High silicate coolant for aluminum protection?

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Jan 2, 2004
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I believe the reason the German OEM's dislike Phosphates is because the water in Europe has a very high mineral content, and when mixed with phosphates they can produce minerals that settle out and cause corrosion. This is why its especially important to use only distilled water with PHOAT's - so this doesn't happen. Most of the OEM packaged PHOAT's come already mixed to ensure this is not an issue.
there’s a new BASF G-code SiPHOAT that VW is using, along with Volvo.

Prestone used to never have a water recommendation - but the latest Cor-Guard formulations have a statement on the back label that “Water Quality Matters. Use only distilled water/good quality water” on the concentrate bottles.
 
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Joined
Jan 2, 2004
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10,017
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California
AFAIK, silicates were a part of old-school green for quick protection of aluminum and other cooling system metals via coating them. The problem is that silicates don’t hold up to cavitation - which is why diesels get a SCA.

The Japanese saw phosphates and a small amount of an organic acid was the way to provide quick protection while the organic acid passivated certain metals. The Europeans augmented silicate with OAT.
 
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Silicate is still the best inhibitor for aluminium, it acts quickly and is very effective, the Silicate passivated the aluminium, it partially "absorbs" the Silicate, the bad part is that the Silicate depletes relatively quickly and can gel, although the problems with gelling have been more or less figured out now.

I don't know about it being the best. There's many millions of cars on the road with modern all aluminum engines and heating & cooling systems that contain no silicates and they work great (and they don't have to worry about the silicates precipitating out). The fact that the European and American manufactures as now adding phoshopate to their Si-OAT and OAT formulas while the Asian P-OAT's aren't changing would mean that perhaps silicate isn't quite the best.
 
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Nov 7, 2010
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Wisconsin
I don’t think most of them around here get shut down long enough to freeze. An engineer told me they have an auto start feature when they’re parked in a siding and if air pressure drops to a certain point they start up to rebuild pressure. I don’t know if that’s true but I do recall seeing one parked on a side track near the house running with nobody around.

Yep, that's correct. It's known as Smart Start. They're set to start if the brake pipe pressure drops below 60 psi or water temperature for the engine drops below 100 degrees. Some have a separate generator that starts to charge the batteries and cycle water to heat it and keep it from freezing. The reason why coolant isn't used is because it becomes an EPA paperwork nightmare when it leaks and for older engines they don't really fix leaks unless it's more than requiring it to be filled more than once a week.
 
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