Nitrite Based Treatment for Closed Cooling Water Treatment

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Hi Everyone,

Please advice the theory behind the Nitrite Based Treatment program for Closed Cooling Water

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5 Answers

  1. what metals are you looking to protect?, what capacity system volume.?  Is it open to the atmosphere / closed break tank.  What continent?

  2. Nitrite is an excellent corrosion inhibitor for hot water systems, usually between 600-1000ppm. Often it is buffered and has azole added for yellow metal protection. For systems that are either seasonal (offline for summer months) or dual-temp, I prefer a blend of Nitrite and Molybdate.

  3. Instead of using nitrite and other chemicals consider using an electronic water treatment system like HydroFLOW. (www.hydroflow-se.com) The low power, high-frequency decaying signal generated by HydroFLOW is induced into the water stream and travels throughout the hot, chilled or condenser water systems. The electrical signal prevents and removes scale, biofilm, & bacteria from system surfaces while adding a film of magnetite that protects the ferrous parts of the system from corrosion. Include an air & dirt separator with SweepCLEAR to physically remove 99% of the entrained dirt (scale, rust)  and air water. www.sweepclear.com

  4. Nitrite is an excellent product for closed systems but does require high levels of nitrite in the order of 500-1,0000 ppm.  It is usually buffered to ensure that it is at its optimum pH within the system of 9.5.  Yellow metal corrosion inhibitors will need to be added to protect copper.  Lower levels of nitrite may be used when combined with materials such as molybdate.  Nitrite should not be used in the food industry unless it is totally separate from any processing.  Certain bacteria will utilise the Nitrate and grow producing nitrate, which is not a good corrosion inhibitor.  So monitoring the closed systems is vital.  Once bacterial growth starts in a closed system, it is very difficult to control.  Dosing biocides may have an impact, but very often it returns.  The selection of biocide is difficult because at the pH involved, many non-oxidising biocides are inactivated over a period of time reducing their effectiveness.  Some of the bacteria which break it down are resistant to a number of biocides, while in other cases the biocide breaks down immediately  killing the bacteria. Any which are left will grow again.  The other issue is that they may have a hazardous classification of toxic and if it leaks into a water course it is a pollutant.  After saying all of this, nitrite is still a very useful corrosion inhibitor. 

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  5. Nitrite is an oxdidising anodic inhibitor. Nitrite forms Y – Fe2O3 passive film by following reaction, 4Fe + 3NO2 + 3H+ ----- >2 YFe2O3 + NH3 + N2, Ddose 700 – 1800 MG / LIT as NaNO2. Depending on presence of aggressive ions like SO4—and Cl-.Under dosing of nitrite can cause severe pitting. Nitrite promote microbiological growth in chilled loop so you need protection by biocide.