Uses and Safety Measures of Hydrofluoric Acid (HF)

What is Hydrofluoric Acid?

Hydrofluoric acid (HF) is an aqueous solution of hydrogen fluoride, appearing as a clear, colorless, and fuming corrosive liquid with a pungent odor. It has a melting point of -83.3°C, a boiling point of 19.54°C, a flash point of 112.2°C, and a density of 1.15 g/cm³. HF is highly soluble in water and ethanol but only slightly soluble in ether. Due to the strong bond between hydrogen and fluorine atoms, HF does not fully dissociate in water, making dilute solutions technically weak acids.

However, HF is extremely corrosive, capable of aggressively attacking metals, glass, and silicon-containing materials. Inhalation of its vapors or skin contact can lead to severe, hard-to-heal burns. In laboratory settings, HF is typically produced by reacting fluorspar (CaF₂) with concentrated sulfuric acid. It must be stored in sealed plastic containers in a cool and well-ventilated place.

Hydrofluoric Acid – Key Properties, Applications & Safety Summary

Common Names and Chemical Properties

• English Name: Hydrofluoric Acid
• Chemical Formula: HF
• Other Names: Hydrogen fluoride solution, fluohydric acid, fluoric acid

Applications of Hydrofluoric Acid

1. Metal Refining:
   HF is used to dissolve oxides in the refining of aluminum and uranium, making it vital in the aluminum electrolysis and nuclear industries.
2. Glass Etching:
   It is widely applied for etching glass to create patterns, scales, or inscriptions—commonly used in glass manufacturing.
3. Semiconductor & Petrochemical Industry:
   In semiconductor manufacturing (e.g., polycrystalline silicon, solar panels, PCBs), HF removes silicon oxides. It’s also used in refineries for the alkylation of isobutane and butenes, and for pickling stainless steel to eliminate surface oxides.
4. Fluorinated Compounds Synthesis:
   HF serves as a precursor for producing various fluorinated organic compounds such as Teflon (PTFE) and refrigerants like Freon, extensively used in refrigerator and air conditioning industries.

Corrosiveness and Chemical Behavior

In dilute form, HF slightly dissociates into ions. In concentrated solutions, it polymerizes to form H₂F₂, which further dissociates into H⁺ and HF₂⁻ ions—both highly corrosive. HF reacts with silicates to produce gaseous silicon tetrafluoride and easily attacks oxides, hydroxides, and metallic salts.

Due to the small ionic radius of fluoride ions, HF penetrates deeply into tissues, causing severe damage upon exposure.

Protective Coatings for HF Handling

For construction or maintenance involving HF exposure, coatings such as ZS-1033 anti-corrosive paint should be applied promptly after sandblasting—ideally within 8 hours. Application conditions require ambient and surface temperatures above 10°C. Apply three coats:

• First coat < 100 μm
• Total thickness ≈ 260 μm
  Allow at least 72 hours of drying before use.

HF Exposure and Symptoms of Poisoning

Acute Exposure:

• Skin contact: Early signs include redness and dryness, followed by tissue necrosis and deep ulcers.
• Eye exposure: Severe pain, potential corneal damage or perforation.
• Inhalation: May cause bronchitis, pneumonia, pulmonary edema, or reflexive suffocation.
• Systemic toxicity: Fluoride ions bind to calcium and magnesium in the body, causing hypocalcemia, hypomagnesemia, and disrupting potassium balance, which can lead to cardiac arrhythmias or death.

Chronic Effects:

• Irritation of eyes and respiratory tract, nasal bleeding, reduced sense of smell
• Dental fluorosis and skeletal fluorosis are long-term complications.

Severity by Concentration:

• Low concentration (<20%): Delayed pain; symptoms may appear 24 hours post-contact
• Medium concentration (20–50%): Symptoms appear within minutes to hours
• High concentration (>50%): Immediate intense pain, necrosis, and ulceration

Emergency First Aid for HF Exposure

1. Skin Contact:
   Rinse with copious running water for at least 30 minutes. Apply calcium gluconate gel or Hexafluorine® after washing. Seek immediate medical attention.
2. Eye Contact:
   Rinse eyes thoroughly with water while holding eyelids open. Follow with 1% calcium gluconate and corticosteroid eye drops. Get emergency care.
3. Inhalation:
   Move to fresh air, maintain airway patency. Administer oxygen if necessary; begin CPR if breathing stops. Avoid mouth-to-mouth resuscitation.
4. Ingestion:
   Rinse mouth, drink milk or egg white, and seek immediate care.
5. Wound Management:
   • Perform complete debridement
   • Apply 10% calcium gluconate via wet dressing, topical gel, or subcutaneous injection at 0.5 mL/cm²
   • Monitor and correct blood calcium levels if TBSA >1%
6. Surgical Intervention:
   For deep burns, early excision and wound closure are essential.
7. Inhalation Injury Treatment:
   Administer oxygen, monitor for airway obstruction or pulmonary edema, and perform tracheotomy if required.
8. Monitor Electrolytes:
   Closely observe and treat hypocalcemia and associated complications with calcium or magnesium compounds.

Protective Measures in the Workplace

• Engineering Controls:
  Work in sealed systems with effective ventilation. Mechanize operations where possible. Provide safety showers and eye-wash stations.
• Personal Protection:
  • Respiratory: Full-face gas mask or air-supplied respirator
  • Eyes: Incorporated in respiratory protection
  • Body: Acid- and alkali-resistant rubber suit
  • Hands: Acid- and alkali-resistant rubber gloves
  • Hygiene: No eating, drinking, or smoking in work areas. Shower and change clothes after work.
• Waste Disposal:
  Neutralize with lime water, landfill the precipitate or recycle, and dilute the supernatant before disposal via wastewater system.

Emergency Response to HF Spills

1. Evacuate personnel from the contaminated area and restrict access with warning signs.
2. Emergency responders should wear full protective equipment, including acid-resistant suits and gloves, and positive-pressure respirators.
3. Cut off the leak source, avoid direct contact.
4. Absorb minor spills with acid-absorbing cotton and dispose of in designated containers. Clean residuals with water.
5. For small leaks, use lime, sand, or soda ash. For large spills, build containment barriers and transfer to storage tanks for recycling or disposal.

Why Early Awareness Matters

Research shows that patients in non-fluorine chemical enterprises tend to experience significantly delayed wound healing compared to those in fluorine-related industries. This is often due to better hazard training and the availability of emergency kits (e.g., Hexafluorine®, calcium gluconate gel) in the latter. Therefore, all workers handling HF must receive proper training, follow strict safety protocols, and seek medical help at the earliest sign of exposure to minimize long-term damage.

About Jinhong Gas – Trusted Supplier of Hydrofluoric Acid

Jinhong Gas is a leading industrial gas supplier in China, providing high-purity hydrofluoric acid and a comprehensive range of fluorine-based chemicals to industries including electronics, metallurgy, pharmaceuticals, and energy. With advanced purification systems and a strict quality control process, we ensure that our HF products meet the highest standards of safety and performance. Jinhong also offers technical guidance on storage, transportation, and emergency response to help our clients handle HF safely and efficiently. Whether you’re in semiconductor manufacturing or specialty chemical production, Jinhong Gas is your reliable partner for high-quality and stable supply of hydrofluoric acid.

Frequently Asked Questions When Purchasing Hydrofluoric Acid

1. What purity levels are available for hydrofluoric acid?
Hydrofluoric acid is commonly supplied in concentrations ranging from 0.5% to 70%, depending on the application. High-purity grades (≥99.99%) are typically used in semiconductor manufacturing and precision etching, while lower concentrations are sufficient for cleaning agents and general industrial uses.

2. What packaging options are available?
HF is highly corrosive and must be stored and transported in plastic containers such as HDPE drums, IBC tanks, or customized fluoropolymer-lined containers. The packaging is usually selected based on order quantity and safety regulations in the destination country.

3. How is hydrofluoric acid transported safely?
Due to its hazardous nature, HF must be shipped as a regulated chemical under UN number 1790. Transportation requires certified carriers, proper labeling, and compliance with international safety standards such as ADR, IMDG, or DOT regulations.

4. Do I need special licenses or documentation to purchase HF?
Yes, in most countries, hydrofluoric acid is classified as a controlled substance, and purchasing it typically requires:

• Business license with appropriate chemical handling scope
• End-user declaration
• SDS (Safety Data Sheet) approval by local authorities
  Jinhong Gas can assist customers in preparing the necessary compliance documentation.

5. What is the shelf life of hydrofluoric acid?
If stored properly in sealed containers, away from sunlight and at stable temperatures, hydrofluoric acid can maintain its stability for 12–24 months. However, concentration and purity may degrade over time, especially in partially used containers.

6. Can Jinhong Gas provide technical support for HF applications?
Absolutely. Jinhong Gas offers application consulting, on-site training, and technical data sheets for industries that use HF. Whether you’re new to HF or working with custom requirements, our specialists are here to help ensure safe and effective usage.