Aluminum storage tank

[Isaac]

I've been searching without much luck on this topic. Can anyone give the advantages and disadvantages of an aluminum storage tank? I've been offered a 1000 gallon aluminum tank from a friend, free. Any issues with aluminum concerning galvanic corrosion, etc? My system will end up as an non-pressurized system at this point. But this project is lagging on for me after 3 years, so could change, like everything...

FWIW, I don't post much, and lurk a lot here, and appreciate all the good wisdom. Trying to pay it back, I finally posted some follow up photos on our spray foam and burial of lines on an old thread - You can see them here if it helps anyone else doing the spray and bury routine:
https://www.hearth.com/talk/threads/1-1-4-pex-al-pex-for-250-run.68981/#post-868336

 

[Clarkbug]

If you are dealing with non pressurized storage, I guess the corrosion issue may depend on your choice for a heat exchanger. What did you intend to use? Coils in the tank or a pumped flat plate? Or something else entirely?

 

[Isaac]

I was hoping not to use a heat exchanger, and instead thermo siphon by having the storage tank at a higher elevation than my boiler. It is a greenwood 200 - for better or worse...I've had it new sitting in the shed for 4 years now. But my hope is with 1000 gallons of storage I can burn in wide open when I burn, and eliminate some of the issues others have had with the greenwood. I know that running an open (non pressurized system) through my boiler can be problematic with corrosion, so I'm prepared to treat and test the water...figure it will be similar to maintenance with a Garn.

Back to your question, where you asking about coils in the tank because copper coils and an aluminum tank won't play nice together?

 

[tom in maine]

The steel heat exchanger in a Greenwood and the aluminum tank will not play well either.
You need to check with a corrosion inhibitor company.

IMHO, it is not worth the potential issues.

Every couple years, somebody comes up with an aluminum something for space heating systems. Whether they are baseboard radiant panels or other devices, they disappear after a year or two due to the galvanic problems.
An open system just compounds the potential corrosion issues due to the oxygen that is always present.

 

[Isaac]

The steel heat exchanger in a Greenwood and the aluminum tank will not play well either.

This is what I was wondering about. So despite them not physically touching each other, it will still be problematic? Also, it seems that the galvanic index of aluminum is between -.75 and -.90 depending on the alloy, and mild steel is -.85, which seems well within the acceptable tolerances to limit galvanic corrosion - but this isn't something I pretend to understand, and hence the question.

 

[bmblank]

You can find galvanic numbers online for various materials. The greater the difference between the numbers the worse the get along. Don't know how separating them with water would change things.

 

[Fred61]

I suspect you'll be plating the steel boiler with aluminum. You're boiler wants a PH above neutral and aluminum wants neutral or lower.