Electrolytic Cleaning

I’ve never uploaded photos before, so thought I would experiment.
There is even a Welding element - number 3 son and I made the engine storage cradle.
I like shiny bits (and pretty pictures), like these:





I did some Nickel Plating of nuts, bolts and small brackets like these:



However the bit I thought you might be interested in was the use of Electrolytic Cleaning (Derusting) of the larger steel and cast iron parts to prepare for painting.

If you want the theory behind it all look at this set of university course notes:

http://nautarch.tamu.edu/class/anth605/File9.htm

I was setting up my bath to prepare a rusty tow bar for painting before transferring from one Rover 800 to another, so I gathered some MX-5 parts which have found their way into my shed and took photos along the way.

Tow bar super shiny bit:


Two complete front suspension uprights and one scrap front caliper ‘as found’:















Stick them in the magic bath and watch the muck come off :



I deliberately restricted the current to 4 amps, thinking that would be within the capability of the typical small battery charger most folks would have lying around, and left them overnight. This is how they came out, after a quick attack with the pressure washer (The Ultimate Authority was lurking about so the weapon of choice - dishwasher - was temporarily out of bounds):



Low current, large surface area – this is going to take ages. I could reduce the number of components or increase the current. I ramped the current up to around 10-12 amps and left them to bubble away again overnight. Pressure wash and scrub in the sink with a stiff brush (she was still around) and we have:





Notice how the threads are cleaned out – makes dismantling rusty components much easier:





Disassemble:



Notice that the parts are also degreased and that good plating is unaffected:





Non-corroded machined surfaces are unaffected:




I was getting bored by now so only put one disassembled back plate and upright into the bath for the very last overnight session, plus the caliper just to demonstrate that you cannot damage the parent metal by 'overcleaning'. Pressure wash, scrub and VERY light wire brushing gives this:














The cleaned surfaces are very ‘active’ and a flash layer of superficial rust can appear if parts are not dried thoroughly, as happened to one small area of the caliper:







Found I'd done a left back plate and right upright on the second go!

If you like belt and braces you could pop the parts in your bath of Bilt-Hamber Deox-C for the ultimate finish. The bath would last forever as there is virtually nothing left to consume the citric acid (or whatever the active ingredient is)
I have my eye on a 90 litre plastic container with a lid that I saw in Homebase – big enough for a small engine block I reckon.

More links:

http://www.stovebolt.com/techtips/rust/electrolytic_derusting.htm
http://myweb.tiscali.co.uk/andyspatch/rust.htm
http://www.instructables.com/id/Electrolytic-Rust-Removal-aka-Magic/
http://www.antique-engines.com/electrol.asp
http://www.rowand.net/Shop/Tools/Electrolysis.htm
http://www.davidbradley.net/ERR.html
http://www.youtube.com/watch?v=R5I5WBG5HPw
http://www.youtube.com/watch?v=-8vT2mdXBs8&feature=related
http://www.youtube.com/watch?v=jF6nStS3_xE&feature=related
http://www.htpaa.org.au/article-electro.php

Not all pictures appear on my machine.

Fascinating subject though.

Trying to do you out of blasting work!

I'm surprised you haven't seen something similar on the LR Forums (Fora?). Marko had a few 100kgs of Land Rover shaped bits through this process.

All the photos appear in my preview mode.

Try here:
http://picasaweb.google.com/robert.cosic/ElectrolyticCleaning?feat=directlink
and here:
http://picasaweb.google.com/robert.cosic/JaguarEngineStand?authkey=Gv1sRgCOWioJbUobW6Qg&feat=directlink

You've got me thinking about setting up a bath to do this, small rusted steel bits could be de-rusting themselves on Economy-7!

Does this technique remove mill scale? Only I've got 180m of 30x3 to clean up! :

Archie said:

Does this technique remove mill scale? Only I've got 180m of 30x3 to clean up! :

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Yes, very well - but that quantity is industrial not hobby scale!

You will need a bath 7 metres long and 180 metres must be nearly 30 lengths!

Two key variables are electrolyte concentration and current density. Also the effect is, to some extent, 'line of sight'.

So a lot of washing soda and detergent - no big deal both as are cheap enough.
You need maybe 2 amps per square foot or 10 amps per square metre. By my calcs 180 of 30mm strip is nearly 11 square metres, so to do all of it in one go needs a 100 amp output power supply. That's a tad more than my battery charger can supply.
It would be best to arrange the lengths to be cleaned (cathode) in parallel rows with sacrificial anodes between each strip. Scrap lengths of rebar make good sacrificial anodes.

Assuming 20mm between each strip, the bath would be:
7 metres long
50mm deep
600mm wide

It could get quite expensive to make a suitable bath that size.
That's near enough 210 litres, so the weight of the electrolyte alone will be a little over 215kg. Then you have the weight of your 180metres of strip. So remember that when 'knocking up' your bath!

Doing them one or two at a time in a length of plastic guttering is going to take you a few weeks!

rtbcomp said:

You've got me thinking about setting up a bath to do this, small rusted steel bits could be de-rusting themselves on Economy-7!

Click to expand...

Complements abrasive blasting very well too. It can (with luck) clean between the faces of spot welded flanges and other 'closed' features that blasting cannot reach if the sacrifical anode is well positioned .
Should be easy enough to make a bath big enough to take a whole scooter body/frame.

Handy to have a small bath permanently set up in a corner with a stainless steel kitchen salad drainer or similar. Chuck in a handful of nuts, bolts, washers or other small bits and bobs, connect up, leave in overnight. Next morning lift out salad drainer, wash vigorously and there's your nice clean bits and bobs

I'm not able to see all the pics either.
IE explorer

bill_gj said:

I'm not able to see all the pics either.
IE explorer

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Sorry this is beyond my knowledge!
All show up for me in preview mode and when I look at the posting, so I've got the links correct.
Maybe there are too many?

I see you're using an external hosting site - if you load the pics into an album on this site you may have more luck. I'll edit the posts for you if you can't do it due to timeout.

Very handy info. Thanks. The 30mm actually comes in length of 4m so it's 45 lengths. Fortunately I've already chopped it all into 1m lengths for later use. I've an old cast iron bath and an old oil tank I could chop the top off to use as a container. I assume it doesn't matter that it's metal so long as neither the cathode not the anode touches the walls? I could easily line it with some plastic. I also have a starter/charger which will supply 50A when charging but there's no way of regulating it. I assume it will just draw full whack? Finally, what are the exact 'ingredients' and their concentrations? Cheers.

If the starter/charger is a simple transformer & rectifier with no electronics you may be able to regulate it by running it through a variac (Google!)

Archie said:

.....
I also have a starter/charger which will supply 50A when charging.....

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Duty cycle???
Very much doubt if it is 100% at 50A. Don't forget it will need to run for 24, 36 or even 48 hours. Check if a duty cycle is stated, otherwise I would suggest limiting to maybe 10A.

Archie said:

....
but there's no way of regulating it. I assume it will just draw full whack?....

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I have 2 options.

1. Wire up car light bulbs as resistors in series with connection to either cathode or anode. One standard 60W headlamp bulb draws 5A, so limits current to 5A. So wire two in parallel and you have limited current to 10A, or three for 15A and so on. You've got 5W and 21W standard bulbs to play with if you want to fine tune the current. Whilst useful for electroplating which is current density sensitive it doesn't really matter that much for electrocleaning.
2. Electrolyte concentration. Wire in an ammeter. Connect up with plain tapwater in the bath. You will probably get a very small, but non-zero current. I usually add some detergent just to help with degreasing and to keep the released crud in suspension. Dishwasher detergent is usually quite alkaline and acts as electrolyte anyway. One tablet crushed in a jug, add hot tapwater and stir until fully dissolved. Keep hands out - it's horrible stuff!. Gently pour concentrated solution from jug into bath a bit at a time whilst stirring the bath with a handy stick. Watch amps and stop when current reaches desired rate or you have added all the detergent whichever comes first. If you haven't reached desired current mix a 'good handful'* of washing soda in hot water in your jug and repeat the excercise as many times as required to reach your desired current flow.

Archie said:

.....Finally, what are the exact 'ingredients' and their concentrations?......

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Washing soda and (optional) detergent. I don't use 'fixed' concentrations. I adjust the electrolyte concentration with an ammeter in series as described above. Best done with the greatest amount of material to be cleaned, then any lower area will just draw less current.
You might find current draw limited by sacrificial anode area rather than electrolyte concentration or workpiece area, but it's unlikely unless you try using just a couple of 300mm lengths of rebar for your entire stock of 30mm strip! If you are using, say, scrap rebar as anodes just add more anodes to increase current. Anode area never needs to be as large as the workpiece (cathode) area though.

I suggest you scan the first few links for more details - seems a little pointless for me to just repeat it all in the post.
* the links indicate the maximum useful concentration.

Archie said:

...I've an old cast iron bath and an old oil tank I could chop the top off to use as a container. I assume it doesn't matter that it's metal so long as neither the cathode not the anode touches the walls?...

Click to expand...

You could use the old oil tank itself as the main sacrifical anode. But it will corrode rapidly. Would be OK for a first trial batch but not last many batches. Add additional rebar anodes between the workpieces.
I actually use a stainless steel tank as both tank and anode (yes I know the US sites blather on about hexavalent chromium, but the bath is alkaline!).
I haven't tried combining a carbon steel tank as anode with additional rebar sacrificial anodes - why don't you try that and report back?

I would be a little bothered by an enamel bath as there are bound to be breaks in the enamel exposing the cast iron and if you didn't electrically isolate perfectly you might risk very rapid pitting corrosion where the enamel is missing.

Archie said:

.... The 30mm actually comes in length of 4m so it's 45 lengths. Fortunately I've already chopped it all into 1m lengths for later use......

Click to expand...

180 workpieces!
Might be worth gathering scrap wood and making up a layer of workpieces, wood spacer/insulator, layer of sacrifical anode, wood spacer/insulator, layer of workpieces etc and lashing it all together with rope or something. Wire up and hoist the whole assembly into the bath in one go.
If I were doing this regularly I would make up a permanent wooden 'cradle', nail the anodes to it and 'hard wire' them up. The just slot the workpieces into their wooden slats in the cradle and wire up with lots of short lengths of cable with crocodile clips at each end.

Hope that helps.

Bob C

rtbcomp said:

..... you may be able to regulate it by running it through a variac..

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They cost cash money!
Against all the rules of this particular game.

rtcosic said:

They cost cash money!
Against all the rules of this particular game.

Click to expand...

But I've already got one, so there!

rtbcomp said:

But I've already got one, so there!

Click to expand...

In that case I'll just PM you with my postal address. Should be about £7 by DHL

Again, thank you. That's all extremely helpful. I, like you, doubted the charger would have a 100% duty cycle but from my cursory glance I couldn't tell. It does say it will give out 500A when is start mode so which it definitely wouldn't do constantly. The 50A max is when in charge mode which would be designed to run for extended periods so there is hope! As far as using the tank as the anode goes I'd be very happy for it to rust away as it'll save me chopping it up to get it in the skip! This is unlikely to be something I do regularly so I think I shall risk it. I'll report back as and when I get round to it. Thanks again.

Oh I think I've got one of those. Have a vague recollection of seeing one in an old ammunition box full of bottle jacks!

Archie said:

Oh I think I've got one of those.

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In that case add it to the pile of reclaimed rebar for my Alexander to collect!

An earlier thread on this topic:-

http://www.mig-welding.co.uk/forum/showthread.php?t=7573