Citric Acid is often incorporated into acid formulations. Its function is to prevent the precipitation of gelatinous ferric hydroxide as the acid spends.
As a sequestering agent, citric acid can hold as much as 3000 mg/L of ferric iron in spent acid solutions for more than 4 hours at temperatures above 80°C.
Citric Acid is one of the most economical iron-sequestering agents available. However, it should not be used at concentrations greater than 2 kg/m³ as it can precipitate calcium nitrate if there is insufficient iron for it to sequester.
As a cementing additive, Citric Acid can be used as a retarder as well as a cement dispersant. It is normally used at between 0.1% and 0.3% by weight of cement. Citric Acid can also be used in a wide range of applications where the pH of aqueous fluids has to be lowered.