Gallotannin is a specific form of tannin, a type of polyphenol. Its weak acidity (pKa around 6) is due to the numerous phenol groups in the structure. The chemical formula for commercial tannic acid is often given as C76H52O46.
Gallotannin also known as Tannic acid (TA) is a natural, non-toxic organic acid with corrosion inhibitive property for metals and alloys. A chemiluminescence (CL) system of KIO4 (potassium periodate)–H2O2 (hydrogen peroxide)–Tween40 has been employed in the detection of tannic acid in industrial wastewater.