corrosion

ht in pa_2

thanks Ray; it is a GB142 Buderus. I've always heard, with a C.I. boiler (with the water at 180+ deg.) the iron pipes won't corrode, because there is no oxygen in the water. With the Mod Con boilers, the system water doesn't get hot enough to get the oxygen out, so will the pipes and radiators corrode?

ht in pa_2

corroding pipes with Mod Con boiler?

I'm about to install my 2nd G-124 condensing boiler. With the system water temp. at 140-150 deg., what keeps the 60 year old black iron pipes and cast iron radiators from corroding? Thanks for any insight on this. ht

Ray Landry_2

do you mean a GB 142 condensing boiler? The inside of CI rads or old iron piping will never corrode due to low system water temps, I think that you are thinking of condensation which can occur in a non condensing boiler if the combusion chamber gets below 136 degrees. That is on the fire side that the wrotting will occur, not on the water side.

Ray Landry_2

nope, with proper air removal devices as well as purging of course that should get rid of any air problems. Pumping away from your expansion tank helps too. But the temperature of the water really doesnt play a factor in air removal.

Perry_2

Half truths....

Hmmm... So where did all the oxygen that was in the water initially in a 180 F system go? I corroded some iron until it was gone. Then, as long as the system is sealed - with no routine water (or air) addition; corrosion stops because there is no more oxygen source.

Same will hold true at lessor temperatures; and yes, it will corrode the pipes and cast iron radiators (you do not need temperature to have corrosion).

Corrosion in and of itself is not bad. The key is that you want the corrosion of steel (and cast iron) to occure as magnatite - the black stuff. This stabilizes and actually forms a protective layer on the pipe and radiators. Red collored rusting in the system is a bad sign as it is an "active" rust that can remove substaintial amounts of material.

My guess is that 140 F will be pleanty to convert the rust into magnitite as long as their is no leakage of oxygen into the system.

Perry

ht in pa_2

thx Ray for the info.

ht in pa_2

thx,Perry for your detailed information.

hr

I'd suggest a Rhomar treatment

especially in a multi metal system like you propose. The aluminumn is very ph sensitive. The Rhomar will scavange remaining O2, balance the ph, and provide a thin film protection. I'd highly recommend their cleaner,also multi metal, first. www.rhomarwater.com

Best not to use a TSP cleaner, or any high or low ph products on aluminum!

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Ken_40

Mmmm

Bob,

As a proponent of TSP cleanings of virtually all (even those with Al) hydronic systems, you may have overlooked one critical point.

My advocacy of TSP cleaning is based on the assumption that the cleansing period is combined with relatively high heat, total circulation and total draining the cleaning the TSP solution and the junk it carries - BE COMPLETELY DRAINED and REFILLING AND RE-BLEEDING THE ENTIRE SYSTEM...

BEFORE putting the system into service.

Examination of aluminum blocked boilers and a few looks at P-A-P tubing shows no evidence of corrosion from a one or two hour system cleaning; but then, we tended to be more thorough than most in this area of water-side cleanliness than most. We assumed rinsing and purging was always as important as the actual TSP cleaning itself.

hr

TSP for steam

I've heard is a good method because it leaves the system a bit on the alkaline side. TSP being about ph 11. But you really want to be sure to flush and buffer that number if it is aluminum, or even copper for that matter.

Clean ALL new and rebuilt systems, and more important flush them well. It takes some time to do this final step. Plan a couple 3 hoursor more in your bid, and generally a second trip after the cleaner works for a 12 hour or longer period.

Really dirty systems mat require a second round of cleaner.

Not a bad idea to check the fill water quality at that time. Hate to see any system filld with real hard water. If defeats the purpose of a good cleaning.

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