I do not know if the lining is plastic, but there is a 'coating' on the inside of these aluminum bottles. If you look inside and catch light at the bottom of the bottle just right you can see what appears to be some type of lining.
When I first got my bottles I noticed it, but could not find a way to remove it. I used vinegar and soaked a test bottle to see if that would remove it, but, alas, nothing came off/out. I did not want to try any other type of chemical (bleach, for example), because that is exactly what I am trying to avoid.
However, in the course of using these bottles for my essential oil mixes, my oregano and tea tree oils seem to have eroded the 'lining' little by little, and were clogging the sprayer to the point of breaking. (I lost several bottles until I figured out what to do.)
In order to keep the sprayers from breaking, when I notice any resistance with the spray mechanism, I check the tubing, and untwist and take off the very tip of the nozzle/sprayer and clean any of the goo/lining that has worn off from inside.
The tip of the nozzle itself is the hardest to clean. In order to get the film out of the nozzle itself, I use a dental gums cleaner that has little tiny 'bristles' that captures the lining and helps to draw it out of the nozzle cap.
I make sure to flush the tubing and sprayer head with clean filtered water to remove any further residue.
A side note: I ALWAYS use filtered water in these spray bottles. Whether you have municipal or well water, there is always some level of minerals, and or other undesirable chemicals (fluoride, chlorine), that I don't want mixed with my essential oils mixes. Regular tap water never fails to leave streaking and or film behind.
For those interested, information on your local city water supplies can be obtained by a report on municipal water treatments via EWG, and/or your city utility/water department websites. If you have to, you can always formally request the data/report(s) - it is 'public information' and every citizen has a 'right' to view the data/information.
People find their not only their sprayers clogging, but their appliances (like humidifiers, misters, etc.) also. This has to do with what is 'in' the water. ALWAYS use filtered water! Your sprayers and appliances will last a lot longer if they are well cared for.