There are also green (I think) barrels that have a chance to contain acid, though not by looting. You have to break it down.
IMPORTANT: Don't ask me why, but for some of these containers (like the medical supply cabinet)
you have to harvest the container before it's looted. If you empty the container, the block itself changes to an 'empty' version and the chance for acid does not apply to empty containers. Also, technically every container in the game is empty until you open it. So if you harvest before opening the container first, the loot won't spawn. Best advice to make sure you get the loot and the chance for acid is to do the following:
- open the container > close container without removing any loot > harvest container (with ax, wrench, pick, etc.) > loot the spawned backpack