Dorgham, A, Azam, A orcid.org/0000-0002-3510-1333, Morina, A orcid.org/0000-0001-8868-2664 et al. (1 more author) (2018) On the Transient Decomposition and Reaction Kinetics of Zinc Dialkyldithiophosphate. ACS Applied Materials and Interfaces, 10 (51). pp. 44803-44814. ISSN 1944-8244
Abstract
Despite the ubiquitous use of the zinc dialkyldithiophosphate (ZDDP) as an antiwear additive, no complete information is yet available on its exact decomposition reactions and kinetics to form triboreactive protective films on contacting surfaces. This hinders the replacement of ZDDP with more environmentally friendly additives of similar antiwear capabilities. Using a multitechnique approach, this study shows that before the formation of a phosphate-rich protective film, the decomposition of ZDDP proceeds by forming intermediate zinc sulfide and sulfate species, which can be mechanically mixed with the iron oxides on the rubbing steel surfaces. The mixed sulfur-oxide layer can play different vital roles including binding the subsequently formed phosphate layers with the metal surface. These layers consist mainly of zinc thiophosphate of initially short chains, which are formed due to the excess concentration of metal oxide on the surface. As the concentration of the oxide decreases in the subsequent layers, the short chains start to polymerize into longer ones. The polymerization process follows first-order reaction kinetics with two distinctive phases. The first one is a fast transient burst phase near the steel surface, whereas the second phase dominates the formation process of the layers away from the substrate and is characterized by slow kinetics. The findings of this study provide new insights into the decomposition mechanisms of the currently most widely used antiwear additive and open future opportunities to find green alternatives with similar superior antiwear properties.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2018 American Chemical Society. This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Applied Materials & Interfaces. To access the final edited and published work see https/doi.org/10.1021/acsami.8b08293. |
Keywords: | antiwear tribofilm; reaction kinetics; tribology; wear; ZDDP |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Mechanical Engineering (Leeds) > Institute of Functional Surfaces (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 24 Jan 2019 11:43 |
Last Modified: | 29 Nov 2019 01:39 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/acsami.8b08293 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:141560 |