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Dissimilar metals and electrolysis

DanHolohanDanHolohan Posts: 14,875Member, Moderator, Administrator
edited August 2016 in THE MAIN WALL
I'd like to put together an article on this for the site and would love to include your thoughts and experiences. When do you think you need to protect against this? In all cases, or just some? How about retrofits to solve corrosion problems? Did it work every time for you? Any frustrations? Thanks for sharing with me.
Retired and loving it.
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Comments

  • nicholas bonham-carternicholas bonham-carter Posts: 8,082Member
    Wasn't there an engineering study made of this phenomenon, maybe in a southern university? In which case there must be a paper published of the research.
    You could also include anything on the effect of electricity flowing through pipes by accident, which could contribute to corrosion.
    This is a very interesting subject, full of popular misconceptions!
    I will be very interested in reading this.--NBC
  • hot_rodhot_rod Posts: 12,584Member
    `One of the key components to electrolysis is the conductivity of the water, or fluid being used.

    Water with a high mineral content, or water softened by ion exchange will show as a high TDS total dissolved solids.

    The more conductive the fluid, the more potential for electrolysis.

    I would suggest installers and troubleshooters invest in a meter to check the TDS of the fluid, and if necessary, reduce or eliminate the components in the fluid that contribute to high conductivity.

    Dan, you are welcomed to use any info in Idronics 18
    http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_18_na.pdf


    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GordyGordy Posts: 9,481Member
    I'll have to agree with Stephen on his own observations.

    It does take the right combination of things to occur.


    https://www.copper.org/applications/plumbing/techcorner/pdf/galvanic_corrosion.pdf
  • DanHolohanDanHolohan Posts: 14,875Member, Moderator, Administrator
    Thanks, guys. The right combination of bad things indeed. Is this a consideration at the start of the job? Or is it more a matter of dealing with it after it happens?
    Retired and loving it.
  • SWEISWEI Posts: 7,356Member
    We test the water if it's not from a known source. No major problems on new jobs since we have control over things like air ingress, make-up water and pH, and we almost always use some sort of conditioner.

    The 'interesting' problems get found on service calls and retrofits. Again, first we test the water -- at least for pH and TDS.
  • MikeSpeed6030MikeSpeed6030 Posts: 69Member
    edited August 2016
    If there is a problem with galvanic corrosion caused by dissimilar metals, then dielectric unions might be considered. However, there are a few problems. My gas-fired water heater (installed by an experienced, union plumber) has dielectric unions between the copper cold and hot water pipes and the water heater. But, a black steel gas pipe is connected to the heater, and the gas piping is grounded. The heater itself sits on steel legs resting on a concrete basement floor.

    My home's water piping, mostly galvanized steel but some copper, including the supply from the city's curb, is grounded - and it is connected to my steel boiler (which is 60+ years old, and working fine).

    The National Electrical Code requires that any metal piping that could conceivably become energized, be grounded. My city water supply comes underground via buried copper pipe, so it is obviously grounded. But, I have to have a solid copper jumper wire around my inside water meter in case the meter is temporarily removed for maintenance, and the downstream side would become electrically energized.

    My point is that it is very difficult, if not impossible, for me, to isolate dissimilar metals - everything winds up being connected together, electrically. The only way, I think, would be to build a new house with all plastic pipe. (In my area, plastic is used by the gas company on their buried supply up to the regulator and meter, which are themselves steel, but after then it's all black steel.)

    The electromotive series shows iron at -0.48V and copper at +0.345V. Apparently, that differential isn't enough to be a big problem. After I begin to hear of steel pipes or boilers and water heaters rupturing due to galvanic corrosion, I will probably not worry too much. The electrical code requires a copper ground rod to be installed at an electrical service entrance - so everybody has copper connected to their steel piping.
  • Solid_Fuel_ManSolid_Fuel_Man Posts: 1,884Member
    In northern Maine, I have only seen dissimilar metals create electrolysis in open systems where galvanized pipe is threaded into copper. Generally that is a water heater. I have a few installs approaching 15 years that I used a brass coupling and threaded a male copper adapter into one end and the galvi into the other with no signs of leakage yet. I have to wonder if some has to do with a female copper adapter threaded over a ferrous metal. Seems as though if copper is threaded into a ferrous metal I rarely (never) see a leak. I've wondered if it may have something to do with female copper adapters stretching.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • MikeSpeed6030MikeSpeed6030 Posts: 69Member
    Copper is relatively ductile while steel isn't. I can visualize a female copper threaded fitting, over a steel fitting, creeping. I don't think this is necessarily due to galvanic corrosion. Probably best to use brass female fittings in that situation. Brass is stronger and can be soldered for a transition to copper pipe.
  • ChrisJChrisJ Posts: 10,502Member
    edited August 2016

    Copper is relatively ductile while steel isn't. I can visualize a female copper threaded fitting, over a steel fitting, creeping. I don't think this is necessarily due to galvanic corrosion. Probably best to use brass female fittings in that situation. Brass is stronger and can be soldered for a transition to copper pipe.

    I stopped using female copper adapters.
    Brass coupler with male copper adapter. Seems to make a far better and stronger connection to me.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • SWEISWEI Posts: 7,356Member
    Same here, but mostly 304SS couplers (half the price of LF brass.)

    Copper FA's are still useful for transitioning to PVC. The best route we have found (which I believe someone here may have suggested) is to cut a threaded Sch.80 nipple in half and glue that end into a PVC fitting. This eliminates the problem of Sch.40 PVC threaded MA's snapping off. The PVC is not hard enough to oval out the copper FA.
  • hot_rodhot_rod Posts: 12,584Member

    Thanks, guys. The right combination of bad things indeed. Is this a consideration at the start of the job? Or is it more a matter of dealing with it after it happens?

    Dan, maybe you could get a lunch date with one of the technical guys from the Copper Development group. I think they have offices on Madison Ave. They have helped me with copper "pin hole" problems in the past, to
    determine causes and solutions.

    www.copper.org
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • DanHolohanDanHolohan Posts: 14,875Member, Moderator, Administrator
    Good idea, HR. Thanks.
    Retired and loving it.
  • Steve MinnichSteve Minnich Posts: 2,516Member
    I've never had problems with copper female adapters. Street 45's are a different story.
    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
    https://heatinghelp.com/find-a-contractor/detail/minnich-hydronic-consulting-and-design
  • Solid_Fuel_ManSolid_Fuel_Man Posts: 1,884Member
    Copper female adapters stretching is exactly what I was talking about. Seems the leaks at the transition where a female copper adapter is used could be mistaken for electrolysis.

    TS
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • delta Tdelta T Posts: 801Member
    I feel like dielectric have their own problems, and maybe this observation is caused by something else, but....

    Almost every single dielectric union I remove from an old water heater (regardelss of whether or not the union was leaking) the nipple into the water heater is packed with what looks like corrosion of the steel (dark reddish brown, chunky and hard). Again I have not really looked into what causes this, but I rarely see it if a female Cu adapter is used directly onto the heater.

    Local municipal water is very good. Since this seems like the appropriate post for discussion, anyone else see this? Anyone know of the cause? Is it just from the water heater going bad? Average age for water heater failure out here seems to about 10 years.

    @Stephen Minnich Yeah 1/2 copper st. 45's are the bane of my existence sometimes. such a pain to clean :s I too very rarely have problems with female copper adapters....
  • MikeSpeed6030MikeSpeed6030 Posts: 69Member
    True story: our buried water service from the street is copper and was installed in 1952. Once inside the basement, it connects to a galvanized steel threaded fitting and thence to galvanized water piping throughout the house. In 64 years there has been no problem. A few years ago, I disconnected that steel/copper joint in order to replace the original gate valve shutoff with a ball valve. I had no problem disconnecting the threaded joint and observed nothing that might be galvanic corrosion of the steel fitting (which I reused).

    The water main in the street is cast iron or coated steel, not sure which. But, my copper service line connects to the main somewhere or another.

    We have hot water heat. All the original hydronic piping is threaded black steel, but for a later room addition, copper piping was used. No problems so far.
  • SWEISWEI Posts: 7,356Member
    The real problem with copper female adapters is installers who insist on using 24" wrenches for 3/4" fittings.
  • ChrisJChrisJ Posts: 10,502Member
    SWEI said:

    The real problem with copper female adapters is installers who insist on using 24" wrenches for 3/4" fittings.

    I use a 12" adjustable on them but never felt I could really trust the joint I was making like I do with the couplers + male adapters.


    I had a leak recently with a street fitting I swear it was a 45. First leak I've had in a long time and it was in front of my dad when I did his recirculating hot water. I would've rather it happen on live tv as long as he didn't see it. Was just a pin hole that was spraying lightly on the block wall, almost didn't even see it.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • delta Tdelta T Posts: 801Member
    You know the one and only time I have seen my dad have a leak on a solder fitting was st 45, and that was two years ago. He has over 45 years in the trade now, 39 in business for himself, he KNOWS how to solder. I at least had little bit of gloating cred for a week or so ;)
  • Mark EathertonMark Eatherton Posts: 5,843Member
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Steve MinnichSteve Minnich Posts: 2,516Member
    I rarely ever have a leak, but when I do you can bet the farm it'll be the male side of a street 45. I keep using them because I'm stubborn and I hate losing to them.
    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
    https://heatinghelp.com/find-a-contractor/detail/minnich-hydronic-consulting-and-design
  • ChrisJChrisJ Posts: 10,502Member

    I rarely ever have a leak, but when I do you can bet the farm it'll be the male side of a street 45. I keep using them because I'm stubborn and I hate losing to them.

    You can say that again!
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • aircooled81aircooled81 Posts: 194Member
    Seperate the conductors, break the conduction.

    I beleive disimilar metals that leak ant point of connection are due to different expansion and contraction rates of the metal.

    Dieelctric unions, great idea, just not long term on hot and cold. I find these to leak over time because the plastic sleeves tend to break-down. Look inside one old one next time you pull it apart, you tend to see a mountain built-up at the steel connection.

    CTS Flanges, love 'em. The metals only come in contact through the bolts. Not the fluid. I can't remember ever fiding a corrosion point from say steel to copper with these babys.

    Always taught, "use 6" of brass to break electrolysis".
    Balogne. I think that doesn't stop the exchange of ions, it's probably brass doesn't corrode as fast as something with iron in it when water is present, so it takes awhile longer to deteriorate.

    Grounding. If your line becomes conductive, of any sort, the grounding point will be where the metal break down occurs.
    Maybe that's why you see disimilar metals fatigue and fuss at the threads. Teflon tape stops some of the threads grounding contact point, so the conduction through the few edges of thread touching the other metal have increased electrical current.

    Frequency drives, or any thing like a motor in the loop that creates emf. Motors create frequencys that can actually be measured. This potential travels through the motor windings, and into the motor shaft down into the impellar and valute. If it doesn't go through the bearings, then it can transmit into your piping system on its way to a grounding point.

    I silver braze copper pipe steel compressor connections often. Seen equipment 30 years old with these connections. Refrigerant vapor passing through that connection for hours a day that long, and no corrosion in sight..... We don't see leaks due to the disimilar metal. These leaks if any are usually due to a poor solder joint.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 6,556Member
    Anything buried in the earth is subject to current flow if it is metal. The earth is basically a big battery (because of the water and chemicals in the earth) and there is a lot of stray current flowing through it hence cathodic protection on underground oil tanks.
  • Jean-David BeyerJean-David Beyer Posts: 2,652Member
    "Was just a pin hole that was spraying lightly on the block wall, almost didn't even see it. "

    When I decided to run my indirect at 140F instead of 120F, I had a professional plumber do the installation. I included two thermometers and shut-off valves. I also had him replace all the 1/2 inch copper tubing with 3/4 inch. He did everything just right, but when he turned on the water, there was a drip running down the wall. It came from a 90 degree elbow. But it was not a bad solder joint. The damned elbow was manufactured with a pinhole leak in it. Plumber said they are getting more of these than ever.
  • Steve MinnichSteve Minnich Posts: 2,516Member
    I've had that happen with a 3" cast iron screwed fitting.
    Never copper but that sure would be an easier fix.
    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
    https://heatinghelp.com/find-a-contractor/detail/minnich-hydronic-consulting-and-design
  • FredFred Posts: 8,278Member
    Interesting, I just noticed I have a 1" copper elbow, in the basement, with a pinhole leak in the side wall. Guess that will get attention very soon.
  • ChrisJChrisJ Posts: 10,502Member
    Fred said:

    Interesting, I just noticed I have a 1" copper elbow, in the basement, with a pinhole leak in the side wall. Guess that will get attention very soon.

    By very soon I hope you mean within the next 10 minutes?

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Larry WeingartenLarry Weingarten Posts: 1,677Member
    Hello: Reading Dan's question, I see it could apply differently to open and closed systems. I've got pretty hard water here, so In open systems, salt softened water can greatly speed up copper corrosion and anode consumption in water heaters. Standard dielectrics can fill with rust pretty fast; one to two years. "Modern" steel pipe fails before the old pipe it was installed to repair.

    To prevent problems around water heaters, I bond and ground everything and use lined steel nipples in the tank to copper or stainless flex connectors that have true dielectrics built in. Once had a commercial water heater lasting only four months! It was stray current, which was fixed with a little six gauge copper wire. Corrosion is an important topic for us all to understand. NACE http://www.nace.org/home.aspx is a good resource. ;)

    Yours, Larry
  • DanHolohanDanHolohan Posts: 14,875Member, Moderator, Administrator
    Very helpful, Larry. Thanks!
    Retired and loving it.
  • hot_rodhot_rod Posts: 12,584Member
    The author talks about to cost of corrosion to the military every year, from ships to vehicles and airplanes sitting around airfields. Everything from the structure to the electronics. Staggering amount of $$
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • ZmanZman Posts: 5,532Member
    hot rod said:

    The author talks about to cost of corrosion to the military every year, from ships to vehicles and airplanes sitting around airfields. Everything from the structure to the electronics. Staggering amount of $$

    Loved the book, I am thinking best seller list...
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • DanHolohanDanHolohan Posts: 14,875Member, Moderator, Administrator
    That book is one of the best I've ever read.
    Retired and loving it.
  • FredFred Posts: 8,278Member
    ChrisJ said:

    Fred said:

    Interesting, I just noticed I have a 1" copper elbow, in the basement, with a pinhole leak in the side wall. Guess that will get attention very soon.

    By very soon I hope you mean within the next 10 minutes?

    Lol, In the next month or two. It's so tiny, it will drip a drop or two for a day or two and then, I guess mineral deposits block it and it doesn't drip for weeks. I said I just noticed it because I thought it was condensation until I saw the rest of the pipe was dry and I looked at the area with a flash light. I can see a little mineral build-up right in the center of the side wall, but not an urgent situation. I'll get to it soon enough (or NOT) :)
  • MikeSpeed6030MikeSpeed6030 Posts: 69Member
    Fred, most hardware stores sell special pipe-clamp repair kits to stop small pinhole leaks. They work OK for a straight section of pipe, but probably not for an elbow. If and when you decide to fix it, you will probably have to cut out and replace the leaking section. You may be able to get by with a Shark-Bite repair.

    It seems like copper pipe is more prone to pinhole leaks - either due to defects or to picture-hanging nails than steel pipe. Probably PEX is also good.
  • FredFred Posts: 8,278Member
    Thanks @MikeSpeed6030 . I figure I will cut through the 90 right in the center of the elbow and heat each end up to melt the solder, clean those ends up and sweat a new 90 there. It's a half hour job, just got to get to it and do it.
  • Larry WeingartenLarry Weingarten Posts: 1,677Member
    Hello: It might be entertaining Dan, to have a look at this report from NACE: http://www.nace.org/uploadedFiles/Publications/ccsupp.pdf It's about the cost of corrosion in the US. They throw around billions the way I throw abound fivers! :o

    Yours, Larry
  • DanHolohanDanHolohan Posts: 14,875Member, Moderator, Administrator
    On it! Thanks, Larry.
    Retired and loving it.
  • rlaggrenrlaggren Posts: 159Member
    Done a hundred water heaters. around the SF bay area. 90% of the dialectrics are just plain ugly awful - doing good duty as filters. FIP's to the lined nipples do better; not real great, though. So it's just flex connectors or brass nips; the brass seems to work OK and the connectors never seem to have a problem, provided they're not installed w/a leak.

    I've been watching a 1" MIP c to cast steel fitting under one of the radiators in my sister house for about 10 years. It was installed sometime maybe late 70's... Radiator can cook eggs most days in the winter so clearly no flow problems. But to be clear, the water here seems very gentle w/galvanized pipes - at least old one. Most water pipes in the house date from the 60's or before and every one I've cut has been virtually clean inside.. The boiler might have been drained twice in the last 15-20 years and AFIAK it's not leaking. So that probably helps w/any corrosion issues, too.

    Rufus
    disclaimer - I'm a plumber, not a heating pro.
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