electrolytic rust removal

[DAPPH]

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

Whilst in HMF many many moons ago , we used to scrub our dirty brasses with OMO or DAZ soap powder & a bit of hot water as the detergent removes the greasy oxidization film , We thought that the washing soda also helped get it deep pore clean .
You could always tell who'd soaped their brasses as the colour stayed a light white colour for several days , whereas after using liquid Brasso & Duralaglit wadding they soon turned the the oxidized colours .

So perhaps the earlier suggestion of using a non bio detergent as well as washing soda could work very well as the electrolyte .
A lot of modern detergent powders have anti oxidisation powers & scum inhibitors .. The one we use has not corroded a jar of water & steel nails set up 12 years ago that has less than half level teaspoon of our washing powder added to it .. The other test jar done at the same time , with three teaspoons of a non bio Persil with the washing machine protection component, this now has a nice fine silt rust in the bottom , rust on the nails and big granules of settled crud made up of such things as lime & soap fillers to bulk up the box contents so the housewife thinks she's getting value for money due to buying a bigger box .

 

[DAPPH]

I couldn't find a suitable bulb for that power supply so I used this Instead.
View attachment 73443
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.

That looks like an old CB radio PSU .

 

[DAPPH]

Can any of you " Electrolytes " give a general surface area of your anode plates wrt the voltage & current available from your power supply ?

I've now got a cut down 310 litre blue food grade barrel for my cleaning tank that is 10 inches deep and 30 inches or so across , along with an ancient 40 yrs plus 12/6 volt battery charger , so I hope to intelligently be able to select the first anode .

I realise that having varying sized cathodes will have an effect , but I'm guessing that the anode surface area ought to be about as big as will fit in the tub especially if there are numerous gas / fluid movement holes in it to get an even distribution of the electrified electrolyte moving around /in out of what's being dipped for cleaning.

 

[DAPPH]

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:

I suspect that the electrolyte has ionized the zinc in the places where it has reverted to copper colour .

 

[T0rnado69]

after seeing that PSU maker has posted it HIT me......
i have a CB psu in the garage, not been used for donkeys years
as havent had a CB radio in ages but still got the psu.
have to dig that out as that could well be good for my needs.

 

[Maker]

That looks like an old CB radio PSU .

That's because it is. Dad used to have a cb radio and he sold it but kept this for some reason.

 

[MattF]

Can any of you " Electrolytes " give a general surface area of your anode plates wrt the voltage & current available from your power supply ?

I've now got a cut down 310 litre blue food grade barrel for my cleaning tank that is 10 inches deep and 30 inches or so across , along with an ancient 40 yrs plus 12/6 volt battery charger , so I hope to intelligently be able to select the first anode .

I realise that having varying sized cathodes will have an effect , but I'm guessing that the anode surface area ought to be about as big as will fit in the tub especially if there are numerous gas / fluid movement holes in it to get an even distribution of the electrified electrolyte moving around /in out of what's being dipped for cleaning.

Don't worry too much about specifics. Just get some scrap iron in there and see how it goes. This is my setup of roughly similar volume:

That's just four old cast iron sash weights as the anodes. Unlike plating, it doesn't need to be precise. Just get some current flowing and you're good.

 

[MattF]

I suspect that the electrolyte has ionized the zinc in the places where it has reverted to copper colour .

I've personally no idea. I'm clueless when it comes to chemistry.

 

[MattF]

It has a really basic heatsink inside it on what I assume is a voltage regulator....

A TO3 style 2n3055 perchance?

 

[Maker]

A TO3 style 2n3055 perchance?

It was a TO3 metal can style, I don't know if it was a 2n3055. I think I know why it was so hot though, the transformer has a 22 volt secondary, but the output is 13.8 volts, supplying 3.4 amps (Higher than it's listed output) means it's trying to dissipate nearly 30 watts of heat. Instead of a nice finned heatsink it has a piece of 0.125" aluminium sheet and no fan. Though I suppose a CB radio doesn't draw that much current so it's not a problem. The big battery charger seems to work well, even if it did heat the tank by 25 degrees in an hour.

 

[Screwdriver]

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.

The electrolysis process actually causes iron atoms to bond to the cathode, replacing the magnetite (black rust) thats under your flaking iron oxide with fresh new iron. If the current is too high, this bonding process will take place too quickly for a decent bond to occur.

A long slow process is best for restoration, a quicker process might be better for cleaning, if only because most of the wasted current will be used to heat up the electrolyte.

 

[Maker]

Well it wasn't very rusty to begin with but it was painted in some places and it cleaned almost all of it off but there's a channel around the perimeter of the part, about 3/4" deep and as wide, where the paint is softened but even heavy wire brushing won't get it all off (It was very thick paint with many coats). Unfortunately the charger can't be turned down (It does have a rotary switch, from 1 to 7, 1 supplies 20 amps, 2 supplies 25/30 amps, 3 makes the needle bounce around at 40 amps (The highest it can display) before tripping it's thermal cutout).

Does it matter if the anode isn't clean?

 

[Screwdriver]

The anode needs to be clean so that it connects with the electrolyte.

At 40 amps I'd expect you to be blowing holes in your anode plate anyway...

 

[Maker]

It was the inside of a butane tank, which is blackened with something, would it work better if I clean it first?

The 40 amps lasted about a second before it tripped.

 

[Wallace]

That looks like an old CB radio PSU .

Yes, I remember the name Bremi, I had a 200W valve amp made by them. Matt, I remember a friend of mine dipping some brass in a chromic acid desmut tank for me and the surface was dead bright in seconds, if you know any electroplaters they might be able to oblige.

A TO3 style 2n3055 perchance?

And a phase plasma rifle in the 40w range?

 

[Maker]

Matt, I remember a friend of mine dipping some brass in a chromic acid desmut tank for me and the surface was dead bright in seconds, if you know any electroplaters they might be able to oblige.

If you can't find a plater to oblige, chromic acid doesn't seem to be available to the general public (Not surprising really, they don't want inexperienced chemists playing with toxic oxidizing carcinogens) but according to wiki, it's very similar to sulphuric acid which you can easily buy on the bay so that may be worth a try. If it doesn't work, I think adding potassium dichromate and filtering it would give you chromic acid...

 

[MattF]

How have you got it set up, to be drawing that much current?

 

[MattF]

Matt, I remember a friend of mine dipping some brass in a chromic acid desmut tank for me and the surface was dead bright in seconds, if you know any electroplaters they might be able to oblige.

Non that I can think of, offhand. Does it leave the base metal untouched and just take off the oxide layer?

 

[Chris Stevens]

Anyone use a basket of some sort to hold small parts for cleaning? Seems very fiddly wiring together a load of small nuts and bolts to be cleaned. For BZP plating I think a Ti basket of some sort would work well, and maybe transferring this from electro cleaning tank, to water rinse, then to acid pickle, rinse again and then plate, would work well? Sheet of Ti mesh is £32 from China, and saves a lot of messing with wire.

 

[Maker]

How have you got it set up, to be drawing that much current?

It's hanging on some wires screwed to the wood, the negative clamp is behind the bit of wood, but it's clamped to a big block of brass and resting on top of the part.