Oxygen-diffusion corrosion in radiant heating systems

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Oxygen-diffusion corrosion in radiant heating systems

Whether you’re doing radiant floor heating or hydronic snowmelt jobs, it pays to give lots of thought to this oxygen-diffusion corrosion business. Since this is one of those areas where the marketing and the engineering can get mixed up, it pays to go back to basics, so here goes.

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DanUK

Excellent guide thank you.

Derheatmeister

Great Article Dan.
IMO the VDI 2035/No Chemical/Mineral free/low EC approch should go hand to hand with the DIN 4726.
Soon the new IAPMO version of this subject will be avaiable in the US.
Thank you for explaining the importance of O2 barrier in Plain English.

Richard.

Mark Eatherton

Thank you Dan for continuing our industry education. As my good friend and business confidant Richard Der Heatmeister said, we do have a standard. ANSI Standard H1001.1 was developed through IAPMO with the input of every segment of the hydronic industry, including chemical and non chemical purveyors. The reason behind developing this standard was the increase in component failures due to oxygen and or magnetite, the byproduct of oxidation. Our hope is that our industry will adopt this standard and apply it to their customers systems. It will ensure that the warranties on their very expensive components will remain in tact. Our eventual goal is that the local AHJ (Authority Having Jurisdiction) will adopt this standard and begin enforcing its use. Thank you to you, and all that participated in the development of this standard. Now the job of education really kicks in and the challenge of applying it to everyday systems can begin. It's about more than just maintaining "dead water". Again, Thank YOU for your eloquent and simple explanations that keep people interested and learning. One last interesting point. There are certain chemicals that are in water whose concentrations for drinking water standards are allowed to be higher in drinking water than our industry allows to occur in a heating system. Chlorides. HMMMmmm... Maybe it's time to review THOSE standards.

hot_rod

There are certain chemicals that are in water whose concentrations for drinking water standards are allowed to be higher in drinking water than our industry allows to occur in a heating system. Chlorides. HMMMmmm... Maybe it's time to review THOSE standards.

Such a cocktail of chemicals being added to public waters these days. Makes it hard for manufacturers to find seals and o-rings compatible with all the chlorine, chloramine, etc blends. They don't usually let our industry know when they modify treatment chemicals.

One additive that concerns me is the orthophosphates, like Denver recently started adding. The intent is to put a protective layer over old lead pipes to prevent leaching.
But that may not be what we want in hydronic or steam boiler water. Does that layer build up and reduce heat transfer? Certainly on any boiler that takes on makeup water it would be a high concern. Hydronic system additives do contain a "film provider" possibly the same phosphate blend. So right out the gate you are adding an additional "layer"

We also know O2 ingress is part of the equation in magnetite formation. It does seem odd that some of the magnetic separators require you open then up to clean out. Would not this allow O2 to enter at every cleaning? The amount of allowable O2 in the various standards is very low. It would seem adding O2 at every flush just keeps the magnetite process ongoing?

Oxygen scavengers are added to hydronic chemicals, various sulfites, but they get depleted in the process of consuming the O2. Same with glycols, they breakdown when the various additive chemicals get depleted.
The boosters you can add to glycols re-establish the level of O2 scavengers mainly. Open system OWF require yearly scavenger doses to protect the metals. Should the same apply to closed loop systems that are continuously opened for cleaning? Should an O2 scavenger be added every time?
Time will tell.