Electrolytic Rust Removal & Power Supplies

[Doug Van Horn]

I wanted to post my experience with this so as to help others who might try this. When I went about trying to gather all of the necessary pieces together for this type of rust removal, I had the hardest time finding a power source.

You see, it seems that many modern battery charges are equipped with some kind of polarity protection (or some such nonsense). This prevented the chargers (2 different ones) I purchased from providing current to my rust removal system. Presumably they wanted a battery at the end of the cables.

So after a few curses I asked for advice from a robot-building friend familiar with chargers and the dark magic of electricity. He recommended a _power supply_. While the goal of a battery charger is to fully charge a battery then turn off, a power supply will churn out electrons so long as it's plugged in.

So a trip to Gateway Electronics and $50 later (which yielded a 14V 5A power supply, some wires, clips, a cheap soldering iron and solder) I was in business.

Anyway, I would highly recommend getting one of them power supplies if you're looking to remove rust. That is if you don't have an old battery charger and are left having to buy a new-fangled one.

FWIW

Here's a link describing electrolytic rust removal in detail:

one for Google:

[Eric Lund]

Great idea. Here's another. Get one of those timers you hook up to lights. I'll bet there's a kind that will turn on only once. Then just set it for the amount of time you want to run.

Cheers, Eric

[Andy Dingley]

Indeed. But cheap and simple battery chargers are still out there.

Watch it with "power supplies". Although any modern home will have some scrap gadget that can be cannibalised for something suitable, there are still a few caveats. Plug-top ("wall wart") supplies won't deliver the couple of amps needed, unless you can find something unusually beefy. Computer PSUs are also of little use - they're mainly "switch-mode" supplies and their foible is that they won't work into a minimal load - they need at least an amp or two before they're happy.

The idea of spending $50 on an electrolysis supply horrifies me. The transformer in mine is 30-40 years old, the meter was rewound for a better calibrated range and the rectifier was soldered up on tag strip by a careless schoolboy owner about twenty years ago. A $5 basic book on electronics will give you all the circuit details you might ever need.

-- Klein bottle for rent. Apply within.

[Andy Dingley]

I don't think this is a good idea.

- It's not adding anything useful. Why not just leave it cooking ? One of the nice things about cathodic cleaning (as compared to anodic electro-polishing) is that it's self-limiting. Leave the piece in for an extra week, it just doesn't care.

- Leaving the piece dunked in the electrolyte but unpowered _is_ likely to to encourage rust. It's a salt solution here, maybe even a caustic one.

- It's another gadget. This is a simple process, lets keep it that way.

-- Klein bottle for rent. Apply within.

[TT]

Had a similar problem with my old Heathkit battery charger - it won't charge unless it sees at least some voltage across it to begin with so it knows it's connected to a battery. My solution (since I had the circuit diagram) was to add a couple of wires from the plus and minus sides of the internal bridge rectifier to red and black binding posts that I added to the front panel. That gave me a little over 16 VDC under load that didn't care whether or not a battery was hooked up. Total cost zip, since I already had the binding posts and wire.

TT

[Silvan]

Speaking of which. Don't dump your electrolyte bucket into your fish pond.

Anybody got any goldfish they want to mail me before SWMBO gets home?

[Mark Jerde]

-- Mark

[The Guy]

Bet you thought they were talented little critters...swimming upside down and all. :)

Tim

Silvan wrote:

[Wood Butcher]

I found that if I leave Stanley planes cooking for more than about 2hrs the japanning starts to loosen up. Once I forgot and left one cooking overnite and it stripped all the japanning and paint clean off.

So a timer could provide a nice balance to one's CRS syndrome.

Art

[Silvan]

Actually, I haven't seen the slightest trace of them. They didn't even float.

Maybe they dissolved...

Ewwwww, I can't wait to clean the pond next spring.

[Charlie Self]

Do it before it really warms up if you value your nose.

Charlie Self "If you want to know what God thinks of money, just look at the people he gave it to. " Dorothy Parker

[Greg]

Has anyone actually tried to figure out how many amps this process consumes at a given voltage? I haven't tried it yet but I do have a garage full of transformers and rectifiers. The wen sites I have looked at all call for battery chargers but I assume that is just what they figure people have. I was with a big corporation that sold business machines internationally and I may have changed the magnetic pole when I dragged all of my dumpster dived transformers south. I just need a starting point if someone has figured this stuff out. After a fire and the water damage that resulted I have lots of rusty stuff to play with.

[Silvan]

Nah, dead goldfish in 90 gallons of pond water don't really stink that much. (DAMHIKT.) I'm more worried about getting a handful of slimy, rotten fish remnants that squooge into black goo when I try to get them out. (I've been there too. My fish died this spring for causes unknown. At least this time I know the cause.)

[Michael Daly]

Some of the web sites specify something in the 1.5-2A range at 12v nominal. I set up a VOM in line when I did some rust removal and measured just under 3A. It depends on how far apart the rusty bit and the sacrificial bit are. If close together, the current increases. My plastic tub limited the distance I could separate things so I couldn't get much less than 3A.

An Incredibly Big Multinational corp, huh? They scrap neat stuff!

Mike

[Andy Dingley]

Enough to fry my rectifier ! It failed just a couple of days ago - I think the next one will be a switch mode.

Voltages for this process should be kept low (12V is convenient, but a bit on the high side). Excess voltage causes outgassing that you don't need and don't particularly want (in another thread, it may encourage hydrogen embrittlement of hardened steels).

Current should be about 1-2A for "typical" woodworking applications. Current is irerelevant for most purporses, it's current _density_ (current / area) that matters. My big tree-felling saw was taking

10A, which I was limiting it too (and which then toasted my poor undersized diodes) and could have used even more.

If your current is too high, separate the electrodes further. If it's too low, check that the electrolyte concentration isn't too weak.

-- Klein bottle for rent. Apply within.

[jo4hn]

Ah. The large computer company that does business under a three letter acronym, the first of which is a roman numeral. jo4hn

[Greg]

I have some big rectifiers but bear in mind these may need heat sinks if you start getting over an amp or two. A fuse is probably a good idea if you are not sure what the load your rig might generate. From what I am reading I think I will shoot for a voltage in the 3-6 range. I may have a 5vPS at some amps. In fact an old PC power supply might work pretty well. They will put out 5v@20a peak which means they should run at the 1-2a recomended forever. The "AT" supplies PCSURPLUSONLINE.COM sells for around $5 will start under a "no load" condition. I am using one for a general purpose bench supply as we speak. I suppose with a fat rheostat (0-5ohm @ 20W) or a transistor "pass" regulator and a ammeter you could set up a very professional rig. You could just use some fat resistors and a banana plug patch panel for that matter. From what I am reading it looks like about a cup of "pH up" (sodium carbonate) from your swimming pool chemicals in 5-6 gallons of water should be pretty close to right.