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Water chemistry w/Aluminum boilers + Iron radiators

Recently I was at a training session held by a PEX manufacturer and received the following information from them when we were discussing system water chemistry and boiler types:

"Issue:
A development in the boiler market has seen the use of Aluminum (AI) heat exchangers in boilers. Aluminum is in greater use for several reasons - the most important being lower cost, lower weight and greater heat exchange when compared to other metals. However, the use of Aluminum does create issues when treating the water for corrosion protection.

Aluminum is amphoteric, which means it will "dissolve" in both acidic and basic environments. Aluminum likes to be in more of a neutral environment compared to brass, copper and steel. The ideal pH range for a system that contains Aluminum is 7.0 to 8.5. The current recommended pH for a closed loop system utilizing ferrous components (i.e. primarily steel or cast iron heat exchangers, piping and fittings., pump housings, etc.) is 9.0 to 10.5.

The approved corrosion inhibitor is still Molybdate at 100 to 150ppm. Unfortunately, the current Molybdate inhibitor is buffered to a pH of approximately 9.5, which is too high and will cause an increase in the Aluminum corrosion. On the other side of the problem, if we were to reduce the pH in to the 7..0 to 8.5 range, we would see a dramatic increase in the corrosion of any Iron in the system. Any brass, copper or stainless steel would perform without any significant damage at the lower pH.

Answer:
When systems are integrated with an aluminum boiler, it will require a Molybdate b1end that will be optimized for Aluminum treatment. This will include a lower pH buffer into a more neutral range. Please contact your local representative for further information.

Additionally, if a boiler with an Aluminum heat exchanger is going to be used and treated at the more neutral pH, it is very important that no Iron based components be used in the system.. If Iron based components are used in the system; you will see rapid degradation of these components. Brass or stainless steel can still be used in the system without issue.

(XYZ) manifolds contain only brass and stainless steel metallic parts. Iron is usually introduced by secondary system components such as pumps and radiators. PEX pipe is also very chemically resistant, and is not affected by pH level that would be required when using an aluminum boiler. "


We now have several aluminum block condensing boilers on the market - Buderus 142, Dunkirk Quantum, Weil-McLain Ultra. I'll bet that a number of these boilers are being installed as upgrades in homes that have cast iron radiators or iron baseboard rads.

If any of the boiler manufacturers are here, I'd appreciate hearing your thoughts about whether or not these aluminum block boilers can be piped-in with cast iron rads at all, and if so, under which conditions without long term detrimental effects on either the boilers or the radiators.

It seems to me that if the pH and corrosion issues listed above are real, the question becomes how long can we expect to wait for failures to start appearing in the field. It's one thing for a boiler manufacturer to replace (quietly) a corroded boiler, but an entirely different thing for radiators to be eventually held together only by the paint on them and having them fail.
Roohollah

Comments

  • Ted_9
    Ted_9 Member Posts: 1,718


    You have my attention.

    I hope you get some manufacture responses.

    PATRIOT HEATING & COOLING, INC.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Great Post--Hope it Gets Great Answers!

    In my own little corner of the world an aluminum HX scares me. I've seen what the local water does to aluminum and even if it is low-grade aluminum, it's not pretty and it's FAST!

    Have also seen the insides of enough OLD steel/iron systems (pipes, radiators and boilers) to know that, untreated, there's amazingly little corrosion and scaling despite our hard, alkaline water.

    Personally, I have zero desire to be committed to continual monitoring/treatment of system water when the tap seems ideal if you're not using aluminum...
  • hr
    hr Member Posts: 6,106
    I'm not sure I follow your statement

    "On the other side of the problem, if we were to reduce the pH in to the 7..0 to 8.5 range, we would see a dramatic increase in the corrosion of any Iron in the system. Any brass, copper or stainless steel would perform without any significant damage at the lower pH".


    Keep in mind in order for corrosion to occur in any system you need O2 present! The treatments for aluminum boilers on the market Rhomar, Fernox, and Nobel No-Burst all contain O2 scavangers, ph buffers, and film providers to handle all these challanges.

    The O2 scavanger is the key component in hydronic glycols that needs to be watched and boosted. This is exactly why non barrier tube will kill a glycoled hydronic system in very short ordes. The O2 scavanger inhibitor gets consumed quickly and ph plumets. The hotter you run a non barriered tube system the higher the O2 ingress through the tube wall. The early non barrier rubber tube systems sure did prove this out. Especially high temperature staple ups! Been there!

    Yes the ph you mentioned is important for a healthy aluminum enviroment, but you are leaving out many other important ingredients from your list :)

    I think the Rhomar product has 30 some chemical mixed to allow aluminum, copper, brass, stainless, iron, steel, plastic among others to get along together in a closed loop system.

    A big part of the reason why these "aluminum friendly inhibitors and glycols are so $$$!

    While fairly new to the US market, aluminum boiler blocks have been around for years. MZ, Dunkirk, Patterson Kelly, Buderus, and others have adopted proven technology when they chose the alloy and casting methods for their boilers.

    Keep in mind also aluminum engine blocks have been around a long time. These see as harsh, or worse, fluid and thermal shock conditions from extreme temperature swings than most boilers. A car engine can go from -30°F or lower to 200°F plus in a matter of minutes. That's a lot of thermal stress. Ever see what gets dumped into a cars cooling system at times.

    Also consuider water cooled outboard motors. talk about a tough living condition. the get salt water and byproducts of two cycle exhaust thrown into the mix! they still use aluminum :)

    Keep in mind stainless boiler blocks face some real water quality issues also. While not as ph sensitive, chlorides and other water issues are very critical in stainless steel boilers.

    How many if any of us are testing the chloride levels in the fill water for stainless boilers?? Anybody? Buehler, Buehler, anybody :)

    Notice in many stainless indirect installation manuals chloride levels are spelled out and warranty void if exceeded!

    The battle of the non ferrous's! Going to be an exciting ride :)

    hot rod

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    Roohollah
  • jerry scharf_2
    jerry scharf_2 Member Posts: 414
    Wait for George @rhomer to post

    Jason,

    Rhomer has researched this carefully and have a treatment that works for all of the above. I believe it's buffered to somewhere around 8.

    I think this treatment is going to become more and more standard as people begin to see the aging problems of new boilers with untreated water. But I forget, people will blame it on the pieces of junk the manufacturers are now making. :(

    jerry
  • hr
    hr Member Posts: 6,106
    I'd be curious, Jason

    to know which manufacture gave you that info. Seems they are seeing a very small part of the issue with aluminum, and possibly spreading some misleading info.

    Sorry I don't have a scanner. Here is some more info on aluminum and hydronics.

    hot rod

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  • Jason Horner
    Jason Horner Member Posts: 58


    Hot Rod,

    I'll give up the manufacturer's name later, after some further discussion on The Wall. I just didn't want to have the discussion reduced to "Vendor X is full of it".

    Their comments during the training were strictly around the importance of understanding all aspects of water treatment including microbiological issues, and was not to say that a compromise in water treatment can't be found for aluminum boilers (for example, a combination of Molyb + nitrite may be the answer). They were NOT saying anything bad about aluminum boilers or indeed any boilers - they were merely pointing out some issues to be aware of.

    In a totally radiant floor application with o2 barrier PEX there is so little ferrous material in all the circulators, valve stems, etc. or o2 in the system that it probably isn't an issue.

    But my question was directed more at the situation where an aluminum block boiler is sold into a replacement boiler situation where the vast majority of the system is iron pipe and rads. You *potentially* wind up with galvanic issues and deposits which can kill an aluminum boiler or kill the rads - and your boiler warranty too.

    I was just hoping to stimulate some enlightened discussion.
  • Jason Horner
    Jason Horner Member Posts: 58


    > "On the other side of the problem, if we were to

    > reduce the pH in to the 7..0 to 8.5 range, we

    > would see a dramatic increase in the corrosion of

    > any Iron in the system. Any brass, copper or

    > stainless steel would perform without any

    > significant damage at the lower pH".



    I recall that they were speaking of galvanic effects when they mentioned this. Even though there is little/no free o2 in the system, there is still electrical potential between the differing metals. Brass, copper, and stainless are relatively 'inert', whereas aluminum and iron are more reactive.
  • DaveC
    DaveC Member Posts: 201


    My experience is in diesel engine cooling systems which are surprisingly similar to hot water heating systems. Here we run pH levels up to around 10.5 with no ill effects on aluminum components and 11.0 is considered the maximum. We like to keep it above 8.5 for iron protection. I would not worry about a pH up to 9.5 or so. There may be issues with galvanic corrosion which happens when dissimilar metals are connected mechanically and in contact with a conductive fluid such as water or antifreeze. These problems might not be identified correctly.
  • Ken_8
    Ken_8 Member Posts: 1,640
    I am still a strong

    advocate of TSP washouts and NO CHEMICALS! Just follow up with clean water rinse outs.

    Hot Rod's right. In a closed system oxygen is not an issue.

    Trace amounts of the TSP will leave the water between 7.2 and 8.

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  • eleft_4
    eleft_4 Member Posts: 509
    OK, Mark

    I have been running and repairing diesel powered equipment for 50 yrs. You are correct on the dissimilar materials used in the cooling system.

    The coolant "always" had to be treated to prevent galvanic corrosion from causing pin holes in the wet sleeve cast iron liners, which allowed coolant to leak into the crankcase oil.

    Most engine units have a water conditioner filter spin on unit. Others required additives, I recall nal-cool, a purple liquid, I used from the early 60's if the equipment did not have a spin on water conditioner.

    Why not learn from another industry with similar circumstances.

    al
  • Mark Mathys
    Mark Mathys Member Posts: 30


    Hi Al

    Yep Nal-cool is one of the more popular coolant additive chemistries in use today. In engines we have a lot of problems with electrical grounds and stray currents causing severe corrosion. I can see where there is a good potential for this to happen in boilers since there are many electrical controls and could leak currents. We also have problems with vibrations and air entry. Every time an engine is shut down is sucks in air. I know this is a cause for many of our problems but I don't know a good cure.

    I put together a presentation on Coolant and Cooling system problems if you are interested. It has some good info on additives and corrosion control.

    It is at http://www.butler-machinery.com/oil.html click on the Coolant and Coolant Analysis Presentation to view the slides.

    I would be very concerned about a pH level near 7.0 in a system that contains iron. I can't argue with success but my training tell me to watch out.

    Mark
  • hr
    hr Member Posts: 6,106
    Most tap and city water

    is going to run somewhere in the 7's from my experience. i would guess maybe 90% of hydronic systems out there run plain potable water from city or well.

    Most do not have corrosion issues UNLESS they have an ingress of O2.

    Older vintage copper and cast iron boiler systems hardly ever have corrosion issues.

    It wasn't until non barrier tubing got throw intothe arena they we started seeing major corrosion issues started with solaroll, pb came along without barrier, then more rubber without barrier...

    hot rod

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  • Buehler, Buehler, anybody :)

    LOL

    hr you are so right. I currently test for Ph level only. Most allways city tap water. The water supply in the US is the best in the world right?





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  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    Nefit Fasto...

    Boschderus' (NEW COMPANY NAME, 20 point bonus...) small boiler maker from Holland, has been applying their aluminum block boiler with Buderus steel panel radiators and other thin panel radiators for over 20 years. If it were a problem, I'm sure they would have brought it to our attention...

    Who is this masked man (company) and what are they selling?

    ME

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  • Dan Peel
    Dan Peel Member Posts: 431
    Bosch

    Word from Boston is that Bosch has purchased Buderus and will be marketing a variety of low water content wall hung boilers along side their instantaneous hot water products in the new year........Stay tuned.....Dan

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  • Drew_2
    Drew_2 Member Posts: 158
    Metal Corrosion

    I've attached the ASTM test results on Water, uninhibitted propylene glycol, our Noburst -100 for standard systems and Noburst AL for aluminum and all metal systems. You may be shocked with the results of plain water and plain PG.
  • Drew_2
    Drew_2 Member Posts: 158
    Metal Corrosion

    I've attached the ASTM test results on Water, uninhibitted propylene glycol, our Noburst -100 for standard systems and Noburst AL for aluminum and all metal systems. You may be shocked with the results of plain water and plain PG.
  • Drew_2
    Drew_2 Member Posts: 158
    Metal Corrosion

    I've attached the ASTM test results on Water, uninhibitted propylene glycol, our Noburst -100 for standard systems and Noburst AL for aluminum and all metal systems. You may be shocked with the results of plain water and plain PG.
  • Drew_2
    Drew_2 Member Posts: 158
    Metal Corrosion

    I've attached the ASTM test results on Water, uninhibitted propylene glycol, our Noburst -100 for standard systems and Noburst AL for aluminum and all metal systems. You may be shocked with the results of plain water and plain PG.
  • Jason Horner
    Jason Horner Member Posts: 58


    Drew,

    Sorry to be so dense....
    I presume that the ASTM test defines a specifc duration for the test - how long are the test specimens tested for? Are the test results are for that duration?

    Also, the last entry in the table-- Cast Alunimum @Heat.....what does that really mean?
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490
    listening

    Retired and loving it.
  • George_10
    George_10 Member Posts: 580
    Rhomar's Answer to multimetal systems.

    Both of our products, the Hydro-Solv 9100 cleaner and the Pro-Tek 922 treamtent can be used with any of the metals currently found within modern hydronic systems.

    We did this on purpose, as we knew that these systems are being built with many different metal componants.

    Both products are enviromentally friendly and safe to use with all of the componants.

    On our website WWW.rhomarwater.com this is can be readily seen in our tech sheets for both of these products. They are printable pdf files which can be found under Hydronic Products. You will need a free version of Acrobat reader to print them out.

    I will answer any questions or concerns by just giving me a call at 800-543-5975.

    Hope this helps. Any help you need is only a phone call away. These new systems must be treated correctly, or they will cause the contractor problems that do not need to happen and are easily preventable.
  • dconnors
    dconnors Member Posts: 215
    water quality

    i will attach our sheet
  • Drew_2
    Drew_2 Member Posts: 158
    ASTM

    Jason, Off the top I don't recall the exact specs for the test, but it goes something like; A coupon of each metal of a specific weight is placed in a glass container with the specific fluid. The fluid is brought to a temp. (I beleive it's 180/190 degrees F)and run at that temp for a specific period of time. The coupons are removed and the weight recorded. The difference in the weight is the loss/corrosion of the metal. This is not the exact test, but it may help.
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    These conditions are not the same as field conditions...

    They are obvioulsy being exposed to a lot of free oxygen in either the hot or cold test.

    How do you explain the +2 reading for aluminum? Scale accumulation?

    ME

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  • Ted_9
    Ted_9 Member Posts: 1,718


    Lets keep this disscusion going.

    PATRIOT HEATING & COOLING, INC.

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  • jerry scharf_2
    jerry scharf_2 Member Posts: 414
    read an article that said treating water could be bad

    Interesting line of reasoning:

    You add a mixture of corrosion inhibitors and oxygen scavengers. The water receives no mainenance (that's easy to believe) and the oxygen scavengers get used up. When a breakthrough finally occurs in the inhibitor layer, the corrosion will be localized and do much greated damage.

    What do people think??

    jerry
  • Constantin
    Constantin Member Posts: 3,796
    Well, I voted with my wallet.

    ... as an engineer, I can readily see the need to perform proper PM on a sophisticated heating system that I just spent $$$ to have installed. George Hunt at Rhomar gave me an informative assessment of the water currently found in our system, suggested cleaning steps, etc. in his inimitable, hospitable style.

    Currently, several gallons of cleaner and conditioner are on their way to me and I look forward to flushing and conditioning the system. In fact, I wish I could do a before and after study to see if the thermal efficiency of the boiler picks up a notch or not as a result of the cleaning/passivation (as I suspect it would) but you can't have everything in life.

    If the above line of reasoning was true, then none of the extant hot water systems in which almost all free Oxygen has been scavenged and turned to rust would be still in existence today. There is a reason that cast-iron-bodied pumps don't last very long on open-systems while the same pump on a closed system may last for decades...

    Along similar lines, if a system has a persistant leak and a water feeder that keeps replenishing it then either scaling or the constant Oxygen supply will kill the rest of the system in short order, right? So, I'm not convinced that an inhibitor would suddenly cause a greater catastrophic failure in the absence of Oxygen scavengers but am happy to be educated otherwise.
  • hr
    hr Member Posts: 6,106
    I agree, Jerry

    if you install treatments or glycols they need to be checked and maintained. We use stickers to alert owners what is in the system, date, and maintenance requirements.

    Theoreticaly (sp) there should not be a lot of O2 ingress once the system is purged and buttoned up. Unless it's non barrier tube, of course :)

    hot rod

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  • Constantin
    Constantin Member Posts: 3,796
    Shouldn't there be tests, regardless?

    Many people send samples of their engine oil to labs to see if there are any metals, etc. in abnormal concentrations. Similarly, an expensive heating system could benefit from periodic benchmarking, whether it has been glygolized, treated, etc. , no? There is far more money in your average heating system than any car, yet I doubt that even the most meticulous maintenance guys and gals would bother to check the water on a non-glycolized system. Besides, how would they do it, short of sending samples into a lab or just measuring pH?

    As George explained it to me, their system contains a marker that allows a contractor in the field to gauge how much treatment is still left in the system. That seems like a pretty good approach rather than sending in samples and trying to track the health of the system that way. For example, short of a water meter on the auto-fill, you'll have a pretty good clue when something is leaking.

    The solar hot water side of our system is what is giving me the willies. I don't like the thought of super-hot solutions with propylene glycol getting zapped on the roof but that's where a lot of care and thought will have to be applied to keep that system happy. Once again, I will try and rely on George and his band of merry water treatment specialists to keep our system well-maintained and happy.
  • George_10
    George_10 Member Posts: 580
    An unchecked system is always a possible nightmare

    We recommend that our system treated systems be checked at least once a yr. The treatment can be used up, with specific concern about our oxygen scavenger. If O2 is diffusing into the system via tubing or leaks or adding fill water, then the oxygen scavenger will be used up. The system will still be protected for a while as the metals have been passivated. However, this is why we suggest the annual inspection.

    This is still far cheaper than replacing 13 cir pumps that a contractor just told me about just last week.

    The real cost in our program is found in the first year. In future years in a tight system, the added treatment should be minimal.

    A properly cleaned and treated system is a far better gamble than not doing it. And I have the contractor problems to prove it in uncared for systems.

    If this idea was not cost effective, then all of our industrial clients would not be doing it. Company comptrollers do not waste money. They want pay back and we deliver by giving them sound advice. This home heating area is no different, it is just a new way of thinking for many contractors that have home owner clients.

    I would be happy to answer specific questions. Call me at 800-543-5975.
This discussion has been closed.