The purpose of silicates?
- Thread starter Chuck1986
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Silicates were used as corrosion protection. I believe Prestone was first to commercially market what, at the time, was the first antifreeze based on silicate technology and could be run longer than a one-year changeout interval. The "con" is that high silicate content antifreeze (conventional "green") is unstable over time, with the silicates first precipitating out as a gloppy gell in the bottom of the radiator, and later forming hard sand-like silicon precipitates that are abrasive to waterpump seals. It's no accident that OEMs typically suggest changing out high silicate level antifreeze solutions at 3yrs./36,000 miles or less. Reduced silicate formulas, such as G-05, which is better stabilized and which also contains OAT corrosion protection, allow for longer antifreeze change intervals. (up to 4 yrs. for G-05) Honda, Nissan, Toyota and DEX-COOL antifreeze/coolant concentrates and pre-mix dispense entirely with silicates. DEX-COOL relies entirely on OAT for corrosion protection, and the listed Japanese syrups add a stiff dose of phosphate for co-corrosion protection.
It is my understanding that the "silicates" scrub the walls of the water jacket. Works for the ferrous metals of the engine. Any rust paticles formed will be removed from the flowing coolant. The silicate is microsopic glass particles bouncing off the walls of the jacket.
If I got this wrong someone straighten me please
J.
If I got this wrong someone straighten me please
J.
Silicates, when everything is working right, are in solution, not suspended as small solid particulates. Their problem is that in the former high concentrations they were typically used (i.e., "conventional green"), they weren't very stable over time and tended to fall out of solution - hence the recommendation to change out silicate formulas no later than 36,000 miles. If left in too long, silicates in the higher concentrations first tend to settle out as a gell-like glop in the bottom radiator tank, and would later dissociate into hard particulates - probably the basis for the urban myth that silicates were useful as passage wall scrubbers (but actually only "useful" as waterpump seal destroyers) Again, when working right they were equally effective for iron, brass, lead (solder) and aluminum. In the case of G-05, a hybrid coolant using both OAT and reduced silicate levels, it appears to be the best of both worlds. Ford and Chrysler both call for G-05 in cars made since model year 2000. Mercedes-Benz has specified G-05 for over two decades in both iron and aluminum engines. (The stuff's been around quite awhile.) I believe BMW, VW, Peugeot and a number of other European companies specifiy G-05, though naturally under their own brand. Nevertheless, G-05 is a specific formula, and there's no point paying $20.00/gallon for boutique auto manufacturer uniquely dyed house brands when yellow Zerex G-05 can be had for around $11.00/gallon. In use, G-05's silicates glom onto metal very quickly, though the OAT chemistry can take several thousand miles to reach full effectiveness. Once the silicates in G-05 are displaced by the OAT layer, the re-dissolved silicates are still available to "heal" any breach in the OAT layer from trapped air* not properly "burped" out of the system, or the odd particulate that always manages to defy flushing, until the OAT layer can re-establish itself.
*Straight organic acid technology coolant, such as DEX-COOL does not tolerate air in the system well as owners of certain GM engine series prone to intake and cylinder head gasket failures have discovered over the past decade. When air is not present, and all old, other type antifreeze is properly flushed out beforehand, DEX-COOL can and does work very well.
*Straight organic acid technology coolant, such as DEX-COOL does not tolerate air in the system well as owners of certain GM engine series prone to intake and cylinder head gasket failures have discovered over the past decade. When air is not present, and all old, other type antifreeze is properly flushed out beforehand, DEX-COOL can and does work very well.
Kestas
Staff member
Ten years ago I examined a number of cylinder head water jacket surfaces under the microscope. These were from engines that used the green coolant popular at the time. The water jacket surface were covered with silicate particles, which are sometimes called "water glass" among chemists. The surfaces looked as though they were covered with heavy dandruff. I can't remember if it was perfect coverage.... they seemed rather loosely attached to the surface.
This doesn't answer the question, but I thought I'd pass on this observation.
I'm guessing, but perhaps this silicate coating provided (or prevented) electrolytic action, thus precluding corrosion on the metal surfaces.
This doesn't answer the question, but I thought I'd pass on this observation.
I'm guessing, but perhaps this silicate coating provided (or prevented) electrolytic action, thus precluding corrosion on the metal surfaces.
Sounds reasonable, though, while I'm no chemist and obviously can't confirm this, I suspect the real protection was tightly bound to the metal at the molecular level. The naked-eye "dandruff" observation may have really been precipitated-out silicates showing that the last coolant fill was at or nearing the end of its usefull life.
Why is it bad to use Dexcool if you do not fully flush beforehand? And is it necessary to "flush" with an acid type flush liquid, or is is OK if you just drain and do a few flush cycles with water?
If there are remains of a non-DexCool coolant when you refill, it will reduce the DexCool to a not-very-long-lived OAT/conventional mix.
Depending on how old and dirty the system is, a water flush may be all that it needs.
I would suggest flushing with distilled water and refilling with coolant and distilled water.
Any residue of silicate, calcium buildup, and the like will slowly dissolve into your new coolant. When you add to that the mineral load (calcium, chlorine, and other chemicals) of tap water, you'll cut the live of the coolant.
.
Depending on how old and dirty the system is, a water flush may be all that it needs.
I would suggest flushing with distilled water and refilling with coolant and distilled water.
Any residue of silicate, calcium buildup, and the like will slowly dissolve into your new coolant. When you add to that the mineral load (calcium, chlorine, and other chemicals) of tap water, you'll cut the live of the coolant.
.
sodium silicate will help to seal small leaks and is a very good corrosion inhibitor for aluminum
that is why it is used.
bruce
that is why it is used.
bruce
I think you're on the right track. Small quantities of silicate remain in solution and bind to bare metal.
The difficulty occurs when the silicates present in antifreeze "drop out", build up, and form a gel.
This can take place when antifreeze concentrations are too high, coolant additives are overused, there are impurities in very hard water, or you have severe engine temperature swings.
In any cooling system you can get "boiler-scale" (calcium salts), which will really get the ball rolling. The silicate drop-out acts like an insulator and can cause the engine to run hot while the coolant itself remains relatively cool.
It can also clog up the radiator and heater core.
Finally it can attach itself to the water pump, where it wears away pump seals causing leakage and failure.
Once the process gets rolling, the gel is not water soluble, so flushing with water alone will not get things sorted out.
.
The difficulty occurs when the silicates present in antifreeze "drop out", build up, and form a gel.
This can take place when antifreeze concentrations are too high, coolant additives are overused, there are impurities in very hard water, or you have severe engine temperature swings.
In any cooling system you can get "boiler-scale" (calcium salts), which will really get the ball rolling. The silicate drop-out acts like an insulator and can cause the engine to run hot while the coolant itself remains relatively cool.
It can also clog up the radiator and heater core.
Finally it can attach itself to the water pump, where it wears away pump seals causing leakage and failure.
Once the process gets rolling, the gel is not water soluble, so flushing with water alone will not get things sorted out.
.
Thanks Ray for that imfo, I am starting to use a low silicate conventional, namely "Peak". I got so many old beaters, that have used conventional, I dont want to change to g5. The Peak conventional says it complies with ASTM d4985, so it should be good for aluminum engines as well as cast iron. Also good for the Cummins b. Peak is everywhere around here and as cheap as $7.00/gal. Dont trust the "no-name" brands anymore cause they dont list anything on the containers other then marketing **.
Thks
J.
Thks
J.
SHOZ-you should use what was originally spec'd for your engine.
Kestas
Staff member
I disagree. Antifreeze is presently undergoing an evolution. Most modern formulations are better than the old green stuff - even for older cars.... just like modern lubes are better than the old ones specified.
I just swithched my 99 Landcruiser with 58K miles on the odo., over to the no silicate 5 year 100K mile antifreeze (stated it was compatible with Toyota systems)(same stuff that came in my 2004 4runner from the factory that is good for 5 years or 100K miles), I changed all hoses water pump timing belt and flushed the system. I will change the antifreeze again at 3 year or 36K mile interval, just like I would with convential antifreeze, just incase I didn't get everything. I also think the new technology antifreeze is superior but want to make sure I baby my Landcruiser through this transition. The 4.7 V8 has the iron block and aluminum heads so incase any residue is being shed I want to be extra careful. What do you guys think of my plan?
SHOZ writes:
jef1ge writes:
Peak is manufactured by Old World Industries, the second largest supplier of antifreeze in North America. OWI is also the number one producer of private label antifreeze, including (but not limited to) AutoZone Valucraft, True Value, "Manny, Moe, and Jack" ProLine, and TSC Traveller. If the label says silicates and phosphates then it probably is re-branded Peak "Classic", a high quality product.
Kestas wries:
Pitbull writes:
It is interesting to note that from a reading of widely available ASTM test results, formulations which contain silicates (whether conventional or hybrids such as G-05) actually provide somewhat better protection to aluminum engine parts. But rather than split hairs, the fact is all major coolant technologies do a highly respectable job of corrosion protection in gasoline engines, and certainly all of them fall well within ASTM limits. System maintenance is the real key.
With aluminum heads it is critically important to guarantee that all air is bled out of the system and that the coolant level remains higher than the top of the head. Aluminum heads are not tolerant of air pockets and low coolant levels. And while some chemistries may be marginally more tolerant of air in the system than others, keeping the air out is an excellent idea for all formulations. It is particularly important with newer OAT technologies like Dex-Cool and others.
Optimal cooling system performance demands zero tolerance for leaks, weeps, seeps, and drips. No cracks in overflow tanks and lines. No loose hose clamps. Air can not be allowed to find a way into the system. If someone finds that he is routinely topping off an overflow tank, he must discover where the coolant is going and fix the problem. If the radiator seeps, fix it or replace it; it is cheaper than replacing a head.
Good choice, good plan, SHOZ. Conventional silicate formulations protect aluminum second to none.
jef1ge writes:
Excellent analysis. Peak "Classic" is a patented low-silicate high-tech "conventional" formulation highly protective of aluminum. See US patents 4,426,309 and 4,382,870 for an eye-opening and interesting read.
Peak is manufactured by Old World Industries, the second largest supplier of antifreeze in North America. OWI is also the number one producer of private label antifreeze, including (but not limited to) AutoZone Valucraft, True Value, "Manny, Moe, and Jack" ProLine, and TSC Traveller. If the label says silicates and phosphates then it probably is re-branded Peak "Classic", a high quality product.
Kestas wries:
True enough. All antifreeze has undergone an evolution. In fact, you would be hard pressed to name a manufacturer of "old green stuff" let alone buy some. "Old green stuff" is largely a strawman which no longer exists. To be sure, there exist green dyed silicate based coolants, but these are not your grandfather's antifreeze. Time and chemistry march on.
Pitbull writes:
Your maintenance plan is excellent. However it is your obvious meticulous attention to system integrity which will serve you better than worrying about the chemistry of your antifreeze.
It is interesting to note that from a reading of widely available ASTM test results, formulations which contain silicates (whether conventional or hybrids such as G-05) actually provide somewhat better protection to aluminum engine parts. But rather than split hairs, the fact is all major coolant technologies do a highly respectable job of corrosion protection in gasoline engines, and certainly all of them fall well within ASTM limits. System maintenance is the real key.
With aluminum heads it is critically important to guarantee that all air is bled out of the system and that the coolant level remains higher than the top of the head. Aluminum heads are not tolerant of air pockets and low coolant levels. And while some chemistries may be marginally more tolerant of air in the system than others, keeping the air out is an excellent idea for all formulations. It is particularly important with newer OAT technologies like Dex-Cool and others.
Optimal cooling system performance demands zero tolerance for leaks, weeps, seeps, and drips. No cracks in overflow tanks and lines. No loose hose clamps. Air can not be allowed to find a way into the system. If someone finds that he is routinely topping off an overflow tank, he must discover where the coolant is going and fix the problem. If the radiator seeps, fix it or replace it; it is cheaper than replacing a head.
Great info vizvo, after the change and new hoses and water pump I did have to top it off to bring it to the full line,(not much) but all hoses were rechecked at that time and it has stayed at the full line since that time (2K miles) and I check the lever every fuel stop. I will continue to check and if there is a change in level I will correct any problem. Thanks for the info.
Kestas
Staff member
Good post by vizvo.
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