Relic M35 rust removal, electrolysis or oxalic acid?

[Glenn66]

I've just received this ground dug M35 and I want to remove as much of the rust as possible. Before anyone jumps up and down I want to stress this will NOT be a restoration, just a cleanup and preparation for display so I don't have lumps of dirt and rust falling off all the time. If the paint can be cleaned up and the decals retained that would of course be a great bonus.

As you can see there is a little of the national decal still visible so i'd like that to remain if possible. The helmet is a reissue of some sort and closer inspection shows some heavy brush strokes of the grey/green paint.



Notice around the rivet further evidence of having been repainted. Also when in hand I can see the outline of a decal underneath the paint on this side right under that big blob of rust. I had hoped the lumps of 'stuff' on the top of the helmet and under the air vent were simply clay but alas, they are big areas of chunky rust. The rust on top seems to have some petrified wood fossilized into it also. So this is what i'd like to remove. From research made so far I think the oxalic acid bath and/or soaking and scrubbing will remove the surface rust (which will be good for revealing the owners name under the rear lip as seen below) but for the chunky rust i'm thinking i'll need to go down the electrolysis route.





So my question is this, if I try electrolysis what concentration of caustic soda in the water should I use and for how long should I zap the lid? How do I know when enough is enough? Should I use the oxalic acid first to remove the surface rust or wait until after electrolysis? At what concentration should I mix the oxalic acid? I see Dimas recommends 200g at 50C temp, what is the problem if I make a stronger mix? I am aware of the dangers of both methods and will do the treatments outdoors wearing suitable protective gloves etc

Also I read that some people claim that using electrolysis will lift the decals, this makes sense to me if there is rust under the decal. But as this helmet is a reissue I think i'm going to end up with a combination of original paint, reissue paint and bare metal at the end of this process anyway. Also i'm expecting some holes to appear as the rust is removed and thats OK by me as it IS a relic lid after all.

I'd really appreciate some advice from those of you who have some experience with this kind of thing so I don't mess this up. As far as the electrolysis technique goes I was planning to use a regular car battery charger and some pieces of reinforcing steel as the anodes.

Cheers
Glenn

[klinger]

i guess oxalic acid will do a lot for ou on this one, i never tryd to do the electro thing as i dont know how it works but oxalic acid must be enoughf for this one as he is still in real nice condition

[Glenn66]

Thanks for your opinion Klinger but how to use the acid? Soak it totally in a bucket or just sponge the acid on? If soak, then for how long and at what concentration/heat? Have you done this before?

[gerrit]

using to much soda combined with high voltage will excelerate the process.
Use as little as possible caustic soda ( add a little and see if the process is starting) use a low Voltage adapter like 9-14Volts and take your time.
To fast cleaning will destroy the surface, and the process is irreversible.
dont forget to wash the helmet afterwards with clean water.

Good luck

[klinger]

i use 250 gramm oxalic acid on 5 liter wather and soak the helmet for 24 houers after that clean under warm water and then 100 gramm oxalic acid and same amount of wather for 2 more houers then clean under running wather ansd a sponge, thats all for me and works fine for me as well

[Glenn66]

using to much soda combined with high voltage will excelerate the process.
Use as little as possible caustic soda ( add a little and see if the process is starting) use a low Voltage adapter like 9-14Volts and take your time.
To fast cleaning will destroy the surface, and the process is irreversible.
dont forget to wash the helmet afterwards with clean water.

Good luck

Thank you gerrit

I was going to buy a regular car battery charger which should put out about 14.4 volts if I remember correctly. If I should use as little caustic as possible should I start the current in water with no caustic then just add the caustic slowly until I see the bubbling start? Would that be a good method?

If so then should I keep the current going for some time, maybe 6 hours then change the water and start again? I've read about people keeping items in the caustic solution for 24 hours...

Glenn

[Glenn66]

i use 250 gramm oxalic acid on 5 liter wather and soak the helmet for 24 houers after that clean under warm water and then 100 gramm oxalic acid and same amount of wather for 2 more houers then clean under running wather ansd a sponge, thats all for me and works fine for me as well

Thanks klinger

It seems you are a big fan of the acid treatment and gerrit favors the electrolysis...

Do you think just the acid soak for 24 hours will shift even the big lumps of rust?

Glenn

[klinger]

Thanks klinger

It seems you are a big fan of the acid treatment and gerrit favors the electrolysis...

Do you think just the acid soak for 24 hours will shift even the big lumps of rust?

Glenn

yes i think it will do the trick and after the first cleaning you can see a difference and then after the second treadment you will be pleased (for me it works)

[Glenn66]

Well i look forward to be suitably impressed by withever method I try!

For the record, some web research has recommended baking soda over caustic soda as caustic is too aggressive.

[3mk]

Watch out, oxalic acid is extremly toxic and can burn your hands and sink through your skin to cause liver problem!

Thats nice helmet, after cleaning it up put some vaseline over it to stabalize the rust