electrolytic rust removal

[Maker]

Forget the deadly basic solution for a minute, what's going on with my power supply?

 

[T0rnado69]

A picture or three when your making it paints a thousand words

indeed i will take lots of pics as i make the tank.

What do you think to using sodium hydroxide (Caustic soda) in place of washing soda?

erm il stick to my soda crystals thanks.

just in case my cat gets a little to nosey

 

[eddie49]

Maker, I suspect that your "11.5 volt 30-60 watt dimmable light transformer" is not really a transformer, its a bunch of clever electronics. However, it needs a lightbulb ( resistive load ) to work correctly. Try a 25W halogen or 21W tungsten bulb in parallel with the rectifier, fan, electrolysis tub.

 

[Maker]

I didn't think about that, but it's too small to be a transformer. I'll try to find a light, thanks.

 

[Screwdriver]

Forget the deadly basic solution for a minute, what's going on with my power supply?

Don't know. I have listed my voltage/amperage findings - roughly the max I aim at is 8 amps (with my old crude battery charger) and it delivers that typically on 12v "high" which iirc was at about 17v (no load).

What I do know is that the concentration of the electrolyte does hugely affect current flow and if you don't insulate any wooden supports, you need to keep them out of the dip or they will conduct.

Hope this helps.

S.

 

[Maker]

A stronger solution is better or worse?
What effect does voltage and current have? I
I've got a massive 40 amp battery charger if that'll be any good.

 

[MattF]

Other than the safety factor though, it should work?

Yes, and at the strength of solution necessary, it's not overly harsh. That photo of the vat I put up a page back. The vat had sodium hydroxide in it when I did that leg, and I obviously had to get my arms and hands into the vat to lug that in and out.

 

[MattF]

A stronger solution is better or worse?

Makes very little difference to the actual process once you pass a certain point. Just chuck in a cupful, (carefully, if using lye), and see how it goes.

What effect does voltage and current have?

Keep it at approx. 12V or below. No need to go any higher. The setup will only draw what it needs current wise. Anode placement and size, size of piece being cleaned, strength of solution; All affect that to some degree. I tend to limit my setup to a max. of 1.5A generally, no matter how large I'm doing. Slow is better than bubbling the crap out of the solution, and there's not a vast amount of difference in time between letting it sink as much current as it can and just limiting it.

I've got a massive 40 amp battery charger if that'll be any good.

That'd be fine. If that's a TX based unit, that shouldn't even break a sweat. The best thing to use though, if your dad can get hold of one for you, is a bench top PSU. You can control what voltage/current you're supplying that way.

 

[Maker]

The setup will only draw what it needs current wise.

I thought, because it's effectively a dead short, it would draw as much current as it can. I've got a half built bench top PSU, but I never bothered finishing it.

 

[MattF]

I thought, because it's effectively a dead short, it would draw as much current as it can. I've got a half built bench top PSU, but I never bothered finishing it.

It's not a dead short. It's a conductive solution, nothing more. How much depends on the factors I mentioned above.

 

[Screwdriver]

A stronger solution is better or worse?
What effect does voltage and current have? I
I've got a massive 40 amp battery charger if that'll be any good.

For me it was more a case of being happy to leave the charger overnight or over a weekend. Unattended. So I was aiming at 6-8 amps current draw. On my charger I can only set the voltage, even then it's just 6v, 12v high or low. If it draws too much current the charger would trip so I experimented with settings to get a sensible current draw.

A stronger electrolyte will allow more current to flow, bigger anode plates will do the same. It is true that "line of sight" between the sacrificial anode(s) and the workpiece will affect the cleaning action and you want approximately the same surface area for anode and workpiece.

How much current you're happy to draw will depend on the power supply but I suspect a longer, lower current dip is more efficient than a high speed, high current setup. You're probably leaving it overnight anyway if you're trying to strip paint.

S.

 

[DAPPH]

The AC rectifier will push the voltage up . perhaps think of it as DC is a continuous run of voltage so has a greater heating effect than an ac of the same value ....as you smooth the AC into DC the tips of the Ac cycle increase the DC values
If you check in the Farnells on line catalogues you find that the differences are shown .


Off the top of my head and most likely out the back end as well .
After 30 or more years of getting my C&G industrial electronics plus a couple of strokes etc etc. I seem to recall figures of 26 to 28 volts DC being produced at the bridge rectifier out put under open circuit conditions via the transformer coils on the bench 12 volt PSU I built . It was tied down to 12 volts using a zenner diode set up

So an open voltage could well be in the region of what you've been seeing , putting the resistive load in the circuit as previously mentioned may show less voltage or it may blow the filament .

 

[MattF]

It should only read a volt or two higher with the bridge connected.

 

[MattF]

This is all I use on my setup btw Maker.

I think the max. output on that is 3A, so obviously I run everything low and slow. (You can probably make out from the photo that it's running 12V, 1A or so there). I've do have a higher output unit, but I've never felt the need to hook that one up. The small one has dealt with everything fine so far, and I've done some fair size pieces. All of the vices, the large Rapidor, the Drummond 5" bits and plinth/leg etc., they've all been derusted using that PSU.

 

[MattF]

Just on a tangent, btw, seeing as we're on the subject of electrolysis, you can also use it for cleaning copper based metals. Just mentioning it as a point to note. Aluminium is a possibility too, though the tests I did with that were patchy in result. Some worked, some didn't.

 

[Maker]

Just on a tangent, btw, seeing as we're on the subject of electrolysis, you can also use it for cleaning copper based metals. Just mentioning it as a point to note. Aluminium is a possibility too, though the tests I did with that were patchy in result. Some worked, some didn't.

Using the same electrolyte? It would be great to be able to clean brass this easily.

 

[MattF]

Yup. Straight in, same as for ferrous. I occasionally dunk copper/brass/bronze pieces in there for cleaning. I have some photo's of a brass handle I did awhile ago. I'll dig them out and post them.

 

[MattF]

This is a brass handle which I dug out of a garden. It had been buried for donkeys. One thing you do notice is that any badly corroded areas may appear the salmon pink of fresh copper, after cleaning. Same happens if you use citric for cleaning brass. I assume something gets leeched out with the corrosion.

As dug up:

After a session in the vat and a tickle with a soft wire brush:

 

[Maker]

I couldn't find a suitable bulb for that power supply so I used this Instead.

It has a really basic heatsink inside it on what I assume is a voltage regulator and it was making the case too hot to touch so I opened it and put a computer fan in it, now it's nice and cool.

 

[Maker]

I wanted to find out what would happen with more current...

That's putting out 21 amps.
It's bubbling a bit more, it's getting quite warm and there's a load of scum floating on the surface. I'm guessing this is simply too much current but it's an experiment so I don't care.