Thioglycolic acid ( TGA or mercaptoacetic acid, CAS 68-11-1) is a high-performance chemical containing mercaptan and carboxylic acid functionalities. TGA is completely miscible in water and is used in industries and applications as diverse as oil and gas, cosmetics, cleaning, leather processing, metals, fine chemistry and polymerization.
Thioglycolic acid forms powerful complexes with metals that give it specific characteristics sought after for the assisted recovery of ore as well as for cleaning and corrosion inhibition.
Chemical name
Thioglycolic Acid, 2-Mercapto Acetic Acid, 2-Mercapto Ethanoic Acid, Glycolic Acid, 2-thio
Key benefits of TGA
At temperatures above 70°C – common temperatures in well bores, TGA is more efficient than classic ferric ion chelating agents (citric acid, acetic acid, EDTA, NTA). Moreover, TGA is more efficient than classic ferric reducing agents, such as erythorbic acid or ascorbic acid.
- TGA reduces Fe3+ (ferric) ions to chelated Fe2+ (ferrous) ions that remain in solution at pH < 7.5
- TGA is stable and efficient at low pH (TGA rapidly reduces high quantities of Fe3+)
- TGA can control very high concentrations of ferric iron – up to about 10%
TGA in corrosion inhibition formulation
Water is present in most crude oil and gas production and is the cause of problems in the recovery and transportation of oil and gas. Water can come either from the formation itself or from the water flooding used in the secondary recovery operations. Corrosion is mainly due to the presence of water with CO and/or H2S.
Corrosion inhibitors could be added to form a film which protects the metal from iron corrosion. Corrosion inhibitors are injected either continuously into the fluid
stream or into a producing well. They can be added in the water flooding operations of secondary oil recovery, as well as pipelines, transmission lines and refinery units.
Although the corrosion inhibition is a complex process, highly dependent of various parameters such as the nature of the inhibitor, fluid composition, pH,
temperature, etc., the mechanism generally involves the anchoring
of the inhibitor and the formation of a protective film.
A variety of corrosion inhibitors are known, particularly nitrogen-containing
compounds such as a morpholine, cyclohexylamine or imidazoline.
However, the sulfur-containing compounds can be also effective especially
at elevated temperatures. With its unique properties (fast adsorption onto mild
steel surfaces, strong chelant), TGA provides good inhibition even in
concentrations as low as 5-10 ppm.
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