Removing Paint from Aluminium Cans: A Scientific Approach

[Juba]

Hi,

My name is Juba and I’ve invented a solar panel based on used pop soda cans.
But in order to apply the black chrome on the exposed aluminium, I need to remove the label (paint) on the cans.

What is the paint made of?
What is the best chemical to remove it?

I thank you in advance for any help you can provide.

 

[Nicodemus]

Hi,

My name is Juba and I’ve invented a solar panel based on used pop soda cans.
But in order to apply the black chrome on the exposed aluminium, I need to remove the label (paint) on the cans.

What is the paint made of?
What is the best chemical to remove it?

I thank you in advance for any help you can provide.

That's easy, but not clean or quick. You can speed things up with heat, but that's an issue too, and using caustics presents its own challenges. If I had to pick one chemical, it would be Nitromors for metal surfaces. It's meant for DIY, and it definitely does the job, but you need to leave it on for a few minutes.

I'd add, this adds a dimension of washing and disposal of toxic agents to your production process, but you won't find a ready source of "blanks". As for what paint is used, I believe (for Coke at least) that it's an enamel applied with a kind of rotary silk-screen.

 

[Juba]

That's easy, but not clean or quick. You can speed things up with heat, but that's an issue too, and using caustics presents its own challenges. If I had to pick one chemical, it would be Nitromors for metal surfaces. It's meant for DIY, and it definitely does the job, but you need to leave it on for a few minutes.

I'd add, this adds a dimension of washing and disposal of toxic agents to your production process, but you won't find a ready source of "blanks". As for what paint is used, I believe (for Coke at least) that it's an enamel applied with a kind of rotary silk-screen.

Nicodemus,

Thank you very much. I really appreciate your effort to help me.
I am going to use thousands of cans in order to produce the panels. :-)

Since I am in France, I don’t know if I can find Nitromors. I’ve read about the product and it looks if it can do the trick.

Once again, thank you.

 

[chemisttree]

You are going to need to sand the surface anyway. Why not sand it off? Two steps in one.

I assume that you are painting it black so it will absorb sunlight and heat up? Sandblasting preps the surface and provides the best finish anyway. I would think that you wouldn't want a shiny black can. Flat black is best for absorbing heat.

 

[Nicodemus]

You are going to need to sand the surface anyway. Why not sand it off? Two steps in one.

I assume that you are painting it black so it will absorb sunlight and heat up? Sandblasting preps the surface and provides the best finish anyway. I would think that you wouldn't want a shiny black can. Flat black is best for absorbing heat.

Sandblasting might be a little tough on such thin cans, but given the numbers and application you're right... sanding or etching, the surface will need to be prepared.

I'm not sure that it wouldn't be cheaper to buy sheet aluminum, sand THAT, and bam. Otherwise you sand carefully, heat to about 600 deg F, or use caustic, watch, sand, wash, etch, wash.

Juba, do you think there might be a French beverage company or branch that would be willing to tell you their paint forumula? If you have something specific, maybe you can make a specific, but very dilute bath and use time as your weapon. It might be that you can buy some industrial concentrations of your preferred solvent, and have a 6 stage system:

Solvent
Wash
Sand
Wash
Dry
Apply

 

[Juba]

Hi Chemisttree,

You understood everything. :-)

Thanks a lot.

I will in effect consider sandblasting.

Do you thing electrolysis can peel of the printed label.

Sorry for asking. Maybe the question dumb, but if I don’t ask it, I will never learn.

 

[Juba]

Sandblasting might be a little tough on such thin cans, but given the numbers and application you're right... sanding or etching, the surface will need to be prepared.

I'm not sure that it wouldn't be cheaper to buy sheet aluminum, sand THAT, and bam. Otherwise you sand carefully, heat to about 600 deg F, or use caustic, watch, sand, wash, etch, wash.

Juba, do you think there might be a French beverage company or branch that would be willing to tell you their paint forumula? If you have something specific, maybe you can make a specific, but very dilute bath and use time as your weapon. It might be that you can buy some industrial concentrations of your preferred solvent, and have a 6 stage system:

Solvent
Wash
Sand
Wash
Dry
Apply

Guys,

I wish you were her!
I would at least buy you a beer (in a can).

I will actually try to contact one of the can producers here in southern France. Ball Packaging Europe has a plant down here.

Believe me, I appreciate your efforts and I hope to do able to do the same if you should need any help some day.

I’ve tried this product today (http://www.leboncoin.fr/bricolage_jardinage/173826508.htm?ca=6_s ).

No can do.

I smeared a can for more than an hour. It didn’t even “blink”.

Once again, thanks guys.

 

[Nicodemus]

Hi Chemisttree,

You understood everything. :-)

Thanks a lot.

I will in effect consider sandblasting.

Do you thing electrolysis can peel of the printed label.

Sorry for asking. Maybe the question dumb, but if I don’t ask it, I will never learn.

You can definitely reverse anodizing, but you'd just be trading solvents for acid baths and electricity, and it's slower than the original process. If sanding sounds right for you (and you'd know!), I'd stick with that. You could even use a tumbler; if the can's deform, who cares, you could stick them in a pressure vessel and blow them right back up. Anything short of serious crushing shouldn't be an issue, and you could use a fine grit to protect the cans.

 

[Nicodemus]

Guys,

I wish you were her!
I would at least buy you a beer (in a can).

I will actually try to contact one of the can producers here in southern France. Ball Packaging Europe has a plant down here.

Believe me, I appreciate your efforts and I hope to do able to do the same if you should need any help some day.

Once again, thanks guys.

It's genuinely a pleasure, just let us know how this all works out, OK? It sounds like a good idea to me.

 

[Juba]

I’ve tried this product today (http://www.leboncoin.fr/bricolage_jardinage/173826508.htm?ca=6_s ).
No can do.
I smeared a can for more than an hour. It didn’t even “blink”.

 

[Juba]

It's genuinely a pleasure, just let us know how this all works out, OK? It sounds like a good idea to me.

I will keep you posted.
My success will be yours too.

Thanks

 

[chemisttree]

You might consider blasting the can with dry bicarbonate. It is used to remove grafitti so it will be abrasive enough to cut the paint and mild enough to save the can and leave a water-soluble residue (bicarb!) on a matte finish can. No pesky silica to breathe in and no serious hazards with SiC.

The ink is crosslinked with UV light I believe so it won't easily come off with a solvent. It's very thin so blasting should go quickly.

I think electrolysis would be problematic. The ink probably doesn't conduct electricity so you would have serious pitting. Too complicated for this application. Be Earth friendly with your recycling project. Use clay, fly ash or bicarb. I like bicarb for safety and easy disposal.

 

[Nicodemus]

You might consider blasting the can with dry bicarbonate. It is used to remove grafitti so it will be abrasive enough to cut the paint and mild enough to save the can and leave a water-soluble residue (bicarb!) on a matte finish can. No pesky silica to breathe in and no serious hazards with SiC.

The ink is crosslinked with UV light I believe so it won't easily come off with a solvent. It's very thin so blasting should go quickly.

I think electrolysis would be problematic. The ink probably doesn't conduct electricity so you would have serious pitting. Too complicated for this application. Be Earth friendly with your recycling project. Use clay, fly ash or bicarb. I like bicarb for safety and easy disposal.

Wow, that is genuinely genius. If you combine the tumbler with the soda, add time, then cut the cans into strips or blow them back up... you essentially eliminate manual labor. I'm doing the "We're not worthy" Wayne's World bow to you right now.

I did check, and you're right: the paint is NOT electrolytic, it's just standard aluminum varnish/enamel applied by a rapid rotary sponge. Makes sense... you don't want that paint coming off to anything less than serious abrasions: makes your product look "used".

 

[wazani]

Just clean it with acetone

 

[Juba]

Just clean it with acetone

Hi Wazani,

I've tried it. It don't work at all.

 

[pantaz]

What prevents you from painting directly over the existing label?

 

[Juba]

What prevents you from painting directly over the existing label?

Because I need the exposed aluminium in order to apply an other layer by mean of electrolysis.

 

[wazani]

Hi Juba
visit this site;
may be solving the problem

 

[Juba]

Hi Juba
visit this site;
may be solving the problem

Thanks a lot. I will take a look.

I really apprciate your help.