![]() North American automotive engineers apparently recognized that Japanese HOAT coolants were superior in aluminum engines to North American coolants. As a result, European coolants have historically used borates (which are abrasive) in preference to phosphates. In addition, phosphates acquired negative environmental associations, so the European automotive industry developed and promoted phosphate-free coolant technology. European automotive engineers reportedly had some negative experience with phosphates reacting with the tap water in some European locales. European engineers also developed a form of HOAT technology (using benzoic acid as the organic acid) about 15 years ago but they used silicates and borates in the inorganic additive package. In Europe, aluminum blocks have been widely used for decades, which has pushed coolant technology along a path much closer to the Japanese model than the North American one. The abrasiveness of the silicates was not much of an issue given the assumption that water pumps (and perhaps cooling system hoses) would be replaced at regular intervals. According to Wikipedia, one of the reasons GM dropped this engine was radiator clogging caused by coolants ill-suited to aluminum.) North American automotive engineers determined that they could accommodate aluminum engine components by adding silicates to their standard coolant originally developed for cast iron engines. ![]() (Buick introduced an aluminum V8 in 1961 but ceased producing it in 1963 and subsequently sold it to Rover. In North America, coolant technology evolved primarily to support cast iron engine technology but it also needed to accommodate some aluminum engine parts including the occasional use of aluminum blocks which first appeared in the early 1960s. Japanese engineers also avoided borates (a form of inorganic additive) because they are abrasive and less effective than phosphates. In this context, silicates were unnecessary and undesirable because of their abrasiveness (which attacks water pump seals). (A HOAT coolant uses a combination of inorganic and organic additives.) They never relied on silicates because their coolant technology was specifically developed for aluminum engines. ![]() The Japanese quietly started using a form of HOAT (hybrid organic additive technology) in automotive applications over 15 years ago. In particular, aluminum fares best with a "low pH coolant" with a pH is in the range 7.8-8.3 while cast iron fares best with a coolant pH in the vicinity of 10.5. (For example, the ubiquitous VW/Audi 2.0T engine has a cast iron block.)Īluminum and iron have very different corrosion properties and require different antifreeze formulations for optimal performance. In Europe, aluminum has been dominant for decades but not as dominant as in Japan. In North America, most engines are still made from cast iron, although aluminum is rapidly gaining market share. The engineers who created these technologies studied and cited each other's patents but developed their respective approaches based more on practical experience than on theoretical models.įor the past few decades, nearly all automobile engines manufactured in Japan have been made primarily of aluminum. Coolant technology has independently evolved in Japan, North America, and Europe.
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