What material is used in coating these aluminum containers for the food industry?

What is the material used to coat (some might use the term 'lacquer') disposable aluminum containers in the food industry? And can it be removed in a safe way (for the environment) with 'home methods'?


I am not talking of the thin oxide layer that covers aluminum foil and most basic (shiny) containers; this layer can be tunneled through and a resistance measurement with an ordinary multimeter will show high conductivity even without scratching it.


I am in particular interested in thin, easily crushable containers like dessert cups (for example mildly acidic fruit mousse).


[![aliberico alucoat](https://i.stack.imgur.com/7VCY4.jpg)](https://i.stack.imgur.com/7VCY4.jpg).
Source: Aliberico (see below)


The coating appears different from that used in aluminum cans, but maybe it is just a different thickness.  

There is no conductivity no matter how much I scratch the surface, and only when I punch through the material with the probes I get aluminum conductivity.  

The label just say Alu 41 and my google-fu has been found lacking when it comes to the coating.


I googlefound the websites of two manufacturers that produce the containers like the ones I am interested in, like [Aliberico](https://www.aliberico.com/en/alucoat-cs-more-than-coated-aluminum-for-packaging/), but I cannot find the name of the coating material, just a tradename (Alucoat) and some vague marketing descriptions.


This is the 'datasheet' I have found for Alucoat: <https://www.paroc.com/-/media/uploaded-product-docs/2023/01/16/15/15/alucoat-en-us.ashx?dmc=1&ts=20230409t1527075538> and there is no mention of the material.


So, let's focus the question to this particular instance: what is the coating of Alucoat made of? Can it be chemically removed, for example to create small pads?




You can experiment to find out what the colored coatings are. For example, to test for lacquers and similar organic coatings (e.g., [cellulose acetate butyrate](https://en.wikipedia.org/wiki/Cellulose_acetate_butyrate), [nitrocellulose](https://en.wikipedia.org/wiki/Nitrocellulose), [formvar](https://en.wikipedia.org/wiki/Formvar), etc.), try various organic solvents (acetone, ethyl acetate, xylene, ethylene dichloride, etc.). **N.B.** Most of these solvents are highly flammable, and some are fairly toxic -- use in a lab hood **with supervision**. Formvar, for example, is *not* readily soluble in acetone, but is in ethylene dichloride.


Nitrocellulose lacquer can be identified by instability to heat, and the characteristic odor of nitrogen oxides as heat decomposes it.


If no solvent affects the coating, it *might* be [colored anodized aluminum](https://www.rapiddirect.com/blog/anodized-aluminum-colors/), though anodizing might be too expensive for disposable foil products. $\ce{NaOH}$ solution will dissolve the $\ce{Al2O3}$, but would not affect most organic materials in the same way (it might wrinkle a lacquer, rather than directly dissolve it).


 3

Ok, after a few experiments and a more focused search, following Dr. Moishe Pippik's answer I have come to the conclusion that:


These cups are made of aluminum, covered with a layer of anodized aluminum and, at least on the interior, an additional epoxy film.


The yellowish exterior can be dissolved by NaOH so it seems it is just a plain anodized aluminum layer. After a few minutes of exposure to concentrated NaOH solution the thin layer dissolves (starting from microscopic scratches) and once the aluminum is exposed, the reaction takes off with generous bubbling and the formation of a white precipitate (which I assume is aluminum hydroxide).


[![Exterior is easily attacked by NaOH](https://i.stack.imgur.com/9soje.jpg)](https://i.stack.imgur.com/9soje.jpg)


The silverish interior is more resistant to NaOH, and that seems to validate the suggestion given in the accepted answer and the comment that some sort of protective film is added. I found confirmation on this other producer's website: <https://www.ablpack.com/> where it shows the same type of packages and says that



> 
> ...the epoxy coating on the surface protects the aluminum foil
> material from direct contact with food and prevents human ingestion of
> aluminum.
> 
> 
> 


After I left the hydroxide inside the container for a few hours, it was able to erode the entire material at the perimeter and leak outside (in a plastic container!). This exposed the plastic film that appears to be on the inside only as can be seen in the following picture:


[![Plastic film is inside](https://i.stack.imgur.com/BRh7Y.png)](https://i.stack.imgur.com/BRh7Y.png)


Note how the exterior (anodised aluminum layer) already started to dissolve.


Therefore, I believe the mystery has been solved (almost literally).


Creation of pads is better done by mechanical abrasion with fine sandpaper and then cleanup of the surface with sodium hydroxide.


 3