rust removal molasses oxalic hydrochloric update

[JonE]

Still faffing about with solutions and this video was good (to fast-forward through the chapters to the summaries).
https://www.youtube.com/watch?v=Qi-tK1jwO-k
There was another frightening video where they showed that vinegar and the higher acids munched through iron filings pretty readily.

I now realise that HCl was a pretty bad idea, and the duff block I did ages ago obviously lost some real steel. He suggests that any bubbles you see are steel corroding with the acid. Phosphoric too.

So 'visible gain' IS actually pain! Or at least, not sensible in the slightest.

Oxalic - I'd been wanting to find out if it has any measurable effect on solid metal and he suggests negligible. I'm presuming thus that if its in one piece, you dont need to worry too much, whereas filings offer a huge surface area so the time the solution is in contact essentially lengthens.

What I hadn't realised is that Molasses includes (and presumably active component is) Oxalic acid; it's a weaker solution of oxalic.

Latest wheel derusting - trying tubtrugs with water-filled 2 litre milk containers as ballast to concentrate the solution nearer the part. The small 15L shallow trug gets 25% of a vertically-sitting rim in and doesn't use too much solution to get rim and lower spoke coverage.

[Oxford Jack]

I have been using molasses for several years now, with excellent result and I love the smell. It takes time, but the outcome is generally good. It seems to continue working for a long time, I have a 25litre barrel with a lid to prevent evaporation. I thought I would buy a cold water tank and lid if I needed a larger capacity.

[Hedd_Jones]

I rescued a huge selection of used pre war whit nuts and bolts from a guy who had restored a traction engine and replaced every fixing. I had sorted these into containers and have been using them on my steam roller as and when. 

Unfortunatley a couple of the containers got wet, and remained so for some time, full of water. I ended up with two big crusty lumps, one 3/4 whit nuts. The other 3/4 whit bolts. I had some oxalic acid powder left, so just tipped the powder in with the water. That was in November sometime. I emptied the containers last week and all the crustiness has gone. And the nuts and bolts look more or less as they should. The acid disolved the crusty rust, and a lot of the paint on them, but the good steel seems totally unaffected. I just left them to dry and resorted into containers.

[Bob Culver]

i have never been impressed by any of the brush on concoctions; never seem to penetrate, and always conscious of embrittlement effects. I have not tried molasses or other long soakage but from reading here and elsewhere the electrolysis methods would seem the simplest and cheapest option. Although again reservations about embrittlement on the likes of spokes.

[JonE]

Would a 4.5aH 12 V battery be enough to deal with something the size of a wheel? May try that next.

[Parazine]

i have never been impressed by any of the brush on concoctions; never seem to penetrate, and always conscious of embrittlement effects. I have not tried molasses or other long soakage but from reading here and elsewhere the electrolysis methods would seem the simplest and cheapest option. Although again reservations about embrittlement on the likes of spokes.

Here here Bob!

Jon, it's not the voltage that counts, it's the current that's important. I aim for about 3A and a battery charger of the traditional type (5A, 6/12V, not a modern smart charger), is ideal. The battery can be used to stabilize the voltage if required or left out if the current is struggling to get up to 3A. 24 - 48 hours in the bath is required at the stated current.

This is by far the quickest, simplest and most effective method of de-rusting steel and CI.

[Parazine]

Here's a before and after; front stub axles being treated at the moment.

   

[Bob Olive]

+1 for me - electrolysis every time.

[David.H]

OK, so can someone put up an idiot's guide to electrolysis using (say) a 12v battery plus an old style battery charger and (?) a plastic container of water(?)....Will it shift paint as well...flaky or still adhering.
Thanks
David (O level Physics - failed!)

[Parazine]

Get a large bucket and a sheet of 20 gauge steel. Cut the steel to make a plate that goes around the inside of the bucket make a connection for a lead to be attached to it; I use a 2BA screw through the sheet.

Connect another lead to the item to be de-rusted, fill the bucket with a solution of washing soda (sodium carbonate). You'll need a handful of soda crystals per couple of gallons of water. Put the item to be de-rusted, attached to its lead, in the centre of the bucket, immersed in the solution, make sure it can't touch the sheet round the edges.
Now connect the lead going to the 20 gauge sheet to the positive pole of a 6/12V battery. Connect the item to be de-rusted to the negative pole. You'll need to connect a charger to hold up the battery...
Leave for between 24 and 48 hours. You should see bubbles rising. Beware, they are bubbles containing hydrogen, so no naked lights! At the end of the time, you can then remove the item, wash it carefully with clean water and wire brush it, the rust will fall off! If there's still stubborn rust, return to the bath for another few hours. Only parts with "line of sight" to the 20 gauge sheet will get cleaned so you may need to reposition the item several times. If no bubbles are rising, check that you have enough current flowing. Not enough soda can cause this problem, or maybe you need to swap to a 12V battery/charger.

Note: DO NOT ALLOW Stainless Steel into the bath, don't use Stainless bolts or nuts. The chromium leaches into the solution and forms some nasty, poisonous compounds. Don't put Aluminium into the bath, the soda will attack it.

You can use a 12V battery to speed up the process but you'll need a heavy duty charger as the current flow will be quite high. You can remove the battery and just power the thing with an old fashioned battery charger if you like. You need to aim for about 3A current flow.

   


You can probably pick out the other stub axle fizzing away....

I find that most poorly adhering paint comes off in the bath, some however may remain.