Basics of lubricant additives

The Basics of Lubricant Additives
or
It’s Not Just Oil!

March 2009

© 2006 Chevron Corporation Copyright 2006 Chevron Global Lubricants, a division of Chevron U.S.A. Inc. Global Lubricants
11/06 JobbersChevronPhaseI LubAdd RFarina All rights reserved. Unauthorized reproduction is prohibited.

It’s Not

G
Just Oil!

ro
up
Ba

II
se
St
oc
k Viscosity
Index
Anti- Improvers
Oxidants
Dispersants
Detergents
Rust and
Corrosion
Pour Point Inhibitor
Depressants
Foam
Inhibitors
Friction
Modifiers
Antiwear
Agents

G010075


Typical Lubricant Composition

Pour Point Depressant
0-2%
Viscosity
Modifier
0-15%
DI
Package
2-30%

Base Oil
70-95%


Formulating a Superior Lubricant Requires Optimizing
Additive Combinations to Meet Performance Targets

Viscosity
Engine Cleanliness
Wear Control
Fuel Economy
Drain Interval
Cost


Graphic Representation of an
Additive Molecule

Sticky End Slippery Tail

Sticky End Slippery Tail
Consists of a Surface Consists of a Hydrocarbon
Active Group Containing Chain
Oxygen, Nitrogen, Sulfur,
or Phosphorus

G010077


Ashless Dispersants


Ashless Dispersants

Function • Control Sludge and Varnish Formation at
Lower Operating Temperatures
• Control Thickening Caused by Soot

Structure • High Molecular Weight Tail With Surface
Active Head

Mechanism • Keep Sludge, Soot, and Deposit
Precursors Suspended in Oil


Dispersants Impede Particle Aggregation

Rate of
Aggregation Slowed

(Solid Particles)

(Dispersant)

G010078


Dispersant Selection

Must Balance Performance Attributes
Need to Control Soot Thickening, Sludge
Too Much May Hurt Seal Performance

(More is Not Always Better!)


Metallic Detergents


Metallic Detergents

Function • Provide High Temperature Cleanliness
• Control Corrosive Wear

Types • Metallic Soaps; Normally Na, Ca, or Mg
• “Soap” Substrates
- Sulfonates
- Salicylates
- Phenates

Mechanism • Neutralize Acids From Engine Blow-By


Overbased Detergent

Soap
Basic
Molecule
Core

CaCO3
CaCO CaCO3
3
CaCO3
CaCO3
CaCO3
CaCO3
CaCO3 CaCO3
CaCO3 CaCO
3
CaCO3 CaCO
3
CaCO3

G010079


Detergency in Oils

Gum Being Polar, Sticks on Polar Surfaces

The Polar Ends of Detergents Also Stick to Polar Surface

An Effective Detergent Displaces Gum (Deposits)

G010080


Detergent Selection

Balance Cost and Performance Requirements
Too Much May Hurt Wear Performance
May Use Multiple Types of Detergent
Phenates for Higher Temperatures
Sulfonates for Lower Temperatures


Relationship of TBN and Ash

100
Total Base Number (TBN)
ASTM D 2896 mg KOH/g

90
80
Marine Oil
70
60
50 Railroad Marine Oil
Oil
40
HDMO
30
PCMO
20
10
0
0 1 2 3 4 5 6 7 8 9 10
Sulfated Ash, %


Antioxidants


Antioxidant Formulation

Function • Control Oxidative Decomposition of Oil
• Minimize Oil Thickening
• Decrease Sludge and Varnish Formation
• Decrease Formation of Corrosive
Compounds (Acids)

Types • Organic – Phenols, Amines
• Metal-Containing – Zinc Dithiophosphates
(ZDP), Molybdenum Compounds

Mechanism • Decrease Rates of Chemical Reactions
With Oxygen


Factors Affecting Oxidation

Temperature
Catalysts (Metal Ions)
Aeration Rate
Additive System
Base Stock


Antioxidant Selection

Most Performance Comes From the Antiwear Additive
(ZDP)
Supplement to Meet Sequence IIIE
Compatibility With Seals
Cost
May Use Multiple Antioxidants


Antiwear Agents


Antiwear Agent

Function • Reduce Wear of Rubbing Metal Surfaces

Types • Amine or Metal Phosphites, Phosphates,
or Thiophosphates (ZDP)
• Boron Compounds
• Sulfurized Olefins

Mechanism • Adhere to Metal Surfaces, Forming a
Protective Film Which Shears
Preferentially Under Wear Conditions


Formation of a Zinc Dithiophosphate (ZDP)
Antiwear Film

Bulk Oil
ZDP
ZDP
ZDP
ZDP

Adsorbed ZDP Layer
ZDP ZDP
ZDP ZDP

Metal Surface
Metal Surface

T
T
EAA
HE
H
Phosphorous Containing
Antiwear Film

Metal Surface
G010081


Friction Modifiers


Friction Modifiers

Function • Reduce Friction of Rubbing Metal
Surfaces

Types • Fatty Compounds With Polar Ends
• Graphite
• Molybdenum Compounds

Mechanism • Forms an Easily Shearable Film on
Metal Surface


Lubricated Metal Surfaces With Friction
Modifier Present

Metal
Oxide/Metal Zone
Oxide Rich Layer
Adsorbed Film of F.M.
(Three Stories High)

Oil Film

Adsorbed Film of F.M.
(Five Stories High)

Oxide Rich Layer
Oxide/Metal Zone
Metal

G010082


Asperity Riding on
Friction Modifier Layer

Moving Asperity

Friction Modifier Film
(Five Levels
Remaining)
Oxide Layer

G010083


Antifoam Agent

Function • Prevent Oil Loss or Oil Starvation
Caused by Foaming
• Reduce Oil Aeration

Types • Polydimethyl Siloxanes
• Polyacrylates

Mechanism • Reduce Surface Tension of Oil
Causing Bubbles to Collapse


Viscosity Modifiers


Viscosity Modifiers on Temperature
Dependence of Viscosity

Viscosity Modifiers Are Materials (Usually Polymers)
Which Improve (i.e., Increase) the VI of a Base Oil

SN 250
SN 250 Base Oil + Viscosity Modifier
(High VI)
SAE 10W Max
SAE 10W Max
Viscosity

SAE 30 Min
SAE 30 Min

SN 100
SN 100

Temperature
Viscosity Modifier (VM’s) Viscosity Index Improvers (VII’s)


Viscosity Modifier Mechanism

Increasing Temperature

Polymer
Molecule
Oil
Associated
With Polymer
Increasing Viscosity Contribution

(Increasing Effective Size of Polymer)

G010075


Pour Point Depressants



Function • Reduce Viscosity Increase at Low
Temperatures Resulting From Wax
Crystallization
• Improve Low Temperature Pumpability

Structure • Organic Polymer

Mechanism • Promote Formation of Smaller, Rounded
Particles Which Are Less Likely to Form
Interlocking Crystals


Wax Crystal Morphology

Without PPD With PPD

G010084

Other Additives
(See Supplemental Materials)

Corrosion Inhibitors
Demulsifiers
Emulsifiers
EP (Extreme Pressure) Agents
Metal Deactivators
Rust Inhibitors


Some Key Points to Remember

Additives Are Carefully Balanced to Enable Base Oils to
Meet Defined Performance Criteria
More is Not Necessarily Better
Additive Interactions Are Strong
Developing a Successful Formulation Requires
Extensive Testing and Verification
Chevron Experience and Commitment to Technical
Excellence is Key


The Basics of Lubricant Additives

Supplemental Information


Where Additives Are Used

Stabilizers And Dyes
Metal Deactivators
Extreme Pressure

Friction Modifiers
Antifoam Agents
Antiwear Agents
Viscosity Index

Rust Inhibitors
Often Used

Demulisifiers
Antioxidants

Depressants
Dispersants

Emulsifiers
Detergents

Pour Point
Improvers

Additives
Occasionally Used

Engine Oils Crankcase Engine Oil

Automatic Transmission Fluid

Rear Axle Lubricants

Manual Transmission Lubricants

Power Steering Fluid

Body/Chassis Greases

Shock Absorber Fluid

Pre-Lubricants

Industrial Oils Turbine and Other R&O Fluids

Antiwear Hydraulic Fluids

Fire Resistant Hydraulic Fluids

Metalworking Lubricants

Industrial Gear Oils

Plant Machinery Greases

Paper Machine Oils

Soluble Oils


Additives Commonly Found
in Lubricants

Additive What It Does How It Works
Antiwear • Minimizes wear caused by metal-to- • Additive reacts chemically and
Agent metal contact during conditions of forms a film on metal surfaces
mild boundary lubrication. under normal operating conditions.
Antioxidant or • Inhibits varnish and sludge formation. • Slows the rate of reaction with
Oxidation oxygen by interruption of chain
• Reduces viscosity increase resulting
Inhibitor reactions or by decomposing
from oil oxidation.
reactive peroxides.
• Reduces formation of corrosive acids.
Demulsifier • Loosens and breaks stable emulsions. • Lowers emulsion stability.
Corrosion • Prevents corrosive attack on • Forms a film on nonferrous metallic
Inhibitor nonferrous metallic surfaces. parts thus protecting them from
attack by contaminants in the oil.
Detergent • Prevents oxidation products (gums) • Chemically react with oxidation
which have formed in the oil from products (gums) so that they
sticking to metal parts. remain soluble in the oil and do not
stick to metal surfaces.
• Neutralizes acidic contaminants.
• Metallic Base Reacts With Acid
Dispersant • Keeps oxidation products separated • Additive adsorbs on surface of gum
and suspended in the oil, retards particles or soot and inhibits
formation of sludge and reduces soot agglomeration.
related viscosity increase.


Additives Commonly Found in Lubricants
(Continued)

Additive What It Does How It Works
Extreme Pressure • Prevents welding and subsequent wear • Additive combines chemically with surface to
(EP) Agents or seizure of contacting metal parts form a surface film.
under extreme or shock load
• Reaction usually occurs at high temperatures,
conditions.
which result when asperities collide.
Emulsifier • Promotes rapid mixing of oil and water • Reduces interfacial tension and permits
promoting formation of a stable intimate mixing of oil and water.
emulsion.
Foam Inhibitor • Prevents formation of stable foam. • Promotes combination of small bubbles into
large bubbles, which in turn collapse more
easily.
Friction Modifier • Alters coefficient of friction. • Forms an easily shearable film on metal
surfaces.
Metal Deactivator • Reduces the catalytic effect of metals • Forms an inactive film on metal surfaces by
on oxidation rate. combining with metallic ions.
Rust Inhibitor • Prevent rusting of ferrous (iron or • Forms a film on ferrous parts thus protecting
steel) machine parts. them from water or other destructive
materials.
Pour Point • Lowers the pour point and enables the • Changes the size and shape wax crystals.
Depressant lubricant to flow at low temperature.
Viscosity Modifier • Reduces rate of change of viscosity • Polymers uncoil as temperature rises, thus
(VM) or Viscosity with temperature and makes possible increasing their effective size and viscosity.
Index Improver the formulation of multigrade oils.
(VII)


Basics of lubricant additives

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