Alloy wheel paint stripping - Caustic Soda

[anto]

I've seen on one of the local car forums that a fella has used caustic soda to strip the paint from his wheels to good effect.
Aside from it being harmful to eyes/ skin etc are there any effects on the actual metal alloy from using caustic soda?

If I use it I intend to do it outside, gloves, goggles etc in a plastic drum.
Anyone any experience of this?

Thanks,
Anton

 

[rikrobson]

ali does not like caustic soda. If you want to turn your wheels to powder I would advise against it.

you can use soda as a medium in blasting, could this be what he was on about?

 

[rtbcomp]

Caustic soda is sodium hydroxide and reacts with aluminium, from Wikipedia:

"In 1986, an aluminium road tanker in the UK was mistakenly used to transport 25% sodium hydroxide solution,[12] causing pressurization of the contents and damage to the tanker. The pressurization was due to the hydrogen gas which is produced in the reaction between sodium hydroxide and aluminium:

2 Al + 2 NaOH + 6 H2O → 2 NaAl(OH)4 + 3 H2"
Soda blasting use bicarbonate of soda (washing soda) which is a fairly gentle blasting medium, it may remove older paints but I doubt that it would be very effective on epoxies and powder coating.

 

[julianf]

Are we talking paint, or anodising?

Caustic will strip both though, i guess.

I, personally, wouldnt be concerned about disolving the entire wheel. Some will go, for sure, but we're talking degrees.


Look on youtube - theres some vids of people stripping alloy with caustic.

 

[MattF]

Caustic won't touch certain paints or powder coating, and it doesn't seem to work great on zinc primer, (not tried it with red oxide as yet), either. Works better when the solution is warm.

 

[anto]

ali does not like caustic soda. If you want to turn your wheels to powder I would advise against it.

you can use soda as a medium in blasting, could this be what he was on about?

No it wasnt soda blasting.
He showed pictures of wheels he had steeped in a caustic soda solution which completely took the paint off it with no serious VISIBLE damage of the wheel (Structurally its hard to tell?)
Alloys arent pure aluminium by definition so perhaps that is why it doesn't seem to affect them too much.

Il give a scrap wheel a test dip to see what effect it has before trying the real deal.

 

[Badger1bear]

Caustic soda is sodium hydroxide and reacts with aluminium, from Wikipedia:

"In 1986, an aluminium road tanker in the UK was mistakenly used to transport 25% sodium hydroxide solution,[12] causing pressurization of the contents and damage to the tanker. The pressurization was due to the hydrogen gas which is produced in the reaction between sodium hydroxide and aluminium:

2 Al + 2 NaOH + 6 H2O → 2 NaAl(OH)4 + 3 H2"
Soda blasting use bicarbonate of soda (washing soda) which is a fairly gentle blasting medium, it may remove older paints but I doubt that it would be very effective on epoxies and powder coating.

Soda blasting will take off powder coat, it did the trick on my truck no problems

 

[Maker]

Works better when the solution is warm.

FWIW, hot caustic soda can dissolve glass.

 

[DanielW]

I've seen on one of the local car forums that a fella has used caustic soda to strip the paint from his wheels to good effect.
Aside from it being harmful to eyes/ skin etc are there any effects on the actual metal alloy from using caustic soda?

If I use it I intend to do it outside, gloves, goggles etc in a plastic drum.
Anyone any experience of this?

Thanks,
Anton

You won't have any trouble with this.......worked wonders on my scoot alloys,its so good they've put the price up...must have got a lot of buyers? considering the nitromors is a joke nowadays.

https://artemisproducts.co.uk/boden-paint-and-glue-stripper-5-litres/

 

[Maker]

nitromors is a joke nowadays.

It's crap now because they changed it by removing the active ingredient, dichloromethane, I believe to conform to EUBS. You can buy dichloromethane (AKA methylene chloride) and use it as it or I think I've heard of people mixing it back into modern nitromorse to make it good again. You can also mix it with methylcellulose (wallpaper paste) to essentially make your own nitromorse.

EDIT; Just seen your link, that stuff uses DCM, that's why it has all those warnings on it.

 

[hotrodder]

Alloys arent pure aluminium by definition so perhaps that is why it doesn't seem to affect them too much.

It does if given the chance. How much and how quickly depends on the strength of the caustic solution, time and a bunch of other stuff... the stronger the solution the faster the reaction and, as it's exothermic, the hotter the stripping solution will get which in turn will make it react more quickly/vigorously* etc
What happens with aluminium alloys (castings being Al + Si + a little other stuff typically) is it eats the aluminium in preference to/more quickly than the silicon (~7 - 10% ish) and other alloying elements typically copper or mag being the other main ingredient for a cast ally wheel. In the world of anodising the result of this is a part covered in 'smut' which is the undissolved stuff left covering the surface

*

Aluminium extrusions are virtually always an alloy, typically a 6xxx series (Al + a bit of silicon, mag and traces of other stuff). The geometry of the heatsink kinda exagerates things due to a high surface area for the mass

Obviously when the part is painted (or anodised) things aren't gonna get that vigorous unless you leave the wheel in a strong solution while you get on with something else and then forget about it. Even then it probably won't due to the dissolved paint & crud in the solution

 

[anto]

So the gist of it is keep the caustic solution only as strong as it needs to be to strip the paint and keep an eye on it.
Thanks @hotrodder

 

[rtbcomp]

Soda blasting will take off powder coat, it did the trick on my truck no problems

It was probably rubbish powder coating then. I've tried to blast powder coating with glass grit and it didn't make an impression on it.

One problem with using caustic soda would be if the paint has already lifted in places. The exposed ally will dissolve whilst the paint on other parts is being stripped, this will leave an uneven surface.

 

[anto]

@rtbcomp il give it a test on a scrap wheel to see how it performs.

 

[Maker]

His bare hand was scary close to that stuff.

 

[anto]

I will be in full biohazard gear if I attempt to do it on mine lol

 

[julianf]

Caustic is worse than acid in some respects.

You feel acid quickly, but you generally don't feel caustic till it's eaten some way in.

I have a greater than average amount of caustic in the garage (50kg or so - enough to do a few corpses!)

Its useful stuff though.

 

[hotrodder]

His bare hand was scary close to that stuff.

He did call himself an idiot

 

[Maker]

He did call himself an idiot

It is refreshing to see this though, after seeing a video with a guy wearing safety gasses under face shield.

 

[DanielW]

So the gist of it is keep the caustic solution only as strong as it needs to be to strip the paint and keep an eye on it.
Thanks @hotrodder

PDF file: see paragraph 2
It corrodes metals, such as aluminum, tin, and zinc. During this process, it
generates hydrogen, which has the potential to behave as an explosive gas

http://www.jsia.gr.jp/data/handling_01e.pdf