Chemical laboratory

Hydrofluorosilicic Acid

High-Purity Fluorine Compound for Industrial Applications

  • CAS 16961-83-4
  • Formula H₂SiF₆
  • Flash Pt N/A °C
  • Density 1.22 g/cm³ (23% solution)
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Physical & Chemical Properties

Property Value Unit
Boiling point 108.5°C (23% solution) °C
Flash point N/A °C
Density 1.22 g/cm³ (23% solution) g/cm³
Solubility Miscible with water -
Ph < 1 (concentrated) -
Molecular weight 144.06 g/mol g/mol
Melting point N/A °C
Vapor pressure N/A mmHg
Autoignition temp N/A -
Appearance Colorless or slightly yellow liquid -
Odor Pungent, irritating -
Vapor density N/A g/cm³

Overview

Hydrofluorosilicic acid (H₂SiF₆) is a highly corrosive, colorless to slightly yellow liquid with a pungent, irritating odor. This inorganic compound, also known as fluorosilicic acid or hexafluorosilicic acid, is typically supplied as an aqueous solution ranging from 20-30% concentration. With its strong acidic properties (pH < 1) and excellent solubility in water, hydrofluorosilicic acid serves as a critical chemical intermediate and processing agent across multiple industrial sectors.

Key Applications

  • Water Fluoridation: Widely used in municipal water treatment systems to prevent dental decay, providing a cost-effective source of fluoride ions for public health programs.
  • Glass Etching & Surface Treatment: Essential for frosting and etching glass surfaces, creating decorative patterns and improving adhesion properties in manufacturing processes.
  • Metal Surface Treatment: Functions as a cleaning and etching agent for metal surfaces, particularly in aluminum processing and steel pickling operations to remove oxides and scale.
  • Concrete Hardening: Acts as a concrete densifier and hardener, penetrating concrete surfaces to increase durability and reduce porosity in industrial flooring applications.

Safety & Handling

Hydrofluorosilicic acid is non-flammable with no flash point, but requires extreme caution due to its highly corrosive nature. Personnel must wear appropriate PPE including acid-resistant gloves, face shields, and chemical-resistant clothing. Ensure adequate ventilation and eyewash/safety shower stations are readily accessible. Never mix with bases or metals, as violent reactions may occur. Store away from incompatible materials and maintain proper spill containment measures.

Storage & Shelf Life

Store in corrosion-resistant containers such as polyethylene or PTFE-lined vessels in a cool, dry, well-ventilated area away from heat sources and incompatible materials. Avoid contact with metals, bases, and organic materials. Maintain temperatures below 25°C to prevent concentration changes due to evaporation. When properly stored in original packaging, the product maintains stability for extended periods. Keep containers tightly sealed to prevent moisture absorption and contamination.

Why Alliance Chemical

Alliance Chemical delivers Hydrofluorosilicic Acid with same-day shipping from our Taylor, Texas facility. We offer flexible shipping options including UPS for smaller quantities, LTL for medium orders, and full truckload for bulk requirements. Every shipment includes comprehensive Safety Data Sheets (SDS) and Certificates of Analysis (COA) to ensure product quality and regulatory compliance for your operations.

Shipping & Availability

Parcel Shipping

UPS Ground supports pints, quarts, and most 1-gallon packages nationwide.

LTL Freight

5-gallon pails, drums, and totes move via LTL carriers such as ABF Freight, SEFL, Saia, and XPO.

Full Truckload

FTL available for palletized bulk orders. Competitive freight rates.

Local Pickup

Same-day pickup at our Taylor, TX warehouse for Texas customers.

SDS, COA, and TDS available for every product • Same-day shipping on orders before 1 PM CT

Frequently Asked Questions

What is hydrofluorosilicic acid (H2SiF6) and what is it used for?
Hydrofluorosilicic acid (H2SiF6) is an inorganic, fluoride-containing acid supplied as an aqueous solution and used as a raw material and reagent in industrial and laboratory settings. Common uses include water treatment, metal surface treatment and cleaning, chemical synthesis, and other process applications that require a soluble fluoride source.
How should 23% hydrofluorosilicic acid be stored and what is its typical shelf life?
Store in a cool, dry, well‑ventilated area in compatible, tightly closed containers (typically HDPE or specialty plastics) away from bases, strong oxidizers and metals. When kept in original containers and under recommended conditions it is generally stable for 12–24 months; verify shelf life with the supplier or the Certificate of Analysis.
Is hydrofluorosilicic acid hazardous and what safety precautions should I take when handling it?
Yes — it is a corrosive fluoride-containing acid that can cause severe skin, eye and respiratory irritation; avoid contact and inhalation. Use appropriate engineering controls and PPE (chemical-resistant gloves, goggles/face shield, acid-resistant clothing) and follow the product SDS for detailed handling and emergency procedures.
What are the differences between a 23% hydrofluorosilicic acid solution and other concentrations?
A 23% solution is a commonly supplied concentration balancing effectiveness and handling risk; higher concentrations increase corrosivity, fluoride content and handling hazards, while lower concentrations reduce activity and dosing requirements. Choose concentration based on application requirements, dosing equipment and compatibility with materials and processes.
What documentation will the supplier provide for hydrofluorosilicic acid?
Suppliers typically provide a Safety Data Sheet (SDS), Certificate of Analysis (COA), and a technical data sheet, and can supply shipping documents and regulatory compliance information on request. Always review the SDS and COA before use to confirm specifications and hazard information.
How is hydrofluorosilicic acid packaged and shipped safely?
It is commonly packaged in HDPE drums, intermediate bulk containers (IBCs) or bulk tankers and shipped as a hazardous corrosive material subject to local and international transport regulations. Use approved packaging, correct labeling and transport documentation, and follow the SDS and carrier requirements for hazardous goods.
What materials are compatible with hydrofluorosilicic acid and which should be avoided?
Compatible materials typically include plastics such as HDPE, PTFE and certain PVC formulations; many stainless steels may be acceptable with proper grades and inhibitors. Avoid carbon steel, aluminum and other reactive metals and consult material compatibility charts and your supplier for application‑specific guidance.
What technical specifications should I expect for a 23% hydrofluorosilicic acid product?
Typical specifications include chemical formula H2SiF6, nominal assay 23% w/w, an aqueous liquid form and a color range from colorless to pale yellow; exact purity, impurity limits and density are provided on the COA. For critical applications request the full technical data sheet and batch COA from the supplier.
Which industries and applications commonly use hydrofluorosilicic acid?
It is used across water treatment operations, metal finishing and pickling, chemical manufacturing, electronics processing and laboratory research where a soluble fluoride source or fluorosilicate functionality is required. Specific applications and regulatory requirements vary by industry and geography.
How can I purchase hydrofluorosilicic acid and are there regulatory or lead‑time considerations?
Hydrofluorosilicic acid is available from chemical distributors and manufacturers in standard pack sizes, with lead times depending on order size and location; many suppliers offer technical support, COAs and bulk delivery. Purchases may be subject to local regulations, permits or customer vetting due to its hazardous nature, so confirm requirements with your supplier before ordering.

Documentation & Downloads

Safety Data Sheet
SDS / MSDS
Request COA
Certificate of Analysis
Technical Data Sheet (TDS)
Available for all products

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