The Adsorption of Zinc Dibutyldithiophosphates on Iron and Iron Oxide Powders

Plaza, S.

doi:10.1080/05698198708981753

Cited by 46 publications

(30 citation statements)

References 20 publications

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“…Perhaps there is an optimum ZDDP concentration for antiwear film formation as has been shown before [29]. Although the adsorption experiments were conducted on iron and iron oxide powders, Plaza did show that the rate of ZDDP adsorption increases with increasing concentration [30]. He worked in the range of 1.6 · 10 -3 moles/kg to 25 · 10 )3 moles/kg, corresponding to roughly 0.088 wt % to 1.3 wt %, the range in which the XANES a/c ratio increases on rubbing.…”

Section: Phosphorus Characterizationmentioning

confidence: 89%

Tribofilms generated from ZDDP and DDP on steel surfaces: Part 2, chemistry

et al. 2005

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The chemical constitution of tribofilms, generated from zinc dialkyldithiophosphate (ZDDP) and ashless dialkyldithiophosphate (DDP), has been examined by X-ray Absorption Near Edge Structure (XANES) spectroscopy. The identification of spectral features and interpretation of the results for P, O, Fe, and S species are given, allowing an overall mechanism to be deduced. The role of Fe in these films was investigated in some detail using P L-edge, O K-edge and Fe L-edge XANES spectra. From the P L-edge XANES spectra, the DDP films are uniformly very short chain iron polyphosphates. In contrast, the ZDDP films are formed initially as short chain polyphosphates; but after more rubbing, a bilayer phosphate film is formed with long chain Zn polyphosphates on the surface and shorter chain in the bulk of the film. The O K-edge XANES spectra show that there is, as expected, more Fe in the DDP phosphate films than in the ZDDP phosphate films. The S K-edge spectra of ZDDP films show the presence not only of ZnS as previously observed, but also the presence of FeS for the first time in the early stages of film formation. The predominant S species in the DDP films is FeS.

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Section: Phosphorus Characterizationmentioning

confidence: 89%

Tribofilms generated from ZDDP and DDP on steel surfaces: Part 2, chemistry

et al. 2005

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“…The bulk of the tribofilm consists of short-chain polyphosphates, and the top layer of the tribofilm consists of long-chain polyphosphates (Sieber,et al (4); Nicholls,et al (5)). The composition of the tribofilm varies with temperature, rubbing time, concentration of ZDDP additive, and load on the metal surfaces (Nicholls,et al (6); Plaza (7)). …”

Section: Introductionmentioning

confidence: 99%

An XPS Study on the Composition of Zinc Dialkyl Dithiophosphate Tribofilms and Their Effect on Camshaft Lobe Wear

Liu

Kouame

2013

Tribology Transactions

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In this study, various zinc dialkyl dithiophosphate (ZDDP)-derived tribofilms were analyzed with X-ray photoelectron spectroscopy (XPS) to determine the relationship between tribofilm chemical composition and wear severity. Samples were generated on camshaft lobes from engine tests conducted at different oil temperatures, and wear depths were measured with a surface profilometer. Tribofilm specimens were analyzed by XPS to assess changes in film chemistry as a function of wear severity. Tribofilms present on all camshaft lobes were found to contain polyphosphate glass of various chain lengths. Long-chain polyphosphates were observed on low wear tracks, whereas short-chain polyphosphates were found on more severe wear tracks. Variations in polyphosphate chain length are also apparent at different wear depths along a low wear track. The presence of long-chain polyphosphates on low wear tracks was indicative of their superior antiwear properties, whereas the occurrence of short-chain polyphosphates on more pronounced wear tracks was indicative of their inferior antiwear properties.

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“…Plaza (24) concluded from adsorption measurements on iron that neutral zinc dithiophosphates form multiple layers when adsorbed on iron. Since the neutral ZnDTP is ellipsoidal (or cylindrical) in shape, orientation effects may also be important, as noted by Plaza (24). From his adsorption results, Plaza (24) inferred that the second layer was not simply laying on the first.…”

Section: Fllm Thicknessesmentioning

confidence: 92%

“…Since the neutral ZnDTP is ellipsoidal (or cylindrical) in shape, orientation effects may also be important, as noted by Plaza (24). From his adsorption results, Plaza (24) inferred that the second layer was not simply laying on the first. Further indication of the difficulties of interpreting these multiple layers comes from Plaza and Margielewski's (25) finding that basic diisobutyl zinc dithiophosphate adsorbed on carbon black has but a single plateau in the adsorption curve at the concentration used in this work.…”

Section: Fllm Thicknessesmentioning

confidence: 92%