly toxic gas (Chromium). This gas is not just very irritating to the skin it has also been directly linked to lung cancer.

Step 6.

Connect the negative lead (cathode) from the DC source to the material that needs to be cleaned. The negative terminal will not corrode like the positive, however the solution is still aggressive and therefore it may be a good idea to insert a short length of thick wire between the item and the charger's negative clamp.

NB. The item will clean more effectively, if a minimal amount is resting against the bottom of the bucket. It may be good to prop it up with something non-conductive and scrap.

Step 7.

Double-check all connections, making sure nothing is touching; the electrodes should not be touching each other, nor should they be touching the sides or the bottom of the bucket. Make sure you have enough electrolyte solution to cover the part being cleaned.

Step 8.

Turn on the power. Bubbles will immediately form on the surface, especially around the positive anode. This is mostly hydrogen (from the cathode) and oxygen (from the anode) being released. Remember, the water is now 'live' so don't stick your fingers in!

Do not breath this gas! This gas is also explosive, so not not smoke! It is best to do this outside. 

 NB. If you charger has not got a high power 'Boost' mode, you could use a fully charged car battery.

Step 9.

Turn off the Power!

Cleaning a Diff flange took around 12 hours. The item was removed regularly and dressed with a wire brush. This seemed to speed up and improve the cleaning process. To re-use the liquid, remove the electrodes and leave to stand for an hour. Carefully drain off the fluid and dispose of the debris in the bottom. Give the electrodes a good scrub with the wire brush. The fluid can be re-used a few times before it becomes too acidic.