LFC coating paints

LFC coatings are special coatings used in the lost foam casting (LFC) process. These coatings are applied to the foam model to form a refractory barrier, whose main function is to isolate the casting from the molding sand, thereby ensuring the quality of the casting and reducing defects such as pores, broken sand, and burned sand in the casting, thereby greatly improving the yield rate of the casting.

The performances of LFC coating are mainly thermal performance and air permeability, which determine its role in the casting process.In practice, it is necessary to measure and control its viscosity, solid content, air permeability, PH value and so on.The quality of epc products can be guaranteed only when the performance of the coating is stable and consistent.

The Four Critical Performance Parameters of LFC Refractory Coating

Any reliable lost foam casting coating must be specified and controlled across four core technical parameters. These determine its performance in actual production — and they must be tested and adjusted continuously, not just at initial supply.

ViscosityViscosity controls coating pickup (thickness per dip pass) and surface coverage uniformity. Too high a viscosity produces uneven thick spots and drip marks; too low produces inadequate film build and insufficient protection. For each metal type and pattern geometry, there is an optimal viscosity range that must be targeted and maintained throughout production. Ruiou provides viscosity targets for each product and advises on on-site adjustment methods when ambient temperature or humidity shifts the behavior of the coating.

Solid ContentSolid content determines the density, strength, and refractoriness of the dried coating film. Higher solid content generally improves resistance to metal penetration and erosion, but can also increase gas evolution during pouring if not balanced correctly with the permeability additive system. Ruiou's formulas are optimized to deliver the solid content level appropriate to each alloy family without compromising gas permeability.

Air PermeabilityPermeability after drying is the most LFC-specific parameter. Ruiou tests the dried film permeability of each batch against reference standards established from our 600+ production case database. Permeability that falls outside the acceptable range for the target metal is corrected before supply.

pH ValueOut-of-range pH affects coating suspension stability, storage life, interaction with foam surface (EPS/STMMA), and compatibility with the pattern adhesive. An unstable suspension separates in the dip tank, producing batch-to-batch variation in coating thickness. Ruiou monitors and controls pH across all water-based LFC coating products to ensure long tank life and consistent application behavior.

FAQ: Lost Foam Casting Coating

Q: What is the difference between LFC refractory coating and sand casting coating?A: Standard sand casting coatings are designed to resist metal penetration and sand erosion but do not need to handle foam decomposition gas or liquid byproducts. Lost foam casting coating must also be permeable to allow EPS/STMMA decomposition products to escape during pouring, and must reinforce the foam pattern mechanically during sand compaction. These dual requirements demand a specifically formulated product — general foundry coatings are not appropriate substitutes.

Q: How many coats of LFC coating should be applied?A: For most standard iron castings, one well-applied dip coat producing a dried film thickness of 0.8–2.0 mm is sufficient. For larger castings, higher-temperature metals (steel, high-Cr iron), or thicker sections, two coats with intermediate drying may be required. Ruiou advises on the appropriate number of coats based on your specific casting geometry and alloy.

Q: Can the same LFC coating be used for both iron and aluminum castings?A: No — a single formula cannot optimally serve both. Iron casting requires higher refractoriness and different permeability than aluminum. Using iron-optimized LFC refractory coating on aluminum produces excess gas resistance and often carbon residue issues. Ruiou supplies separate validated formulas for ferrous and non-ferrous LFC applications.

Q: How long can mixed LFC coating be stored in the dip tank?A: Ruiou's water-based lost foam casting coating is formulated for good suspension stability, but tank life depends on temperature, pH maintenance, and contamination from foam residues. As a general guideline, monitor viscosity daily and adjust with water as needed; check pH weekly and correct if out of range. In warm climates (>30°C), biological activity in water-based coatings can shorten tank life — Ruiou provides guidance on additive solutions for these environments.

Q: What causes LFC coating to delaminate from the foam pattern during drying?A: The most common causes are: inadequate surface wetting (pattern surface contamination from mold release agent or adhesive); foam surface moisture; coating applied too thick in a single pass; or a formula incompatibility between the coating binder and the EPS/STMMA surface chemistry. Ruiou's on-site assessment identifies which factor applies to your production and corrects the formula or application process accordingly.

Q: Do you provide coating samples before ordering?A: Yes. Contact Ruiou to request a sample of the LFC refractory coating appropriate for your alloy type and pattern material. We recommend testing on your actual production patterns and comparing casting quality against your current coating before committing to a full supply order.

Ruiou, as a leading Lost Foam Coating Plant in China, offers customizable coatings to meet your specific casting parameters. We bring the proper coating directly to your site and provide services including stirring, brushing, drying, and pouring. Our experts adjust the coating formula slightly according to the site situation to ensure optimal performance. We continuously research and develop the appropriate coating for your product until you can produce qualified castings.