Cleaning Corrosion - good idea?

SteamIsNotMyThing

If this isn't seen as directly steam related, I can post in another forum.

https://forum.heatinghelp.com/discussion/182417/time-for-a-new-radiator

Dunkirk P4B - no idea install date but I bought the house in 2009.

A while back, I posted photos and got excellent feedback above.

Today, I was cleaning up and noticed a lot of corrosion on the back of the boiler (near the return) See photo.




Few questions.
1) Any idea how long do I have? Despite how it looks, underneath is currently dry.

2) Can I clean this with a wire brush or similar? Or, it way too late and would this likely create a massive issue?

3) Time for a new furnace or can a plumber actually repair this?

Thank you.

KC_Jones

That was leaking as can be seen by the streaks. To my eye it looks like it either rusted closed or has a bunch of mineral deposits sealing it back up.

I wouldn't touch it unless it was to fix the pipe. It could hold for a day, it could hold for 2 years, can't really predict it.

A professional should be able to fix that, how expensive and how long it takes depends on how hard it is to get out. Seeing the copper indicates to me it shouldn't be too hateful of a job.

acwagner

My guess is that's galvanic corrosion, since it's around the whole pipe and the bushing into the boiler. It may also be eating the boiler vessel, in which case time for a new boiler.

Definitely get someone to come out and look at it. As @KC_Jones said, hard to predict how long it will hold. Better to have a plan to deal with it than have it be an emergency call.

ethicalpaul

Don't touch it nor let anyone else touch it until spring

Why don't I ever follow my own advice?

The Steam Whisperer

We regularly se this nipple fail on older steam boilers. Typically the fresh water enters at this point into the boiler and a lot of oxygen is freed from the water as it hits the hot boiler water. Pretty unlikely it has anything to do with galvanic corrosion. We see it all the time on boilers all piped in steel pipe, and CI or Maleable Iron fittings. I'd look to see if you are using excessive amount of feed water into the system.

Ron Jr._3

Looks like it had a slight leak at one of the threads for a good long while. Like EthicalPaul suggested , I wouldn't touch it till warmer weather is here. But it can be removed and replaced if you're going to hang on to the boiler. 

SteamIsNotMyThing

Thank you all, as @ethicalpaul and others suggested, will not touch until spring! @The Steam Whisperer (Formerly Boilerpro) - I definitely was adding water regularly due to other issues that I have now repaired - valve spitting 32oz water daily due to clogged radiator return.

I now look at the manual feed valve as a slow poison and avoid unless absolutely necessary.

SlowYourRoll

newbie question here...could the pH of the boiler water influence the rate of corrosion? galvanic corrosion uses the boiler water as an electrolyte to complete the circuit, and i'm seeing a couple articles that indicate the rate of galvanic corrosion jumps up as the electrolyte gets farther away from neutral pH (in either direction) which seems to make intuitive sense, since saltwater is much more conductive than freshwater. i was thinking if OP is trying to squeeze a few more months out of this system before replacement, maybe bringing the pH closer to neutral could help.

ethicalpaul

The accepted wisdom says that a higher ph of 9-11 will greatly reduce or prevent iron oxidation 

SlowYourRoll

ethicalpaul said:

The accepted wisdom says that a higher ph of 9-11 will greatly reduce or prevent iron oxidation 

i was going off this article that showed the galvanic corrosion staying low from pH of 6-10 but then really shooting up over 10

https://iopscience.iop.org/article/10.1149/1.2428681/pdf

SlowYourRoll

but that's just one paper

ethicalpaul

That paper is discussing galvanic corrosion in an aluminum-steel coupling.

SlowYourRoll

ethicalpaul said:

That paper is discussing galvanic corrosion in an aluminum-steel coupling.

the two metals used wouldn't matter for determining the influence of pH. in terms of equating galvanic corrosion to an electric circuit (which is essentially what GC is), the two metals determine the voltage drop (so aluminum-steel will have a different voltage drop than iron-copper), but the electrolyte completing the circuit (the boiler water) determines the resistance in the circuit. so regardless of if you had either aluminum-steel or iron-copper, if you theoretically had deionized water with a perfect pH of 7.0, there would be no galvanic corrosion.

(as an aside, i said "theoretical" because actual deionized water would start ripping ions off of those metals the second it came into contact with them. it is the ions that carry charge through an electrolyte, so it makes sense that deionized water can carry much less current. i suspect this is why the accepted wisdom leans towards pH over 8, cause if you were trying to drive the pH down much lower the water would just end up leaching ions right from the metal)

so with the electric circuit analogy, the current in the circuit represents the rate of corrosion, since the movement of ions (anions and cations) to and from the anode and cathode (the dissimilar metals) is both what constitutes the movement of charge (electrical current) and the displacement of material from one metal to the other.

so bringing it all together, different metal pairings have different voltage drops between them driving the reaction, but more electrolytic the boiler water is (i.e. the more alkaline it is from having more electrolytes dissolved in it), the lower its resistance to current flowing across that voltage drop, and the more galvanic corrosion you will have.

ethicalpaul

Thanks for that! But my next question is...where is the copper? I see an iron fitting going into a presumably steel nipple. There is copper on the other side of the iron fitting, but there is no significant corrosion there...it only appears on the other side of the iron fitting.

but I am very ignorant of how galvanic corrosion works so maybe there's a simple explanation

AdmiralYoda

Below is from the Peerless 63/64 series manual.  I shoot for a ph of 10ish but still haven't had the other properties checked.  We are on city water.

SlowYourRoll

The Steam Whisperer said:

Pretty unlikely it has anything to do with galvanic corrosion. We see it all the time on boilers all piped in steel pipe, and CI or Maleable Iron fittings. I'd look to see if you are using excessive amount of feed water into the system.

There's still a voltage drop across steel pipe and cast iron fittings. how much depends on which type of steel. if it's galvanized steel then it's basically designed to give off ions in galvanic corrosion (zinc is one of the most anodic metals, so a galvanized steel pipe can have galvanic corrosion with pretty much any common metal aside from other galvanized steel fittings). the other steels can have a smaller voltage drop to cast iron, but even carbon steel and stainless steel have a potential for GC with iron according to this chart (https://www.grabberman.com/Media/TechnicalData/127.pdf). of course the voltage drop is only one of the requirements for GC, the boiler water will also need to be a strong enough electrolyte to carry the current, but, respectfully, i do not believe GC can be ruled out between steels and iron, although the risk of GC is definitely lower for all steel-iron pairings other than galvanic steel.

SlowYourRoll

ethicalpaul said:

Thanks for that! But my next question is...where is the copper? I see an iron fitting going into a presumably steel nipple. There is copper on the other side of the iron fitting, but there is no significant corrosion there...it only appears on the other side of the iron fitting.

but I am very ignorant of how galvanic corrosion works so maybe there's a simple explanation

well you could be right, the GC could be between the steel and the iron. the copper is threaded on there, and i don't know enough about plumbing to know what's going on with that pipe paste at that threaded connection. basically if the pipe paste manages to perfectly isolate the copper from the iron so that the copper and iron never directly touch, then the copper would not be connected to either the iron fitting or the steel nipple, and could not be part of that electric circuit. however if the copper and iron do come into contact anywhere then that copper would very much be part of that electric circuit.

as to your second point, galvanic corrosion has a one-way transfer of material from the metal that's the most anodic to the metal that's the most cathodic, leaving every other metal in the "circuit" untouched. so if this were GC between the steel and the copper piping, the steel would be the cathode, the copper would be the anode, the iron fitting would be untouched, there'd be a flow of electrons through the pipes themselves from the copper to the steel, and there'd also be a flow of copper ions through the boiler water that would then land on and attach to the steel. so like in the figure in this link shows, the material is all leaving the anode and accumulating on the cathode (https://www.solaracks.com/wp-content/uploads/galvanic-corrosion-explained-1024x654.jpg).

BUT! actually your question raises more questions for me and i'm about at the limit of what i know, but i will put my new theory in the next post cause it explains something i should've noticed before but didn't. so thank you for that.

SlowYourRoll

sorry for the above posts, i'm not an expert and not trying to pretend to be an expert, just kind of trying to piece this together. and in the process i missed something, which is that it seems like all the material has accumulated on the outside of the steel nipple. so for that to be GC, the electrolyte should really be on the outside of the pipe. that's where that pesky leak comes in to my new theory.

so that aluminum jacket that surrounds the boiler is actually going to be in electrical contact with that steel nipple, since both are going to be attached to the boiler structure. so we've got (1) two dissimilar metals (and aluminum alloys are very anodic, they love to give up ions of whatever metal they were alloyed with, and (2) those metals are in electrical contact. and then (3) along comes a leak that comes into contact with both the metals, along with a localized region of high humidity around the steel and aluminum, where humid air can also serve as the electrolyte in GC. so the GC electric circuit is leaching ions from really anywhere on that aluminum jacket and depositing them on the steel nipple and fittings. the aluminum jacket is so big (in terms of surface area) that you don't even really see any material that's been removed (and it would all be on the unpainted side), but that material has definitely visibly accumulated on the steel.

so that's my final guess. i could be totally wrong. like i said, i'm no plumber, or any kind of expert on corrosion. but if this is what's happening, first i'd check to see that the aluminum jacket isn't directly contacting any of that steel or accumulated gunk (they'd still be electrically connected, but instead of a direct path the circuit would have to wind through the entire pathway through the housing, and would have much greater resistance). then i'd check the humidity in the basement and try to bring that down.

EBEBRATT-Ed

Chances are the boiler is ok. The steel nipple will rot before the cast iron. I would buy some fittings and keep them on hand.

And whatever you do, don't touch it until your ready