Ammonium Bifluoride Application

Ammonium Bifluoride Application

Chemical Names: Ammonium Bifluoride

CAS Number: 1341-49-7

Molecular Formula: NH4HF4

Product Characteristics

Ammonium bifluoride is an inorganic salt with distinct physical and chemical properties that dictate its applications.

1. Physical Form: Typically appears as white or colorless, transparent rhombic or flaky crystals.

2. Hygroscopicity & Solubility: It is hygroscopic (readily absorbs moisture). It is highly soluble in water, forming a strongly acidic solution. It is also soluble in alcohols but insoluble in ether and acetone.

3. Thermal Instability: It is thermally unstable. Upon heating above approximately 125°C, it begins to sublime. At higher temperatures, it decomposes into ammonia gas (NH₃) and hydrogen fluoride gas (HF), a critical safety consideration for handling and storage.

4. Chemical Dual Nature: Its structure contains both an ammonium ion (NH₄⁺) and a bifluoride ion (HF₂⁻). This allows it to act as both a source of fluoride ions (F⁻) and a source of hydrofluoric acid (HF) activity. Consequently, it serves as a moderate fluorinating agent and a potent acidic etching agent, more effective than ammonium fluoride (NH₄F) alone.

5. High Corrosivity & Toxicity: It is highly corrosive and irritating to the skin, eyes, and mucous membranes. Inhalation of its dust or decomposition gases, or skin contact with its solutions, can cause severe chemical burns. Fluoride ions also pose a risk of systemic toxicity. This is its primary hazardous property.

6. Reactivity with Oxides: It reacts readily with silicon dioxide (SiO₂) and other metal oxides (found in glass, ceramics, and metal surfaces) to form soluble fluorosilicates. This reaction is the core principle behind its use in etching, cleaning, and derusting.

Primary Applications

Based on the above properties, the main industrial uses of ammonium bifluoride are:

1. Glass Industry (Core Use): Used for glass etching and frosting to create matte finishes, light bulb coatings, and decorative glassware.

2. Metal Treatment: Serves as a highly effective cleaner and etchant for surface treatment of aluminum, stainless steel, and titanium to remove oxide layers, welding slag, and impurities prior to welding, plating, or coating.

3. Industrial & Domestic Cleaning: A key active ingredient in heavy-duty cleaners for removing mineral scale, rust, cement residues, and ceramic contaminants from equipment and surfaces.

4. Petroleum Industry: Used in oil well acidizing to dissolve siliceous materials in sandstone formations, thereby enhancing permeability and production rates.

5. Chemical Synthesis & Fluoride Source: Acts as a fluorinating agent in organic synthesis and is used in the production of other fluorides (e.g., cryolite, aluminum fluoride).

6. Electronics Industry: Employed for cleaning and micro-etching of silicon wafers, making it a critical chemical in semiconductor and photovoltaic manufacturing.

7. Other Applications:

Wood Preservative (Historical Use): This use has declined significantly due to its high toxicity.

Sterilizing agent for brewery equipment.Process aid in uranium extraction from ores.

Important Safety Notice: Ammonium bifluoride is a high-hazard chemical. It must be handled with full personal protective equipment (acid-resistant gloves, goggles, face shield, acid suit) under adequate ventilation. Any exposure requires immediate flushing with copious amounts of water and urgent medical attention, as fluoride burns can have a delayed onset and penetrate deep tissue. Store in a cool, dry, well-ventilated area away from alkalis and moisture.

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