Electrifying rust removal

I'm familiar with electrolysis for rust removal but have never actually tried it. So, after pulling the super-crusty HP manifolds from the engine I decided to give it a try. If you have a media blast cabinet (which I do) I think you'll find blasting faster and, in some case, more effective than electrolysis but it does have it's place.

Your electrodes consist of the part to be cleaned (cathode) and a sacrificial anode. In this case I used pieces of steel rebar because it's really cheap. Sheets of metal or scap iron will work too. Stainless steel is not recommended (though it stays cleaner and lasts longer) because it creates toxic waste. You'll also need a power supply. In this case I used a battery charger set at 35 amps. Smaller chargers in the 2-6 amp range will work too but might take a little longer to do the job.

The final piece of the puzzle is the water solution. You'll need sodium carbonate - more commonly known as Washing Soda. Baking soda is sodium bicarbonate and is similar but the not same. Since washing soda can be hard to find you can do what I did and go to a pool/spa supply and pick up a package of 100% sodium carbonate for a few dollars. By the way, you can also make it by placing baking soda on a tray in your oven and baking it at 300 degrees for an hour or so to drive away water and CO2 molecules - converting it to washing soda. At temperatures above 300^o  Fahrenheit (149^o Celsius), baking soda decomposes into sodium carbonate, water, and carbon dioxide - but I digress. 1/3 to 1/2 cup of soda for every 5 gallons of water will do. More soda will not make the process work better.




My basic setup

 

Electrolysis is s line of sight process so your sacrificial electrodes should be placed around the part to be de-rusted. They need to be tied together electrically. You can tie them altogether with copper wire. I tack welded a coat hanger to the ends which not only joins them electrically but helped hold them in place. Your container can be anything large enough to accomodate your part(s). Plastic is recommended for a host of reasons. Make sure the part to be cleaned does not touch your electrodes or you'll create a short which will kill the process and possibly your charger.

Connect the POSITIVE cable to your electrode grid and the NEGATIVE cable to the part to be cleaned. Get the cables reversed and you'll get the opposite result than the one intended: your part will be sacrificed and your electrodes will be derusted. The nice thing about the process is you can't overdo it. You could leave your part in for days with no ill effect.



Now, once everything is properly connected, turn the charger on and you'll see champagne style bubbles form off the surface of electrodes and your piece. A few hours later (or overnight) and theoretically your rust will be removed leaving behind an inert black oxide coating. This film can be removed under fresh water with the help of a wire brush.







I got fair results on an exhaust manifold which had a lot of surface rust. The manifold was too big to fit in my 5 gal. bucket so I had to turn it. When I turned it I decided to add sodium hydroxide (lye) to the mix to see if it would work any better. I think it improved the process considerably BUT you're creating a nastier and potentially more dangerous water solution by doing do. Drano Kitchen Crystals is a good source of lye. Proceed at your own risk, however. If you burn your skin, put an eye out, or otherwise poison yourself, you're on your own.

Derusting a battery tray brace worked really well. In the picture below, the right end of the manifold spent time in the soda/lye solution, while the left side got soda only.





"De-rusted" battery tray brace and exhaust manifold





SAFETY PRECAUTIONS: Use rubber gloves and face protection - especially if you introduce lye to the mix. The process also gives off hydrogen gas (that's what those bubbles are) so do it outside or in a well ventilated area. Hydrogen gas is potentially explosive. The wash soda only solution can safely be poured on your lawn or down the drain without any environmental concern.

For more detailed information on the process with additional links click here.