One complete paper and one front page teaser. The interesting implication of these studies is that solvents remove the outer layer of the ZDTP tribofilm.
I was unable to retrieve the 2nd paper to read about the structure in more detail, but, it does provide some evidence for the "fuel dilution" theory of increased iron wear for DI engines, since gasoline is a pretty decent solvent.
Surface Chemistry in Tribology
Relationship between mechanical properties and structures of zinc dithiophosphate anti-wear films
Some interesting quotations:
Quote:
In many of the analytical approaches used to investigate this system, it has been
necessary to rinse the sample in organic solvent prior to analysis. Depending on the
aspect of the films under investigation, some workers have found that solvent washing
does not affect the outcome of the analysis[39], while others have noticed a
significant effect[27,41]. Bec et al.[27] used a unique version of the SFA to Bec et al.[27] used a unique version of the SFA to
Quote:
The film consists of at least three non-homogeneous layers: on the steel surface there is a sulphide-oxide layer, which is almost completely covered by a protective phosphate layer, with the addition of an overlayer of ZDTP degradation precipitates. This later layer is removed when the film is washed with an alkane solution. Therefore, the properties of the ZDTP file layers have been studied both before and solvent washing with n-heptane. .... From these observations and previous film analyses, a schematic picture of the 'full' anti-wear ZDTP film structure and its mechanical properties was obtained. A highly viscous layer of alkyl phosphate covers islands of solid polyphosphates. These islands are partially adherent to the steel surface through a sulphide layer and accommodate the real contact pressure in the tribotest. These results show that the exceptional wear resisting properties of ZDTP films arise from their ability to respond to a wide range of imposed conditions. As the severity of loading increases, so too do the resistive forces within the film. ZDTP anti-wear films can truly be described as SMART materials.
I was unable to retrieve the 2nd paper to read about the structure in more detail, but, it does provide some evidence for the "fuel dilution" theory of increased iron wear for DI engines, since gasoline is a pretty decent solvent.
Surface Chemistry in Tribology
Relationship between mechanical properties and structures of zinc dithiophosphate anti-wear films
Some interesting quotations:
Quote:
In many of the analytical approaches used to investigate this system, it has been
necessary to rinse the sample in organic solvent prior to analysis. Depending on the
aspect of the films under investigation, some workers have found that solvent washing
does not affect the outcome of the analysis[39], while others have noticed a
significant effect[27,41]. Bec et al.[27] used a unique version of the SFA to Bec et al.[27] used a unique version of the SFA to
Quote:
The film consists of at least three non-homogeneous layers: on the steel surface there is a sulphide-oxide layer, which is almost completely covered by a protective phosphate layer, with the addition of an overlayer of ZDTP degradation precipitates. This later layer is removed when the film is washed with an alkane solution. Therefore, the properties of the ZDTP file layers have been studied both before and solvent washing with n-heptane. .... From these observations and previous film analyses, a schematic picture of the 'full' anti-wear ZDTP film structure and its mechanical properties was obtained. A highly viscous layer of alkyl phosphate covers islands of solid polyphosphates. These islands are partially adherent to the steel surface through a sulphide layer and accommodate the real contact pressure in the tribotest. These results show that the exceptional wear resisting properties of ZDTP films arise from their ability to respond to a wide range of imposed conditions. As the severity of loading increases, so too do the resistive forces within the film. ZDTP anti-wear films can truly be described as SMART materials.
Last edited:
