Corrosive Glue tower
Corrosive Glue button in Bloons TD 4. Corrosive Glue (upon being unlocked) in BTD5. Glue Gunner with Corrosive Glue upgrade in Bloons Tower Defense 4 Corrosive Glue icon in BTD5 Corrosive Glue in BMC
Corrosive Glue is the Glue Gunner's level 3 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, $325 on Hard, and $360 on Impoppable. 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 except on mobile.
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 makes it effective for Regen Farming.
This can destroy a Rainbow Bloon on any beginner track with Stickier Glue, 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.
Upgrades in the Bloons TD series Current Towers Former Towers