Nitrite, typically in the form of sodium nitrite, is the most common corrosion inhibitor used in closed loop cooling systems. It reacts with oxygen in the system to create a protective oxide layer on metal surfaces. Nitrite works best with ferrous metals and is generally not advised for use with copper or copper alloys; as the oxide layer forms, the reaction produces ammonia which can cause corrosion on copper surfaces.
Why Measure Nitrite?
Measuring the concentration of nitrite corrosion inhibitors in cooling water is critical to preventing damage and costly maintenance of your cooling system. Since nitrite is an anodic inhibitor, an insufficient concentration of nitrite could lead to localized anodes establishing and causing intense “pitting,” a particularly harmful form of corrosion. Generally, a minimum concentration of 500 ppm sodium nitrite (335 ppm nitrite) is maintained in cooling water. The effectiveness of the nitrite inhibitor can decrease over time due to fouling, oxidation and other factors.
- Fouling – the accumulation of unwanted deposits, such as scale or sediment, on the surfaces of pipes, heat exchangers, or other components, which can reduce system efficiency and potentially cause equipment failure. Along with scale and sediment, microorganisms can create a slime layer that can foul the system.
- Oxidation – The reaction between oxygen and metal surfaces, which can lead to corrosion and degradation of the system components, reducing their lifespan and potentially causing leaks or failures.
- Pitting – A type of highly localized corrosion where cavities are created in the material. It is considered to be a dangerous corrosion in systems that can lead to inefficiencies or equipment failure.
Since open re-circulating cooling systems are more prone to fouling and oxidative processes, nitrite treatments are usually applied to closed loop cooling systems.
By testing the nitrite levels in the system, operators can ensure that the inhibitor is present in the proper concentration to provide corrosion protection. When nitrite levels are properly maintained, systems will operate more efficiently and last longer. Testing can also prevent overdosing of nitrite which can lead to an increase in microbes and wasted chemical.
How Do Nitrite Test Kits Work?
How Do Nitrite Test Kits Work?There are multiple ways to test for nitrite including Azo dye formation, ceric sulfate, permanganate, and ceric ammonium nitrate (CAN).
Glycol is commonly used in systems that may freeze, which is a concern in many parts of the United States. Therefore, methods that resist glycol interference are often preferred due to the compatibility with glycol-containing systems.
- Azo Dye Formation Method– In the azo dye formation method nitrite diazotizes with a primary aromatic amine in an acidic solution to produce a colored azo dye. The intensity of the color is directly proportional to the concentration of nitrite in the sample. Using the primary aromatic amine N-(1-naphthyl)ethylenediamine dihydrochloride or NED, with this method allows for testing at lower ranges.
- Ceric Sulfate Titrimetric Method– The ceric sulfate method is a titrimetric method where ceric sulfate is the titrant and ferroin acts as the indicator. This chemistry has the benefit of being resistant to glycol interference and is popular for applications where nitrite corrosion inhibitors are being used.
- Permanganate Titrimetric Method– The permanganate method is a way to test for nitrite by using a titrant that oxidizes nitrite to nitrate. Excess permanganate’s purple color is used to determine the endpoint of the reaction, which is when all the nitrite has been oxidized to nitrate and no further reaction occurs. Glycol interferes with this method, making the CAN method a more widespread alternative.
- Ceric Ammonium Nitrate (CAN) Method– The CAN method uses a ferroin indicator that turns green/blue in the presence of excess CAN. This method also relies on using a titrant that oxidizes nitrite to nitrate. This method has resistance to glycol interference.
Available nitrite test kits express results as ppm sodium nitrite (NaNO2), ppm nitrite (NO2), or ppm nitrite as nitrogen (NO2-N).
To convert from NaNO2to NO2, multiply results by 0.67.
To convert from NO2to NaNO2, multiply results by 1.5.
Popular Nitrite Products
Common Uses for Nitrite Test Kits
Nitrite test kits are most commonly used for ensuring efficiency and corrosion control in closed loop cooling systems.
Nitrite in water test kits are also used for environmental applications. Testing for nitrite can help determine if a body of water contains excess nutrients that could be harmful to the environment. Test kits provide a convenient way to test for nitrite in the field immediately upon sample collection. Immediate analysis minimizes the potential for the conversion of nitrite to nitrate when the sample is exposed to the atmosphere.
Drinking water is also tested for nitrite contamination. The USEPA has set a Maximum Contaminant Level of 1 mg/L for nitrite-nitrogen.
The Benefits of Using AquaPhoenix Nitrite Test Kits
AquaPhoenix is a leading manufacturer and distributor of nitrite test kits.We can customize control panels, reagents and test kits withcustom packaging,private labelingandcustom test factors, making the finished product unique for your business.
In addition to testing kits, AquaPhoenix offers excellent customer service. Our team is committed to providing support to every customer. We have quick response times and order turnarounds, with same- or next-day shipping often available.
