Potassium Fluorozirconate (K2ZrF6): Industrial Grades, Uses, and Sourcing Guide

A ceramic glaze batch starts to speck, a welding consumable run becomes inconsistent, and an aluminum-alloy trial shows uneven grain structure—all in the same week. The common thread may be a white crystalline fluoride salt that looked identical on two certificates of analysis. Potassium fluorozirconate, K2ZrF6, is a narrow-purpose industrial material with a surprisingly broad set of quality variables. Its performance is rarely decided by the product name alone. Assay, moisture, chloride, sulfate, iron, heavy metals, and particle size decide whether a lot behaves as a reliable zirconium source, a flux component, or a surface-treatment additive.

The practical conclusion is simple: specify potassium fluorozirconate by process, not by CAS number alone. A buyer who compares only price per kilogram is comparing the visible part of the quotation. The invisible part—batch consistency, impurity limits, packaging integrity, and documentation—usually determines whether the material works in production.

Start With the Process, Not the CAS Number

Potassium fluorozirconate is often purchased as a technical-grade salt, but “technical grade” is not a specification. Two suppliers can both ship K2ZrF6 with a 98% assay and still deliver materials that behave differently in a glaze, an alloy flux, or a conversion-coating bath. The difference comes from the impurity profile, the particle-size distribution, the moisture content, and the physical form.

A useful purchasing rule is to begin with the process window and work backward. If the material is used as a zirconium source in a ceramic or glass formulation, the important questions are zirconium content, iron and heavy-metal limits, and whether the salt dissolves or disperses cleanly. If it is used in an alloy-treatment flux, chloride and sulfate may matter more because they affect slag behavior, fume, and equipment corrosion. If it is used in surface treatment, insoluble matter and particle size can influence bath stability and coating uniformity.

For ceramic and glass use: prioritize zirconium content, iron, heavy metals, and consistency of particle size.
For alloy and flux use: prioritize assay, chloride, sulfate, moisture, and melting behavior in the customer’s flux system.
For surface treatment: prioritize solubility, insoluble matter, turbidity, and freedom from coarse particles.
For general chemical conversion: prioritize lot-to-lot consistency, packaging protection, and a complete COA and SDS package.

This process-first approach also prevents over-specification. A buyer does not need a 99.9% ultra-pure grade for every application, and paying for one can be waste. Conversely, accepting an unspecified technical grade in a sensitive glaze or alloy process can create far more cost than the apparent saving.

What Potassium Fluorozirconate Is and What the Numbers Mean

Potassium Fluorozirconate K2ZrF6 Technical GradeWhite crystalline powder with ≥98% content, used as zirconium and fluoride source; check grade and solubility before specifying for glazes or alloys.View Product →

Potassium fluorozirconate is also called potassium hexafluorozirconate or dipotassium hexafluorozirconate. Its formula is K2ZrF6, its CAS number is 16923-95-8, and its theoretical molecular weight is about 283.39 g/mol. It is typically a white crystalline powder or fine crystal, and it is used as a source of zirconium and fluoride in several industrial systems. The compound is not a generic fluoride salt that can be swapped freely with potassium fluoride, ammonium fluorozirconate, or potassium fluoroaluminate; each has different solubility, thermal behavior, and impurity sensitivity.

Table 1. Reference properties for potassium fluorozirconate; final limits should always be confirmed on the supplier COA and SDS.
Property	Typical reference point	What buyers should confirm
Chemical formula	K2ZrF6	Identity and grade on the COA
CAS number	16923-95-8	Consistency between label, SDS, and COA
Molecular weight	Approximately 283.39 g/mol	Theoretical value; not a substitute for assay
Appearance	White crystalline powder or crystals	Visual standard and color limits
Assay	Common technical grades around 98–99.5%	Analytical method and batch result
Moisture	Often controlled below 0.5%	Karl Fischer or loss-on-drying method
Particle size	Available in several mesh or micron ranges	Sieve analysis or laser diffraction
Density	Approximately 3.4–3.5 g/cm³	Method and whether bulk or tapped density is relevant
Solubility	Slightly soluble in water; temperature-dependent	Lab test in the actual process medium

The numbers in Table 1 are useful for orientation, not for release decisions. A certificate of analysis should state the test method and the actual result for the lot. For example, an assay result obtained by titration and an assay result obtained by ICP or XRF may not be directly interchangeable. A buyer who receives a COA without method information has a number, but not necessarily a specification.

Why the Name on the Label Is Not Enough

Potassium fluorozirconate can be produced by reacting zirconium-containing feedstock with hydrofluoric acid or fluorozirconic acid, followed by neutralization with a potassium source, crystallization, drying, and milling. Each step creates quality variables. Incomplete reaction can leave residual zirconium or fluoride imbalance. Washing efficiency affects chloride and sulfate. Drying controls moisture and caking. Milling controls particle size and dust. Crystallization conditions influence crystal habit and dissolution behavior.

That is why a supplier’s process control matters as much as the final assay. A well-controlled crystallizer and dryer can produce a consistent white salt with predictable dissolution. A less controlled process can produce material that passes a 98% assay but varies in fines, moisture pickup, or trace impurities from batch to batch.

Where Potassium Fluorozirconate Earns Its Place

Potassium fluorozirconate is not a high-volume commodity in the same sense as soda ash or caustic soda. Its value comes from specific chemical functions: supplying zirconium in a fluoride-compatible form, participating in flux systems, and supporting zirconium-based surface chemistry. The applications below are the practical contexts in which buyers most often evaluate it.

Aluminum and Magnesium Alloy Processing

In some aluminum- and magnesium-alloy flux and grain-refining routes, potassium fluorozirconate serves as a zirconium-bearing component. Zirconium can influence grain structure, and fluoride salts can influence flux melting, oxide removal, and slag behavior. The exact role depends on the alloy system and the flux design. A supplier’s material that works in one alloy shop may not work in another if the particle size, moisture, or chloride level changes.

For alloy applications, the purchasing conversation should include the flux or refiner formulation, the operating temperature, the holding time, and the allowed chloride and sulfate limits. A low-moisture, free-flowing grade is usually easier to handle, but the buyer should confirm that the drying method has not altered solubility or created hard agglomerates. More detail on zirconium-fluoride chemistry in alloy development is available in this review of potassium fluorozirconate in high-performance alloys.

Ceramics, Glass, and Glazes

In ceramic glazes, frits, and glass formulations, potassium fluorozirconate can act as a zirconium source. Zirconium compounds are used to influence opacity, thermal expansion, chemical durability, and surface appearance. The fluoride component also participates in melt behavior, which means the material is not simply a neutral zirconium carrier. Small changes in assay or impurity profile can shift glaze color, surface texture, or firing behavior.

For these uses, iron and heavy-metal limits are often more important than a small difference in assay. A glaze that is sensitive to iron may show color drift even when the potassium fluorozirconate assay is on target. Buyers should request a COA with iron, titanium, and other color-sensitive elements, and they should test a small batch in the actual glaze formulation before scaling up.

Metal Surface Treatment and Conversion Coatings

Zirconium-based conversion coatings and surface-treatment baths use zirconium salts to form thin protective layers on metal surfaces. Fluoride often plays a role in etching, activation, and bath stability. Potassium fluorozirconate can be used as a zirconium and fluoride source in such systems, but bath performance depends on free fluoride, pH, temperature, and the presence of other metal ions.

For surface-treatment buyers, insoluble matter and coarse particles are practical concerns. A fine, clean-dissolving grade reduces the risk of sediment, nozzle blockage, and uneven coating. The buyer should also confirm the chloride and sulfate levels because these ions can accumulate in a bath and affect corrosion performance.

Zirconium Chemistry, Welding, and Catalysis

Potassium fluorozirconate is used in the preparation of other zirconium compounds and in some welding-flux and catalyst-related applications. In welding consumables, fluoride salts can influence arc stability, slag formation, and metal transfer. In catalyst systems, zirconium compounds may serve as supports, promoters, or Lewis-acid sites, although the exact function depends on the catalyst design.

These applications are less standardized than glaze or alloy use, so the buyer should test the material in the actual process rather than relying on a generic technical datasheet. A sample qualification run is usually cheaper than a production trial with an unverified lot.

Reading a Certificate of Analysis Like a Buyer

A COA is not a marketing document. It is a lot-specific record of what was tested and what was found. The most useful COAs are short, complete, and method-specific. They identify the product, grade, lot number, manufacturing date, test methods, specification limits, and actual results. A COA that lists only assay and appearance is thin for most industrial buyers.

Table 2. Example impurity and physical specifications for potassium fluorozirconate, with the process risk each limit is intended to control.
Specification	Example target or limit	Process risk if uncontrolled
Assay as K2ZrF6	≥98.0% or ≥99.0% depending on grade	Lower zirconium delivery; dosing drift
Zirconium content	Confirmed by supplier method	Inconsistent glaze opacity or alloy response
Moisture	≤0.5% typical	Caking, weighing errors, dust, and bath dilution
Chloride	Low, typically ≤0.1–0.3% depending on grade	Corrosion, fume, and flux behavior changes
Sulfate	Low, typically ≤0.1–0.3% depending on grade	Bath accumulation and glaze defects
Iron	≤50–200 ppm for color-sensitive grades	Color drift in glazes and glass
Heavy metals	Application-specific limits	Regulatory or product-safety failure
Insoluble matter	Low, with a clear test method	Sediment, nozzle blockage, and coating defects
Particle size	Sieve or laser range agreed with buyer	Dust, dissolution rate, and segregation

Assay and Zirconium Content

Assay is the first number most buyers check, but it should not be the only number. A product can meet a 98% assay and still deliver a lower effective zirconium content if it contains moisture, occluded salts, or other impurities. The buyer should ask whether the assay is calculated on a dry basis, as-received basis, or by a specific titration method. For process control, zirconium content may be more directly relevant than the combined assay.

Chloride, Sulfate, and Insoluble Matter

Chloride and sulfate are common quality markers in fluoride salts. They can enter through raw materials, water, or incomplete washing. In a glaze or glass melt, they can affect volatility and surface quality. In a metal-treatment bath, they can accumulate and influence corrosion. In an alloy flux, they can change slag behavior and fume. Insoluble matter is a separate concern: it can clog filters, settle in tanks, or create surface defects.

Iron and Heavy Metals

Color-sensitive applications such as white glazes, optical glass, and specialty ceramics are vulnerable to iron and other transition metals. A buyer may need iron below 50 ppm for one formulation and below 200 ppm for another. Heavy-metal limits depend on the final product and the applicable regulatory framework. The supplier should be able to provide consistent analytical results, not just a one-time laboratory report.

Moisture and Loss on Drying

Moisture is a quiet source of variation. It changes the effective mass of the material, can cause caking in storage, and can affect dust and flow. A buyer who weighs potassium fluorozirconate by mass without correcting for moisture may introduce a small but real dosing error. For sensitive formulations, loss-on-drying or Karl Fischer results should be reported lot by lot.

Particle Size and Dust

Particle size affects dissolution, dust, flow, and segregation in a blended product. A coarse crystal may dissolve more slowly but generate less dust. A fine powder may dissolve faster but can be harder to handle and more likely to become airborne. The right choice depends on the process. The buyer and supplier should agree on a sieve range, a laser-diffraction specification, or a practical dispersion test rather than relying on “fine powder” as a description.

For a deeper comparison of the fluoride–zirconium family, including fluorozirconic acid and its ammonium and potassium salts, this technical guide to fluorozirconic acid and potassium fluorozirconate is a useful reference for specification discussions.

Why Particle Size and Moisture Matter More Than Buyers Expect

In a laboratory, potassium fluorozirconate is often treated as a simple reagent. In a plant, it is a powder that must flow, weigh, convey, dissolve, and react consistently. Particle size and moisture influence every one of those steps. A lot with excessive fines can create dust and handling loss. A lot with hard agglomerates can dissolve slowly or leave undissolved particles. A lot with high moisture can cake in the bag and change the effective batch weight.

The practical answer is not to demand the finest possible powder. The right specification is the one that matches the feeding and dissolution system. A plant with a dust-collection system and a high-shear mixer may handle a fine grade well. A plant that charges bags manually may prefer a free-flowing crystalline grade with low fines. A blended product may require a particle size that resists segregation during transport.

Dust control: specify a maximum fines fraction if the handling system is open or manual.
Dissolution: test the actual grade in the actual medium at the actual temperature.
Storage: require moisture-barrier packaging and a defined re-test period.
Blending: match particle size to other components to reduce segregation.

Moisture also affects safety and housekeeping. A damp fluoride salt can adhere to equipment and form hard deposits. Dry material is easier to vacuum, sweep, and contain. The buyer should ask how the supplier dries and cools the product, how the packaging is sealed, and whether the material is tested for moisture at the time of packing or only at an earlier stage.

Supplier Evaluation: Five Questions That Reveal More Than a Price List

Price lists are easy to compare because they are standardized. Capability is harder to compare because it is revealed through questions. A supplier with strong inorganic fluoride experience will usually answer process and quality questions in specific terms. A trader or less experienced supplier may answer in generalities. The following five questions are a practical starting point.

How is the product crystallized, washed, dried, and milled? The answer indicates whether the supplier controls the variables that affect impurity profile and particle size.
What does a typical COA include, and which methods are used? A complete answer covers assay, moisture, chloride, sulfate, iron, insoluble matter, and particle size.
How is batch consistency verified? Look for batch records, trend data, retained samples, and a defined release specification.
What packaging and storage conditions are recommended? The answer should address moisture barrier, bag integrity, palletization, and shelf life.
Can the supplier support a sample qualification and a scale-up? A supplier who understands industrial qualification will offer a sample, a COA, an SDS, and a technical discussion before the first commercial order.

For a manufacturer with decades of inorganic fluoride production experience, these questions often reveal strengths that are not visible in a quotation: fluoride handling know-how, crystallization control, analytical discipline, and packaging experience. The buyer should still verify the answers with documents and a sample. Experience is useful, but it is not a substitute for lot-specific evidence.

How to Compare Quotes Without Leaving Risk Off the Spreadsheet

A quotation that lists only price per kilogram is incomplete. The true cost of potassium fluorozirconate includes freight, packaging, duties, inspection, sampling, storage, and the cost of a failed batch. Table 3 shows how to compare offers on a more realistic basis.

Table 3. Cost elements to compare when evaluating potassium fluorozirconate quotations; the lowest unit price is not always the lowest cost of use.
Cost element	What to ask	Hidden cost if ignored
Unit price	Price basis, Incoterm, and currency	Freight and duty surprises
Packaging	Bag type, liner, net weight, pallet	Moisture damage and disposal cost
Quality testing	COA scope, third-party inspection	Incoming retest and rejected lots
Lead time	Production lead time and shipment schedule	Expedited freight and stockout
Batch consistency	Historical range, not only specification	Process adjustment and off-spec product
Technical support	Sample testing and troubleshooting	Longer qualification and trial cost

The best comparison is cost per accepted batch, not cost per kilogram. A slightly higher-priced supplier with consistent moisture, low fines, and complete documentation can be cheaper than a low-price supplier whose material requires rework, extra testing, or production downtime.

Packaging, Storage, and Transport

Potassium fluorozirconate is a hygroscopic fluoride salt and should be protected from moisture during storage and transport. Common industrial packaging includes 25 kg net woven bags with a polyethylene liner, and larger jumbo bags for bulk users. Pallets should be stable, wrapped, and labeled with product name, grade, lot number, net weight, and handling information. The packaging should be strong enough to survive normal handling without seam failure or liner damage.

Store dry: keep bags closed and away from damp floors and condensation.
Avoid incompatible materials: segregate from strong acids, oxidizers, and materials that could generate hazardous gases on contact.
Protect the liner: a torn liner can allow moisture pickup and caking.
Use first-in, first-out: rotate stock and respect the supplier’s re-test period.
Inspect incoming lots: check bag integrity, lot labels, and COA before unloading.

For export, the documentation package should include the commercial invoice, packing list, COA, SDS, and any country-specific transport or import documents. The SDS should be current and in the required language. The buyer should confirm the HS classification with the supplier and customs broker because classification can affect duties and import requirements.

Safety, Environment, and Waste

Potassium fluorozirconate is an industrial fluoride salt and should be handled with standard chemical hygiene. Dust can irritate the respiratory tract and eyes, and ingestion or repeated exposure should be avoided. The exact hazard classification depends on the supplier’s SDS and the regulatory jurisdiction, but the practical controls are consistent: dust extraction, local ventilation, suitable personal protective equipment, eyewash access, and good housekeeping.

Engineering controls: use closed transfer where possible, local exhaust ventilation, and dust collection.
Personal protection: follow the SDS for gloves, eye protection, respiratory protection, and protective clothing.
Spill control: sweep or vacuum dust without generating airborne clouds; do not use uncontrolled water washing that spreads fluoride-containing liquid.
Acid contact: avoid contact with strong acids because fluoride salts can generate hydrogen fluoride under acidic conditions.
Waste: dispose of empty bags, dust, and off-spec material according to local regulations and the SDS.

Environmental controls should focus on containment and wastewater management. Fluoride-containing rinse water and spill cleanup liquids may require treatment before discharge. The buyer should confirm the supplier’s packaging take-back or disposal recommendations and should train operators on the difference between a dry spill and an acidic spill.

A Practical Qualification Checklist

A sample qualification should be planned like a small production trial, not like a quick laboratory check. The goal is to confirm that the material is not only chemically acceptable but also physically compatible with the plant. The following checklist helps organize the work.

Confirm the grade, assay basis, and impurity limits against the process window.
Review the COA, SDS, and technical data sheet for completeness and consistency.
Test particle size, bulk flow, and dust behavior under plant-like conditions.
Run a small dissolution or dispersion test in the actual process medium.
Check moisture pickup after opening the bag and after short-term storage.
Verify that the packaging protects the liner and is easy to discharge safely.
Run a pilot batch and compare yield, appearance, and process stability with the current material.
Review batch-to-batch variation over at least three lots before commercial release.
Confirm the documentation package for customs, quality, and safety review.
Agree on a re-test period, storage condition, and change-control notification.

This checklist is intentionally practical. It does not replace a formal supplier audit, but it catches the problems that most often appear after the first order: unexpected fines, slow dissolution, caking, high chloride, or inconsistent color in the finished product.

Related Zirconium Fluoride Products

Fluorozirconic Acid 45% Liquid Zirconium SourceColorless 45% liquid acid for zirconium compounds, optical glass, and catalysts; corrosive handling and storage differ from solid fluorozirconate salts.View Product →

Fluorozirconic acid is the parent acid in the zirconium-fluoride family. Buyers who need a liquid zirconium source, or who are adjusting a reaction step before neutralization, often evaluate it alongside potassium fluorozirconate. The handling and storage requirements differ because the acid is corrosive and must be contained in suitable equipment.

Ammonium Fluorozirconate White Crystals ≥98%Water- and alcohol-soluble white crystals for metal treatment and ceramic glazes; consider ammonium chemistry and moisture protection before use.View Product →

Ammonium fluorozirconate is another salt in the same family. It can be relevant when ammonium chemistry is acceptable or when a different solubility and thermal behavior is needed. It is not a drop-in substitute for potassium fluorozirconate; the cation affects solubility, thermal decomposition, and the way the salt behaves in a formulation.

Buyers should compare the full family—fluorozirconic acid, potassium fluorozirconate, ammonium fluorozirconate, and related zirconium salts—on the basis of the process chemistry, not only on the fluoride content. The cation and the physical form can change handling, reaction rate, and final product quality.

Potassium fluorozirconate is a small-volume industrial salt with a large specification surface. The product name identifies the chemistry, but it does not define the grade. Assay, zirconium content, moisture, chloride, sulfate, iron, heavy metals, insoluble matter, and particle size all influence whether a lot performs as expected. A buyer who writes the specification around the process, requests method-specific COAs, qualifies a sample in the real system, and compares suppliers on cost per accepted batch will usually avoid the most expensive surprises.

The next step is not a generic inquiry. It is a short specification sheet with the application, required limits, packaging preference, annual volume, and qualification requirements. That document gives the supplier something concrete to quote against and gives the buyer a basis for comparing responses. In a material like potassium fluorozirconate, clarity at the specification stage is the cheapest quality control available.