1. n. [Drilling Fluids]
A negatively charged ion. Clay surfaces, groups on polymer chains, colloids, and other materials have distinct, negatively charged areas or ions. Anionic characteristics affect performance of additives and contaminants in drilling fluids, especially water muds, in which clays and polymers are used extensively.
Antonyms: cation
See: acrylate polymer, calcium contamination, carbonate ion, cation exchange capacity, clay, colloid, mixed-metal hydroxide, polar compound, potassium ion
