Coronic acid

Coronic acid was a type of acid that was harmful to Sontarans, causing damage to both their bodies and their armour, effectively killing them on contact. Outside of its container, the substance produced large showers of white sparks, similar to magnesium.

It was used against them in 1985 by Chessene of the Franzine Grig (DW: The Two Doctors), and in 2370 by Raghi defence forces. (MA: Lords of the Storm)