electrolytic rust removal

[Screwdriver]

One might argue running a mains circuit outside into a bucket of iron filled electrolyte is a recipe for disaster.

All I am saying is yes, batteries are of course inherently dangerous but there is no specific danger involved in their use with this process.

 

[MattF]

One might argue running a mains circuit outside into a bucket of iron filled electrolyte is a recipe for disaster.

I never mentioned mains equipment or voltage outside. 12V supply run from an internal source to an external vat.

All I am saying is yes, batteries are of course inherently dangerous but there is no specific danger involved in their use with this process.

Again, there is no valid reason to use one, and several valid reasons why not to. Why introduce an extra, unnecessary level, theoretical or otherwise, when there is no need. All it takes is one mishap for a battery to become a liability.

 

[Screwdriver]

The main reason is voltage rectification. My old crude charger pumps out 18v no load DC, falling to about 10v when in use. I dread to think what the rectified output looks like and I'd be willing to bet there's at least a volt of AC on top. Any AC signal in this delicate process can interfere with the transfer of metal ions, meaning you end up with a dusty iron coating which you can brush off as opposed to a fully reduced iron surface. Never mind the theory though, I am going to try it because I would like to optimise the process for my own purposes and if using a battery gives me better results, I am going to use one.

S.

<edit> "several reasons why not to"? Sorry must have missed that. Give me one.

 

[MattF]

Putting a full wave rectifier and smoothing caps on a charger will give you practically perfect DC. Much cheaper and simpler than farting around with a battery.

With regards to good reasons not to use a battery, the ability of them to go into melt down mode mentioned earlier is one. You also have the problem of limiting the current without ancillary items or circuits. You don't want to be sinking as much current as humanly possible, and a battery is capable of supplying a damn sight more current than a TX based unit will. Usable lifespan compared to a TX based unit is another. Initial cost yet another.

I'm not saying that batteries aren't useful, but in this situation, they're not. Btw, DC ripple is a vastly different thing to AC. An unsmoothed DC output isn't putting any AC out. It merely has some ripple on top of the DC.

p.s: You'll still never get any transfer of iron to the piece in this type of setup. The conditions are neither closely enough controlled nor specific. There's good reason platers use specific chemicals and exceptionally tight current ranges.

 

[Screwdriver]

None of those "reasons" apply specifically to the process of electrolysis except the current limiting which I do by using a dilute electrolyte. The voltage will be more stable since the battery acts as a load and will be self rectifying. I appreciate that current flow is not lit. reversed with a superimposed AC waveform but recieved wisdom tells me that it does in fact interfere with the delicate process of coaxing ions to flow in and out of their respective materials. Like I say, I'll want to see that for myself.

Yeah, I could build a dedicated full wave rectifier fit some smoothing caps etc. etc. ad. infinitum but frankly, I can't be arsed. I've had plenty of really good results with a crude old charger and since I use it a LOT now, I am investigating easy ways to optimise it. I don't have to buy a battery either because I have fecking loads of them dotted about, as has virtually anyone with a spare battery charger I'd wager.

Anyway, I am writing this in good humour and I hope it's coming across that way. We may have to agree to disagree on the use of a battery for now. I will try it next time I have a go, probably with some large lumps of Meddings!

 

[slim_boy_fat]

I will try it next time I have a go, probably with some large lumps of Meddings!

And a video?

 

[MattF]

None of those "reasons" apply specifically to the process of electrolysis except the current limiting which I do by using a dilute electrolyte. The voltage will be more stable since the battery acts as a load and will be self rectifying. I appreciate that current flow is not lit. reversed with a superimposed AC waveform but recieved wisdom tells me that it does in fact interfere with the delicate process of coaxing ions to flow in and out of their respective materials. Like I say, I'll want to see that for myself.

Yeah, I could build a dedicated full wave rectifier fit some smoothing caps etc. etc. ad. infinitum but frankly, I can't be arsed. I've had plenty of really good results with a crude old charger and since I use it a LOT now, I am investigating easy ways to optimise it. I don't have to buy a battery either because I have fecking loads of them dotted about, as has virtually anyone with a spare battery charger I'd wager.

Anyway, I am writing this in good humour and I hope it's coming across that way. We may have to agree to disagree on the use of a battery for now. I will try it next time I have a go, probably with some large lumps of Meddings!

I take everything in good humour. I just ignore people if I can't be arsed responding. With a charger, it would actually be no bad thing to fit a full wave rectifier and some smoothing. It would improve the output a lot, as most of them only tend to use half wave rectifiers with no smoothing. For charging batteries, that matters not a jot, but for use as a DC power supply, they can be improved for little cost. It would only require two cables cutting and four crimp connectors fitting to alter one for adding a cap and rectifier, (you can shove the cap leads into the terminals for the output wires when you do the crimping).

Edit: If you want to have a play, I can post you a full wave through. I have some knocking about somewhere. Could probably dig a suitable cap out too, for adding some degree of smoothing. It'll honestly be a lot less farting around than using a battery.

 

[MattF]

Been a long time since I delved into one, but can't recall ever seeing a full wave bridge in one?

 

[Screwdriver]

I'm not a chemistry expert so I don't know the truth behind the theory but since the effect is a very subtle transfer of ions at an atomic level, the presence of a superimposed waveform on top of a direct current is, according to recieved wisdom - a bad thing. I would go look it up but frankly, I am more minded to fix this potential issue rather than analyse it.

Meantime, today I cleaned out the big tank. I had filled it up with some thick rod, bent into shape and one huge sheet. The rods are still useable but are going to fall apart in the next few sessions (I would have to say, this would be one very good reason NOT to have a battery in the system! LOL)

The big sheet came out like this:

And when cleaned, the outward facing side had a lovely "camo" effect.

The side facing the plastic bucket shows how the process is influenced by "line of sight".

What is interesting is that all of the anodes show the most erosion right at the bottom where the gunge lives. I have to wonder if that layer of iron rich crud is acting as a conductor in its own right (and helping) or if the rusty residue is using up all of the cleaning action. I suspect the latter so it's going to get disposed of.

I guess now is the time to replace some of those rods and come up with a better solution than the current one where I twist loose wires onto the anodes. Oh and maybe fit a low wattage (say up to 10 amp) rectifier to the bucket. And a fuse.

S.

 

[MattF]

Do you always argue over semantics, or just when online? Overkill the use may be, but it caters for all interpretations. I'll be sticking my nose in a charger or two later out of curiosity now, just to see what's in those.

 

[MattF]

Which terms?

 

[Screwdriver]

Either its a full wave rectifier or a bridge is what he's getting at but you can have a full wave bridge rectifier so...

 

[MattF]

That's what had confused me. I think PDG and my opinion of what's a full wave device might differ slightly.

 

[GW8IZR]

A rectifier, a full wave rectifier and a bridge rectifier are very different things. The terms do get mixed up in use sometimes but most people that understand them will work out what's meant from the context. For example earlier in the thread someone referred to using a battery as it would be 'self rectifying and adding load' of course this description is totally incorrect but as we understand what was meant we know he meant 'it would regulate and smooth' the resulting waveform. In my view its pedantic to criticise unless it isn’t obvious what the intended meaning was.

For the purposes of describing battery chargers the generic term rectifier conveys what is meant, a single diode can be used as a half wave rectifier.

Two or more diodes can be configured as a full wave wave rectifier provided a phase difference is available, for example when using a centre tap transformer or two transformers, multiple windings on an alternator etc.

Four or more diodes can be configured as a bridge and can be used as a rectifier to create a similar waveform to the output of a full wave rectifier where no such phase difference is available.

Now, more importantly.. what is the requirement for a plating or electrolysis tank? well, when scoping the load current on an electrolysis tank you will find that the tank itself acts as a pretty big capacitor. During plating a rough DC supply, meaning DC with an AC component superimposed on it will cause a reversal of the current on the second half of each cycle caused by the tank itself trying to maintain the potential applied. This is bad as you damage the surface you are trying to plate ( or in this case strip ) so a smooth DC is important. You also need some form of regulation to control the current and reduce out gassing etc.

Therefore I would suggest the output from a power supply with either a full wave or bridge configured rectifier and a modest smoothing capacitor and a big rheostat will work perfectly well. After all thats what we used to use. Today though small regulated and metered power supplies are so cheap I cant see why anyone wouldn’t invest in them unless it was a simple experiment with no intention of efficient repeatable workflow.

When I messed about with plating I found a constant current power supply with a cut off at a pre determined safe maximum potential at the end of the process gave me best results.

HTH

 

[Screwdriver]

Some really good info thanks Paul. I knew I had read somewhere about the effect of a superimposed waveform, now I am even more determined to optimise my set up.

I'll get myself a full wave bridge rectifier as you suggest.

 

[droopsnoot]

For example earlier in the thread someone referred to using a battery as it would be 'self rectifying and adding load'

If that was referring to my earlier post about batteries, I was only mentioning it as a means of adding load to persuade the battery charger to do some work, all the talk about different methods of rectifying is beyond me.

Today though small regulated and metered power supplies are so cheap I cant see why anyone wouldn’t invest in them unless it was a simple experiment with no intention of efficient repeatable workflow.

I have used a selection of battery chargers and have been struggling to get decent operation recently. I did have a look in Maplin for a power supply and was appalled at the price, I saw someone on here, not far from me, giving one away but unfortunately not until long after it had been claimed. Could you point at one that might be suitable and reasonably cheap please, as I also have a plating kit that has a very crude method of power control? I am convinced I can get much better results than I am getting, because the first few experiments worked very well. I've got a large-ish panel with a lot of surface rust that I could do with cleaning off, so it would be good to get it set up again once the weather has stopped threatening to freeze my tank.

 

[GW8IZR]

If that was referring to my earlier post about batteries, I was only mentioning it as a means of adding load to persuade the battery charger to do some work, all the talk about different methods of rectifying is beyond me..

For sure and it matters not what terms are used as we know whats meant.. If I asked about the speed at the end of the wiggly bit hanging out of the spinny round thing on my mill I now some would laugh and some would get stressed .. hopefully someone points me at a speed and feed calculator .. or just let me carry on listening to it and thinking ooh thats a bit fast :-)

Modern automatic chargers have built in safety mechanisms to stop users charging the battery the wrong way etc, unless they see a real battery connected they refuse to make any output thus keeping themselves and the user a bit safer. Adding a battery in parallel to the tank is making the charger think its being used as intended and charges as required. Its a bit of a concern as its possible to over charge the battery causing hydrogen to be made in quantities that will explode given a suitable spark.. but in a well vented situation and being careful its all going to work.

I have used a selection of battery chargers and have been struggling to get decent operation recently. I did have a look in Maplin for a power supply and was appalled at the price, I saw someone on here, not far from me, giving one away but unfortunately not until long after it had been claimed. Could you point at one that might be suitable and reasonably cheap please, as I also have a plating kit that has a very crude method of power control? I am convinced I can get much better results than I am getting, because the first few experiments worked very well. I've got a large-ish panel with a lot of surface rust that I could do with cleaning off, so it would be good to get it set up again once the weather has stopped threatening to freeze my tank.

Having worked in the electronics and comms industry all my life I have a good selection of supplies so I've not actually bought a bench supply at the hobby end of the market for donkeys years so making a recommendation here is based on specification not actually pulling one to bits to see if its good and safe. I dont like doing that as you could be buying a pile! The Chinese 0-20V 2A variable bench supplies on ebay for about 25 UKP _should_ be good.

If you can find an older linear bench supply , thats one with a big transformer in it rather than a switching regulator like an inverter mig etc. is likely to be more reliable and easier to fix if it goes wrong. If you lift it up and its heavy its more likely to be good for this application.

This kind of thing would do a small plating tank http://www.ebay.co.uk/itm/Farnell-E...824830?hash=item43e9c536fe:g:tm8AAOSwuAVWu3yB

This kind of thing would do a bigger one and has a constant current mode. http://www.ebay.co.uk/itm/FARNELL-S...472063?hash=item2c9b530bff:g:NmYAAOSwBahVXI77

These are an excellent GP power supply and I have a few dotted round the bench here http://www.ebay.co.uk/itm/DC-Bench-...780834?hash=item3abc735f62:g:l7cAAOSw14xWMSTk

I'm not suggesting these sellers or the item, they are just examples of good supplies - you can find them at disposals from time to time as professional shops use more modern tools ( assuming modern repair shops actually repair things )

HTH

 

[droopsnoot]

Many thanks for those links, I'll keep an eye open. I have been looking at various car boot sales and so on, just trying to keep the costs down. Maybe a cheap Chinese ebay one would show me whether a proper PSU performs better than the current (sorry...) arrangement.

 

[Turbo]

For anyone wanting to use an electronic smart charger for electrolysis - don't bother! This is the type of thing I'm talking about, mine is the Lidl version.

To get it to work you need to add in an old car battery to fool the charger and get it to charge. This is a fiddly process coz if the battery has <7v or >12v the charger wont switch on. But the main problem is that the charger is not designed for a steady high current draw over a long period. I damaged my charger & it is very temperamental now when using it normally to charge batteries.

 

[GW8IZR]

I just spent five mins on ebay and they seem to have gone up a bit since I last looked, maybe thirty odd quid is a better estimate than my original 25 !

Car boot and the like will turn something up if your patient.

Cad plating for railway signalling components was the thing I had to mess with but you can get nice results at home with all the different techniques.