The incident occurred last night as the tanker-lorry container opening was not closed and as the vehicle entered, it suffered a jerk and the acid spilled over and fell onto three workers, Mettur DSP Ravikumar said.
The three suffered acid burns and have been admitted to a private hospital.
The lorry driver and cleaner were today arrested under various IPC sections including 337 (causing hurt by act endangering life or personal safety of others), police said, adding, the sulphuric acid was meant for cleaning purposes of the plant.