Aluminum Pot as Glycol Reservoir - Will it corrode?

[NeoBrew]

I'm just setting up for using glycol to cool my fermentation. For budget reasons I'm using my old fermentation chamber/chest freezer as my glycol cooler for now. My plan is to use an old aluminum pot in there with about 3 gallons of glycol:water mix at 1:2 parts.

I set the whole thing up with water last week just to test things out. I had planned to replace the water and put the glycol in there today. When I dumped the water there were crystalline deposits on the inside of the pot. I'm fairly certain this is aluminum corrosion. They brushed away pretty easily, but seem to have left the pot with "bumps" on the inside. Not sure if this is remaining salts or if it is pits in the pot.

I was using this pot to try to improve the temperature transfer from the freezer chamber to the glycol. This is an inherent weak spot of this setup. Can anyone tell me if I need to worry about the pot continuing to corrode? Will this affect the performance of the glycol?

Thanks in advance.

 

[day_trippr]

I typed "glycol aluminum" and Google filled in "corrosion" for me. That probably means something

"Studies show that uninhibited ethylene glycol will degrade into five organic acids - glycolic, glyoxylic, formic, carbonic, and oxalic - in the presence of heat, oxygen, and common cooling system metals such as copper and aluminum." Accompanied by a photo of some badly eaten up aluminum.

Further reading indicates there are many types of glycol solutions with some of them loaded with up to a dozen corrosion inhibitors. If your glycol isn't enhanced in a similar fashion you might want to find out if there's some kind of anti-corrosion package you can add. Otherwise I'd be looking for a plastic vessel...

Cheers!

 

[NeoBrew]

Yeah, I tried Google before I posted that. It was sufficiently technical enough that I couldn't really tell. I'm planning to use propylene glycol, which apparently has different properties than ethylene glycol which "RV antifreeze" is typically made from.

This paper looks interesting, but it is really studying the combination of copper and aluminum in a system. I don't believe there is any copper in my cooling loop. The coil is stainless, the fittings are plastic, and the pump is a magnetic drive pond pump with no visible metal in the water stream.

I also tried the system with a plastic bucket, which I have plenty of. I was just hoping to maximize heat transfer through the sides and bottom of the pot by using aluminum.

 

[day_trippr]

I expect plastics have higher thermal resistance coefficients than pretty much any metal, so if you think you need the lower resistance in the reservoir you probably want to find out about anti-corrosion packages...

Cheers!

 

[lablover]

A cheap stainless pot would be a better bet if you are worried about degradation.