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Hydrofluosilicic Acid

Controlling heat to avoid hazardous reactions

Hydrofluosilicic acid is used in water fluoridation, ceramic production, electroplating, bottle sterilizing, brewing and many other applications. This colorless, fuming liquid presents a host of challenges in storage:

  • It decomposes in heat, giving off toxic fluoride compounds, which may react violently with alkaline materials.

  • Hydrofluosilicic acid is corrosive to most metals – and it attacks glass and stoneware.

  • Like lye and sodium hypo, hydrofluosilicic acid has a tendency to find leak paths.

  • The chemical is incompatible with strong alkalis and strong concentrated acids. It reacts with oxidizing agents, combustible solids and organic peroxides.

  • Its reaction with metals produces flammable hydrogen gas.

A complete system equipped with specialized features can reduce the risks associated with this toxic chemical.

Talk to a chemical storage tank expert

The Poly Processing Hydrofluosilicic Acid System

Hydrofluosilicic acid is an extremely dangerous chemical. Human contact with it can result in severe injury or fatality. But when the chemical is controlled in a stable environment, risk can be dramatically reduced.

XLPE tanks are ideal in this situation. The thermosetting of XLPE’s polymer chains acts as a netting to prevent permeation, leakage or seepage.

With its full drain design, a built-in IMFO® flange can help eliminate any buildup of sediment, lessening the potential for lead and arsenic deposits over time. The IMFO® system’s design also keeps the tank intact, which is important for chemicals that try to find leak paths. If an IMFO® isn’t an option, wetted fittings should be kept to an absolute minimum to avoid failure.

If secondary containment is not available, a SAFE-Tank® is recommended instead of an IMFO® tank. This tank within a tank greatly reduces the chance for leaks.

For additional information on storing hydrofluosilicic acid, including recommended storage tanks and components, download our Hydrofluosilicic Acid Guide below. 


Chemical Resin Type Specific Gravity Rating Fitting Material Gasket Material Bolt Material
Hydrofluosilicic Acid XLPE 1.9 PVC EPDM C-276


Tank Specifications

Tank options include: 

High-density crosslinked polyethylene (XLPE) construction for maximum strength

OR-1000™ antioxidant inner surface 

Integrally Molded Flanged Outlet (IMFO®) for complete drainage 

SAFE-Tank® design for "tank-within-a-tank" protection 

Recommended System Components

SAFE-Tank® Double Wall Tank System

SAFE-Tank® Double Wall Tank System

Secondary containment: SAFE-Tank® if concrete containment is not available.

Alternative: PPC secondary containment basin or other secondary containment suitable for chemical, of adequate size for use

IMFO® Fittings

IMFO® Fittings

Fittings: IMFO® eliminates the need for confined space entry. 

PTFE Expansion Joint

PTFE Expansion Joint

Plumbing: Requires flexible connections to allow for lateral and vertical tank contraction and expansion, and to reduce vibration stress. 

SAFE-Surge® Manway Cover

SAFE-Surge® Manway Cover

Venting: SAFE-Surge® manway cover is recommended on pneumatically loaded systems to support tank longevity.

Technical Overview

NOTE: We recommend always venting this chemical outside a confined environment due to health risks from the fumes and to the damage it will cause to glass and metals.

IMFO® Vertical Flat Bottom of XLPE:

  • 230–13,650 gallons

  • 1.9 spg rating

Non -IMFO® alternatives:


  • 55–8,700 gallons

  • 1.9 spg rating for primary tank

  • Spg ratings for secondary tanks ≥ 3,000 gallons may be equal to or 1 less spg than primary tank.

  • All other tank sizes must equal primary tank spg rating.

Standard Vertical Flat Bottom XLPE:

  • 30–13,650 gallons

  • 1.9 spg rating

Alternative secondary containment: PPC secondary containment basin or other secondary containment suitable for hydrofluosilicic acid, of adequate size for use

Plumbing: Requires use of flexible connections with fittings on lower third of sidewall. See Fittings & Accessories for flexible connections options.

Venting: See Venting Chart

Foundation: PPC IMFO® tank pad or smooth concrete, asphalt or steel foundation designed to accommodate IMFO®, SAFE-Tank® or vertical tank

Temperature: Product should not exceed 100°F at delivery or during storage to maintain ASTM D1998 design parameters.

Lid: Fume-tight manway cover to manage release of chemical gases

Options: Restraint systems for wind and seismic, level gauges, ladders, heating pads, insulation, mixer mounts, OR-1000™ for NSF-61 certification and engineering stamp