Acid Man is a Robot Master who appears in Mega Man 11. Originally a chemist robot manufactured by the Mecha-Chuchets Institute of Robology, he was reprogrammed into a stereotypical "mad scientist" after being stolen by Dr. Wily, and now uses his chemistry skills to do Wily's bidding. Acid Man was also given a Speed Gear to boost his combat abilities. His Special Weapon, Acid Barrier, generates a shield made of acid that not only protects him from all damage, but also lets him shoot globs of acid at enemies. This ability extends to Mega Man after he defeats Acid Man. Acid Man has a green body with his right arm ending in a cannon and a white glove on his left hand. His feet divide into two toes that point in opposite directions. His serial number is DLN-084.
Acid Man can be swimming around throughout his stage before his boss battle, but you cannot interact with him.
Acid Man's weakness to the Block Dropper can be viewed as an allusion to how acid-resistant bricks can be.
His weapon's ability to deal critical damage to Pile Man is a callback to acid's ferrovorous nature.
Acid Man is the only Robot Master in Mega Man 11 whose name starts with a vowel (unless you count Pile Man's name change to "Impact Man").
Blast Man, Block Man, and Bounce Man start theirs with B. In Japan, Bounce Man is called Rubber Man, starting his name with R, while Block Man had the name "Renga Man" for his preliminary name, which also started with R.
Fuse Man starts his name with the letter F. (Though Fuse Man's Japanese name is "Hiuse Man", which starts with an H.)
Pile Man starts his (true) name with the letter P.