Rusting is an important phenomenon accompanied with the corrosion of carbon steel and the formation of corrosion products such as iron oxides is an a biotic process of chemical reactions. It was generally agreed by most of the researches that carbon steels are generally attacked by uniform corrosion or general corrosion. The term ‘uniform’ or ‘general’ corrosion is used to describe the corrosion damage that proceeds in a relatively uniform manner over the entire surface of an alloy. It is an even rate of metal loss over the exposed surface. It also characterized by a chemical or electrochemical reaction or metal loss due to chemical attack or dissolution that proceeds uniformly over the entire exposed surface or over a large area. During this process, the material becomes thinner as it corrodes until its thickness is reduced to the point at which failure occurs.
Dissolved oxygen refers to the volume of oxygen that is contained in water. Oxygen enters the water by photosynthesis of aquatic biota and by the transfer of oxygen across the air-water interface. Fresh make-up water entering a closed loop cooling system contains large amounts of oxygen and need to be controlled to reduce corrosion of the metal inside the pipe reticulated system.
Oxygen can destroy the protective hydrogen film that can form of many metals and oxidize dissolved ions into insoluble forms. Deposits of rust in a plumbing system is such an example of differential aeration cells and accelerate corrosion.
An oxygen scavenger is a corrosion-inhibiting substance that is added in small amounts to an environment that is prone to oxygen-based corrosion. Its cathodic nature enables it to combine with oxygen and form harmless compounds-salts. This process eventually reduces the corrosion rate in the systems under protection.
Oxygen scavengers increase the shelf life or service life of the components under protection.
Sodium nitrite is an effective corrosion inhibitor and is used as an aqueous solution in closed loop cooling systems, Sodium Nitrite has been used as a corrosion inhibitor for closed loop water systems for many years. Sodium Nitrite offers excellent corrosion protection for ferrous metals. Nitrite functions best when used in the pH range 9.0-10.5 and formulations for closed systems. ScaleAwayA900 is a Sodium Nitrite based water treatment product used protect the pipes in closed loop water cooling systems.
Closed Loop Dosing with ScaleAwayA900
A900 for Steel and Copper coils
A908 for Aluminium coils
A171 Biocide and Algaecide for Cooling Water systems
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