Cover Flux Aluminum Covering Flux · NaCl–KCl Base
The cheapest way to stop losing metal you already paid for. Molten aluminum oxidizes the moment it meets air, and every pound of oxide skimmed off as dross carries good metal with it. A cover flux melts into a thin salt layer over the bath, keeps air and moisture off the surface, and leaves a drier dross that gives its metal back.
Chelora Chemicals is a cover flux supplier and sourcing partner serving foundries, die casters and remelt operations across the United States. We match the grade to your alloy and furnace, including sodium-free grades for magnesium-bearing alloys, with a batch COA and SDS on every consignment.
- Product type
- Covering flux for aluminum
- Base salts
- Sodium chloride · potassium chloride
- Typical additions
- Fluoride salts
- Function
- Protective layer on the melt
- Form
- Powder or granules
- Grades
- Standard · sodium-free
- Application
- Spread on the melt surface
- Packaging
- Moisture-barrier bags or drums
- Documentation
- Batch COA & SDS
Note: match the flux to the alloy. Sodium in a flux can embrittle aluminum-magnesium alloys and interfere with phosphorus refinement in hypereutectic aluminum-silicon. Tell us the alloy and we will specify a sodium-free grade where it matters.
How a cover flux protects the melt
A flux that melts below the metal temperature spreads into a continuous film between the bath and the air.
Why it matters: dross is mostly metal you are throwing away. A flux that wets and breaks up the oxide lets trapped aluminum drain back into the bath before you skim
What cover flux is and does
Cover flux is a salt mixture built on sodium chloride and potassium chloride. The two salts together melt well below aluminum melting and holding temperatures, so the flux turns liquid on contact and spreads across the bath. A classic covering composition is about 47.5% NaCl, 47.5% KCl and 5% of a fluoride salt.
The chlorides provide the cover; the fluoride does the chemistry. Fluoride salts lower surface tension and dissolve and break up the oxide film, which lets oxide inclusions separate and lets aluminum trapped in the dross drain back into the melt. Adding sodium fluoride takes the system to a ternary eutectic of about 607 °C, making the flux more fluid still.
What the grade choice controls
- Melting point and fluidity. The flux must be liquid at your melt temperature to form a continuous cover.
- Fluoride level. More fluoride means stronger oxide stripping and a drier dross, and more care in handling.
- Sodium. Sodium-free grades for aluminum-magnesium and hypereutectic aluminum-silicon alloys.
- Form. Powder for general use; granulated flux where dust and fume matter.
Handling character
Cover flux must go onto the melt dry. Damp flux on molten aluminum is a steam eruption hazard. Details in the Safety section.
| Parameter | Typical value |
|---|---|
| Base salts | NaCl–KCl, ratio per grade |
| Fluoride content | Per agreed specification |
| Sodium | Standard or sodium-free grade |
| Moisture | Per grade specification — kept low |
| Form | Powder or granules |
| Particle size | Per agreed specification |
Important: the figures above are indicative of commercial material and are offered for planning only. The batch certificate of analysis is the governing document.
| Property | Value |
|---|---|
| Physical form | White to off-white powder or granules |
| Base system | NaCl–KCl |
| NaCl–KCl minimum melting point | ≈ 660 °C |
| With NaF | Ternary eutectic ≈ 607 °C |
| Water solubility | Chloride base is water-soluble |
| Hygroscopic | Yes — store sealed |
| Function | Surface protection; oxide separation |
Melting points are reference values for the salt systems that cover fluxes are built on and are given for orientation. The exact composition, fluoride level and particle size are grade-specific and stated on the producer's COA. Treat the table as orientation, not as a specification.
Where cover flux pays for itself
Melting, holding and remelting, wherever an open aluminum surface meets air.
Foundry melting & holding
Crucible, reverberatory and holding furnaces where the bath sits exposed to air and combustion gases.
- Grade matched to melt temperature
- Even surface coverage
- Dosing guidance shared
Die casting
Holding furnaces feeding the cell, where oxide carried into the shot becomes an inclusion in the part.
- Low-dross grades
- Sodium-free options
- Batch traceability
Scrap & remelt
Remelting returns and scrap, where oxide-coated charge generates heavy dross and metal recovery decides the margin.
- Higher-fluoride grades
- Metal recovery focus
- Trial packs available
Magnesium-bearing alloys
Aluminum-magnesium alloys, where sodium from a standard flux can cause embrittlement.
- Sodium-free grades
- Alloy reviewed before quoting
- COA per batch
Hypereutectic Al-Si
High-silicon alloys refined with phosphorus, where sodium works against the refinement.
- Sodium-free grades
- Compatible with P refinement
- Technical desk review
Scheduled supply
Flux goes on every melt, so steady call-off supply matters more than spot price.
- Annual contracts with call-off
- Price held across the contract
- Second source held in reserve
Delivered to US plants and ports
We ship cover flux to nominated delivery points across the United States. The regions below are destinations we serve — Chelora Chemicals is a sourcing and supply partner, not a US manufacturer, and does not hold US stock.
Gulf Coast
The largest US chemical cluster, and the usual entry point for bulk consignments.
- Houston & Galveston, TX
- New Orleans & Baton Rouge, LA
- Mobile, AL
Northeast
Container and bulk delivery into the mid-Atlantic and New England manufacturing belt.
- Newark & Elizabeth, NJ
- Philadelphia, PA
- Boston, MA
Southeast
Port-side delivery for the Carolinas, Georgia and Florida processing plants.
- Savannah, GA
- Charleston, SC
- Jacksonville, FL & Norfolk, VA
Midwest & Great Lakes
Inland rail and truck forwarding from the nearest coastal port to the industrial Midwest.
- Chicago, IL
- Detroit, MI
- Cleveland & Columbus, OH
West Coast
Pacific routing for West Coast processors and formulators.
- Los Angeles & Long Beach, CA
- Oakland, CA
- Seattle & Tacoma, WA
Southwest & Mountain
Inland delivery to interior states, forwarded from the Gulf or Pacific gateway.
- Dallas–Fort Worth, TX
- Phoenix, AZ
- Denver, CO
Importing into the United States
Cover flux is a chemical mixture, so TSCA looks at each component rather than the product name. Under TSCA section 13 the importer of record, or its authorized agent, must certify to US Customs and Border Protection that each shipment either complies with TSCA or is not subject to it. We confirm the Inventory status of every component with the producer and agree in writing who files that certification before the first consignment moves.
Which party carries that duty follows the Incoterm. On FOB, CFR or CIF terms it is usually the US buyer; on DDP terms it can be the seller or its agent. Safety data sheets and labels are supplied to OSHA's updated Hazard Communication Standard, and the grade-specific transport transport documentation is prepared before booking.
| Item | How it works |
|---|---|
| Delivery points | Any nominated US plant, terminal or port of discharge |
| Incoterms quoted | FOB · CFR · CIF · DDP |
| Importer of record | Agreed in writing before the first shipment |
| TSCA certification | Section 13 positive certification filed at entry |
| Documentation | Batch COA, SDS, packing list, certificate of origin |
| Pack formats | 25 kg bags, drums or bulk bags |
Note: regional coverage describes where we deliver, not where we hold inventory. Lead time depends on producer scheduling and ocean transit to your nominated US port — we confirm both in the quotation.
How we supply cover flux
Chelora Chemicals is a cover flux supplier and sourcing partner, not a manufacturer. We place your order with a qualified producer whose grade fits your alloy, your furnace and your melt temperature.
We start with the alloy, because that decides whether sodium is acceptable. A standard NaCl–KCl flux that suits a general-purpose casting alloy can be the wrong choice for an aluminum-magnesium alloy or a phosphorus-refined hypereutectic.
Then we look at what you are losing to dross. Flux priced per pound is the visible cost; aluminum skimmed off with the oxide is the real one. A grade that leaves a drier dross can be the cheaper buy at a higher price.
- Alloy reviewed before quoting. Sodium-free grades where magnesium or phosphorus refinement make it matter.
- Grade matched to melt temperature. The flux has to be fully liquid to cover.
- Moisture-barrier packaging. Salt fluxes are hygroscopic and damp flux is a hazard.
- Composition data for your air permit. We supply what you need to assess cover flux versus reactive fluxing.
- Trial packs before a contract. Prove the dross difference on your own furnace.
- Batch traceability to the producing plant. Full chain of custody documentation on request.
Bagged, drummed or in bulk
Moisture-barrier bags, lined drums or bulk bags, all with full documentation.
25 kg moisture-barrier bags
Poly-lined bags, the standard unit for powder and granular flux.
Lined drums
Lined, resealable drums where flux is used from the container at the furnace.
500–1,000 kg bulk bags
Bulk bags for high-volume casthouse and remelt operations.
Small trial quantities
Small packs for trial on your alloy before a commercial order.
Incoterms to suit you
Quoted on the Incoterm your purchasing team works to.
Scheduled deliveries
Annual volume released against your melt schedule.
Salt, fluoride and molten metal
Cover flux is a salt mixture, but it is used on metal above 650 °C, and that sets the hazards. The two that matter most are moisture — damp flux on molten aluminum can erupt — and fume, since some volatilization is unavoidable at melt temperature. Fluoride-bearing grades carry their own toxicity classification. The summary below is orientation only; the safety data sheet supplied with your batch is the authoritative document.
Classified hazards
Cl⁻Chloride salt base: irritating to eyes; dust irritates the respiratory tract.F⁻Fluoride-bearing grades: harmful or toxic if swallowed; classification depends on fluoride content.FumeFumes are evolved at melt temperature: use local exhaust ventilation at the furnace.H₂OMoisture in flux contacting molten aluminum can cause violent steam eruption.SDSThe GHS classification is grade-specific and set out in the batch SDS.
The US air rule worth knowing. EPA's secondary aluminum NESHAP, 40 CFR Part 63 Subpart RRR, defines reactive fluxing as any gas, liquid or solid flux, other than cover flux, that results in a hazardous air pollutant emission, and it defines cover flux as salt added to the melt surface without surface agitation to prevent oxidation. Foundries, die casters and extruders melting only clean charge, customer returns or internal scrap are outside the definition of a secondary aluminum production facility. Whether your fluxing practice brings you inside the rule is a determination for you and your permitting authority; we supply the composition data you need to make it.
Storage
Store in sealed original packaging in a dry, covered area, off the floor and away from food and feedstuffs. Salt fluxes are hygroscopic: reseal part-used containers immediately, because flux that has picked up moisture both performs worse and creates a steam hazard when it meets molten metal. Rotate stock first in, first out.
Handling
Handle with gloves, eye protection and dust control, and apply only with dry, preheated tools. Never add damp or cold material to a melt. Fumes evolve at melt temperature, so furnace-side local exhaust ventilation is appropriate. Follow the exposure controls set out in the batch SDS and your own foundry safety program.
Transport
Most chloride-based fluxes ship as non-dangerous goods, but that is a grade-level question, not a product-name one: fluoride content can bring a formulation into a toxic or environmentally hazardous class. We confirm and document the classification for your specific grade, packaging and destination before booking.
Every batch, documented
We verify documentation before dispatch so there are no surprises at your incoming-goods bench.
Specification agreed
Alloy family, melt temperature, application method and the grade chemistry confirmed against your process before the order is placed.
Producer batch testing
The producing plant tests each batch against the agreed specification before release.
Documentation review
COA, SDS, TSCA position and transport classification checked by our desk before the shipment is booked.
Traceable dispatch
Each shipment is traceable to its producing batch, with full chain-of-custody records on request.
Why sodium is an alloy question
Most cover fluxes are built on sodium chloride and potassium chloride because the pair is cheap, stable and melts below aluminum melting temperatures. For a large share of casting alloys that is exactly right, and a standard grade does the job.
Two alloy families are different. In aluminum-magnesium alloys, sodium picked up from a flux can cause embrittlement and cracking during hot working, which is why wrought casthouses running these alloys specify sodium-free fluxes. In hypereutectic aluminum-silicon alloys, primary silicon is refined with phosphorus, and sodium works against that refinement.
That is why the first question on a cover flux order is the alloy, not the price. Sodium-free and sodium- and calcium-free grades exist for precisely these cases, and a standard grade used in the wrong alloy turns a cheap consumable into a metallurgical problem.
We do not publish operating process parameters here; this is background only. Full technical documentation accompanies every shipment, and any process-specific detail you need is best confirmed directly with our technical desk.
| Product family | Aluminum melt treatment flux |
|---|---|
| Base salts | NaCl–KCl |
| Classic composition | ≈ 47.5% NaCl · 47.5% KCl · 5% fluoride |
| Function | Surface protection; oxide separation |
| Grades | Standard · sodium-free |
| US air rule | "Cover flux" defined in 40 CFR 63.1503 |
Related foundry & melt-treatment products
Other aluminum melt-treatment inputs supplied from the same desk.
Cover flux, answered
What is cover flux used for?
What is cover flux made of?
Why does cover flux contain fluoride?
When do I need a sodium-free cover flux?
How is cover flux applied?
What is the difference between cover flux and drossing flux?
Is cover flux covered by EPA's secondary aluminum rule?
Is cover flux hazardous?
How should cover flux be stored?
Do you manufacture cover flux?
Get a quote on cover flux
Tell us your alloy, your furnace type, melt temperature and roughly what you skim per melt. We will match a grade, flag where sodium-free is needed, and quote a trial pack so you can measure the dross difference yourself.