Electrolytic De-Rustification
Electrolic de-rustification (I made up the name!) is the reverse of plating. In this case you are reducing the iron oxide (rust) into iron and oxygen. It is very simple and gives good results. You need:
- Battery Charger (free - the forgotten one sitting on your shelf covered in dust)
- Stainless steel sink ($2 from a garage sale)
- Water (from the tap)
- Washing soda (Arm and Hammer $4)
- Rusty part (priceless)
El-cheapo battery charger
$2 garage sale stainless steel sink and new clean mixture
And you thought that this was an advertisement free website!
You fill the sink up to about 2" from the top with water. Add 1 tablespoon washing soda (NOT baking soda) for each gallon of water. Place the part in the sink and use plastic insulators so that the part does physically touch the sides of the sink. There should be at least 1" between the part and any part of the sink (as I found out). Attach the positive lead of the battery charger to the sink and the negative lead to the part to be de-rustified. You should measure about 1 to 3 amps of charging current at the start and rising to about 4 to 5 amps.
Initialy, the solution will be clear but pretty soon, it'll start bubbling and foam will appear as in the above picture. The current will rise steadily also. If it rises above 5 amps, you may have too much washing soda in the mixture. Drain and start over again.
I've had the best success when I've left the piece in the soup overnight. The rust turns into a sludge that can be wiped or scraped off. You should clean and dry it as quickly as possible as the sludge turns rockhard quickly and the piece rusts quickly. I use paper towels and my shop air hose to dry them. There's a slight dusty residual that's left on the piece but it easily sands or wire brushes off. By the way, the piece will change to a dark color or black.
Here's the soup after a week of use - pretty digusting
Headlight bucket with 50 years of crud on it immediately after being pulled from the soup
I tried one of my 1954 headlight buckets and left 50 years of crud on it. I didn't even take the caked on dirt, screws, rusted on rubber gasket or plastic adjustment nuts off. Threw it in the de-rustifier and let it sit overnight. Well, the results were outstanding. The rust either flaked off or rubbed off as a kind of sludge. The rubber gasket that was rusted in place pulled off easily.
Here's the headlight bucket after cleaning the sludge off, drying and a quick wirebrushing
And here they are painted - almost as good as new!
Exhaust manifold after cleaning and painting - looks pretty damn good!
I did a test and put one exhaust manifold through the process and did the other one by normal wirebrushing and sand blasting. The de-rustified one required much less work overall, less time and was way easier to bring up to a better condition than the other. I highly recommend this method.
Things to know before you start
You probably know by know that I learn a lot of things the hard way. Electrolic de-rustification was no exception. Here's a list of things that will help make the process easier:
- Measure the washing soda carefully. I guesstimated how much I needed the first time and ended up with
a runaway mixture. The initial current reading was 3 amps, then after 1/2 hour it rose to 5 amps. Then slowly
went to 7 amps then when I checked on it again, it was up to 11 amps. This was from a 6 amp battery charger!
Since it was the first time, I thought that this was normal. When it reached 15 amps and the battery charger's
over-current protection kept clicking off and on, I knew I better start over.
- Make sure that there is a least 1" between the part and the sides of the stainless steel sink. I used thin
cutup yoghurt containers for insulators and they were too thin. As the rust flaked off, it bridged the insulator
and provided an electrical path between the part
(negative electrode) and the sink (positive electrode). After a week of use, the sink ended up with pin holes
corroded through it and can't be used anymore. Thankfully, I only paid $2 for the sink, so it wasn't a
great loss. Cleaning out the crud after each use would of helped also.
- The Arm and Hammer washing soda is a soap and is pretty harmless, the water/soda mixture feels like
what it is: soapy water. You can drain it down the toilet but make sure that the rust crud is cleaned out first.
There's no special handling or draining procedure required.
- If a piece is too big to fit completely in the sink, you can do part of it and then flip it over and do
the other side. You should clean the sludge off before you flip it over as the portion that sticks up in
the air will dry and rust.
- The process only affects rust. It leaves the nonrusted metal alone and doesn't affect any plastic
or rubber pieces. It separates the rust (iron oxide) from solid iron.
- The preferred sink size is the large stainless sink but it is harder to find. I could just fit an exhaust
manifold into it. The other choices are double sinks and bar sinks expect to pay about $10-20 per sink at
a garage sale. The condition of the sink is not too important as long as it holds water. I was lucky and only paid
$2 which is a real good deal.
- The biggest problem that I had was finding a stopper that wouldn't leak for the sink. I eventually used
some gasket maker to seal the stopper so that it wouldn't drip. An alternative would be to put a pipe plug
on the end of the sink drain.
- A single large sink holds 10 gallons of water so you need 10 tablespoons. Once the mixture has been used,
the problem arises on how to empty it. I had a 5 gallon bucket that I filled and hauled the soup away with.
- The 5 gallon bucket worked great as a stand for the sink. The sink balanced perfectly fine on top and any drips from the stopper were caught in the bucket. I used a laundry detergent bucket which was semitransparent, just enough so that I could see the water level inside the bucket to track the stopper leakage.
Here's the link to the The Electrolytic Rust Removal FAQ By Ted Kinsey where I first came across this process. It will answer any other questions that you have.