Sulfamic Acid Application Guide in Descaling and Acid Cleaning
Industrial Equipment Maintenance: Sulfamic Acid Descaling Guide
In the field of industrial equipment maintenance, descaling and acid cleaning are essential measures to ensure efficient equipment operation and extend service life. Sulfamic acid aqueous solutions are acidic and react with metal oxides, hydroxides, and carbonates to form soluble salts. This enables effective removal of iron oxide rust, scale, and other deposits. As a result, sulfamic acid is widely used in various water systems, cooling equipment, heat exchangers, and pipeline cleaning applications.
I. Basic Properties and Advantages
Sulfamic acid (also known as sulphamic acid or amidosulfonic acid) is a white crystalline solid that dissolves easily in water to form an acidic solution.
Compared with traditional liquid cleaning agents, its solid form offers significant advantages in transportation and storage, substantially reducing the risk of leakage and associated hazards.
As a mild, moderate-strength acid, sulphamic acid is characterized by its low corrosivity toward metals. It does not cause intergranular corrosion in stainless steel and has virtually no corrosive effect on non-metallic materials such as rubber, plastics, and nylon.
These favorable properties make it particularly suitable for the internal cleaning of large boilers, refrigeration units, air compressors, plastic injection molding machine cooling systems, condensers, and various types of pipeline equipment.
In practical applications, the cleaning effectiveness of sulfamic acid is influenced by several key factors, including the type of scale, solution temperature, concentration, and the use of additives.
When dealing with calcium carbonate-based scale, the optimal concentration is typically determined according to the thickness of the deposit: lower concentrations are generally sufficient for thin scale layers, while higher concentrations may be appropriately used for thicker deposits to achieve the desired cleaning results.
II. Cleaning Mechanism
The solution of sulfamic acid reacts effectively with various types of scale and deposits, converting them into soluble salts. This reaction loosens the deposits from the equipment surfaces, allowing them to be easily removed and achieving thorough cleaning.
During the cleaning process, the acid is gradually consumed. As the pH of the cleaning solution rises, its reactivity decreases significantly. At this point, sulfamic acid should be added promptly to restore cleaning performance. It is generally recommended that when the pH rises to 3.5, the active ingredient has been essentially depleted, and additional solution should be introduced to regain effective descaling capability.
Temperature Control
Temperature has a pronounced effect on the reaction rate. Appropriately increasing the temperature can accelerate the cleaning process; however, it is advisable to keep the operating temperature below 60°C.
This helps prevent hydrolysis of the acid into sulfuric acid, which could increase the risk of corrosion or lead to unwanted precipitation.
To enhance the overall cleaning performance, anionic or non-ionic surfactants such as TX-10, sodium dodecylbenzenesulfonate are commonly added to the solution at a concentration of approximately 0.1% by weight. These surfactants have functions such as wetting, penetration, emulsification and dissolution.
Additionally, an appropriate amount of polyacrylic acid-based dispersants (about 0.1%) is usually added to assist in dispersing calcium scale and prevent any interference with the descaling process.
III. Cleaning Preparation
1. System Assessment
Prior to cleaning, a comprehensive evaluation of the equipment must be conducted.
This includes determining the type and thickness of the scale deposits, identifying the materials of equipment (such as carbon steel, copper, aluminum alloys, titanium tubes, stainless steel, galvanized steel, etc.).
Appropriate corrosion inhibitors should be selected based on the specific materials involved to provide maximum protection to the equipment.
2. Selection of Additives
- Corrosion Inhibitors: Amines, thiourea, alkynes (particularly alkynols, which perform well), and inorganic salts (such as KI), among others.
The correct combined use of these additives enables a more efficient and safer cleaning process.
IV. Precautions and Safety Guidelines
- Strict Temperature Control: The operating temperature must not exceed 60°C to prevent hydrolysis of sulfamic acid into sulfuric acid, which could intensify corrosion or cause precipitation.
- pH and Concentration Monitoring: Regular testing and timely adjustment of chemical dosages are essential to maintain sustained reaction effectiveness.
- Material Compatibility: Different metals require matching corrosion inhibitors. Sulfamic acid is relatively friendly to galvanized surfaces, but corrosion monitoring remains necessary. For titanium materials, process parameters should be carefully controlled to avoid potential hydrogen embrittlement risks.
- Environmental Protection: Waste cleaning solutions must undergo neutralization treatment before compliant discharge.
- Operational Safety: Operators should wear appropriate personal protective equipment, and the work area must be well-ventilated. When preparing concentrated sulfamic acid solutions, pay attention to the correct dissolution sequence and ensure thorough stirring for uniform mixing.
VI. Application Value of Sulfamic Acid Cleaning
Sulfamic acid cleaning effectively removes water scale and sludge, thereby improving equipment thermal efficiency and reducing energy consumption. For plastic injection machines, condensers, and similar equipment, it helps restore normal cooling and heat exchange functions, directly supporting stable production operations.
Compared with mechanical cleaning methods, this chemical approach provides more thorough treatment of complex internal structures, making it particularly suitable for areas with thick scale deposits or locations that are difficult to access mechanically. Its mild nature ensures effective cleaning while offering good protection to the equipment.
As an excellent cleaning agent, it demonstrates significant practical value in industrial descaling and acid pickling applications. Through scientific control of concentration, temperature, additives, and process parameters, highly efficient yet relatively gentle cleaning results can be achieved. Regular professional maintenance enables enterprises to enhance equipment performance while reducing long-term operational costs.