Corrosion in glycol heating system
Corrosion in glycol heating system
(OP)
Hi everyone,
I'm looking after a propylene glycol heating system.
There has been corrosion issues with the system since installation, particularly for the aluminium boilers. I had taken samples of the system and measured a ph of 8.5 and chlorides as high as 150ppm. No other contaminants i.e. calcium, magnesium, sulphates were out of recommended range
Can someone suggest what I can do to remove the chlorides? I had flushed the system out last year and put in a new batch which I also had measured and found little to no chlorides or contaminants, I'm not sure how it developed in the system. Also what reactions does the presence of chloride induce? especially ones that would cause the pH to rise. The glycol in the system has also turned yellow colour from initially being clear, with a strong chemical smell to it.
Thank you.
I'm looking after a propylene glycol heating system.
There has been corrosion issues with the system since installation, particularly for the aluminium boilers. I had taken samples of the system and measured a ph of 8.5 and chlorides as high as 150ppm. No other contaminants i.e. calcium, magnesium, sulphates were out of recommended range
Can someone suggest what I can do to remove the chlorides? I had flushed the system out last year and put in a new batch which I also had measured and found little to no chlorides or contaminants, I'm not sure how it developed in the system. Also what reactions does the presence of chloride induce? especially ones that would cause the pH to rise. The glycol in the system has also turned yellow colour from initially being clear, with a strong chemical smell to it.
Thank you.





RE: Corrosion in glycol heating system
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RE: Corrosion in glycol heating system
can you give some more info on system design and its operating conditions?
the questions you ask will be hard to answer without sufficient information.
RE: Corrosion in glycol heating system
RE: Corrosion in glycol heating system
Corrosion inhibitors were added by the supplier, i know molybdenum is one of them.
The temperature of the system can be 170 deg. F.
The flow is approximately 80gpm.
I believe it is 40% propylene glycol.
There is a mechanical de-aerator in the system, but to ensure it was working i did test for dissolved oxygen and found minimal amounts and based on that air is not dissolving in it.
Hope this is helpful, please let me know if more is needed.
RE: Corrosion in glycol heating system
RE: Corrosion in glycol heating system
Could someone also suggest techniques of removing it without too much effort and costs.
There is no nitrogen blanket but there are air traps that expel any air to ensure there is no air-glycol interface. And no oxygen scavengers were added. Is the oxygen the cause of the rising pH? is it creating hydroxide ions? if so what reaction is taking place?
Your help is much appreciated, as BronYrAur said at a pH 8.5 the boilers are at high risk.
RE: Corrosion in glycol heating system
In the oil gas business I've worked in, all heat transfer media loop expansion drums I've come across were N2 blanketed.
RE: Corrosion in glycol heating system
RE: Corrosion in glycol heating system
RE: Corrosion in glycol heating system
In the case of the chlorides, would the use of an ion exchange resin specific to chlorides be applicable? Both from an ability to rid the system of chlorides and do it at a reasonable cost? This solution of course will be in addition to locating the source of chloride to prevent it from being present again and inducing corrosion.
RE: Corrosion in glycol heating system
Have not heard of anyone using ion exchange resins in this recirc loop for chloride control, though it sounds sensible enough - the only solution is to find the source.
As you already know, aluminum leaches out into solution at both ends of the pH spectrum. Here also, there may be some link between how readily aluminum leaches into solution and dissolved O2 content - a materials selection engineer should help to advise.
A materials selection engineer may be able to advise on a suitable reference book - I'm only speaking from past experience from what I've learned from materials selection / corrosion management engineers.