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MG Midget and Sprite Technical - Electrolysis Rust Removal

Hi,

Just thought I would share my science experiment during lock down.

Decided to have a go at removing rust using electrolysis.

Items required:
1. plastic bucket - 40 ltrs
2. car battery charger - I'm using a 2amp 12v
3. copper wire - stripped from main cable
4. Soda crystals - 3/4 of a 1 kg bag
5. 4 x steel plates
6. length of steel wire
7. length of wood
8. a rusty object

So hopefully the photo is clear enough to show the set up. Things to note are not to get the copper wire in the water. Use the steel wire to hold the metal in the water and wrapped around the length of wood and then connect the negative lead on the charger.

I have 4 metal plates to surround the rusty metal. Just improves the process.

Make sure the soda crystals are well mixed in. I put them into the bucket before filling with water.

I left the spring in for only 4 hours and it came up really well after a small amount of wire brushing and washing in clean water.

Only thing to really be careful is the build up of hydrogen and oxygen, so needs to be in a ventilated room to avoid potential explosion.

I am now trying to find as many parts for my midget that need rust treatment.







James Paul

Cool. Clever.
Malcolm Le Chevalier

I tried it a couple of years ago, but didn't have much luck.
Dave O'Neill 2

I saw someone do this on a naff TV programme to a Panzerschreck that had just been dug up. It was amazing how well it came up - but they did leave it in about 24 hours.

I think my zinc plating kit has instructions on how to do something similar before plating.


John Payne

Good result on that spring.
Are all four steel strips wired together as one big anode?
Do you know if the voltage is critical? For example I have a 24vdc charger - any idea how that would affect the process, if at all?

(Had to Google Panzerschrek. Nasty bit of ironmongery).
Greybeard

That looks interesting. I'm currently de-rusting items with Bildt Hamber products. Really good results if left long enough but the stuff seems to off a bith quicker now than when I first bought the packet some years ago)

Working my way through pedal box, various lids/covers, suspension shackles and so on. Etch primer , rub down then satin black. It's beginning to look likea smart car.
Clive Berry

Hi,

Greybeard - yes they are wired with copper wire, but not in a complete loop. As you can see plates 1 and 4 are not joined between.
I understood that it was the amps that mattered. 24volts is quite high and probably a lot of current to pass around in the experiment. lots of water and all.
I read that between 2 and 15amps was the range, running at 12v.

Most parts are coming up quite well and real easy to clean afterwards.


James Paul

I fancy having a go at that but, from a point of complete ignorance, is there any reason why a 12v car battery couldn't be used instead of the charger?

I have a couple of superseded batteries that have enough life left in them for testing things off the car but not enough to start a car reliably.

Using a battery would avoid bringing mains power anywhere near water but, unless there's a proper switch in the circuit, would there be an increased risk of sparks igniting hydrogen if the ventilation's not good enough?
C Mee

please be mindful that production of hydrogen from metal surfaces can lead to hydrogen inclusion which weakens the metal...best used for non-stressed parts. Dave
David Cox

James,

As David just mentioned hydrogen embrittlement might be an issue as the hydrogen is liberated at the part being de-rusted and effects high strength items like springs, low strength stuff isn't effected. High tensile fasteners which are electroplated are given a bake cycle after plating to remove the hydrogen. I had a quick look online about hydrogen embrittlement with electrolytic de-rusting and it has certainly been discussed and I didn't find a conclusive answer but if in doubt do the bake, the details are online.

3/4 of a 1kg bag sounds excessive compared to any instructions I've seen before.
David Billington

I got good results using a battery charger. Don't know what the resistance of soda water is but sea water is appr. 30 ohms. 12/30 = 0.4 Amps. pretty low,using a car battery shouldn't be a problem if the resistance of soda water is similar.


L Langley

Hydrogen embrittlement!! Oh well, back to the wire brush then!
James Paul

L Langley I have been pondering that myself. Personally I might have cautioned against the idea of a battery but I hadn't properly researched the relevant circuit resistance.
I confess my feeling was simply a gut reaction against the idea shortcircuiting a battery without any overcurrent protection. The power contained in these innocent looking black boxes is awesome if unleashed injudiciously.
I'm sure you're right but my gut urges caution.
Greybeard

Interesting on the hydrogen embrittlement thing. I am well aware of the concepts, yet find it hard to believe you could have knackered a spring that quickly and easily.

But them Hydrogens sure can be pesky!
Malcolm Le Chevalier

Does it not help to agitate or gently warm the solution to increase the rate that it works at, and then to remove and rinse/ scrub off the black residue as soon as it's done the surface rusting. Don't leave it overlong so that the good steel under the rusted layers is exposed to the electrolysis and begins to degrade.
GuyW

Hi,

I am not even going to pretend that I know what I am talking about or try to justify what I have done to my springs is safe, but just thought it was kind of interesting to explore this.

So I have found this statement on Wikipedia:

Steel with an ultimate tensile strength of less than 1000 MPa (~145,000 psi) or hardness of less than 32 HRC is not generally considered susceptible to hydrogen embrittlement.

I am correct in saying that the spring rate of a midget spring is around 400 lbs/in? Does anyone know the full specifications of the springs? i.e. tensile strength or hardness?

References:

https://en.wikipedia.org/wiki/Spring_steel
https://en.wikipedia.org/wiki/Hydrogen_embrittlement#Counteractions

Many thanks

James

James Paul

Hi Guy,

This website gives a good explanation of the process and theory.

Also includes section on hydrogen embrittlement.

http://www.cablesfarm.co.uk/393/
James Paul

James
A std Midget spring is around 270lb/in
William Revit

Unfortunatly the spring rate doesn't tell you much about the ultimate tensile strength nor help you derive it.

The spring rate is a function of the stiffness of the material (pretty much the same for all steels) and the geometry (wire D, spring D, no. of coils).

The ultimate tensile strength is the breaking strength of the material. How much load it can take. There isn't really a practical way to figure that out without a destructive test.

You could do a PMI (positive material identification) test on it to determine the alloying elements and figure out the material from there. But it would be cheaper to buy new springs ;-)

Malc.
Malcolm Le Chevalier

Hi,

I am not even going to pretend that I know what I am talking about or try to justify what I have done to my springs is safe, but just thought it was kind of interesting to explore this.

So I have found this statement on Wikipedia:

Steel with an ultimate tensile strength of less than 1000 MPa (~145,000 psi) or hardness of less than 32 HRC is not generally considered susceptible to hydrogen embrittlement.

I am correct in saying that the spring rate of a midget spring is around 400 lbs/in? Does anyone know the full specifications of the springs? i.e. tensile strength or hardness?

References:

https://en.wikipedia.org/wiki/Spring_steel
https://en.wikipedia.org/wiki/Hydrogen_embrittlement#Counteractions
http://www.cablesfarm.co.uk/393/


Many thanks

James

James Paul

James,

The spring steel wiki reference is not very useful as most of the tensile strength figures are in the annealed state, you need to look for the quenched and tempered tensile strength figures which will be much higher.
David Billington

I have been talking to a neighbour he is an authority on the electroplating industry. He said more or less what is in James’s cablefarm link. The trade use chemicals to clean so they don’t have the problem of brittleness and it is quicker and more effective. On my last job Greybeard, 3 truck batteries were used in parallel, on a Heath Robinson contraption, to generate 2000 Amps, but then they would rapidly fall. Still powerful things, that link suggests a 10 Amp fuse in the battery circuit.
L Langley

Hydrogen embrittlement?

I wonder if those guys on the the TV programme I saw took that into consideration when they ‘fired’ that Panzerschreck after restoration?!

So if I use my home plating kit I guess I shouldn’t plate critical parts?
John Payne

Just added soda crystals to the Morrisons order!
There's a rusty battery holder which needs treatment and this is a great idea, thank you.

On a (slightly) related note did anyone see the Repair Shop last night? It was the episode where a skeleton clock, transistor radio and a pair of German WW1 wire cutters were restored?

How did that Dom bloke blag his way onto the programme? He decided to remove the rivets on the wire cutters by grinding off the peened over edges and then hammering the rivets out.
Unfortunately he was hammering directly onto the workbench and wondering why the rivet wasn't coming out, someone must have told him to place spacers under the piece but even then he used metal blocks rather than something softer.
He then abraded it clean and applied oxide gel to make it look more original - James' method would have been a better approach i.e. removing the rust but leaving some patina.
He spent more time making a wooden box than on the restoration, when a leather pouch might have been more appropriate.
When he tested the cutters I thought I saw them not spring back open, whereas when they were returned to the owner, they opened perfectly or am I being too picky?
Compared to some of the others, Steve the clock guy or his sister Susie the leather restorer, who are truly skilful and know what they're doing this guy Dom looks pretty amateurish,a bit like Jay who has all the gear but seems to have no idea?
Jeremy MkIII

Actually his bench is covered in holes where he has drilled into it - so the rivet would have gone in one of those (hehehe).

I would have centre punched the rivet and drilled out to just kiss the part and then used the press to push the rivets through.
Chris at Octarine Services

Haha Chris, didn't notice the holes but says it all really.
Your approach is more professional and I reckon most of us on here would have made a better job than he did. It was an easy restoration compared to what was needed (and the finished outcome) of the skeleton clock.
Jeremy MkIII

I recall trying this a few years ago without dramatic success, but you all have nudged me into trying again. The problem is power. The battery charger is too intelligent and shuts off after a few minutes because it thinks the battery is fully charged. I am charging the car battery at the moment and will try that when it's ready. Meanwhile I found an old 1 amp power supply but it really isn't up to the job.

Also I tried different electrolytes. Common salt worked fairly well, but a bit smelly as it generates chlorine. Also the salt fooled the charger into keeping going. I am using caustic soda for the present run because the item is a front wishbone and it's slightly greasy in parts. Once I have the process right I'll work through my stock of cylinder heads.

BTW I found this excellent video on all the various derusting options:

https://www.youtube.com/watch?v=Qi-tK1jwO-k&t=985s

Les
L B Rose

I've used old battery acid for de-rusting cylinder heads and a block water passages and it worked great. Surfaces like the cylinder head face and top of block need to be protected with something like Vaseline and a sacrificial thermostat housing and water pump were used to seal those holes. All thoroughly rinsed and neutralised afterwards.

I've successfully used electrolytic de-rusting on a number of things but my battery charger isn't intelligent and just keeps going.
David Billington

It's taken a while to get round to it, blame lockdown laissez faire.

Used James' set up and the pictures tell the story.
The solution may have been a bit weak as it took a couple of days to work but the results are pleasing.
A scrap piece of steel was the sacrificial anode.

Before images.





Jeremy MkIII


After images.





Jeremy MkIII

Sacrificial bit.
That's a fair bit of rust.
As I'd no idea what I was doing (gave up Chemistry before O Level) the shed door was left wide open to allow the hydrogen? gas to escape and the battery charger was switched off overnight.


Jeremy MkIII

I have used this method on many items, I had to derust some 30 pieces of steel pipe for a project. I always put a 21watt buld in the circuit so should the part being derusted touch the plates it avoids a short circuit. it also limits the amerage to just under 2 amps at 12 volts.

Mike
M J Pearson

Using the battery I have just successfully derusted a front wishbone. Caustic soda for electrolyte, 21W bulb in the circuit. Immersion heater from the winemaking kit! It took a whole day, which considering the state it was in was not bad. Also did 2 cylinder heads - it gets the old oil off too. I have seriously under-used this method over so many years!

Les
L B Rose

I've been using this setup (bucket,soda,lump of steel, wooden stick)for a couple of years to clean up small parts. I use a 12V laptop charger. Max 2A. It works brilliantly.
B M Le Page

Brendon, what is the soda that you use? Is that caustic soda. Is it the same stuff sold in UK stores as a "drain unblocker"
GuyW

Guy, caustic soda is Sodium Hydroxide which used to be called lye. I have an idea that our American friends still call it that.
It's sold in powder or crystal form in hardware shops and it's not expensive. It's also available as a premixed solution but it costs more like that.
If you get the dry form and mix your own be very careful to read the safety cautions. It can be dangerous if one is negligent.
The drain cleaner you refer to is based on the same stuff but it's a ready mixed solution or sometimes a gel. Goodness knows what else is in it.
I'm honestly surprised you can simply walk in and buy the stuff over the counter, given that it's so nasty.
Greybeard

The reason I asked, Greybeard, was that I have looked for it under its chemical name in the past and not found it. But then for local hardware shop read B & Q. They do however sell several brands of drain cleaner though without saying exactly what is in it. I wondered if that was maybe an alternative way of getting hold of it.
GuyW

Washing soda (sodium carbonate) works well and is far safer than sodium hydroxide and available in the laundry/cleaning products aisle.
David Billington

Just to add some confusion to the mix, I used something called Soda Crystals which are used for sink unblocking but also as a laundry aid!
£1.10p from Morrisons.


Jeremy MkIII

Jeremy,

That's sodium carbonate same as I buy at Sainsbury's, it says so on the data label on the packet.
David Billington

Hi

Yes I use washing soda. I bought it for a soda blaster. It's very benign and works great.

The soda blaster was a bit rubbish anyway.

Sorry for slow response.
B M Le Page

BM Le Page,

Are you sure about washing soda as that's sodium carbonate and a different chemical to sodium bicarbonate ie baking soda that's normally used for soda blasting but not so much for electrolytic de-rusting as I understand it due to its lower solubility compared to sodium carbonate.
David Billington

I used the same soda crystals as in Jeremy’s photo above that worked really well.

During my research for electrolysis there were several posts online from the US that recommended Arm and Hammer washing soda, rather than the baking soda version that looks similar.

Whether or not the baking soda works or not I don’t know for sure. It might create the right type of solution required for electrolysis.







James Paul

This thread was discussed between 04/05/2020 and 20/06/2020

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