Foundry Coating Grade Bentonite for Refractory Coatings | Solvent-Based or Alcohol-Based Foundry Coatings

Foundry Coating Grade Bentonite for Refractory Coatings

In foundry production, refractory coatings are applied to sand molds and cores to improve casting surface quality, reduce metal penetration, and support cleaner mold release. These coatings commonly contain refractory minerals such as zircon, graphite, alumina, silica or other heat-resistant fillers.

Because these mineral particles are dense and tend to settle during storage, the coating requires an effective rheology-control and suspension additive. This is where Foundry Coating Grade Bentonite plays an important role.

It is important to distinguish this product from conventional foundry bentonite for green-sand molding. Foundry Coating Grade Bentonite is designed for the refractory coating formulation itself—not as a binder for molding sand.

Functions in Foundry Coating Formulations

A properly selected bentonite grade can help refractory coatings achieve:
Better suspension of zircon, graphite and other refractory fillers
Reduced hard settling during storage and transportation
Improved viscosity control and thixotropic behavior
More even coating application by brushing, dipping, flow coating or spraying
Better resistance to sagging, dripping and uneven coating thickness
Improved redispersibility after storage
More stable and consistent coating performance from batch to batch

The objective is not simply to increase viscosity.A suitable grade should provide a balanced rheology profile: stable enough to keep solids suspended, while still allowing smooth application and good coverage on molds and cores.

Bentonite Selection for Water-Based and Solvent-Based Foundry Coatings
Foundry coating systems may be water-based or solvent/alcohol-based. The bentonite grade should be selected according to the complete formulation system.

Water-Based Foundry Coatings

For water-based refractory coatings, selected natural or activated inorganic bentonite grades can be used to support thickening, suspension and anti-settling performance.

Key evaluation points include:
Hydration and swelling behavior
Particle-size distribution
Rheology profile at the required solids content
Compatibility with refractory fillers, binders and additives
Storage stability and ease of redispersion

Solvent-Based or Alcohol-Based Foundry Coatings

For solvent-based or alcohol-based refractory coatings, organophilic bentonite, also known as organoclay, is generally more suitable. It can build a controlled thixotropic structure in low-polarity systems and help prevent sedimentation of heavy refractory minerals.

The correct organoclay grade, activator level and incorporation procedure should be evaluated in the actual formulation.

Why Formulation Testing Matters
The performance of Foundry Coating Grade Bentonite depends on more than the clay itself. Refractory filler type, resin or binder system, solvent polarity, solids content, dispersing agents and application method can all affect final coating behavior.

For this reason, bentonite selection should be based on laboratory evaluation in the customer’s own coating system.
Important tests may include:
Initial and storage viscosity
Settling tendency
Redispersibility
Application behavior
Coating thickness and uniformity
Sag resistance
Surface quality of the final casting

Hermano Foundry Coating Grade Bentonite
Hermano New Materials supplies application-oriented bentonite and organoclay solutions for industrial coating systems. With controlled mineral resources and processing capability, we can recommend suitable grades for water-based or solvent-based foundry refractory coatings.

Technical support can include:
Product selection based on coating type
TDS, COA and MSDS documentation
Suggested addition levels and incorporation guidance
Small samples for formulation evaluation
Stable supply for regular production

If you are developing or improving a refractory coating for sand molds and cores, please share your coating system, refractory filler, solvent or water base, solids content and target application method. Our technical team can recommend a suitable Foundry Coating Grade Bentonite for testing.

Contact Hermano New Materials for technical information and evaluation samples.