Search results

The purpose of this paper is to study a novel Mannich adduct of benztriazole-containing diphenylamine (coded as BD) and its anti-oxidation properties as an additive in two typical synthetic ester-based oils.

The anti-oxidation properties in two typical synthetic ester-based oils were evaluated in detail, using rotating pressure vessel oxidation test. The tribological properties of BD in synthetic ester-based oil (A51) were also tested with Optimal SRV-I oscillating friction and wear tester at atmosphere.

The results of tests demonstrated that the novel BD compound is, indeed, a high-performance anti-oxidation additive that was able to remarkably improve the oxidation stability of synthetic ester-based oils, when it was added at only 0.5 per cent concentration and compared with the base oils containing 0.5 per cent of the commercial available antioxidant additives such as 2, 6-di-tert-butyl-4-methylphenol and octyl-butyl diphenylamine. A plausible mechanism of exceptional synergistic anti-oxidation was proposed.

This paper first investigated the anti-oxidation properties and mechanisms of the compound with the structure of BD, which can be very useful and would promote the application of BD antioxidant in the lubricant industry.

The response to antioxidants of different types (aminic, phenolic and sulphur‐based) has been evaluated for three base stocks intended for industrial lube production: a paraffinic solvent neutral, a hydrotreated naphthenic, and a naphthenic technical white oil. Furthermore, three different oxidation test methods were used: IP 280, DSC (in‐house), and ASTM D 1934 (open beaker). A statistical experimental design was used to evaluate the effects of the different inhibitors. For the naphthenic base stocks tested, the higher degree of refining, the better response to oxidation inhibitors. Since the test methods differ in severity, different inhibitors will be those giving the best effects in different tests. Severe tests require peroxide‐destroying inhibitors, while aminic or phenolic inhibitors show effects in milder tests. High oxidation stability can be achieved for various types of base stocks, naphthenic as well as paraffinic, if the right inhibitor system is chosen.

Molybdenum dithiocarbamate (MoDDC) has good antiwear and friction‐reducing properties in lubricants, and can be protected against thermo‐oxidative degradation. However, MoDDC‐containing lubricants may lose their ability to reduce friction over time, which may result from its concentration in oils below a critical concentration owing to oxidative degradation of MoDDC. Thus, in order to enhance the durability of the low friction performance of MoDDC, the paper aims to investigate good synergistic antioxidants with MoDDC.

The antioxidation properties of molybdenum dialkyldithiocarbamate (M 807) – and p,p‐dioctyldiphenylalmine (V 81) – or mixed octylated and butylated diphenylalmines (V 961)‐containing poly‐α‐olefin (PAO)‐derived lubricants were evaluated by differential scanning calorimetry (DSC) and modified penn state micro‐oxidation test (PMOT). DSC test measures incipient oxidation temperature (OT) and oxidation induction time (IT) of the lubricant at high temperatures and the oxidation stability of oil weight loss is measured by PMOT. Moreover, the oxidized samples were analyzed by Fourier transform infrared (FTIR) and electron spin resonance (ESR).

A DSC test shows that OT and IT of V 81‐ or V 961‐containing PAO were improved significantly by M 807 addition. A PMOT indicates that when combining with V 81 antioxidants, M 807 can also effectively reduce the increase in weight loss of PAO and deposits formed in oils. These results suggest that the M 807 shows a good antioxidative synergism with alkylated diphenylamine antioxidants. In addition, FTIR results from a PMOT confirm that the addition of M 807 can significantly enhance the oxidation IT of oils containing V 81 and inhibit formation of oxidation products including carbonyl bonds or hydroxyl group. ESR analysis from a PMOT indicates that M 807 may form stable radicals with arylamine by the coordination effect.

This paper provides simple and quick methods to evaluate synergistic antioxidation properties between different types of additives, and a mechanism of the inhibition involving a synergy was proposed. They can offer practical help in industrial applications and to an individual starting out on an academic career.

To evaluate the corrosion resistance of four different stainless steels often employed in hot end exhaust components.

This paper evaluated the outcomes of the hot salt test and the cyclic oxidation test on four different stainless steels, used as hot end exhaust components. The specimens were analyzed by means of SEM for surface changes and the weight loss was considered.

The general corrosion rate and pitting resistance under all the test conditions for hot end exhaust components indicated that 434 was by far the most corrosion resistant alloy, followed by 1.4509 and 321, and lastly 304 was the least corrosion resistant. In general, the ferritic stainless steels, especially 434, outperformed the austenitic ones under all the test conditions.

The comparison of the corrosion resistance and rate, between the frequently used ferritic and austenitic stainless steels used in the exhaust system, gave a clear indication that the ferritic steels will provide prolonged service and this could be beneficial information to the manufacturers.

A new approach to summarise the materials' behaviour and their relative performance in the tests performed was developed. This proposed summary of a number of corrosion indicators could serve as a relative guide to alloy selection for use in hot end automotive exhaust systems for both manufacturers and users.

The aim of this paper is to study the effects of commercially available antioxidants on the oxidation stability of white mineral oils (paraffin oil).

Twelve commercially available antioxidants (Chimassorb 81, Tinuvin 326, Tinuvin 765, Tinuvin 571, Irganox L57, Irganox L109, Irganox L101, Irganox L115, Irganox L06, Irgafos 168, Naugard 445, BHT) were added to pharmaceutical and technical grade white mineral oils at 0.1%, 0.2%, 0.3%, 0.6% and 0.8% (w/w) concentrations. Light, heat and oxygen were applied to induce and accelerate oxidation. Total acid number, viscosity and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity of the oils were measured to evaluate the performance of the antioxidant additives.

Results showed that combined heat and oxygen treatment was the most effective of the three conditions tested to cause oxidation. Based on the data, the best antioxidant additives to be used in white oils are decided to be Irganox L06 and Irganox L101. It was also found that the grade of oils (technical or pharma) did not create a significant difference in the results obtained.

To the best of the authors’ knowledge, this is the first study that reports effects of antioxidant addition on the oxidative properties of white mineral oils. This study advances knowledge of the behavior of white mineral oils under real atmosphere and provides comprehensive data on how the antioxidants affect the light, thermal, oxidative degradation of white mineral oils. The data presented also provide an insight to extend life expectancy of white mineral oils.

This study aims to improve the oxidation resistance of SS304 stainless steel by fabrication of Mn–Co–Ni-coated layer. Mn–Co–Ni coating with the thickness ranging from 1.76 to 8.50 micron were prepared by electroplating process on SS304 stainless steel, focusing on the plating time which play significant roles on the performance of the film thickness and crystallize size.

Mn–Co–Ni coating layer was applied on AISI 304 stainless steel using electroplating process with solution consisted of cobalt sulfate (CoSO₄), manganese sulfate (MnSO₄) and nickel sulfate (NiSO₄). Variation of Mn–Co–Ni coating, the morphology of the film and oxidation kinetics were investigated by using scanning electron microscopy and x-ray diffraction analysis. Furthermore, the sample with coating layer was tested by oxidation and Cr evaporation test.

From the formation parameter due to plating time for the conversion coating, it was found that plating time plays significant roles in the performance of the coating thickness and crystallize size. The crystallize size has an inverse relation to the full width at half maximum of diffraction peak. Film thickness higher than 6.07 micron causes a decrease in oxidation resistance and an increase of Cr evaporation from SS304 stainless steel. In this study, the Mn–Co–Ni coating with a thickness lower than 3.77 micron showed coating protection of oxidation better than SS304 substrate.

The effect of coating thickness was investigated to understand the properties of the coating. Furthermore, oxidation and Cr evaporation test were applied to evaluate the oxidation resistance of the coating layer.

In order to formulate ashless GL‐5 gear oils and high‐pressure antiwear hydraulic oils, the performances of extreme‐pressure (EP) and antiwear (AW), and the thermal and hydrolytic stability of series ashless P‐containing additives with different chemical structures are investigated by four‐ball EP test, high‐temperature oxidation test and hydrolytic stability test.Design/methodology/approach – Series ashless P‐containing EP and AW additives with different chemical structures were designed and selected, their EP and AW performances, high‐temperature oxidation, hydrolytic stability compared with the traditional zinc dialkyldithiophosphate (ZDDP) additive were investigated according to relative testing standards, and their applied performances compared with the traditional ZDDP additive were investigated using the CRC L‐37 gear oil rear axle test, Deniso T‐5D Vane Pump test and Deniso P‐46 Piston Pump test.Findings – The results indicate that two ashless neutral thiophosphate esters exhibit excellent EP and AW performances, high‐temperature oxidation and hydrolytic stability. The application performance of these P‐containing additives is also examined by CRC L‐37 rear axle test. The results show that only the oil samples with the addition of neutral thiophosphate esters correspondingly to API GL‐5 automotive gear oil can pass the CRC L‐37 gear oil rear axle test successfully. The results of further Deniso T‐5D Vane Pump and Deniso P‐46 Piston Pump tests prove that the ashless neutral thiophosphate ester is a very effective EP/AW additive for high‐pressure antiwear hydraulic oil. In one sentence, the neutral thiophosphate ester is the excellent ashless EP/AW additive and the useful substitute for ZDDP.Research limitations/implications – From the results, the neutral thiophosphate ester is the excellent ashless EP/AW additive and the useful substitute for ZDDP, however, their tribological mechanicsm and their synergic effect with the other additives used in the test base oil for the applied performance tests may be done in the future works.Practical implications – These results may be useful for the researchers to formulate some ashless high EP/AW industrial oils.Originality/value – This paper proves that the two ashless neutral thiophosphate esters exhibit excellent EP and AW performances, high‐temperature oxidation and hydrolytic stability, and is the useful substitute for ZDDP for formulating ashless GL‐5 gear oils and high‐pressure AW hydraulic oils.

The use of CO₂ as a replacement for conventional air in combustion gas streams of gas turbine power‐generation equipment is a novel idea and a potential method of providing an almost pure CO₂ stream for subsequent disposal/sequestration. The purpose of this paper is to investigate the effects of this novel gas environment on conventional gas turbine component part materials over the same range of temperatures found in service.

Test samples of candidate materials were tested in simulated environments using controlled gas and steam supplies to sealed horizontal laboratory furnaces. Conventional weight change tests, metal loss tests and electron microscope examination were used to assess the performance of the materials and compare the oxidation morphology. Spectra of the oxidation products were also used to determine the nature of the oxides formed on selected materials.

It is found that changes in the percentage of steam in the novel gas environment made little difference to the performance of the selected alloys. However, when the results of the program are compared with typical data from previous works, where the same alloys are exposed in air, there is a distinct trend. Comparison between the data from air exposed samples and data from those in this paper show the high CO₂ environment, envisaged for the GAS‐ZEP concept, to be more aggressive to all of the alloys tested.

This paper describes the first investigation into the performance of candidate materials for the various components around a GAS‐ZEP system in the novel operating environments anticipated. The work has shown that current power plant materials can be considered for use in first generation GAS‐ZEP systems, but that care is required in their selection at the higher operating temperatures.

This paper aims to study the thermal oxidation performance of antioxidant additives in ester base oils deeply.

ReaxFF molecular dynamics was used to simulate the thermal oxidation process of butyl octyl diphenylamine and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate as two antioxidant additives act on the Trimethylolpropane trioleate (TMPTO) base oil. Meanwhile, combining with the infrared spectroscopy characterization results of the thermal oxidation test, this paper provides theoretical support for the development of high-performance synthetic lubricants and their antioxidant additives.

The results show that butyl octyldiphenylamine easily removes the hydrogen atom on the secondary amine, which promotes the formation of more long carbon chain diene radicals or polyene hydroperoxides from TMPTO. Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate could easily decompose into octadecyl hydroperoxide and 2,6-di-tert-butyl 4-propionylphenol, which could convert into 2-tert-butyl-4-peroxyethyl-6-hydroperoxy-tert-butylphenol in the middle of the thermal oxidation reaction, prompting TMPTO to form more short-chain alkenyl and olefin hydroperoxide or other oxide.

The main change characteristics of base oil molecules are the first thermal decomposition to form oleic acid groups and ethane cyclopropane methyl oleate. Under the action of butyl octyldiphenylamine and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate, the deep oxidation and decomposition reaction are slowed down.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0037/

Use of hydrotreated, hydrocracked and catalytically dewaxed base oils in hydraulic and industrial applications is increasing on a global scale. The hydrogenation and dewaxing processes involved in the manufacture of these products can result in base oils of exceptionally low aromatic content and sulphur level and raised viscosity index (VI). The aromatic content, sulphur level and VI are parameters used by the American Petroleum Institute (API) to categorize the base oils as Group II or Group III. The performance of additives in these Groups II and III base stocks differs from that in Group I base stocks. In addition, different processes used by different manufacturers will not only create different base stock oxidative stability and solvency from that of Group I base stocks, it will also create differences between Group II base stocks and between Groups II and III base stocks. Several different base stocks have been examined using methods including mass spectrometry and aniline point. Variations in properties, such as aromatic content, cycloparaffinic content and aniline point, appear to relate to differences in oxidation stability and solvency. With the improved response of Groups II/III base stocks to antioxidants, a performance level of 10,000 hours or greater in the ASTM D 943 is common. This necessitates addition of specific antioxidants which result in extended oxidation performance but lead in some cases to the formation of insoluble degradation products in Group II/III base stocks, and more so in Group I base stocks. Phenolic‐ containing and phenolic‐free antioxidant systems have been identified that allow for extended oxidation stability in a wide range of Group II base stocks without sludge formation in either Group I, II or III base stocks.