Seeking advice on the automatic decrease in pH in a closed chilled water system
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I would like to ask everyone: our factory has a small closed-loop chilled water system, with 20-30% ethylene glycol added to the production water. The nitrite formula used as a corrosion inhibitor seems to cause the system’s pH to drop rapidly; it can go from 8.8 to 8.0 in half a month. When the equipment is turned on, it appears that the carbon steel parts are severely corroded. The experienced workers at the factory have been manually adding sodium hydroxide to adjust the pH level. Is it possible to use sodium hydroxide in this case? Previously, I was working with the addition of baking soda, sodium bicarbonate, to adjust the alkalinity pH.
I added sodium hydroxide on my end, but the pH still continued to drop. Under normal conditions, the pH should be 8.0; with 20-30% ethylene glycol present, the system temperature should be around -5°C, so corrosion should not occur. This is exactly the situation we are facing with our current system
I don’t know what the level of iron ions in your chilled water is; if sodium hydroxide is added, could the iron ions turn into iron hydroxide and precipitate out, thereby causing greater harm? I’m wondering whether bicarbonate (a weak base) should be used to neutralize free hydrogen ions; I just need actual examples or expert opinions to confirm this, but thanks anyway for your response!
With iron ions at over 100 ppm, no iron hydroxide deposits were formed