Sulphuric acid, H2SO4 is used in many scientific and industrial applications, including batteries, fertilizers and chemical reagents. Wikipedia writes:Sulphuric acid is a chemical compound of sulphur with the molecular formula H₂SO₄. The 100% sulphuric acid is a colorless, oily, very viscous and hygroscopic liquid, which is sometimes referred to as monohydrate in technical terms. Sulphuric acid is one of the strongest acids and is highly corrosive. Due to its strong acidic properties, it can be used effectively to remove impurities, rust or limescale deposits. For example, it can be used in industry to clean metal parts or in households to clean sanitary facilities.
We use sulphuric acid in a dilution of 10 % to clean objects that have been heated to a high temperature during production, such as during welding, soldering or casting. Here, the oxidized workpiece is immersed in the diluted sulphuric acid for a few minutes, then rinsed and cleaned under running water with a brass brush, known as “scraping”. This dissolves the contamination and exposes the bare metal