Molten aluminum that sticks to a ladle or mold costs twice: once in scrap, and again in the time spent chipping buildup off the tooling. A boron nitride release coating gives the metal a surface it will not wet, so it flows, releases and leaves the tooling clean.
Q: What Is a Boron Nitride Release Coating for Metal Casting?
A: A Non-Wetting Ceramic Layer That Keeps Molten Metal From Sticking
Boron nitride is a ceramic that molten non-ferrous metals do not wet well. Coated onto ladles, troughs, molds and refractory parts, it keeps metal from bonding to the surface and building up. Incure’s Epo-Weld™ high temperature coating line includes two boron nitride grades and one graphite grade for release and parting:
- Epo-Weld™ HTC-347: a hard-coat boron nitride for long-lasting, non-stick surfaces on ladles, troughs and molds.
- Epo-Weld™ HTC-365: a soft-coat boron nitride, applied as a consumable layer each cycle or as needed.
- Epo-Weld™ HTC-374: a pure graphite coating for lubrication and release in glass forming and wire drawing.
All three are single-part thixotropic pastes. Each lists a cure of 2 hours at 77°F followed by 2 hours at 200°F in Incure’s catalog.
Hard Coat vs. Soft Coat: The Core Decision
The main choice between HTC-347 and HTC-365 is how long the coating should last on the part.
HTC-347 hard coat is designed as a durable surface. Incure lists resistance to molten aluminum, magnesium and salts, and recommends it for ladles, troughs and molds. Choose it where recoating every cycle would slow production and the surface sees repeated metal contact.
HTC-365 soft coat is designed to be consumed. It is reapplied with each cycle or as needed, giving a fresh release layer every time. Incure recommends it for hot-top rings and transition plates, and lists strong thermal shock resistance and chemical inertness. Choose it where a renewable layer is easier to manage than keeping a permanent one intact.
A practical way to decide is to count how often the coating has to be renewed today. If the answer is every shift or every cast, a consumable soft coat fits the existing routine. If recoating is a downtime event, the hard coat pays back by staying on.
Where Graphite Fits Instead
HTC-374 is a graphite coating, not boron nitride. Incure lists 1,100 PSI flexural and 300 PSI tensile shear strength for it, and recommends it for glass forming molds and wire drawing lubrication. Its catalog description stresses a low coefficient of friction and high thermal conductivity, and notes that it stays effective in reducing and neutral atmospheres.
That atmosphere note is the key difference. Graphite is a strong lubricant, and Incure’s catalog specifies its effectiveness in reducing and neutral atmospheres. Where the process runs in open air and the job is release from molten non-ferrous metal, the boron nitride grades are the better match. Graphite parts in the same cell often need joining as well as coating, which Incure covers in its guide to bonding graphite to metal with high-temperature epoxy.
Email Us with your alloy, tooling material and how often the coating is renewed to confirm the right release grade.
Getting a Clean Release From the First Cast
- Start with a clean, dry surface. Moisture trapped under a coating can turn to steam on first contact with molten metal and lift the layer.
- Coat the full contact area. Uncoated patches become anchor points for buildup, and buildup spreads from there.
- Finish the cure before use. Let each grade complete its full room-temperature and 200°F cure before it meets molten metal.
- Inspect and renew on a schedule. Hard coats wear at high-contact points such as pour lips; soft coats are renewed by design. Either way, a set inspection interval prevents surprise sticking.
Reading the Spec Data Before You Qualify
The catalog data for these three grades is uneven, and that matters when you plan a trial. HTC-374 lists 1,100 PSI flexural and 300 PSI tensile shear strength. HTC-347 and HTC-365 list no flexural or shear figures at all, because their job is release, not bonding strength. Their performance is better judged on the line than on a data sheet.
A short qualification run answers the questions that matter: does the metal release cleanly, how many casts does a hard coat survive at the pour lip, and how much soft coat each cycle uses. Record those three numbers on your own tooling. They will tell you more about cost per cast than any catalog value.
How These Grades Relate to the Rest of the Line
These release coatings sit alongside graphite protection coatings, refractory sealers and quartz marking coatings in the same Epo-Weld™ HTC range. The complete line, grouped by function, is in Incure’s overview of Epo-Weld™ high temperature glass coatings.
Final Thoughts
A boron nitride release coating for metal casting is chosen by how long it should last and what atmosphere it runs in. Incure’s Epo-Weld™ HTC-347 hard coat stays on through repeated aluminum and magnesium contact. HTC-365 soft coat renews each cycle. HTC-374 graphite handles lubrication and release in reducing or neutral conditions. Contact Our Team to match a release coating to your casting line.
Visit www.incurelab.com for more information.