Boron in metals and gold

Using borax as a flux helps remove metal oxides, improves slag control

From mining to processing to metal recovery, borates serve a versatile role in metallurgical applications.
Their functions include:

  • Making excellent fluxes, removing metal oxides and dissolving impurities

  • Stabilizing metallurgical slags, to enable greater waste control

  • Passivating ferrous metals, to reduce harmful corrosion

  • Producing more corrosion resistant alloys (steel and aluminum)

The right borate purity, concentration, and granulometry influences these properties and determines their efficacy. With it, you can recover more high-quality material, improve flux functionality, and avoid costly defects in finished products such as cracking and pitting in electroplating.

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Borax in metallurgy

Borates’ uses span a wide range—from stabilizing blasting holes to fluxes, refinement, and oxidation protection.

As a metal producer, you’re seeking ways to become more cost efficient, increase yields, and reduce energy consumption. Borates enable improvement across metallurgical processes, from using borax for flux formulations to their ability to enhance product quality.

Key metallurgical uses include:

  • Borax for fluxes: During smelting, borates reduce melting temperature and viscosity, dissolve metallic oxide impurities at a relatively low temperature, lowering energy costs
  • Refinement and impurity removal: Any oxides, impurities, or siliceous material will be subject to borates’ high solvent action when used as a refining flux
  • Electroplating: By controlling pH, boric acid prevents nickel deposits from cracking and pitting, so you can avoid costly defects
  • Stabilization: Metallurgical slag is problematic, wasting time and money on proper disposal. Borates modify the slag into a stable rock-like material, simplifying slag handling and give you great control over slag to lower your environmental impact
  • Reducing fluorine emissions: If you’re looking for an alternative to fluorine-containing flux, potassium pentaborate is an effective solution to reduce fluorine emissions

Why is borax used in melting gold?

When used in a gold refining flux, borates keep recovery high and equipment degradation low.

In gold metallurgy, borates are:

  • Incorporated in refining flux formulations to dissolve metal oxides

  • Used as a flux in gold assaying

The right borate concentration helps you save energy, reduce damage to melting equipment, and recover more precious metal. That’s because borates dissolve metal oxides at lower temperatures.

Dehybor logo

Use an anhydrous borax product, such as Dehybor, in flux formulations or as a flux in gold assaying.

Learn more about why borax is used in gold melting.

  • Promote a substantial reduction in the sintering temperature of the charge
  • Facilitate better gold ore recovery at lower temperatures
  • Reduce slag viscosity
  • Produce easily fusible borates
  • Prevent combustibility and minimize fuming
  • Form highly fluid slags with only mild attack on refractories
  • Easily thicken slag if necessary and slammed
  • Avoid intumescence and puffing
  • Reduce the loss of precious metal content to slag
  • Prevent “spit and crackle” problems

Slag stabilization

Borates impart greater control and stabilization of slag in fluxes for stainless steel.

As a stainless-steel producer, you can rely on borates to help stabilize slag. If a slag becomes unstable (or even partially stabilized), a fragile, dusty slag can form. In that case, recycling becomes impossible, and more waste is generated.

By using borates in a flux for stainless steel, slag is modified into a stable rock-like material. As a result you can reduce slag dust to:

  • Save money on handling and treatment

  • Lower disposal costs

  • Improve regulatory response and adherence

Learn more about how borates enhance control over steel slag stabilization.

Borates in lead recycling and metal recovery

Your goal is to produce a product that’s as pure as a primary metal. Reaching it requires a high-performing borate-based flux formulation to surface oxides and impurities so you can easily decant or skim them off. Using borax as a cover flux provides safe and easy handling, greater slag control, and reducing harm to refractories.


What can happen if your borate concentration is insufficient?

Lead recovery

Insufficient boron levels may result in a higher liquidus temperature, ultimately causing less lead to be recovered. Energy use and costs subsequently increase because your furnace must operate at higher temperatures.

Copper recovery

An inadequate borate concentration produces more slags and serious scaling—causing more equipment maintenance. It also increases the likelihood that you will lose more copper to the slag.

Nickel recovery

Borates ensure neutral pH during the last stage of nickel recovery—electrolysis. The right borate level (in boric acid, boric oxide, or anhydrous borax form) enables greater pH control and proper separation of contaminants from pure nickel deposits.


Adding borates in your crucible melt can improve aluminum’s appearance and help reduce tearing on rolling into thin sheets.

Learn more about how borates aid the metal recovery process

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What makes U.S. Borax the right partner for your metal application?

Technical expertise, premium quality, and extensive product offerings separate us from market alternatives.

Unmatched quality, consistency

Your metallurgical process demands reliable, effective inputs. That means you need high-quality products with low impurity levels, consistent granulometry, and product options such as anhydrous borates. As a world leader in refined borates, you can trust our products to deliver superior quality.

Proven technical expertise

Our technical team provides the knowledge you need to meet your specific metallurgical application. Whether it’s supplying technical information, suggesting a packaging format, or help with proper loading percentage, we’re a trusted partner always there for you.

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Recommended for metals

Ammonium pentaborate by U.S. Borax logo

This product is suitable for a range of metallurgical fluxes where alkali borates can’t be used, acting as an excellent solvent for metal oxides at high temperatures.

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Borax decahydrate by U.S. Borax logo

This natural sodium borate is great for dissolving metal oxides in non-ferrous metal recovery and can be used as a cover flux in ferrous metallurgical applications.

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Boric oxide by U.S. Borax logo

This product is versatile—it’s used as a solvent for metallic oxides at high temperatures, in special welding and soldering fluxes, hardening of steel, and producing iron, nickel, or manganese-based alloys.

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Dehybor logo

Available in multiple grades to accommodate your process, Dehybor is a highly concentrated and consistent product that delivers superior performance for your flux.

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Neobor logo

This product is a common form of sodium borate that protects ferrous metals against oxidation and improves performance of metal-working fluids.

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Optibor logo

A widely used borate in industrial applications, Optibor is effective at preventing the oxidation of metal surfaces and strengthens metal alloys and steel.

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Potassium pentaborate by U.S. Borax logo

Used as a cover flux in metal refining, potassium pentaborate is a great choice for those who need an alternative to fluorine-containing flux compounds that release harmful emissions.

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Potassium tetraborate by U.S. Borax logo

Unlike sodium borates, potassium tetraborate dispels “glare” in non-ferrous metal fluxes, while still providing excellent solvent capabilities for metallic oxides at high temperatures.

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U.S. Borax, part of Rio Tinto, is a global leader in the supply and science of borates—naturally-occurring minerals containing boron and other elements. We are 1,000 people serving 650 customers with more than 1,800 delivery locations globally. We supply around 30% of the world’s need for refined borates from our world-class mine in Boron, California, about 100 miles northeast of Los Angeles.  Learn more about Rio Tinto.

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