Sulfamic acid (amidosulfonic acid, CAS 5329-14-6) is one of the most useful solid acids in industrial chemistry — a strong acid that is safe to handle, low in corrosivity to metals, and widely used for descaling, cleaning, sweetener synthesis and catalysis. This article covers its manufacturing process, properties, applications and buying considerations.
1. What Is Sulfamic Acid?
Sulfamic acid (NH2SO3H) is a white crystalline solid, freely soluble in water, with a strong acid character (pKa about 1) similar to mineral acids. Unlike liquid acids, it is a stable, non-volatile solid that can be handled, measured and transported safely. Its key practical advantage over hydrochloric or sulfuric acid is low corrosivity to many metals (stainless steel, copper alloys) while still dissolving scale — which makes it the preferred descaling acid in many industries.
2. Manufacturing Process
2.1 The industrial route: urea and fuming sulfuric acid
Sulfamic acid is produced commercially by the reaction of urea with fuming sulfuric acid (oleum) or sulfur trioxide:
NH2CONH2 + SO3 + H2SO4 → 2 NH2SO3H + CO2
Process steps:
- Sulfonation: urea is added to fuming sulfuric acid (or SO3) under controlled temperature; the reaction releases CO2 and forms sulfamic acid.
- Crystallization: the product crystallizes from the reaction mass as the temperature and composition are adjusted.
- Separation and washing: the crystals are separated (centrifugation/filtration) and washed to remove residual sulfuric acid.
- Drying and packaging: the washed crystals are dried and packed, typically in 25 kg bags.
Temperature control is the key process parameter — too high a temperature degrades the product and increases sulfate by-product; too low slows the reaction. Product purity (minimal free sulfuric acid and sulfate) is set by washing and drying discipline.
2.2 Quality-defining points
- Purity of the fuming sulfuric acid and urea
- Reaction temperature profile
- Washing efficiency (removes free H2SO4)
- Drying (moisture affects caking and assay)
3. Specifications
| Parameter | Typical value | Significance |
|---|---|---|
| Assay | 99.5% min (technical grade) | Effective acid content |
| Sulfate (as H2SO4) | Low (e.g. <0.5%) | Impurity; high sulfate affects some uses |
| Water | Low (<0.2%) | Prevents caking |
| Iron | Low | Matters for sensitive applications |
| Appearance | White crystalline powder | QC check |
4. Applications
4.1 Descaling and cleaning
Sulfamic acid is the standard descaling agent for boilers, heat exchangers, cooling towers, condensers and reverse-osmosis membranes. It removes calcium and magnesium scale and rust efficiently while being far less aggressive to equipment metals than hydrochloric acid. It is also used in household and industrial descalers for kettles, coffee machines and evaporators.
4.2 Sweetener intermediate
A major use is the production of cyclamic acid / sodium cyclamate (a sweetener): sulfamic acid reacts with cyclohexylamine to form the cyclamate salt. This ties sulfamic acid demand to the sweetener industry.
4.3 Catalysis
As a solid, non-volatile strong acid, sulfamic acid is used as a catalyst in esterification, acetalization and other acid-catalyzed reactions, where it can be more convenient and safer than liquid mineral acids.
4.4 Other uses
- Metal surface treatment (pickling, cleaning)
- Dye and pigment processing
- Bleach stabilizer and sanitizing formulations
- Chemical intermediate (sulfamates) for agrochemicals and pharmaceuticals
5. Sulfamic Acid vs Hydrochloric Acid for Descaling
| Aspect | Sulfamic acid | Hydrochloric acid |
|---|---|---|
| Form | Solid crystals | Liquid (fuming) |
| Handling safety | Higher (non-volatile) | Lower (acid fumes) |
| Metal corrosivity | Lower | Higher |
| Scale removal | Effective (Ca/Mg scale) | Effective |
| Storage/transport | Easier (solid) | Corrosive liquid logistics |
6. Safety and Handling
- Irritant: sulfamic acid powder is irritating to eyes, skin and respiratory tract; use gloves, goggles and dust protection.
- Aqueous solutions are acidic: handle with care; neutralize spills appropriately.
- Storage: store dry, sealed; keep away from strong oxidizers and bases.
- Dust: avoid generating dust; use local exhaust where handled in bulk.
7. FAQ
Is sulfamic acid safe to use on stainless steel?
Yes — one of its main advantages is low corrosivity to stainless steel and many alloys compared with hydrochloric acid, which is why it is used for boiler and heat-exchanger descaling.
What is sulfamic acid used for in food?
It is an intermediate for the sweetener sodium cyclamate (in regions where cyclamate is approved); it is not a direct food additive itself.
Can sulfamic acid replace hydrochloric acid for descaling?
In many scale-removal applications yes, and with safer handling and less metal corrosion; the choice depends on scale type, equipment and process.
What is the difference between sulfamic acid and sulfuric acid?
Sulfamic acid is a solid crystalline strong acid (NH2SO3H); sulfuric acid is a liquid mineral acid (H2SO4). Sulfamic acid is non-volatile, less corrosive to metals, and easier to handle and store.
8. References and Further Reading
- Peer-reviewed literature on sulfamic acid synthesis and applications
- Industrial literature on descaling and cleaning chemistry
- Sweetener industry technical references (cyclamate production)
This article is published for industrial and technical reference by PolyblueChem. Specifications are typical industry values; always verify against the supplier’s COA.
Other Names for Sulfamic Acid
Sulfamic acid is known under several equivalent names that appear in product specifications, technical literature, and search queries. The most common alternatives are amidosulphonic acid (British spelling), amidosulfonic acid, and amidosulfuric acid. All of these names refer to the same compound, H3NSO3, with CAS number 5329-14-6.
Frequently Asked Questions about Sulfamic Acid
Is sulfamic acid the same as amidosulphonic acid?
Yes. Sulfamic acid (CAS 5329-14-6) is also called amidosulphonic acid, amidosulfonic acid, or amidosulfuric acid. The names describe the same solid strong acid and are used interchangeably in procurement lists and technical documents.
What is the chemical formula of amidosulphonic acid?
The chemical formula of amidosulphonic acid (sulfamic acid) is H3NSO3, with a molecular weight of 97.09 g/mol. It is a white crystalline solid, highly soluble in water, and widely used for descaling, industrial cleaning, and as a sulfating and sulfonating agent.
Is amidosulphonic acid the same as amidosulfuric acid?
Yes. Amidosulphonic acid, amidosulfonic acid, and amidosulfuric acid are synonyms for sulfamic acid (CAS 5329-14-6). Suppliers may use any of these names on a certificate of analysis or safety data sheet.
PolyblueChem supplies sulfamic acid (CAS 5329-14-6) in technical grade with COA and MSDS. Contact us for specifications and quotations.
Further technical detail on sulfamic
The following sections expand on the technical and practical aspects covered above.
Synthesis Methods
Aminosulfonic acid can be synthesized using several methods, with the most common being the reaction of ethylene oxide with sulfur dioxide. In this reaction, the ethylene oxide serves as a starting material, which is reacted with sulfur dioxide to form an intermediate product, and through hydrolysis, aminosulfonic acid is obtained.
Another method for producing aminosulfonic acid involves the reaction of chloroethanesulfonic acid with ammonia or amines. The resulting product is aminosulfonic acid, which is purified for use in industrial applications.
Aminosulfonic acid can also be produced through the reaction of sulfonating agents (like chlorosulfonic acid) with amines, leading to the desired aminosulfonic acid product.
Agricultural Applications
Aminosulfonic acid also plays a crucial role in the agricultural sector, particularly in improving soil health, enhancing plant growth, and improving the effectiveness of crop protection products.
5.1 Soil Conditioner and Fertilizer Additive
Aminosulfonic acid is used as a soil conditioner to enhance the availability of micronutrients like zinc, iron, and copper in the soil. These essential nutrients can sometimes become unavailable to plants due to soil pH imbalances, particularly in alkaline soils. By chelating these metal ions, aminosulfonic acid helps to solubilize them, making them more accessible to plant roots. The result is improved plant growth, especially in nutrient-deficient soils.
5.2 Pesticide and Herbicide Formulation
Aminosulfonic acid is incorporated into pesticide formulations as a surfactant or stabilizer. It helps the active ingredients spread more evenly across plant surfaces, improving the efficacy of the pesticide or herbicide. This property also helps in reducing the spray drift of chemicals, ensuring that they are delivered directly to the target areas.
5.3 Growth Regulator
Although research is still ongoing, aminosulfonic acid (specifically taurine) has been explored as a potential plant growth regulator. Some studies suggest that it may enhance seed germination, promote root development, and increase plant resistance to environmental stresses such as drought. As a result, it holds promise as a tool for improving agricultural yields and overall plant health.
Sulfamic Acid: Physical and Chemical Properties
Sulfamic acid (H3NSO3, CAS 5329-14-6) is a dry, non-volatile, strongly acidic solid – one of the few mineral acids that is easy and safe to handle in solid form. Its properties explain why it is preferred over liquid acids in many cleaning and industrial duties.
| Property | Value |
|---|---|
| Chemical name | Sulfamic acid (amidosulfonic acid / amidosulphonic acid) |
| CAS Registry Number | 5329-14-6 |
| Molecular formula | H3NSO3 (H2NSO3H) |
| Molecular weight | 97.09 g/mol |
| Appearance | White crystalline solid |
| Solubility in water | Readily soluble (roughly 20 g per 100 mL at 20 °C) |
| Acidity | Strong acid; a 1% solution has a pH of about 1 |
| Thermal behaviour | Decomposes on strong heating rather than melting cleanly |
| Key advantage | Dry, non-volatile solid – safer to store and dose than liquid mineral acids |
Two properties set sulfamic acid apart from hydrochloric and sulfuric acid. First, it is a solid, so it can be weighed, shipped and stored without the hazards of a liquid strong acid. Second, in many descaling and cleaning duties it is less aggressive to common metals and does not introduce chloride, which is one of the main reasons it is used on heat exchangers, boilers and cooling systems.
Grades and Specifications
| Grade | Typical use | Key specification points |
|---|---|---|
| Technical grade | Descaling, cleaning, industrial processes | Assay, moisture, sulfate and iron content |
| High-purity grade | Where low impurity levels are required | Tighter limits on sulfate, iron and heavy metals |
| Food / catalyst grade | Sweetener and food-related catalysis | Compliance with the relevant purity requirements |
Because sulfamic acid is used both as a cleaning acid and as a synthesis reagent, buyers should confirm the assay and the impurity limits appropriate to their application rather than relying on a single headline figure.
Descaling and Cleaning: How Sulfamic Acid Is Used
The largest use of sulfamic acid is as a descaler. Scale – mainly calcium carbonate and related deposits – builds up on heat-transfer surfaces, boiler tubes, cooling towers, heat exchangers and reverse-osmosis membranes, reducing efficiency and increasing energy use. Sulfamic acid dissolves carbonate scale efficiently while being gentler on the underlying metal than a strong liquid acid.
| Application | Why sulfamic acid fits |
|---|---|
| Boilers and heat exchangers | Dissolves carbonate scale; solid form is easy and safe to dose |
| Cooling systems | Removes scale without the chloride introduced by hydrochloric acid |
| Reverse-osmosis (RO) membranes | Used in controlled membrane-cleaning procedures to restore flux |
| Dairy and food-equipment cleaning | Effective descaler where a dry, controllable acid is preferred |
| General industrial cleaning | Descaling of metal surfaces, tanks and process equipment |
The practical attraction is not only performance but handling: a dry, non-fuming, non-volatile acid is far easier to store, transport and dose than a liquid strong acid, and the absence of chloride reduces the risk of chloride-induced corrosion on stainless steel.
Sulfamic Acid vs Other Acids for Descaling
| Acid | Form | Advantages for descaling | Cautions |
|---|---|---|---|
| Sulfamic acid | Dry solid | Safe to handle; less aggressive on many metals; chloride-free; good on carbonate scale | Not a strong choice for removing sulfate-type scale |
| Hydrochloric acid | Liquid | Fast, cheap, strong on carbonate scale | Fumes; introduces chloride (risk to stainless steel); hazardous to handle |
| Citric acid | Solid/liquid | Mild, food-safe, good for light scale | Weaker; slower on heavy scale |
| Phosphoric acid | Liquid | Effective; can leave a protective phosphate layer | Liquid handling; acid strength and cost considerations |
Other Industrial Uses of Sulfamic Acid
- Sweetener and food-related catalysis. Sulfamic acid is used as an acid catalyst in certain sweetener and food-ingredient processes, where a dry, controllable acid is an advantage.
- Electroplating and metal finishing. It is used in plating baths and metal-treatment formulations.
- Pulp, paper and textile processing. It finds use as an acidulant and in process cleaning.
- Dyes and pigments. It serves as an acid source in certain dyeing and pigment processes.
- Herbicide and industrial formulations. It is used in some agricultural and industrial formulations.
Frequently Asked Questions about Sulfamic Acid
What is sulfamic acid used for?
Its main use is descaling and cleaning – boilers, heat exchangers, cooling systems and RO membranes – together with sweetener production, electroplating, pulp and paper, and other industrial processes.
Is sulfamic acid the same as sulfuric acid?
No. Sulfamic acid (H3NSO3) is a different compound from sulfuric acid (H2SO4). Sulfamic acid is a dry solid, whereas sulfuric acid is a liquid; they are used for different purposes.
Why use sulfamic acid instead of hydrochloric acid for descaling?
Mainly handling and corrosion. Sulfamic acid is a dry, non-fuming solid that is easier and safer to store and dose, and it contains no chloride, so it is less likely to cause chloride-induced corrosion on stainless steel.
Does sulfamic acid damage metal?
Used as directed, it is generally more forgiving than liquid strong acids on many metals, which is one reason it is chosen for heat exchangers and boilers. Compatibility with the specific alloy should still be confirmed for each application.
What grades are available?
Technical, high-purity and food/catalyst grades are common; the choice depends on the required impurity limits. Assay, moisture, sulfate and iron are the usual specification parameters.
How should sulfamic acid be stored?
In a dry, sealed container, protected from moisture and away from strong bases and oxidising agents. Its solid, non-volatile form makes storage straightforward compared with liquid strong acids.
How do I buy sulfamic acid?
PolyBlueChem supplies sulfamic acid (CAS 5329-14-6) in technical and higher-purity grades. Contact our team for specifications and a quotation; see also our sulfamic acid buying guide.
Sulfamic Acid in Mining and Mineral Processing
Sulfamic acid is a solid, easy-to-handle acid used across mineral processing and metal-production plants for cleaning and descaling, where a liquid mineral acid would be harder to transport, store and control.
| Application | Why sulfamic acid |
|---|---|
| Descaling of process equipment | Removes carbonate and hydroxide scale from pipelines, pumps, tanks, heat exchangers and evaporators |
| Evaporator and crystalliser cleaning | Cleans scale in salt, potash and brine circuits, including lithium-brine plants |
| Pickling and rust removal | Removes oxide and rust from steel and equipment; a solid alternative to hydrochloric acid |
| Chloride-free cleaning | Introduces no chloride, so it is gentler on stainless steel than hydrochloric acid (less risk of pitting and stress-corrosion cracking) |
Why mines use it instead of hydrochloric acid
- Solid, safe to ship and store – no fuming liquid acid, easier handling and transport.
- Chloride-free – avoids the chloride attack that hydrochloric acid can cause on stainless steel and some alloys.
- Controllable – dissolves in water to the working strength; the cleaning solution is made up on site.
- Lower hazard on site – less severe storage and spill management than a liquid mineral acid.
Cleaning is set by solution strength (typically about 5-10%), temperature (about 40-80 deg C) and contact time; always check the compatibility of the equipment materials first, and never mix sulfamic acid with nitrites or strong oxidisers.
Buying Sulfamic Acid: Cost and Supply
Sulfamic acid is a commodity acid, bought on price, purity and reliable supply. Because it is produced at large scale in China, we can offer competitive prices on bulk volumes with consistent, batch-to-batch quality.
| Packaging | Use |
|---|---|
| 25 kg PP/PE bags | General; palletised for container shipment |
| 1000 kg jumbo bags | Bulk plant use |
| Full container loads | Best price for large, repeat volumes |
What to confirm on a quotation: purity (so the dose is predictable), particle form (powder vs granular, for dissolving), packaging and the delivery port. Because the price is volume-sensitive, tell us your annual tonnage for the best terms. Per-batch COA and SDS are supplied.
FAQs on Sulfamic Acid in Mining and Buying
Is sulfamic acid used in mining?
Yes – mainly for descaling and cleaning process equipment (pipelines, pumps, heat exchangers, evaporators and crystallisers) and for pickling and rust removal, where a solid, chloride-free acid is preferred over hydrochloric acid.
Why use sulfamic acid instead of hydrochloric acid in a plant?
It is a solid, easier to store and transport, and it introduces no chloride, so it is gentler on stainless steel and alloys. It is also easier to handle than a fuming liquid acid.
Do you offer competitive pricing on sulfamic acid?
Yes – as a large-scale producer we can offer competitive prices on bulk volumes, with per-batch COA and SDS. Tell us your tonnage and delivery port for a quotation.
Related reading
- Sulfamic acid price and supply: what drives the cost
- Sulfamic acid supply to Africa: packaging, ports and documents
- Sulfamic acid in nickel plating and metal finishing
- Sulfamic acid for chloride-free pickling vs hydrochloric acid
- Sulfamic acid in mining and mineral processing
- Sulfamic Acid for Descaling Boilers and RO Membranes
- Sulfamic Acid in Sweetener Production
- How to Buy Sulfamic Acid: Specs and COA