Calcium Soap Greases:

Tallow (animal fat) based calcium greases were the earliest lubricants developed during 1845. As a result, calcium greases were relatively inexpensive to manufacture and are still in use since then.[3]. While there are three types of calcium greases but anhydrous calcium grease is the most economical multipurpose grease. Besides, the other two greases are hydrated calcium and calcium complex. In addition to multipurpose anhydrous calcium, hydrated calcium or lime grease is one of the most economical greases for general-purpose wet applications.

Three common types of calcium greases:

  • Hydrated calcium grease (lime grease)
  • Anhydrous calcium Grease
  • Calcium complex  

Hydrated calcium soap grease

Hydrated calcium grease has mineral oil, animal fat (tallow), and lime in its composition. Grease has a 90°C (194°F) dropping point, whereas the useable temperature is around 65°C (149°F). Still being manufactured on a large scale, it is one of the most economical greases.  Due to the chemical reaction of hydrated lime with tallow, lime greases need water to retain their grease structure. A small amount of water acts as a stabilizer. Lime greases have limited use because of lower useable temperatures and the need for water to stay as grease.

Uses (applications) of hydrated calcium grease

  • Machines in a wet environment
  • Agricultural and farming machinery exposed to water
  • Water pumps
  • Non-bearing axles
  • Chassis lubrication

Advantages of hydrated calcium (lime) grease

  • Smooth structure
  • Good low-temperature properties (depending upon the base oil)
  • Excellent water resistance (don’t form an emulsion with water)
  • Good adhesion (adhere to surface applications)
  • Pumpable

Disadvantages of hydrated calcium lime grease

  • Low drop point 90-100°C (195-210°F)
  • The maximum working temperature is 65°C (149°F).
  • Not suitable for high-speed application (bearings)
  • Grease structure breaks without water
  • Poor storage stability
  • Poor shear/mechanical stability

Anhydrous calcium soap grease 

Anhydrous calcium grease is an economical multipurpose grease. Calcium 12-Hydroxy Stearate, or anhydrous calcium grease has 12HSA (12-hydroxystearic acid) instead of animal fat (tallow/stearic acid) as a thickener. As a result, 12HSA eliminates the need for water in calcium greases. In the same way, it is also possible to use blend of 12HSA and HCO (hydrogenated castor oil) or stearic acid with an 85:15 ratio. The grease has a 150°C (300°F) dropping point, good thermal stability, excellent water resistance, and good mechanical stability. Therefore, it is the best multipurpose grease for applications where equipment running at the ambient temperature or up to 90°C (194°F) max. Theoretically, it is okay for up to 110°C (230°F) because of 150°C (300°F) dropping point, but as layman selection criteria use it for non-powered machinery.

Composition/formulations of anhydrous calcium grease

Learn More:

Composition/formulation of multipurpose NLGI-2 anhydrous calcium grease (target ISO VG 110)
Components Percent Wt
Base Oil (Group I SN600) 75%
Bright Stock 5%
12-Hydroxystearic Acid 11.9%
Hydrogenated Castor Oil 2.1%
Calcium Hydroxide 2%
Additives 4%
Composition/formulation of multipurpose NLGI-2 anhydrous calcium grease (target ISO VG 220)
Components Percent Wt
Base Oil (Group I SN600) 41%
Bright Stock 39%
12-Hydroxystearic Acid 11.9%
Hydrogenated Castor Oil 2.1%
Calcium Hydroxide 2%
Additives 4%

How to make grease:

The process to make anhydrous calcium soap grease. See the above example for composition or formulation.

1. Charged 15% of the total base oil to an open kettle. 

2. Heat is applied to reach 50-60°C (122-140°C) with stirring.

3. 12-hydroxy stearic acid and hydrogenated castor oil added (the preferred ratio is 85:15 up to 50:50).

4. Reached 80°C (176°F) with continuous stirring to melt the acids. 

5. At 80-90°C (194°F), the slurry of calcium hydroxide is added slowly to the kettle over 20 minutes. 

6. Added the calcium hydroxide slurry; 30 minutes further mix time is completed, maintained below 100°C (194°F) temperature to avoid foaming.

7. Following the 30 minutes mixing time, the temperature increased stepwise to complete the reaction and water removal.

8. At 110°C (230°F), the heat increased to initiate the temperature ramp to the 140°C (284°F) process maximum. A portion of the base oil is added multiple times during this process.

9. At 140-145°C (284°F) temperature stage, cooling oil is applied at a slow, controlled rate. 

10. Cooling started, below 90°C (194°F), antioxidants, EP, and other additives added. The grease is milled, and the penetration and dropping point tested. 

11. Final adjustment base oil added to achieve the desired grade.

Comparison and specification of calcium greases
Description Hydrated Calcium Grease Anhydrous Calcium Grease
Dropping Point 90°C (194°F) 150°C (300°F)
Useable Temp °C Max 65°C (149°F) 110°C (230°F)
Appearance Fibrous Buttery
Good for Use as Economical General-Purpose Economical Multi-Purpose
Water Resistance Good to Excellent Excellent
Work Stability Fair to Good Good to Excellent
Oxidation Stability Poor to Excellent Fair to Excellent
Rust Protection Poor to Excellent Poor to Excellent
Oil Separation Poor to Good Good

Uses (applications) of calcium 12-hydroxystearate grease

  • Multipurpose grease for wet environment
  • Wet industrial machinery
  • Sewage plant and machinery
  • Agricultural, farming machinery exposed to water, tractors, mine cars, and textile machinery
  • Water pumps and bearings
  • Slow-moving axle grease
  • Chassis lubrication

Advantages of calcium 12-hydroxystearate grease

  • Smooth translucent structure
  • Good low-temperature properties (base oil-dependent)
  • Available in EP (extreme pressure)
  • Excellent water resistance (don’t form an emulsion with water)
  • Good adhesion (good for adhere-to-surface applications)
  • Excellent shear stability
  • Pumpable

Disadvantages of calcium 12-hydroxystearate grease

  • Low drop point of 150°C (302°F)
  • The low continuous use temperature of 52 to 66°C (125 to 150°F) up to 90°C(194°F). The absolute max is 110°C (230°F)
  • Fair storage stability
References:

[1] Dropping Point of Lubricating Grease

[2] ASTM grease definition

[3] History of Automotive Lubrication SAE Technical Paper 961949 By SQA Rizvi

[4] NLGI Grease Guide

Leave a Reply

Your email address will not be published. Required fields are marked *