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A900 - Antiscalant and Corrosion Inhibitor in Closed Loop Systems
When considering chemical treatment programs for closed loop systems, A900 is a Sodium Nitrite based corrosion inhibitor and is an economical and effective
treatment option.
A900 has been used as a corrosion inhibitor for closed loop water systems for many years. A900 functions as an anodic corrosion
inhibitor. Nitrite works to form a protective gamma iron oxide film on a metal surface. This layer is formed by the reaction of nitrite and dissolved
oxygen and then kept in repair by the nitrite alone. Nitrite is not consumed to any practical extent since little is needed to form this film. It is this film that protects the metal surface from corrosive attack. Nitrite consumption is directly influenced by oxygen entering the closed loop system by the addition of oxygenated make-up water.
A900 offers excellent corrosion protection for ferrous metals. Nitrite functions best when used in the pH range 10.5 - 13.5 and formulations for
closed systems often make use of borate buffers. In addition to buffering the pH into the desired range, borates promote passivation by facilitating the
absorption of oxygen, and also provide some microbiological control. The concentration of nitrite required for inhibition increase with temperature.
A900 is an oxidizing agent and is not compatible with reducing agents such as sodium sulphite. It also has reduced effectiveness when chlorides
and sulphides are present in the water, unless the dosage of nitrite is increased. In general, maintain no less than 2000 ppm of sodium nitrite
(preferably 3000 ppm), keeping levels of at least 850 ppm above the total concentration of chloride and sublet present in the closed loop system.
The reactions that affect nitrite are controlled by varying forms of bacteria. Some fungi and other forms of microorganisms have the ability to react
with other forms of Nitrogen. The nitrite ion is included either as a primary food source or as an intermediate food source in a number of autotrophic
reactions.
The reactions that affect nitrite are controlled by varying forms of bacteria that use nitrite as food. Some fungi and other forms of microorganisms
have the ability to react with other forms of Nitrogen. The nitrite ion is included either as a primary food source or as an intermediate food source
in a number of autotrophic reactions. Within the context of the Nitrogen Cycle there are three microbiological processes that are relevant to the use
of Sodium Nitrite as a corrosion inhibitor closed recirculating water systems. This is where A171 is used as a primary biocide.
The use of A900 is a closed system as a corrosion inhibitor at levels 2000 - 3000 ppm of nitrite offers an excellent source of nutrition
for the three processes described above. Most closed recirculating water systems will have areas of anaerobic and aerobic conditions. Therefore, it
is possible to have more than one process operating within the same system. At the present time, there are no field tests available to determine
either qualitatively or quantitatively if these processes are occurring.
A171 is a combination broad spectrum biocide and algaecide for use in cooling water systems where bacteria and biofilm are expected to be present. It
provides microorganism control and clean systems.
A171 is a Gluteraldehyde based biocide and is normally dosed rate: 500 - 1000 ppm in system depending on degree of fouling. A171 can be dosed continuously
or slug dosed.
Can be dosed directly from the drum or other suitable container. May be dosed full strength or diluted to any convenient concentration.
A171 rapidly kills algae, bacteria, viruses, fungi, moulds and other microorganisms.
Effects of Oxygen Corrosion in Closed Loop Cooling Systems
A900 for Steel and Copper coils
A908 for Aluminium coils
A171 Biocide and Algaecide for Cooling Water systems
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