Hybrid OATs usually require more maintenance than pure OATs due to the higher depletion rates of the inorganic additives. Refer to ASTM D6210 for industry standards in the testing of heavy-duty coolants like N-HOAT. While nitrites are also depleted as quickly as the main components of IAT coolants, the organic carboxylates do most of the protection, hence N-HOAT chemistry still avoids most of the disadvantages of IAT chemistry. Nitrites are used in heavy-duty vehicles, to assist with corrosion inhibition and cavitation. N-HOAT (or Nitrited OAT): This technology is a hybrid OAT (HOAT) that combines inorganic nitrites and organic carboxylic acids.Refer to ASTM D3306 for industry standards in the testing of light-duty coolants like OAT. They are used in most light-duty vehicles. They do not utilize inorganic additives, require the least maintenance, last the longest among all the types here, and are compatible in most nations. They act directly upon the metal corrosion sites, rather than forming a surface-film on the metal. OAT: As mentioned, these purely use carboxylate additives to inhibit corrosion, which extends the life of the coolant superlatively.Now, let’s look at some of the more common additive variations of OAT coolants along with a little information about each one: As such, their overwhelming advantages have made them the premier choice for most vehicles all over the world. These organic components also avoid most of the problems inorganic additives fall into, per their reactivity with the minerals in the water. Carboxylic acids form carboxylates during the heating process, and these compounds deplete far more slowly compared to the inorganic counterparts, while also preventing corrosion as effectively. OAT coolants, on the other hand, use carboxylic acids as the main inhibitors within their product. Finally, the inorganic oxides often react with the minerals in the water to cause defective deposits that clog the cooling system-these water-based problems are intrinsic to nation, as you will find out. The second problem is that the surface-film itself causes reduced heat exchange between the coolant and the cylinder liner, and this disorganizes the engine’s heat balance. This leads to a shorter life for the coolant, and shorter service intervals, at which one is either supposed to add supplemental coolant additives (SCAs) or drain one’s cooling system and buy new coolant. What wasn’t covered in the previous post was that, in the process of forming this surface-film, the inorganic inhibitor components of the coolant-silicates, phosphates, borates, etc.-are depleted at a faster rate than is desired. It also represents most of the market in both the automotive and heavy-duty industries.Īs you would have learned in the previous post, IAT coolants form a protective surface-film on the cylinder liner’s coolant side to inhibit corrosion there. In this post, we will look into OAT family of coolants, their types, and why their chemistry has revolutionized the engine coolant industry in the last two decades. These additives may seem diverse, but there are really only two major types used in the world today - IAT & OAT. Since the dyes don’t always match the standard colour conventions, the only objective way to evaluate coolants is, then, through their additives. Coolants are only differentiated from each other through their inhibitor additives and their dyes. In Coolants 101, we provided a high-level overview of the types of coolants we typically see in the automotive industry. We divided these coolants into two broad categories of products: IAT (Inorganic Additive Technology) and OAT (Organic Additive Technology). The real value of a coolant, and that which differentiates one from another, is the additive or inhibitor package which makes up the balance at only about 2.5%. This is the water/glycol mixture that represents around 97.5% of a finished, ready-to-use product. It is often said that coolants are a commodity, which is true in part, but refers only to the base fluid.
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