Details of Grant 

EPSRC Reference:	GR/M57583/01
Title:	ROPA:APPLICATION OF ELECTROCHEMICAL TECHNIQUES TO METAL/LUBRICATING OIL SYSTEMS
Principal Investigator:	Spikes, Professor HA
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Mechanical Engineering
Organisation:	Imperial College London
Scheme:	ROPA
Starts:	29 November 1999	Ends:	28 November 2001	Value (£):	103,238
EPSRC Research Topic Classifications:	Eng. Dynamics & Tribology
EPSRC Industrial Sector Classifications:	No relevance to Underpinning Sectors
Related Grants:
Panel History:
Summary on Grant Application Form
Supporting electrolytes able to dissolve freely in conventional lubricating base oils will be synthesised and used to carry out electrochemical kinetic measurements of additive/base oil blends in order to study additive reaction mechanisms at surfaces and to measure effective additive concentrations in formulated oils. The practical applicability of the electrolytes in conventional macro-, micro- and nanoscale electrode systems will be investigated.Additives such as anti-oxidants, antiwear agents and friction modifiers are used in almost all lubricating oils to enhance performance and thus meet modern environment- and efficiency-constrained specifications. The use of these additives is still something of a black art, both because the mechanism of action of some of these additives is not well understood and also because many of the polar, surface-active additives employed interact with one another in solution and at surfaces in unpredictable ways. new techniques are badly needed by both researchers and formulators to investigate additive behaviour in lubricants. The applicant has recently established the feasibility of using electrochemical techniques such as cyclic voltammetry and impedance spectroscopy to study lubricant additive reactions at surfaces and the consequent films formed (1). Such techniques are routinely used in aqueous systems and, more recently, have begun to be applied in non-aqueous, although generally quite polar, media (2). By adding dissolved supporting electrolytes (conductivity-enhancers such as LiC104 and (BU)4NBr) at low concentration, the applicant was able to make electrochemical measurements in model lubricants (low molecular weight esters). This provided valuable insights as to how additives such as carboxylic acids are able to reduce friction and wear (1).The two major existing barriers to the approach were found to be as follows: (a) commercially available conductivity-enhancers were not soluble enough to be used in relatively non-polar fluids such as mineral oils; (b) when lubricant additives were subject to oxidation/reduction as a result of applied potentials, they often formed charged species which were themselves insoluble in the lubricant, and therefore deposited out on solid surfaces, suppressing further reaction.A recent paper, not related to tribology, describes the preparation and use of a group of supporting electrolytes based on tetraalkylammonium-tetraphenylborates, which are soluble in quite non-polar solvents (including cyclohexane) and also contain both soluble cation and anion species (3). These electrolytes should make it possible to extend previous electrochemical work to realistic lubricating base fluids such as mineral oil. The proposed research programme is concerned with preparing this class of electrolyte (and related ones) and using them to enable electrochemical measurements to be made in lubricating oils without the local precipitation at the electrode suffered previously with inorganic-organic electroytes. Such a tool would be of value in investigating a wide range of lubricant additive issues.Proposed ProgrammeThey can be used to drive and study redox processes between additives and solid surfaces (which normally take place in a chemically-driven and uncontrolled fashion), to investigate the mechanism of action of surface active additives such as antiwear and extreme pressure additives. Cyclic voltammetry and chronoamperometry can be used for determination of the kinetics and mechanisms of reaction of additives with metal surfaces and to identify the separate redox stages taking place, whilst concurrent friction/wear measurements can be used to determine the practical effectiveness of the films produced. The oxidation state of metal surfaces or solution species can be controlled via the applied potential and electrode charge densities have been shown to affect friction (1).
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