Lubricant Analysis

Engine lubricants play an important role in lubrication, cooling, cleaning, and rust prevention for vehicles, construction machinery, ships, airplanes, and other equipment with internal combustion or turbine engines.
Lubricants deteriorate due to decomposition and chemical changes of oil components and additives caused by physical and thermal stresses, as well as contamination by metal wear particles and incorporated fuel. As the lubricant deteriorates through use, its performance will decline and the inside of the engine can wear, leading to a decrease in service life and potential malfunction. Therefore, it is recommended to analyze the lubricant throughout its lifespan to assess its quality, utility, and remaining service life. These analyses can be accomplished with a number of instruments.



 
Typical causes of engine lubricant deterioration

Typical causes of engine lubricant deterioration

Analytical Techniques

 
 
 
 
 
 

2. Analytical Application to Lubricating Oil

 
 
 
 
 

1. lubricant deterioration analysis and additive analysis

 
Lubricant Analysis by FTIR, GC, and ICP-MS
Analysis items (Elements) Needed system Standards
Deterioration Oxidation FT-IR ASTM E2412
Nitration
Sulfate by-products
Contamination Water FT-IR ASTM E2412
Soot
Gasoline GC
FT-IR ASTM E2412
Diesel GC
FT-IR ASTM E2412
Coolant (B, Na, K) ICP-AES ASTM D5185
FT-IR ASTM E2412
Antifreeze (Na) ICP-AES ASTM D5185
Dust (Si)
Seal materials (Si)
Wear Metals (Al, Fe, Cu, Cr, Ni, Zn, etc.) ICP-AES ASTM D5185
Additives Anti-oxidant (Zn, Cu, B) ICP-AES ASTM D4951
FT-IR ASTM E2412
Anti-wear agents (B, Cu, K, S, Zn, etc.) ICP-AES ASTM D4951
FT-IR ASTM E2412
Detergent inhibitors (Ba, Mg, Ca, etc.) ICP-AES ASTM D4951
Corrosion inhibitors (Ba, Zn)
Anti-rusting agents (K, Ba)
Friction modifier additives (Mo)

Lubricant deterioration analysis using compact FT-IR

IRSpirit Fourier Transform Infrared Spectrophotometer
FTIR Spectrophotometer

Applicable Method

Condition Monitoring of Lubricant oil (ASTM E2412/D7418/D7414/D7415/D7412)





 

Analysis of Additive Elements, Wear Metals, and Contaminants in Used Lubricants using ICP-AES

ICPE-9800 Simultaneous ICP Atomic Emission Spectrometers
ICP Emission Spectrometer

Applicable Method

Elements analysis in Lubricating oil (ASTM D4951/D5185)

 Poster Download 

A poster can be downloaded that details some examples of lubricant deterioration analysis and additive analysis.

[Abstract]
Engine lubricants play an important role in lubrication, cooling, cleaning, and rust prevention for vehicles, construction machinery, ships, airplanes, and other equipment with internal combustion or turbine engines. As the lubricant deteriorates through use, its performance will decline and the inside of the engine can wear, leading to a decrease in service life and potential malfunction. Lubricants deteriorate due to decomposition and chemical changes of oil components and additives caused by physical and thermal stresses, as well as contamination by metal wear particles and incorporated fuel. Therefore, it is recommended to analyze the lubricant throughout its lifespan to assess its quality, utility, and remaining service life. These analyses can be accomplished with a number of instruments, including FTIR, GC, and ICP-AES.

[Standards]
ASTM E2412-10、 ASTM D7593-14、 ASTM D5185-18、 ASTM D4951-14

2. Analytical Application to Lubricating Oil



 

Visualization of Lubricant Structure by SPM

In engine oil and other lubricants, additives are added to the base oil to improve performance. The additives form a thin adsorption film (tribofilm) on the metal surfaces of the sliding parts, reducing friction and wear. However, it is difficult to analyze the film in the lubricant. As a result, lubricant development sites repeatedly perform actual vehicle tests, engine tests, and other tests, to narrow down the search for additives and their optimal concentrations. This causes issues with time and expense.

Using a mere 500 µL of lubricant, the SPM-8100FM high-resolution scanning probe microscope can analyze metallic surfaces in contact with a lubricant, at molecular level resolution. This holds promise as a new method, which will enable accelerated lubricant development by replacing a screening at the initial development stages with laboratory-scale materials testing.



 

Example Analyses
-Structural Analysis of a Phosphate Ester Adsorption Film Formed in a Lubricant-


Molecular Structure (a) PAO, (b) Phosphate Ester

When a scanning probe microscope is used, structure at the molecular level can be evaluated by acquiring a topographic image (XY) of the adsorption film originating from the additive in the lubricant, and a Z-X cross-sectional Δf mapping image.

In this example, the SPM-8100FM next-generation scanning probe microscope, which features frequency modulation, is used to analyze the adsorption structure of a phosphate ester in a base oil of polyalphaolefin (PAO) on an iron oxide substrate. It is observed that the adsorption layer is different depending on the presence or absence of the phosphate ester.

 
Analysis of the Topography of an Iron Oxide Film Interface


 
PAO

The surface is not covered by the phosphate ester adsorption film, so the contours of the particles are clearly visible.

PAO + Phosphate Ester (200 ppm)

The surface is thinly covered by the phosphate ester adsorption film, so the contours of the particles are unclear.

 
 
Stress Response Analysis of the Lubricant-Iron Oxide Film Interface


 
PAO

A layered structure is visible.

PAO + Phosphate Ester (200 ppm)

The disappearance of the layered structure suggests that the PAO molecules do not make direct contact with the iron oxide film surface. In other words, the iron oxide film surface is covered by the phosphate ester adsorption film.

Expected molecular model 1

A multilayer structure is formed when the PAO molecules, which are in contact with the iron oxide film surface, lie horizontally and adopt a parallel orientation.

Expected molecular model 2

The PAO molecules do not make direct contact with the iron oxide film surface, so no layered structure is formed.

〔Source: Tribology No. 64, Vol. 11 (2019), Shiho MORIGUCHI, Ryohei KOKAWA, Teppei TSUJIMOTO, Akira SASAHARA and Hiroshi ONISHI: Analysis of Solid-Liquid Interface by Frequency Modulation Atomic Force Microscopy〕

 References 
 

For Research Use Only. Not for use in diagnostic procedures.

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