25 May 2005
4. Test daily to maintain pH and sulfite levels within range.
5. Deaerator can be used to help reduce incoming oxygen in high make-up
Nitrite-Azole Treatment Program. This program is not recommended for
systems having water temperatures exceeding 121 C (250 F), or for (CL + SO4)
concentrations>800ppm. Also, avoid nitrate-based programs if (CL + SO4)
concentrations is > 800ppm. It can be used in low-temperature water and chilled water
systems. Water is treated with a nitrite-borax compound to a nitrite level of 1000 ppm
(as NO2). This level will require about 0.77 to 0.81 kilogram (1.7 to 1.8 pounds) nitrite-
borax per 0.38 cubic meters (100 gallons) of water in the system. Most water treatment
service companies offer this treatment as a formulated product. There is also a generic
nitrite-borax compound product that is a premixed blend containing approximately 68%
sodium nitrite, 10% borax, 17% sodium carbonate (soda ash) and 5% copper corrosion
inhibitor. Adjust to a pH of 9.0 to 9.5 with sodium carbonate (soda ash), if necessary.
This chemical treatment program is compatible with ethylene glycol water mixtures used
for freeze protection. A recommended procedure for maintenance is described below.
1. Soften makeup water if the hardness is over 250 ppm as CaCO3.
2. Add sodium nitrite-borax-azole blend to maintain a nitrite level of 600 to
1000 ppm (as NO2) in the system.
3. Add sodium carbonate, if necessary, to maintain a pH range of 8.5 to 9.5.
4. If copper is present, maintain a minimum of 10 ppm of tolyltriazole.
5. Test after chemical addition and then monthly for pH and nitrite levels.
Molybdate-Azole Treatment Program. This program is not
recommended for systems where water temperatures exceed 121 C (250 F). Most
water treatment service companies offer this as a formulated product. There is also a
generic molybdate-azole compound product that is a pre-mixed liquid containing
approximately 10% sodium molybdate, 3% caustic soda, and 3% azole (copper
corrosion inhibitor). Maintain a molybdate level of 125 ppm (as Mo) and adjust pH to the
range of 8.5 to 9.5 with sodium hydroxide (caustic soda). NOTE: Some restrictions may
pertain to discharge of water containing molybdate. This chemical treatment program is
compatible with ethylene glycol or propylene glycol. A recommended procedure for
maintenance of the system consists of five steps:
1. Soften makeup water if hardness is over 250 ppm as CaCO3 (calcium
2. Control the molybdate-azole compound to maintain a molybdate level of
100 to 125 ppm (as Mo).