Electrolytic rust removal -- when to quit?

[montanajohn]

I am de-rusting some running boards in a 50-gal. plastic garbage can with TSP as the electrolyte and 3 4x12-inch graphite plates as the anodes off and on for several hours (8 to 10, maybe) for over a week. Power comes from a battery charger feeding through a 12v battery with the leads going from the charger to the battery to the tank ( 2 to 8 amps). Everything is going well, hydrogen bubbles coming up, etc. I have assumed that the bubbles come from converting rust to iron phosphate. Do I keep going until no more bubbles? Is there a risk of eating-up good metal? Thanks for any comments or advice.

[Kevin in NJ]

It can not eat up good metal. You can look up all the chemical details at other websites. As I understand it the red iron oxide will be removed. The black oxide of iron (I forget the name) is reconverted back to iron and left on the surface.

You need to go until the iron oxide is removed all the way at the bottom of the pits. You should not see a dark spot at the bottom of the pits. The dark spot will quickly bloom surface rust around the pit.

[mot]

it should take overnight
you will have to use a wire wheel to remove the black oxide
it will come off very easy
if like Kevin said ,if theres more black in the pits,just stick it back in overnight
The TSP or sodium carbonate is only used for a path of the current
even rusty water works good
tom

[montanajohn]

I looked at several websites describing the setups and electrolytes. Some preferred sodium carbonate, and some TSP. Most said that it didn't matter much, so long as the brew was of sufficient strength to conduct efficiently (there was one mention of using molasses!!). TSP won because I already had some on hand. How's that for a good reason?

[Vic in E-TN]

TSP is getting hard to find. Sodium carbonate is easy to find at the hardware or feed supply store.
Vic

[40 Deluxe]

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I don't think molasses is used as the electrolyte. It itself is a rust remover (the sulphated kind found at a feed store). Just mix it 5 to 1 or so with water and soak your part for a week or so. Yeah, it is slower but does a good job. Just keep a few inches of liquid above what you're soaking or a gooey slime will be deposited.

[d.j. moordigian]

I've had it take 2-4 sessions, at 12 hour shifts. I must drag home rustier junk.

[Tom Wesenberg]

I used washing soda in tap water and my 6 amp battery charger. My very rusty Cub Cadet wheel came out great after two days. I did have to pull up the steel rods a few times to clean the crud off them. Here are some pictures. Someone used calcium cloride in the tires for weight and the wheels had very heavy rust from it. After the rust removal had done it's job I rinsed in hot water while giving it a light wire brushing.

[texas webb]

What is the ratio water to TSP or sodium carbonate?I"d like to try this for some wire rims I have should be better/cheaper than blasting,thanx Webb.

[d.j. moordigian]

Texas,

I used "fordgarage" ratio on his site( #3 above ) works good..

.............................www.fordgarage.com........................

[Tom Wesenberg]

I used about half a cup of washing soda in the laundry tub about half full of warm water.

[Cool Hand Lurker]

I did a flathead V8 block with sodium carbonate (washing soda) and it took about 2 weeks continuous with the charger hooked up through a battery, but it cleaned out the insides too. The main problem I had was that the re-bar that I used for electrodes had to be cleaned off every day and pretty much ate away to nothing before I was done. I have since purchased some graphite rod but have not used it yet. Vince's Ford Garage site says it doesn't have the same crud problems that the re-bar has.

[mot]

rebar is a waste of time
find some old 4 in pipe or even an old disc brake
i use any old heavy scrap of iron
you MUST clean the sacrificial iron every day

[CarlG]

Originally Posted by 40 Deluxe

... molasses ... itself is a rust remover ... Yeah, it is slower but does a good job...

That must be where the term "slower than molasses" came from that my mother use to use all the time!

[1952henry]

PH Plus sourced from pool supplies in Walmart is about $7 for 5 lbs, pure sodium carbonate. Powdered lye works well as electrolyte and gets rid of paint at the same time!

[Terry, NJ]

It really doesn't matter! The "Pollutant" that you use merely helps the conductivity of the water. The dirtier the better! To flip the situation, Try doing it in distilled with zero conductivity! You'd have to contaminate the water with something to get a result. Once the water has been used for de rusting, it's good. I will concede that maybe some products are better at conducting than others. But almost anything will work. One to try is rocksalt. Sodium Chloride works well in other forms of analysis.
Terry

Originally Posted by texas webb

What is the ratio water to TSP or sodium carbonate?I"d like to try this for some wire rims I have should be better/cheaper than blasting,thanx Webb.

[redmodelt]

I don't know about TSP or other concoctions but with washing soda the brew can be dumped on the ground for your iron loving plants.

[socalplanedoc]

My gawd, that's beautiful (wiping away a tiny tear of joy)


seriously, I need to try this on *something*.

Originally Posted by Tom Wesenberg

I used washing soda in tap water and my 6 amp battery charger. My very rusty Cub Cadet wheel came out great after two days. I did have to pull up the steel rods a few times to clean the crud off them. Here are some pictures. Someone used calcium cloride in the tires for weight and the wheels had very heavy rust from it. After the rust removal had done it's job I rinsed in hot water while giving it a light wire brushing.