The world's most widely manufactured grease — and for the new producer, the most economically sensible entry point. Lithium 12-hydroxystearate soap grease accounts for roughly 70 % of all grease consumed globally and the same is broadly true of the Indian market. This guide covers the complete saponification SOP, raw-material specifications, NLGI grade range, ASTM performance targets, common failure modes and the production-plant equipment a serious manufacturer needs to make a consistent product.
Lithium grease is fundamentally a colloidal dispersion of lithium 12-hydroxystearate soap fibres in a mineral or synthetic base oil. The soap is formed in situ by reacting 12-hydroxystearic acid (12-HSA, a hydrogenated castor-oil derivative) with lithium hydroxide monohydrate (LiOH·H₂O) directly inside the base oil. The chemistry is straightforward saponification: R-COOH + LiOH·H₂O → R-COOLi + 2 H₂O.
What makes the resulting grease useful is the hydroxyl group at the C-12 position of the fatty acid chain. During controlled cool-down from 200°C, the lithium 12-HSA molecules self-assemble into long twisted ribbon-like fibres held together by intermolecular hydrogen bonds at the C-12 hydroxyl. These fibres form a three-dimensional matrix that traps the base oil — converting a free-flowing liquid into a semi-solid with a defined yield point. The grease melts (drops) at 175–195°C when those hydrogen bonds finally break and the fibres dissolve back into the oil.
This is why lithium grease is dramatically superior to plain lithium-stearate (which has no C-12 hydroxyl, no hydrogen bonding, and a drop point near 140°C). It is also why processing temperature control matters: the fibre structure is established during cool-down, and a botched cooling profile produces a grease that looks right but bleeds and softens over weeks of storage.
| Component | Grade / Specification | Treat Rate (NLGI 2) | Function & Sourcing |
|---|---|---|---|
| Base oil — primary | Group II SN500, KV40 95–105 cSt, VI 100+ | 55–65% | Carrier fluid and lubricant phase. From IOCL, BPCL, HPCL, Reliance or imported Group II. Higher viscosity helps soap retention. |
| Base oil — secondary | Group II SN150, KV40 28–32 cSt | 20–28% | Diluent used to dissolve fatty acid and reduce blended viscosity. Used in the initial charge to keep saponification mass mobile. |
| 12-Hydroxystearic acid | Tech grade, AV 175–185 mg KOH/g, SV 180–195, iodine value <5 | 7–9% | The fatty acid for saponification. Sourced as hydrogenated castor-oil derivative from Indian (Jayant Agro, Itoh) or Chinese suppliers. |
| Lithium hydroxide monohydrate | LiOH·H₂O, technical grade, ≥56% Li₂O | 1.1–1.5% | The alkali. Stoichiometric ratio to 12-HSA is roughly 1:7 by weight (1 mole LiOH·H₂O per mole 12-HSA + 5–10% excess). |
| Antioxidant | Aryl-amine (PANA / ODPA) or hindered phenol | 0.5–1.0% | Prevents oxidation of base oil and soap at service temperature. Aryl-amine preferred for higher-temperature lithium NLGI 3. |
| EP / AW additive | Sulfurised olefin / ZDDP / amine phosphate | 1.0–3.0% | For EP-grade NLGI 2 (industrial). Skip for chassis-grade automotive. ZDDP also functions as antioxidant. |
| Rust inhibitor | Petroleum sulfonate / amine succinate | 0.3–0.6% | For wet-environment applications. Calcium sulfonate also boosts EP. Critical for marine and wheel-bearing variants. |
| Tackifier (optional) | Polyisobutylene (PIB) 2400 cSt | 0.5–2.0% | For applications needing extra adhesion — CV joints, slow-speed bearings, open chains. Adds stringy texture. |
The base oil viscosity choice is the single most important formulation lever. For NLGI 2 lithium grease, target a blended base-oil KV40 of 100–160 cSt — achieved by blending SN500 with SN150 in roughly 70:30 ratio. Lower viscosity blends bleed; higher viscosity blends do not pump cold. For NLGI 0–1 (centralised lubrication), drop to SN150 alone or with a small SN500 addition.
The following SOP is for a typical 200–400 kg batch in a jacketed reactor with anchor or paddle stirrer. Total cycle time is approximately 8–10 hours. Reactor temperatures are measured with a calibrated immersion thermocouple in the bulk grease — jacket temperature reads differently.
| Property | ASTM Test Method | Typical Value | BIS IS 7623 Limit (Type 2) |
|---|---|---|---|
| Worked penetration, 60 strokes | ASTM D217 | 265–295 (0.1 mm) | 265–295 |
| Penetration change, 10,000 strokes | ASTM D217 | +10 to +25 dmm | +50 max |
| Dropping point | ASTM D566 / D2265 | 180–195°C | 175°C min |
| Water washout @ 79°C | ASTM D1264 | 5–10% | 10% max |
| Four-ball wear scar | ASTM D4172, 40 kg, 75°C, 1h | 0.45–0.55 mm | 0.60 max |
| Four-ball EP weld point | ASTM D2783 | 200–250 kgf (EP grade) | 200 kgf min |
| Oxidation stability, 100h @ 99°C | ASTM D942 | 5–10 psi pressure drop | 15 psi max |
| Copper corrosion, 24h @ 100°C | ASTM D4048 | 1a–1b | 1b max |
| Oil separation, 24h @ 100°C | ASTM D1742 / D6184 | 3–5% | 5% max |
| Failure Mode | Root Cause | Diagnostic Test | Fix |
|---|---|---|---|
| Drop point below 175°C | Top-temperature hold below 195°C; or 12-HSA contaminated with plain stearic acid | ASTM D566; check 12-HSA SV and AV | Raise top temperature to 200°C and hold 20 min; reject 12-HSA outside SV 180–195 spec |
| Oil bleed >5% at 24h/100°C | Base-oil viscosity too low; soap content too low; quench cool above 120°C | ASTM D1742 / D6184; recalculate soap % | Raise base-oil KV40 to 100+ cSt; increase soap to 8–10% for NLGI 2; slow cool-down to 90 min |
| Penetration drift between drums | Inconsistent milling — variable pass count or mill gap | ASTM D217 multiple samples from batch | Standardise three-roll mill at 50–100/50/25 µm gap, 3 passes; verify mill temperature <80°C |
| Grease appears lumpy or stringy | Under-dispersed soap fibres; milling skipped or insufficient | Microscope check; penetration variance >5 dmm | Increase mill passes; reduce final gap to 25 µm; verify discharge temperature 60–70°C |
| Copper corrosion fail (2a or worse) | Free fatty acid in grease (incomplete saponification); aggressive EP additive | ASTM D4048; acid value of grease | Extend dehydration hold; add small LiOH excess; switch EP from active sulfur to passive sulfurised olefin |
| Bleed only in storage (1–2 weeks) | Cool-down too fast; metastable fibre crystallisation | D6184 at 48h, 1 week, 2 weeks | Slow controlled cool-down 60–90 min from 210°C to 90°C; use jacket cooling, not air |
| Saponification stalls; AV stays high | LiOH dosage wrong; water-of-saponification not driving out | Acid value (should drop to <3 mg KOH/g) | Re-verify LiOH stoichiometry (1 mol LiOH per mol 12-HSA + 5–10% excess); extend dehydration to 90 min |
A lithium grease plant is built around four pieces of equipment: a jacketed reactor with high-temperature capability, a controlled-cooling system, a finishing mill, and a packaging line. For a typical 1 TPD (one ton per day) production scale, capex falls in the ₹35–80 lakh range; for 5 TPD scale, ₹1–2 crore. See our Plant Setup service for complete specification, layout and commissioning support.
For a Group II base oil blend (SN500 + SN150 at roughly 70:30 ratio), 7–10 wt% lithium 12-hydroxystearate soap typically yields NLGI 2 worked penetration of 265–295. Higher soap content (10–12%) is needed for NLGI 3; lower (5–7%) for NLGI 1; below 5% gives NLGI 0 semi-fluid consistency.
The base-oil viscosity also drives soap requirement — lower viscosity blends need more soap, higher viscosity blends need less. We always recommend a small-scale optimisation batch when changing base-oil source or viscosity.
Tell us your target NLGI grade, application, and reactor scale. We respond within one business day with an honest assessment and indicative timeline.