Extended Life Coolant: Why You Should Monitor Your Corrosion Inhibitors

Extended Life Coolant formulations contain organic acid inhibitors for corrosion protection similar to how conventional formulations use inorganic inhibitors. With extended life coolants becoming more popular testing, the organic acid inhibitors can be trickier in the field and require additional testing in the laboratory than what the conventional formulation would have used. For conventional formulations, monitoring nitrite and/or molybdenum was the main way to determine if corrosion protection levels were adequate or not. Now with all different possible organic inhibitors used in extended life coolants, the fluid may or may not contain inorganic inhibitors, nitrite and/or molybdenum, with the addition of organic inhibitors. Some may contain only organic inhibitors in the formulation.

Organic Acid Inhibitors

Not all extended life coolants are applicable for testing on all test strips used to determine organic levels. The test strip testing may only work on certain organic formulations because the strip is looking for a certain organic acid(s) present which may or may not be present in the formulation in use. Some of the more common organic acid inhibitors found are Benzoic Acid, Sebacic Acid and 2-Ethylhexanoic Acid for iron and aluminum protection. Azoles that are commonly used are Benzotriazole (BZT), Tolyltriazole (TTZ) and Mercaptobenzothiazole (MBT) for copper and brass protection. Coolant manufacturers might not use all of these inhibitors in their formulations which is why laboratory testing is beneficial in determining the type of inhibitors present in the coolant formulation.

High Performance Liquid Chromatography (HPLC)

In the laboratory, the only testing that can report in parts per million the organic acids (carboxylic acids) is with the High Performance Liquid Chromatography (HPLC) testing. The HPLC will report the organic acids present in the formulation and determine if the levels are adequate for corrosion protection. The testing can indicate if mixing of coolant formulation has occurred as well. To determine if mixing occurred, make sure the laboratory testing will include the testing of both the inorganic and organic inhibitors when submitted to the laboratory. If the coolant formulation is unknown it is important to include testing for both inorganic and organic inhibitors as well. If mixing did occur already, then testing will show the current level of inhibitors and help determine if levels are adequate for corrosion protection. Receiving testing that includes identification of all types of inhibitors will be the only way to help determine the type of inhibitors present currently in the system and how to maintain the fluid.

Why Add HPLC to Your Program?

Adding this testing to your current test package will help to indicate if someone has topped off with a different coolant formulation which can cause dilution of the organic acids that protect the metal in your engine or if the current fluid inhibitors are still adequate for corrosion protection. If the organic acid inhibitors are low cavitation, pitting and premature failure can occur. Overall, HPLC testing will help to ensure you achieve longevity with your Extended Life Coolant and engine. The Technical Bulletin, Benefits Gained from High Performance Liquid Chromatography Testing, will provide additional information on the benefits of HPLC testing and explain how the HPLC instrument operates.   

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Published July 10, 2018