Study of the Effect of Physicochemical Degradation and Contamination of Motor Oils on Their Lubricity
Abstract
:1. Introduction
2. Materials and Methods
2.1. Tested Samples of Motor Oils
2.2. Reichert Test
2.3. Viscosity Measurement
2.4. FTIR Spectroscopy
2.5. Data Processing
3. Results and Discussion
3.1. Evaluation of Fresh Motor Oils Lubricity
3.2. Influence of Degradation and Contamination of Motor Oils on Lubricity
3.3. Correlation Analysis
4. Conclusions
- Current motor oils used in Czech Railways motor trains have excellent lubricity, which they retain throughout their service life.
- The lubricating properties of motor oils are not limited by the depletion of the antioxidant and anti-wear additive ZDDP and a high degree of chemical degradation. Chemical degradation products (oxidation, nitration, and especially sulfation products), which, unlike hydrocarbons, are of a polar nature, ensure better adhesion of the lubricant to lubricated components. The sulfur contained in the sulfation products also increases the lubricity. For these reasons, some oils had better lubricity at the end of the change interval than fresh oils.
- Correlation analysis confirmed a relatively strong significant correlation between oxidation, nitration, and sulfation products (R ≥ 0.90). At the same time, these chemical degradation products are significantly negatively correlated with the concentration of ZDDP, i.e., with the loss of this additive.
- Due to the low concentration of sulfur in fuels on the European market, the formation of sulfation products can be explained mainly by the reaction of sulfuric acid as a decomposition product of ZDDP with the base motor oil, to a lesser extent as the reaction of SOx from exhaust gases with the base motor oil.
- No significant effect of chemical degradation products on the kinematic viscosity value of motor oils has been demonstrated. However, in none of the analyzed samples did the concentration of these products exceed the limit value.
- Contamination of oil with diesel has the most significant effect on reducing the viscosity of motor oil; this result was supported by a high correlation between the variables. Even with a high concentration of diesel in the oil, the lubricating film of the tested samples retained its load-bearing capacity. Contamination of motor oils with soot did not confirm a significant increase in viscosity, but the concentration of soot did not reach the limit values given in the literature.
- It has been demonstrated that the low water contamination in motor oil does not cause a significant negative effect on lubricity, which led to the observation that the water droplets do not come into tribological contact but bypass it.
- The lubricity and anti-wear properties of motor oils are not factors that would limit the life of motor oils.
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Oil Sample No. | Motor Oil | Specifications | New/Worn Motor Oil | Oil Drain Mileage (km) | Motor Train No. |
---|---|---|---|---|---|
1-1 | M7ADS III | SAE 15W-40 API CF-4/SG | new | 0 | - |
1-2 | M7ADS III | SAE 15W-40 API CF-4/SG | worn | 20,800 | 742,144 |
1-3 model sample | M7ADS III sample (1-2) + 15.6 wt.% diesel | SAE 15W-40 API CF-4/SG | worn | 20,800 | 742,144 |
1-4 model sample | M7ADS III sample (1-2) + 25.6 wt.% diesel | SAE 15W-40 API CF-4/SG | worn | 20,800 | 742,144 |
1-5 | M7ADS III | SAE 15W-40 API CF-4/SG | worn | 24,750 | 742,144 |
2-1 | M7ADS V | SAE 15W-40 API CI-4 CH-4/SL | new | 0 | - |
2-2 | M7ADS V | SAE 15W-40 API CI-4 CH-4/SL | worn | 12,335 | 810,578 |
2-3 | M7ADS V | SAE 15W-40 API CI-4 CH-4/SL | worn | 25,888 | 814,031 |
2-4 | M7ADS V | SAE 15W-40 API CI-4 CH-4/SL | worn | 25,900 | 814,085 |
3-1 | URANIA LD | SAE 15W-40 API CI-4 | new | 0 | - |
3-2 | URANIA LD | SAE 15W-40 API CI-4 | worn | 33,256 | 841,007 I |
3-3 | URANIA LD | SAE 15W-40 API CI-4 | worn | 33,260 | 841,007 II |
3-4 | URANIA LD | SAE 15W-40 API CI-4 | worn | 37,805 | 841,015 I |
3-5 | URANIA LD | SAE 15W-40 API CI-4 | worn | 37,805 | 841,015 II |
4-1 | OMV | SAE 10W-40 API SL/CF | new | 0 | - |
4-2 | OMV | SAE 10W-40 API SL/CF | worn | 39,800 | 841,097 |
Oil Sample No. | WS (mm2) | KV100 °C (mm2·s−1) | ZDDP (%) | Soot (%T) | Fuel (wt.%) | Water (wt.%) | Oxidation (A/0.1 mm) | Nitration (A/0.1 mm) | Sulfation (A/0.1 mm) |
---|---|---|---|---|---|---|---|---|---|
1-1 | 9.0 | 14.62 | 100.0 | 100 | 0.0 | 0.0 | 0.00 | 0.00 | 0.00 |
1-2 | 7.9 | 12.15 | 69.3 | 72 | 4.4 | 0.0 | 0.17 | 0.08 | 0.16 |
1-3 | 8.3 | 9.23 | 69.3 | 72 | 20.0 | 0.0 | 0.17 | 0.08 | 0.16 |
1-4 | 8.8 | 7.47 | 69.3 | 72 | 30.0 | 0.0 | 0.17 | 0.08 | 0.16 |
1-5 | 6.3 | 14.75 | 63.4 | 54 | 2.7 | 0.2 | 0.05 | 0.08 | 0.14 |
2-1 | 5.9 | 14.29 | 100.0 | 100 | 0.0 | 0.0 | 0.00 | 0.00 | 0.00 |
2-2 | 7.6 | 12.94 | 74.0 | 81 | 17.0 | 0.0 | 0.21 | 0.12 | 0.19 |
2-3 | 6.3 | 13.30 | 67.0 | 78 | 0.0 | 0.1 | 0.07 | 0.10 | 0.14 |
2-4 | 7.9 | 15.48 | 59.0 | 79 | 7.0 | 0.0 | 0.07 | 0.09 | 0.17 |
3-1 | 5.8 | 14.14 | 100.0 | 100 | 0.0 | 0.0 | 0.00 | 0.00 | 0.00 |
3-2 | 5.9 | 14.07 | 11.5 | 93 | 0.0 | 0.0 | 0.15 | 0.23 | 0.26 |
3-3 | 6.1 | 14.07 | 13.8 | 93 | 0.0 | 0.0 | 0.14 | 0.22 | 0.26 |
3-4 | 6.3 | 14.68 | 5.0 | 88 | 0.0 | 0.0 | 0.26 | 0.40 | 0.38 |
3-5 | 5.8 | 14.65 | 6.0 | 88 | 0.5 | 0.0 | 0.26 | 0.40 | 0.38 |
4-1 | 3.5 | 14.37 | 100.0 | 100 | 0.0 | 0.0 | 0.00 | 0.00 | 0.00 |
4-2 | 2.1 | 15.58 | 23.2 | 75 | 0.0 | 0.2 | 0.42 | 0.62 | 0.57 |
Parameter | KV | ZDDP | Soot | Fuel | Oxidation | Nitration | Sulfation |
---|---|---|---|---|---|---|---|
KV | 1 | - | - | - | - | - | - |
ZDDP | −0.20 | 1 | - | - | - | - | - |
soot | 0.34 | 0.15 | 1 | - | - | - | |
fuel | −0.87 | 0.18 | −0.45 | 1 | - | - | - |
oxidation | −0.06 | −0.72 | −0.35 | 0.16 | 1 | - | - |
nitration | 0.30 | −0.83 | −0.14 | −0.22 | 0.90 | 1 | - |
sulfation | 0.17 | −0.87 | −0.31 | −0.07 | 0.94 | 0.97 | 1 |
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Sejkorová, M.; Hurtová, I.; Jilek, P.; Novák, M.; Voltr, O. Study of the Effect of Physicochemical Degradation and Contamination of Motor Oils on Their Lubricity. Coatings 2021, 11, 60. https://doi.org/10.3390/coatings11010060
Sejkorová M, Hurtová I, Jilek P, Novák M, Voltr O. Study of the Effect of Physicochemical Degradation and Contamination of Motor Oils on Their Lubricity. Coatings. 2021; 11(1):60. https://doi.org/10.3390/coatings11010060
Chicago/Turabian StyleSejkorová, Marie, Ivana Hurtová, Petr Jilek, Martin Novák, and Ondřej Voltr. 2021. "Study of the Effect of Physicochemical Degradation and Contamination of Motor Oils on Their Lubricity" Coatings 11, no. 1: 60. https://doi.org/10.3390/coatings11010060
APA StyleSejkorová, M., Hurtová, I., Jilek, P., Novák, M., & Voltr, O. (2021). Study of the Effect of Physicochemical Degradation and Contamination of Motor Oils on Their Lubricity. Coatings, 11(1), 60. https://doi.org/10.3390/coatings11010060