Cheap glycol reactivity question.

[dustinstriplin]

Hi, I am building a DIY glycol chiller from an old AC unit. I'm looking to save a few bucks on glycol, so I found a non-toxic antifreeze that may (or may not) be suitable. I'm concerned that this may contain a chemical that is reactive with one of the metals on the AC unit's condenser coil (copper, aluminum, tin, lead, possibly silver). Any chance anyone knows? I'm unsure whether or not DiPotassium Phosphate will react with the metals in the coil.

The composition of the antifreeze is:
Propylene Glycol 25% - 30%
Water 64% - 70%
Glycerol >=4.0%
DiPotassium Phosphate 0.5% - 1%
Dye, FG % Varies


https://www.homedepot.com/p/South-Win-RV-Antifreeze-147005/202530435

 

[dustinstriplin]

So I did a little digging on DiPotassium Phosphate. This is a common food additive and chelating agent. The spec sheet I found doesn't list corrosive to metals in the precautionary code list.

https://pubchem.ncbi.nlm.nih.gov/co...ate#datasheet=LCSS&section=GHS-Classification
Since none of the ingredients are corrosive to metals, and the solution is non-toxic, I think it would make a suitable antifreeze for chiller lines. If anyone out there knows more than I do (which sets the bar pretty low ) and has anything to add, or can confirm whether or not this is safe, then I'd love to hear from you.

Thanks!

 

[bracconiere]

lol, i like it when the bars low! buy a jug and try the different metals out in it?

 

[dustinstriplin]

lol, i like it when the bars low! buy a jug and try the different metals out in it?

Not a bad idea, I might just do that.

 

[bracconiere]

Not a bad idea, I might just do that.

i'd say get your metals and the containers for them, glass of course...then weigh the metals before and after letting them sit in the collant for a week.....?? think that would be a good guess at if it's doing anything to them.....

 

[TheMadKing]

That's just inhibited glycol that's not intended for for food grade applications and pre-mixed with water. I don't know if its safe or not but you're just paying for water really. So in order for that to be effective you need to buy enough of it to fill your entire reservoir. You can't dilute it much and keep it's antifreeze properties.

My only recommendation is to go with the food grade propylene glycol. You only need 20 -30% mixed with water for it to be effective and it's $35/gallon on Amazon. 1-2 gallons should do it depending on the size of your reservoir.

 

[dustinstriplin]

I wasn’t planning on diluting the cheap solution. 4 gallons of the rv antifreeze would contain approx 1 gallon of glycol, at about $22.
Although the more I think about this, I think you’re right, madking. The pros of mixing pure glycol seem to outweigh the cons in this situation. The cost of knowing exactly what percentage is glycol, and the piece of mind in knowing that the solution won’t cause any problems Is worth a little extra money.