Is calcium carbonate a thickener, a filler, or an EP helper?
All three, depending on how it got there. In calcium sulfonate complex grease, calcite particles are grown in place from overbased sulfonate — they are part of the thickener. In cheap greases, ground CaCO3 is a bulking filler. Recent public filings (for example WO2025217529) argue that selected carbonates at high treat can carry load and cut the amount of expensive soap. Those are different jobs. Mixing them up is how plants make a dull, noisy grease that still fails four-ball.
Same mineral, different job
Converted calcite (CaSX)
Overbased calcium sulfonate is cooked so amorphous carbonate becomes calcite. The solid is part of the thickener network and brings inherent EP and rust resistance. See calcium grease explained.
Filler / extender
Milled limestone or precipitated CaCO3 added to a lithium or calcium soap grease to bulk volume. Cost goes down; unworked penetration, water spray-off and noise often get worse at modest treats.
Structural solid at high load
Filings such as WO2025217529 describe greases where CaCO3 is a large fraction of the mass, sometimes with little soap, aimed at EP and water spray-off without a full sulfonate process. That is a public R&D direction, not a drop-in for NLGI 2 lithium MP.
The industrial problem: cost versus EP and wash-off
Soap thickeners and sulfonate complexes are expensive. Fillers (clays, oxides, carbonates) have always been the way to add bulk. The open question in WO2025217529 is whether selected calcium carbonates, at high concentration, can do more than bulk — specifically improve four-ball weld / SRV pass load and, at the right loading, water spray-off (ASTM D4049) — while leaving crystal structure intact (unlike the sulfonate conversion route).
The same disclosure notes synergy with ZDDP and anti-synergy with some active sulphur additives. For a working chemist that is the useful sentence: carbonate is not a universal EP booster; it depends on the rest of the package.
Do not copy treat rates from a patent into a plant batch. Patents are legal claims plus examples, not a validated SOP for your base oil and mill.
If you already see CaCO3 on a TDS
- Ask whether it is converted calcite in CaSX or added powder. The TDS should say thickener type.
- High ash with a lithium soap label is a hint of filler. That grease may still be fine for slow, wet pins and poor for high-speed motors.
- Noise, poor pumpability, and crumbling on a bearing are classic over-filled textures.
- For which grease to use in the field, start with lithium vs lithium complex vs calcium — not with a filler debate.
Public sources
Public patents and papers cited as field references. Lubechem does not own these inventions and this page is not a formula.
- WO2025217529A1 — Calcium carbonate greases (VGP IPCO LLC, published 16 Oct 2025) — Public PCT application discussing CaCO3 as a structural solid. Cited as a field reference only.
- NLGI — lubricating grease glossary (NLGI grade, thickener) — Industry definitions for grease and consistency.
Calcium carbonate in grease FAQ
Is calcium sulfonate grease “full of chalk”?
The calcite in a proper CaSX grease is generated in the thickener reaction. That is not the same as dumping agricultural limestone into lithium grease.
Does adding CaCO3 always raise weld load?
Not always. Public examples show load benefits in some systems and little help — or harm — with some sulphur EP packages. Test the finished grease.
Can I use this patent as a plant formula?
No. It is a legal publication. Using a patented composition commercially can infringe. This article explains the question the filing is asking.
Lubechem formulates calcium, lithium and sulfonate greases for manufacturers
If you want to see how thickener chemistry is chosen in practice, start with the grease formulation guide. This page stays with the public CaCO₃ question.
See how a grease is built →