Removing Plastic Liners from Aluminum Soda Cans

Have you tried putting the can in an oven?

http://cr4.globalspec.com/blogentry/9993/Soda-Cans-Are-Really-Plastic-Bottles

I cant be using heat for that purpose since my nest step would

be annealing the aluminum and the oven process just leaves too much residue on the material, would have to sand it right after the oven.

Thanks

use a hot oil bath

This isn't going to be easy as the coating is epoxy resin based.

http://en.wikipedia.org/wiki/Beverage_can

http://www.google.com/search?q=aluminum+beverage+can+epoxy&hl=en&safe=off&start=20&sa=N

The use of Sulfuric acid is mentioned however.

http://www.google.com/search?hl=en&safe=off&q=aluminum+beverage+can+de-coating+epoxy&aq=f&oq=&aqi=

Need to use aluminum sheet from pop (soda) can. FOR?

How to I get rid of the plastic film inside and the ink (plastic?) on the outside. Because I want to>>>>>

That's right: because s/he wants to.

How about real sand not sand paper --- loose sand sweep it over it the sheeting or put in the cans and shake.

I would contact a manufacturer of plasma cleaning machines and ask them for a demonstration. Probably an argon plama. It will remove all organics without affecting the properties of the aluminum can.

0.5 (N) nitric acid will degrade plastic and then washing will take this out. Based on the type of plastic or epoxy one may need to heat it to about 50C .

Please make sure you do this in well ventilated area or under fume hood. If this is every day work you will need to do in fume hood to avoid smell and bad effect of acid fumes

The BEST answer is highly dependent on how much 'clean' aluminum you need, how often, and the degree of 'clean' you need. Any answer proposed now, with so little information, is only slightly better than a wild guess. It may even be better to BUY clean sheet stock in a roll!

Spoken like a PMP. Op didn't ask whether it would be cost effective to strip the plastic from the cans, he was simply inquiring about procedures to accomplish it. You are correct, it may be better to buy clean material on a roll, but you won't know that until you have explored other options.

Is this a dig? There is NO safe and effective method for removing the inner coating and exterior paint and adhesive from individual soda cans that would allow its reuse for anything other than scrap. The metal has been subjected to excruciating stress during drawing and then carefully stress relieved and tempered, surface treated for adhesion,etc. The post consumer condition is quite hard with very low ductility.

One COULD remove exterior coatings with a cloth soaked in MEK, and the interior coating COULD be removed similarly with a cloth soaked with acetone or methyl alcohol (and rubbing in both cases.) However, the metal surfaces will still be VERY DIRTY compared to the cleanliness needed for semiconductor manufacturing, aero-space components, and LOTS of other seemingly 'ordinary' uses. Multiple passes and rinses with different solvents will be required to totally remove the coatings, and there is still particulate contamination galore as well as stray molecules of the coatings and solvents hanging around.

How clean does CLEAN mean?

Keith,

No offence intended. I just feel that we should concentrate on answering the question and let op decide if it's worth pursuing. Since we don't know the application, we have no idea how clean the product must be. Incidentally, O2 plasma cleaning is used to remove organic photoresist from semiconductor wafers. It is also used in countless aero-space applications. A big advantage is that it involves no chemicals, only a vacuum cleaner to remove the ash. I work in the semiconductor and aero-space industries, so I have a concept of what clean is. I also build bird feeders out of empty cans and bottles and know that they don't need to be atomically clean. Aluminum cans are a marvel of engineering. If someone has an application that involves recycling cans and can utilize their amazing mechanical properties, I say, more power to him.

Great to have your expertise in the loop! My concern is we can waste a lot of time and energy working on the wrong problem. 'Tis' just my nature -a lifetime of making things better

I plan on using aluminum cans as scrap for melting into different shapes and parts, mostly for craft applications, but also for scientific curiosity. Would I still need to remove the paint and other coatings, or do they just burn off?

Just soak it in Drano. That will separate the plastic from the aluminum I can assure you.

BUT, BUT, BUT, DrAno comes in a plastic bottle, right?.

You'll get a chemical reaction that will dissolve all the aluminum rapidly and leave the plastic.

I found this out when I was a kid and we thought it was turning the aluminum clear.

It made the glass container so hot that when we touched it the container broke.

The basic polymer coating on aluminium is bound to have some metal adhesive.

Based on the assumption that it could be epoxy you may try MEK AND CHOLINATED SOLVENTS.

The other option worth trying is to try acidified Hydrogen Peroxide[ controlled dosages] or Hypochlorite solution soaking.

Peroxide is likely to swell well the composition of printed polymer coating.

The trial is less costly and over to you for try.

Remember controlled conditions -you may find the aluminium sheet dissolved if treatment is prolonged.

Er, <...acidified Hydrogen Peroxide...> and <...alumin[i]um...>?

Please ensure all other CR4 readers are well away from this experiment before it starts!

Heat will damage the bond on the outside and the inside. There is a nice difference between the temp that will melt/ soften the metal, and that will damage the epoxy and other coatings.

New metal is so cheap that I cannot understand why more complete coating removal would even be contemplated. Do you really need the work-hardened weirdness of a pop can? There has been a lot of science applied in the allocation and 'working' of metal in a finished can, to save weight and have the strength to contain the pressure and resist physical abuse in service.

Sandblast it with "baking soda"...saw a demonstration that removed the "paint" from a soda can and didn't hurt the can. They use it to remove paint from fibreglass and other soft materials. Google... sandblasting baking soda

Hello everyone.

First of all thank you all for the precious opinions on the subject.

The use I will be making of it is to have it clean and softened (annealing) so that I can "cut" (photo etching) panels to apply on my airplane models.

To buy a roll of aluminum for that purpose it's just too expensive and beside it's nice to have the different aluminum stock on a project of this nature ... it makes the end product look a lot more realistic.

Thank you all.

Cool. Send some pictures. Join up.

Hello,

Even though this topic is very old I am sure some people still look for the answer (as I did while googling).

Here is what I just did: simply saturate a sponge with a scotch brite side with acetone. Polish firmly the entire inside of the aluminium sheet (from a can). Do it on a very flat surface (I used plexi, but better would be glass or marble). Then I used regular detergent and rinced it. It does not take too much time and should not harm the surface.

It makes a conductive flat surface, which is what I am looking for to mill PCB stencils.

OK, I am one of the people who is still looking for an answer to this problem. This is, so far, the method that worked for me, but it took a minute of vigorous scrubbing to get half of the coating off, left coarse scratch marks, and made a mess. Still not what I want.

The only method I have found online––Remove Ink Coke Can from Coke - DIY How to Polish a Coca Cola Can - YouTube––that completely removes the coatings with acetone and leaves a smooth shiny unscratched surface, involves pressure cooking the can for 20 minutes before applying acetone with a cotton pad. I threw away my pressure cooker long ago and I don't like the idea of using one in the first place. Too time consuming and awkward.

So far I have tried steel wool and 3M Scotch Brite, with and without acetone, 400 grit wet-or-dry sandpaper, both wet and dry, ironing the metal sheet at maximum temperature (450ºF) with a clothing iron, followed by acetone wipe, torching the finish with a propane torch until it smoked and turned brown––smelly toxic fumes, followed by acetone wipe, and other metods. They all fall short of the goal of simplicity, speed, smooth results, without noxious chemicals. There is a Japanese soda can stove 'sensei' on Youtube who buffs it off with a soft brass polishing wheel but it leaves light scratches. So I think the question is still open.

Some interesting references I came across that might help others:

Can coatings | Food Packaging Forum

Beverage can printing - Wikipedia

Removal of Cured UV Adhesives and Resins [PDF]

Rework and Removal of UV Light-Curable Conformal Coatings [PDF]

The bottom line seems to be applying heat in excess of 150ºC (302ºF), a seemingly modest temperature, yet it has yielded poor results for me and good results for the pressure cooker proponents. Is it just the 20 minutes heating in a moist environment that makes a difference, or maybe a different material than is on my cans? I don't know but I really don't want to go that route if at all possible.

Just buy a cheap pressure cooker off the Ebay and be done with it....

https://www.ebay.com/itm/Vintage-PRESTO-PCS6-6-Qt-Pressure-Cooker-wBox-NIB-Never-Used-J0938/303246342342?epid=1330625839&hash=item469ae3f8c6:g:9~oAAOSwJPVdSgM4

That would be a last resort at this point. There must be a better way.

Not necessarily...aluminum flashing is really cheap, and can be easily polished I'm thinking....

$5.64 at the Walmart...

Now that's the easy way...!

Oh, absolutely, and I have some, but it is much thicker than the ultra-thin can material. Then there's the recycling aspect to consider.

Aluminum cans are already largely recycled, in fact the flashing you buy at Walmart is probably from recycled cans....and you can get aluminum flashing in several thicknesses...

..."A beverage can body usually is made from AA3004. Alloys from the 3XXX series have about 1 percent manganese (Mn) added, but AA3004 also has 1 percent magnesium (Mg) for further strengthening that allows the finished can to maintain sufficient integrity with the thinnest possible wall. The incoming sheet aluminum starts at about 250 microns, or 0.01 inch. After forming with a draw and wall ironed (DWI) operation, beer can bodies have a wall thickness of 100 microns (0.004 in.) at their thinnest point."...

https://www.thefabricator.com/article/metalsmaterials/sheet-aluminum-alloys-for-cans-and-cars

https://www.onlinemetals.com/en/buy/aluminum-sheet?gclid=Cj0KCQjwv8nqBRDGARIsAHfR9wBJGKYPpBIIi5JrlpOxzaDRXmIutpI0MpK7YrSQ7EXUfJIMiIDQKI4aArlgEALw_wcB

Recycling aspect? Consider that some processes are better done in bulk. When recycling is done on a commercial scale, it becomes necessary to effect a safe disposal protocol for chemical and plastic waste so generated, at least within the developed world where there are regulations to prevent unsafe disposal and/or promote the recycling of solvents/chemicals used.

Removal and disposal of the plastic to reuse the metal at home is not free of environmental costs. Your chemicals and dissolved inks/plastic must go to the landfill, likely without any special treatment since it is on such a small scale. If you buff it off you will likely be using power tools/grid energy for efficient use of time, this too is creating a microplastic dust that goes into your environment or to the landfill if you are able to capture it effectively. It may appeal to your customers as a marketing point, that the material is salvaged from cans. However don't deceive yourself that this is better for the environment, unless you thought through and implemented a disposal process for your waste.

From that POV I would forget about the solvent approach for its contribution to the environmental cost. I don't think there is any metal worker who didn't have to remove scratches from material before (and often after) working it, not to mention polishing when you're done. What you need is the right tool and grit to remove the coatings as quickly and effectively as possible without making deep scratches. The brass wheel and other 'scratch brushes' always leave a scratchy texture. If I had to try it, I would start with the white 120 grit 3M bristle disks. Set up your rotary tool in a clamp and use both hands to grip and pass the metal surface underneath the bristles - and set up a vacuum to the right, where the dust will be ejected. Wear appropriate mask. You will likely remove the coating in a single pass with 120 grit. It removes scratches and leaves a very light texture that is uniform - you can anneal and work it at this stage, or move on to do a pass with the blue 400 grit or pink pre-polish for a smooth and relatively polished surface to work on. When all your working is done, give the item a run with the light green 1 micron for a high polish finish. I haven't found any product more effective than these 3M bristle disks for metal, and they have the light touch which is necessary for working with such a thin gauge as a pop can.

There really isn't any substitute for using more than one grit, when it comes to finishing metal. You will need more than a single step. Use the right grit for a very short time.. or start with a high grit and you'll be doing it for a long tedious time, not to mention clogging your fine polisher with the plastic crap.

It's a good thing not to find a problem for every solution. Try it!

Just buy the cans plain...$0.20 each

...or craft aluminum sheet 36ga is .005...very close

St. Louis Crafts 36 Gauge Aluminum Metal Foil Roll, 12 Inches x 5 Feet

$7.00