For manufacturers of fireproofing boards, the choice of binder directly determines product performance, cost efficiency, and fire resistance ratings. Bulk magnesium chloride hexahydrate (MgCl₂·6H₂O) has become the preferred inorganic binder for magnesium oxychloride cement (MOC) boards, widely used in interior partitions, ceiling panels, and decorative fire-resistant cladding. Its hygroscopic nature, excellent bonding strength, and ability to form a crystalline matrix with magnesium oxide make it irreplaceable in high-quality fireproofing board production. As a procurement manager or technical director, securing a reliable supply of consistent, high-purity magnesium chloride hexahydrate is essential to maintaining production throughput and meeting international fire safety standards. In this comprehensive guide, we explore every aspect of sourcing this critical raw material—from chemical characteristics and quality specifications to logistics and supplier evaluation—keeping the needs of industrial bulk buyers firmly in focus.
Magnesium chloride hexahydrate is the most common commercial form of magnesium chloride, appearing as white to colorless flakes, granules, or crystalline powder. Its chemical formula MgCl₂·6H₂O indicates six water molecules bound to each magnesium chloride unit. This hydration state gives the material a characteristic melting point of 117 °C and a high solubility in water (approximately 167 g/100 mL at 20 °C). In the context of fireproofing boards, the hexahydrate form provides controlled moisture release during the curing reaction with magnesium oxide, enabling the formation of a complex magnesium oxychloride phase that delivers exceptional fire resistance and mechanical strength. The product supplied by Hailei Chemical typically offers a purity of up to 46% MgCl₂ (with the balance being water of crystallization and minor impurities), optimized for industrial binder applications.
While magnesium chloride has many uses in daily life—from de-icing roads and sidewalks to coagulating tofu and suppressing dust on unpaved surfaces—the fireproofing industry demands precisely engineered grades that meet strict limits on sulfate, calcium, and alkali metal content. These impurities can interfere with the setting reaction and degrade board performance, which is why sourcing from a specialized chemical supplier is critical.
Magnesium oxychloride cement (also known as Sorel cement) is the heart of most inorganic fireproofing boards. The system is formed by mixing reactive magnesium oxide (calcined magnesite) with a magnesium chloride solution. The resulting exothermic reaction produces a complex matrix of interlocking crystalline phases, primarily 5Mg(OH)₂·MgCl₂·8H₂O (the 5-form phase). This structure is inherently non-combustible, dimensionally stable under fire exposure, and capable of encapsulating lightweight fillers such as perlite, vermiculite, or wood chips.
Magnesium chloride serves multiple functions in this formulation:
Without consistent bulk magnesium chloride hexahydrate, board manufacturers would struggle to achieve the class A1 or A2 fire ratings required by building codes in Europe (EN 13501-1) and similar international standards.
Understanding the characteristics of magnesium chloride is fundamental to optimizing board formulations. The following properties are of particular importance:
MgCl₂·6H₂O is highly hygroscopic—it absorbs moisture from the air. While this trait is beneficial during initial curing, it can cause issues if boards are exposed to high humidity without proper sealing. Manufacturers must balance this property through admixture selection and coating systems. Bulk hexahydrate should be stored in sealed containers or low-humidity warehouses to prevent caking and degradation before use.
Rapid dissolution in water allows efficient preparation of magnesium chloride brine on-site. Typically, a solution density of 22–30°Bé (Baumé) is targeted for board production. The high solubility of the hexahydrate ensures minimal sediment and easy handling with standard mixing equipment. Purity level directly affects solution clarity and the presence of insoluble residues—critical for achieving uniform binder consistency.
The rate of the acid-base reaction between magnesium chloride and magnesium oxide depends on the reactivity of the MgO, but also on the concentration and purity of the chloride. Impurities like sodium chloride (NaCl) can accelerate setting, while calcium sulfate can cause efflorescence and reduced strength. High-grade magnesium chloride hexahydrate minimizes these negative interactions, enabling predictable working times and consistent board quality.
Upon heating, magnesium chloride hexahydrate first melts in its own water of crystallization, then dehydrates stepwise, eventually forming anhydrous MgCl₂. This dehydration absorbs considerable energy, which contributes to the fire-resistant performance of boards. The residual MgO and MgCl₂ further interact at high temperatures to form ceramic-like phases, ensuring structural integrity during prolonged fire exposure.
For industrial-scale fireproofing board production, the hexahydrate form—specifically in flake or granular consistency—is overwhelmingly favored over anhydrous powder or liquid brine. Here’s why:
When ordering bulk magnesium chloride hexahydrate, a standard container load consists of 25 metric tonnes, typically packed in 25 kg or 50 kg woven polypropylene bags with inner PE liners, or in 1,000 kg flexible intermediate bulk containers (FIBCs). This packaging protects the material from ambient moisture while allowing efficient handling with forklifts.
Sourcing the right grade requires a clear understanding of technical specifications and a systematic supplier evaluation. The following checklist helps procurement teams ensure they receive material that performs reliably in MOC board production.
| Parameter | Typical Specification | Impact on Fireproofing Boards |
|---|---|---|
| MgCl₂ content | Min 46% (as MgCl₂) | Determines reactive binder yield; lower content reduces strength. |
| MgO content (from MgCl₂) | Typically 20–21% | Indirectly measures active magnesia equivalent. |
| Sulfate (SO₄²⁻) | Max 0.5% | Excess sulfate causes efflorescence and late strength loss. |
| Calcium (Ca²⁺) | Max 0.5% | Interferes with crystalline phase formation. |
| Alkali chlorides (NaCl/KCl) | Max 1.0% | Affects setting time and moisture susceptibility. |
| Water-insoluble matter | Max 0.2% | Sediment can block spray nozzles and create surface defects. |
| Particle size (flake) | 2–5 mm typical | Ensures uniform dissolution rate. |
Request a Certificate of Analysis (COA) with every shipment, and cross-check critical parameters against your internal quality-control samples. Reputable suppliers like Hailei Chemical provide detailed COAs and are open to third-party inspection during loading.
Most fireproofing board factories rely on imported bulk magnesium chloride hexahydrate, with China being the world’s largest producer. Key logistical factors include:
Once received, store magnesium chloride hexahydrate in a cool, dry, covered warehouse. Avoid stacking pallets directly on concrete floors without plastic sheeting—even minimal moisture can harden the surface layer and reduce dissolution efficiency.
Choosing a supplier is more than just comparing price per metric ton. In an industry where production uptime and board certification depend on raw material consistency, the following evaluation criteria will safeguard your supply chain.
Understand whether the supplier is a producer (with access to salt lake brine or underground resources) or a pure trader. Vertically integrated producers or those with exclusive procurement rights from trusted salt lake operations in Qinghai or Shanxi can often guarantee more stable quality and pricing. Hailei Chemical sources magnesium chloride from well-managed brine ponds and refining facilities, ensuring traceability back to the basin.
Fireproofing board manufacturers may require specific dissolution profiles, low iron content for white boards, or adjustments in bulk density. A technically adept supplier can blend batches to meet these needs and provide application guidance. They should also be willing to share accelerated aging test results for MOC samples produced with their chloride.
Look for ISO 9001 certification, REACH compliance for exports to Europe, and adherence to GB standard GB/T 2605-2003 for magnesium chloride hexahydrate. A supplier that regularly undergoes third-party audits and can provide a full safety data sheet (SDS) demonstrates commitment to international standards.
Assess the supplier’s export history, customer references, and financial health. Long-established enterprises are better positioned to weather raw material fluctuations and logistic disruptions, ensuring uninterrupted supply. Request a trial order of 2–3 containers before committing to annual contracts, and audit the loading process via a third-party inspection agency if possible.
Magnesium chloride hexahydrate is classified as a low-hazard substance with no dangerous goods classification for transport by sea under the IMDG code. However, it is an eye and respiratory irritant in dust form, so workers handling flakes or preparing brine should wear protective goggles and gloves. The material is not flammable, corrosive (except to some uncoated metals in the presence of moisture), or toxic. It has minimal VOC emissions, making it suitable for green building certifications.
From an environmental perspective, magnesium chloride released in production wash water can raise chloride levels in local water bodies. Manufacturing facilities must incorporate wastewater treatment or recycle spent brine. The final fireproofing board product is inert and can be recycled as construction aggregate, adding to its sustainability profile. Many specifiers now prefer MOC-based boards over gypsum or cement boards for projects pursuing LEED or BREEAM credits due to the lower embodied carbon of magnesia-based chemistry.
While magnesium oxychloride cement dominates, other inorganic binders like magnesium oxysulfate (MOS) or calcium chloride are sometimes considered. Below is a brief technical comparison:
| Property | Magnesium Chloride (MgCl₂·6H₂O) | Magnesium Sulfate (EPS Salt) | Calcium Chloride (CaCl₂) |
|---|---|---|---|
| Strength development | High early and final strength | Lower strength; slower setting | Moderate; can cause efflorescence |
| Water resistance | Requires additives (e.g., phosphates, fly ash) | Better inherent water resistance | Very poor, deliquescent |
| Fire resistance | Excellent – melting/cooling effect | Good; but lower heat absorption | Not recommended – decomposes |
| Cost per active oxide | Low – hexahydrate is abundant | Higher raw material cost | Low, but quality issues offset |
| Efflorescence risk | Manageable with correct MgO ratio | Low | Very high |
For most board manufacturers, the proven performance-to-cost ratio of bulk magnesium chloride hexahydrate remains unbeatable. Advances in additive technology have largely solved historical concerns about water sensitivity, allowing MOC boards to be used even in moderately humid interior applications when properly formulated.
While fireproofing board production is a substantial and growing market, the same magnesium chloride hexahydrate finds parallel demand in:
For buyers who also purchase magnesium chloride for ice melt or dust abatement, consolidating volumes with a single supplier can yield significant freight savings and improved price negotiation. We encourage you to discuss your total demand with our technical sales team.
A minimum of 46% MgCl₂ content is standard. However, the levels of calcium and sulfate are just as important—insist on less than 0.5% each to avoid strength loss and efflorescence. Always ask for a COA before shipment.
Some plants purchase pre-made brine at 30–32% concentration to eliminate on-site dissolving. While this reduces labor, shipping water is inefficient globally. Unless you are located near a brine source, buying bulk magnesium chloride hexahydrate flakes and dissolving them at your plant is far more cost-effective. Our flake product dissolves rapidly with simple agitation.
Storage in a cool, dry environment with relative humidity below 50% is ideal. Use intact vapor-barrier bags and stack pallets on plastic sheets. Open bags should be consumed promptly. Hailei Chemical’s packaging includes an inner PE liner to protect product during transit and storage.
If kept sealed and dry, the product remains chemically stable for over two years. However, gradual caking may occur if exposed to humidity. Always rotate inventory on a first-in-first-out basis.
Yes. While we specialize in bulk container loads, we understand the need for qualification. We can supply 1–2 metric ton pallets for lab-scale and pilot trials. Contact us to arrange sample shipment and technical documentation.
As a leading Chinese exporter of fine chemicals, Weifang Hailei Fine Chemical Co., Ltd. understands that fireproofing board manufacturers demand more than just a commodity chemical. You need consistent quality, reliable logistics, and technical partnership. Our magnesium chloride hexahydrate meets the stringent requirements of the magnesia construction materials industry, backed by over a decade of experience serving global clients. Every batch is tested in our in-house laboratory and verified by third parties upon request.
Whether you are formulating standard partition boards, high-performance fire doors, or lightweight ceiling tiles, our bulk magnesium chloride hexahydrate provides the reactive foundation your products rely on. Explore how we can support your manufacturing operations with competitive pricing, flexible packaging, and dependable container shipments.
Ready to secure your supply chain? Request a custom quote today and let our team develop a proposal tailored to your volume, delivery schedule, and technical specifications. Together, we can build safer, fire-resistant structures.