SYMPOSIA PAPER Published: 01 January 1993

An Investigation of Carboxylic Acids as Corrosion Inhibitors in Engine Coolant


The ability of carboxylic acids to inhibit corrosion in automotive cooling systems was first reported more than 40 years ago. Aromatic carboxylic acids, such as benzoic acid and its derivatives, have been extensively studied and are used in Europe as corrosion inhibitors in commercial coolants. There are few studies of corrosion inhibition by aliphatic carboxylic acids in the open literature. Aliphatic dibasic acids, such as 1,10-decanedioic, and aliphatic monobasic acids, such as octanoic, have recently been proposed as inhibitors in automotive coolant formulations. To date, ASTM performance test data have not been available.

This paper presents a comparison of the performance of selected carboxylic acid coolants with each other and with a traditional North American coolant in laboratory and fleet tests. Protection of cooling system metals, inhibitor depletion, and mixed coolant effects were investigated.

Author Information

Mercer, WC
Coolant Group, First Brands Automotive R&D Laboratory, Danbury, CT
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Developed by Committee: D15
Pages: 44–62
DOI: 10.1520/STP25156S
ISBN-EB: 978-0-8031-5244-1
ISBN-13: 978-0-8031-1851-5