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Inhibited Sulfamic Acid (H3NSO3): A convenient and effective metal-safe carbonate scale remover

All surfaces that come into contact with raw water in processes involving heat transfer are susceptible to carbonate scale deposition. The amount and type of scale deposited on the heat exchange surfaces will depend on the quality of the make-up water, the temperatures of the materials in contact with the process water, and the possibility of some of the process water evaporating.

As carbonate scale forms on heat exchange surfaces, heat transfer efficiency is reduced. If scaling becomes severe enough, heat transfer can be hampered to the point that heat exchange surfaces must be cleaned to restore their original design efficiencies. Removing deposited carbonate scale with acids that do not destroy the materials from which heat exchangers are made is often one of the most economical solutions to restore heat exchanger efficiency.

To avoid damaging metal heat exchange surfaces, pure acids are modified by adding other compounds during the manufacturing process. These additional compounds are called inhibitors if they are selected to protect the different types of surfaces that the acids come into contact with during the descaling process. Acids that are formulated in this manner are designated as inhibited. Inhibitors are also specifically selected to avoid adverse impact on the performance of the acid in its intended use. Surfactants and wetting agents may also be added in some cases to improve the effectiveness of the acid.

Inhibited sulfamic acid has become a popular choice for removing carbonate scale from heat exchangers and other heat rejection equipment. When properly inhibited, sulfamic acid can be used safely as an encrusting agent on carbon steel, copper, admiralty brass, galvanized and austenitic stainless steel.

Although in some cases more expensive than other acids, inhibited sulfamic acid has some very distinct advantages over other types of acids used for carbonate scale removal:

• Sulfamic Acid is a white, dry, crystalline powder that is easy to handle. It is safe to store until mixed with water. (Refer to an appropriate MSDS sheet for safety and handling information)
• Powdered sulfamic acid is less expensive to ship than liquid acids.
• The fumes are less harmful than other acids that are normally used for this purpose.
• Sulfamic acid does not produce etching or localized pitting.
• Will effectively remove ferric oxide (iron oxide) when mixed with sodium chloride or citric acid.
• Safe to use in many types of heat transfer equipment such as molds, radiators, shell and tube exchangers, plate heat exchangers, steam boilers, hot water boilers, chiller condensers, evaporative condensers, and cooling towers . It will not pierce stainless steel as can hydrochloric acid.

The many advantages of inhibited sulfamic acid make it an excellent, convenient, and effective metal-safe option for removing carbonate scale in industrial heat rejection and processing equipment.

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