Abstract
Zinc dialkyldithiophosphates (ZDTPs) are widely incorporated in lubricant formulations as antioxidant and antiwear additives. Using the model compound zinc n dibutyldithiophosphate (Bu-ZDTP) in dimethylformamide (DMF) solution, cyclic voltammetry is applied to a detailed study of Bu-ZDTP electro‐oxidation. Bu-ZDTP is shown to be oxidized in a chemically irreversible electron transfer process under diffusionf‐limited conditions. A similar study of Bu-ZDTP reduction revealed nucleation of zinc at the electrode surface. A chronoamperometric investigation of zinc deposition classified the nucleation according to a progressive mechanism with the diffusion coefficient for Bu‐ZDTP in (DMF) solution as . By comparison with diffusion coefficients obtained via Levich analysis of Bu-ZDTP oxidation, the oxidation process is assigned as a two‐electron transfer. The use of atomic force microscopy as a means of directly visualizing zinc nuclei formed as a result of Bu-ZDTP reduction is described. © 1999 The Electrochemical Society. All rights reserved.
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