Use Antifreeze to winterize? Here's a choice few think of.....

[Lou C]

If you use antifreeze to winterize (and there is as much debate on this point, as there is on motor oils), but let's just say Mercruiser has recommended it for years....for the purpose of reducing corrosion...not freeze protection per se....you always manually drain first...here's another I think better choice than the standard Marine and RV antifreezes....for one thing...the only marine antifreeze I feel comfortable using is -100 (burst temp) because this stays liquid well down to below zero, vs the -50 and -60 which start to get hard slightly above zero. Now they don't expand, but I still think having a hard substance in a cast iron block or manifolds, is risky. Maybe OK for PVC pipe but for cast iron....the issue is....the -100 is usually between 12 and 14 bucks a gallon.....

So last year I started looking around for Sierra PG antifreeze, this is an engine antifreeze not just for storage, that is no tox propylene glycol. The difference between PG and EG (toxic) is that the PG does not provide as much boil over or freeze protection at the extremes of hot and cold. But, for this purpose, mixed at 50/50, it gives you freeze protection to -26*F. So I buy 3 gallons of the Sierra at $15/gallon, mixed 50/50 that brings the cost of each gallon down to $7.50. This will make 6 gallons of AF which is more than enough to do the job...price wise it works out to only a bit more than the -60 stuff. Used it last year to winterize and just mixed up my batch for this year's winterization. In New York you can find it at ACE Hardware and a few auto parts stores. You can go even higher if it gets colder where you are in terms of AF vs water.....I think this stuff protects better at a better price.

PS on another marine parts website when discussing the various antifreezes they sell...

for -50, it is recommended for low temps between 14-18*F
for -60, it is recommended for low temps between 7-10*F

for colder regions (that includes us since we do get colder as low as zero or slightly below) they recommend the -100.

Most people probably use the -60, but to me that's cutting it too close....

 

[dingbat]

What people need to understand is that polyethylene or ethylene glycol are not in themselves corrosion inhibitors. They are used solely to prevent freezing

Only “inhibited” (additive) glycols protect from corrosion. Leaving stagnant, uninhibited, glycol treated water in contact with metal is a lot worst than leaving the system dry.

The corrosion rate of ethylene glycol on iron, for example, is more than 2.5 times faster than plain water. On steel, it is 4.5 times faster.

Use an inhibited glycol or nothing at all.

 

[Lou C]

Correct and Sierra is sold as an engine coolant with corrosion inhibitors.

 

[QBhoy]

What people need to understand is that polyethylene or ethylene glycol are not in themselves corrosion inhibitors. They are used solely to prevent freezing

Only “inhibited” (additive) glycols protect from corrosion. Leaving stagnant, uninhibited, glycol treated water in contact with metal is a lot worst than leaving the system dry.

The corrosion rate of ethylene glycol on iron, for example, is more than 2.5 times faster than plain water. On steel, it is 4.5 times faster.

Use an inhibited glycol or nothing at all.

Hi

but it isn’t filled with water...it’s a horrible mixture of oxygen and damp that’s in there...if you don’t put AF in. That’s much worse than it being filled with AF.

 

[QBhoy]

What people need to understand is that polyethylene or ethylene glycol are not in themselves corrosion inhibitors. They are used solely to prevent freezing

Only “inhibited” (additive) glycols protect from corrosion. Leaving stagnant, uninhibited, glycol treated water in contact with metal is a lot worst than leaving the system dry.

The corrosion rate of ethylene glycol on iron, for example, is more than 2.5 times faster than plain water. On steel, it is 4.5 times faster.

Use an inhibited glycol or nothing at all.

But. Agree. Should use inhibitor AF.
but something in there is better than the perfect storm of oxygen and damp.

 

[Lou C]

Some have said that if you leave it dry and replace the drain plugs, once the available oxygen is used up no more corrosion can take place. I donno, I like having corrosion inhibited antifreeze in there all winter. But remember rust, is iron oxide, FE O2 . Keep out the O2 and corrosion stops.

 

[Scott Danforth]

not to mention, without anything in there, your good to go to -461F

 

[Starcraft5834]

Service manuals for mercruiser is to drain the water from the block and manifold........... save yourself money.. air does not freeze on planet earth

 

[dingbat]

But remember rust, is iron oxide, FE O2 . Keep out the O2 and corrosion stops.

Iron Oxide (Rust) is Fe[SUB]2[/SUB]O[SUB]3. [/SUB]

That would be a good trick.... how do you remove the oxygen molecules from an electrolyte (H2O) consisting of a 1 hydrogen and 2 oxygen molecules?

The issue you run into using uninhibited glycol compounds is a decrease in pH from oxidative reactions which can be far more damaging than the presence of O2 alone.

 

[Lou C]

What I meant was simply fill up the engine with inhibited propylene glycol vs storing dry. Thereby keeping air out, since it's the oxygen in the air that causes corrosion when combined with water.
All I can say is that when I took the engine apart 2 years ago to fix blown head gaskets, the block had no rusted through areas nor did the cyl heads after 15+ years of raw water cooling in salt water. I wound up replacing the heads due to cracks from a previous overheat and the fact that the cooling passages were starting to get eroded due to raw water cooling. However, the question is does filling a raw water cooled cast iron engine with inhibited glycol really slow down corrosion? Mercruiser does say to do so and has for a long time, in their shop manuals.

 

[muc]

Service manuals for mercruiser is to drain the water from the block and manifold........

And then they recommended filling with antifreeze. The newer manuals require antifreeze.