A technical guide for formulation engineers and procurement managers. How graphite grade, particle morphology and purity determine performance in dry lubrication, grease thickener, mould release and wire drawing applications.
Graphite's lubricating action is governed by its crystal structure. The hexagonal lattice of sp²-bonded carbon atoms forms parallel basal planes with very low shear force between them — sheets slide across one another with minimal resistance when loaded in the right direction. This mechanism makes graphite a solid lubricant effective across temperature ranges where liquid lubricants decompose or oxidise: from sub-zero applications through to over 400°C in ambient air, and above 2000°C in inert or reducing atmospheres.
The key differentiator between graphite sources for lubrication is crystallinity. Natural flake graphite from metamorphic deposits has a high degree of crystallographic order — large, well-defined basal planes with low interlayer defect density. This produces the high aspect-ratio platelets that deliver effective lubrication at low filler loadings. Amorphous graphite (also natural) has much lower crystallinity and is best suited to low-end applications where purity and morphology matter less. Synthetic graphite (manufactured from petroleum coke) has controlled purity but typically smaller, less anisotropic particles and higher cost per tonne.
For lubrication applications where performance is measured — coefficient of friction, load-bearing capacity, film durability — large flake natural graphite is the specification of choice.
Skaland mine produces six natural flake graphite grades from SGF-80 to SGF-99. For lubrication applications, the relevant range is SGF-91 to SGF-96, with grade selection driven by the contaminant tolerance of the end application and whether the graphite contacts electrical or reactive components.
Dry graphite lubricants — applied to sliding surfaces, bolts, bearings and fasteners operating at high temperature — require good film formation on metal surfaces and resistance to wash-off. SGF-94 (≥94% Cg) provides an effective balance of crystallinity, purity and cost for most anti-seize formulations. The D50 for dry lubrication applications is typically 50–100 µm; finer particle sizes reduce film thickness and load capacity.
For high-temperature anti-seize (stainless steel bolts, exhaust manifolds, kiln furniture), the moisture and ash content of the graphite must be specified carefully: residual mineral ash from processing can catalyse oxidation of the graphite layer at temperatures above 500°C, reducing service life. SGF-96 (≥96% Cg, ash ≤4%) extends high-temperature performance relative to SGF-91 in these applications.
Graphite-thickened greases and lubricating oils use natural flake graphite as both a thickener and a solid lubricant carrier phase. The graphite's platelet morphology creates a structured matrix in the grease that improves load-carrying capacity and boundary lubrication performance. Typical addition rates are 3–15% by weight.
For grease formulations, purity is moderate (SGF-91 to SGF-94 covers most applications), while particle size distribution is critical: a broad D10–D90 span improves packing density and film continuity. Specify D10, D50 and D90 when ordering for grease formulation. Skaland can supply to target particle size distributions confirmed on CoA for every shipment.
Graphite mould release agents are used in foundry die casting (aluminium, zinc alloys), hot forging and glass moulding. The release mechanism combines thermal stability, low surface energy and the graphite platelet's tendency to align with the die surface under pressure, forming a thin, coherent film.
SGF-91 (≥91% Cg) is the recommended starting grade for most mould release formulations — the residual mineral content is acceptable for non-precision casting, and the lower cost per tonne supports high application rates. For glass mould applications requiring a cleaner release surface and less ash residue, SGF-94 is preferred. Particle size for mould release typically ranges D50 50–150 µm: finer particles give better coverage at low film weight; coarser particles improve film durability during repeated casting cycles.
Wire drawing lubricants use graphite to reduce friction at the die, lower drawing force and improve surface finish on steel wire, copper and aluminium rod. The lubricant is applied as an aqueous graphite dispersion that dries to a solid film on the wire surface before entering the die.
Performance in wire drawing is strongly correlated with flake size and aspect ratio. Larger, thinner platelets form a more continuous film and give better die life. For this application, Skaland's SGF-91 at D50 80–150 µm is the standard grade: large flake, high crystallinity, sufficient purity for the metal forming environment. Finer grades (D50 < 20 µm) are used for fine wire and precision drawing where surface defects from coarser particles are not acceptable.
| Application | Recommended Grade | Typical D50 | Key specification |
|---|---|---|---|
| Dry lubrication / anti-seize | SGF-94 | 50–100 µm | Ash ≤6%, moisture ≤0.5% |
| High-temp anti-seize (>400°C) | SGF-96 | 50–100 µm | Ash ≤4%, low Fe content |
| Graphite grease / oil additive | SGF-91 to SGF-94 | Custom — specify D10/D50/D90 | Particle size distribution on CoA |
| Mould release — foundry | SGF-91 | 50–150 µm | Film formation, thermal stability |
| Mould release — glass | SGF-94 | 50–100 µm | Low ash, clean surface |
| Wire drawing — standard | SGF-91 | 80–150 µm | Large flake, high aspect ratio |
| Wire drawing — fine wire | SGF-91 to SGF-94 | 10–30 µm | Narrow PSD, low grit content |
All Skaland flake graphite grades are supplied with a Certificate of Analysis confirming carbon content, ash content, moisture, and D10/D50/D90 particle size distribution. REACH SDS (CAS 7782-42-5), Country of Origin certificate and MSDS are included on every shipment. MOQ is 20 metric tonnes; spot and contract supply are both available, FCA Skaland or CIF.
If you have a specific lubricant formulation with defined purity or particle size requirements, contact us with your target specification and we will confirm grade suitability, achievable D50 range and pricing within one business day.