Corrosive Glue is the Glue Gunner's level 4 upgrade in Bloons Tower Defense 4 and the second upgrade on the first path in Bloons Tower Defense 5. It costs $255 on Easy, $300 on Medium, and $325 on Hard. It allows the Glue Gunner to shoot corrosive glue that pops one layer of a bloon every two seconds. Corrosive Glue can pop Lead Bloons and Ceramic Bloons, although it still does not slow down Ceramic Bloons.
- In Bloons Tower Defense 4, if you upgrade a Glue Gunner to Corrosive Glue during a round, all of the bloons that the Glue Gunner already glued in that round will have corrosive glue.
- The artwork of the Glue Gunner with Corrosive Glue in Bloons Tower Defense 5 has green glue dripping from his gun even though he shoots yellow glue, however the Bloon Liquefier shows yellow glue even though it shoots green glue.
- This is the only upgrade for the Glue Gunner in Bloons TD 5 that has yellow corrosive glue.
- Corrosive Glue pops slightly faster than the speed of which Regrowth Bloons regenerate at.
- This can destroy a Rainbow Bloon on any beginner track, and a Ceramic Bloon on any beginner track in Bloons TD 4 iOS.
- The reason is that when popping a Ceramic Bloon with corrosion, all 10 layers of the shell count as 1 layer. It is unknown if it is a glitch or not.