Which one is NOT a classification of antifreeze?

The classification of antifreeze typically encompasses various technologies based on their chemical formulations and additives used to improve their performance. Inorganic Additive Technology (IAT), Organic Additive Technology (OAT), and Hybrid Organic Additive Technology (HOAT) are established classifications.

IAT involves traditional solutions that mainly utilize inorganic compounds to provide protection against corrosion, especially within older cooling systems. OAT incorporates organic acids to offer extended service life, ensuring reduced corrosion and better performance in modern engines. HOAT combines both inorganic and organic additives to harness the strengths of each, providing a balance between corrosion protection and extended maintenance intervals.

On the other hand, Hybrid Inorganic Additive Technology (HIAT) as a specific classification does not exist within established antifreeze technology frameworks, making it the correct identification of what is not recognized as a standard category. Consequently, the answer aligns with the understanding that HIAT is not used in antifreeze classification discussions, ensuring a clearer differentiation among the current recognized technologies.