Simon S. Wang

The application of a.c. impedance technique for detecting glycol contamination in engine oil

Abstract A few hundred ppm of ethylene glycol (a major component in antifreeze) can cause detrimental changes m engine oil. In this work, the a.c. impedance technique has been employed to measure the bulk-layer resistance of engine oil containing glycol. It is found that the bulk-layer resistance declines abruptly as the glycol concentration increases from 50 to 150 ppm. In addition, the bulk-layer resistance for glycol-contaminated engine oil remains constant during a 10-day time span, indicating that the measured resistance is not affected by the formation of micelles between glycol and detergents/dispersants. However, commercial engine oils contain different amounts of detergents, and the bulk-layer resistance for fresh oils varies. Therefore, a software program is necessary to compare the bulk-layer resistance measured from fresh and glycol-contaminated engine oil in order to determine precisely the extent of glycol contamination.

The development of in situ electrochemical oil-condition sensors

Abstract The useful life of an engine oil may vary considerably; therefore, an on-board sensor would be helpful in monitoring the oils condition continuously. In this work, in situ macro and micro oil-condition sensors have been developed and tested in two sets of engine-oil samples. It is found that after suppressing the high output current associated with fresh engine oil, the microsensors output correlates with the total acid number (TAN) of engine oil. Because an oils TAN will increase with use, this microsensor has the potential to detect the end of useful oil life and signal the need for an oil change.

In situ monitoring of high-temperature degraded engine oil condition with microsensors

Abstract Using proper oils to lubricate an engine is very important. There is a need for a sensor to monitor the condition of the oil to ensure the engine is properly protected. In this paper, a microsensor is put in a test engine which is operated at the ASTM Sequence IIIE conditions. The sensor has two electrodes with an interdigitated pattern. The spacing between electrodes is about 5μm and the sensing electrodes cover 7 mm×7 mm in area. With an a.c. sawtooth waveform voltage applied to the electrodes, an oil-condition-dependent current can be collected by the sensor. This current is rectified and converted to a d.c. voltage output. Different brands of engine oils are used in the test. Results show that the sensor has a voltage output that increases with the oil degradation time. The sensor is able to detect glycol contamination in oil as well.

In-situ electro-charging for friction reduction and wear resistant film formation©

A technique has been developed to form friction-reducing and antiwear films in-situ by means of an electric field applied between rubbing metal surfaces. Using this in-situ charging technique, the effectiveness of zinc organodithiophosphate (ZDP) additives as antiwear and friction reducing agents can be enhanced by electrochemical reactions which form surface coatings. The coatings formed on sliding surfaces compared with uncharged surfaces reduce friction by up to 35 percent. In addition, during the sliding process, the films formed on the surfaces are replenished and protect the rubbing surfaces from wear. A steel plate subjected to rubbing and in-situ charging for four hours had a smooth surface and a yellowish reaction film; the one without charging was rougher and no yellowish reaction film was formed. The improved tribological characteristics are attributed to an increase in the electrochemical reactivity of the ZDP-mineral oil blends and the formation of phosphate or sulfate films on the metal surf...

Friction Reduction From Electrochemically Deposited Films

The lubricated sliding friction characteristics of both electrochemically precharged and uncharged piston ring specimens were determined m a laboratory friction apparatus. The iron phosphate films deposited on precharged piston ring specimens from a specific lubricant blend reduced both static and dynamic friction by as much as 25 to 35 percent. The mechanisms of friction reduction using electrochemically deposited films were investigated and interpreted in terms of surface roughness reduction and reaction film formation. The bulk metal properties influenced both the degree to which precharged films could be applied to a metal surface and the friction measured in a lubricated sliding contact. In addition, the friction characteristics and surface morphology of the iron phosphate films deposited on precharged piston ring specimens from a hydrocarbon-based medium were compared with those of traditional phosphate coatings made in an aqueous solution of phosphoric acid. The iron phosphate film deposited on pre...

An Electrochemical Technique for Characterizing Metal-Lubricant Interfacial Reactions

An AC impedance technique, in combination with an electrical property cell, was employed to measure the electrical resistance and capacitance of lubricants. A comparison of the combined surface coating plus bulk fluid resistance and capacitance values measured for different additives blended in mineral oil, demonstrated that different metal-lubricant interaction mechanisms occur. The electrical measurements indicated that additives such as the mixed alkyl acid orthophosphate (acid phosphate) reacted with the cast iron electrodes to firm reaction films, whereas oleic acid was absorbed on the electrodes. Although the implied reactivity from electrical measurement for N-oleyl-1-1,3 diaminopropane (fatty amine) is comparable to that for acid phosphate, no reaction film for the former was detected by elemental analysis. Presented at the 41st Annual Meeting in Toronto, Ontario, Canada May 12–15, 1986

The nature of electrochemical reactions between several zinc organodithiophosphate antiwear additives and cast iron surfaces

This printing supersedes the publication in the July, 1988 Tribology Transactions pages 382-390 in which Fig. 16 and Table 5 were omitted along with the Discussion and Closure. The electrochemical reactivities of four commercial zinc organodithiophosphate (ZDP) antiwear additives, each blended with a common mineral oil, were measured during thermal decomposition tests. The results imply that electrochemical reactions between the decomposition products of ZDP and the electrode surfaces produce surface coatings on cast iron electrodes. This observation suggests that electrochemical methods might be useful tools for understanding the mechanism by which ZDPs reduce wear. The electrochemical reactivity of the blends was proportional to the thickness of surface coatings formed on the electrodes at the end of the test, and inversely proportional to the ZDPs decomposition temperatures. The effects of oxygen, oleic acid concentration, and surface coating on the electrochemical reactivity were measured. Presented ...

AC Impedance Measurements of the Resistance and Capacitance of Lubricants

An AC impedance technique in combination with a thin-film (12 μm) cell was employed to separately meusure the electrical resistance and capacitance of electrode-lubricant interfaces and bulk lubricant layers. In this study, three different additives were investigated by measuring the AC impedance spectrum of each additive mixed separately with a commercially available mineral oil. These additives were oleic acid, N-oleyl-1,3 diaminopropane (fatty amine), and mixed alkyl acid orthophosphute (acid phosphate). For lubricants containing 2 mass percent of an acid phosphate or fatty amine, the capacitance of the electrode-lubricant interface, Ci, and the capacitance and resistance of the bulk lubricant layer, Co and Ro, respectively, were evaluated separately from the AC impedance spectra. The lower limit of the resistance of the electrode-lubricant interface, Ri, was aDo estivnated. For additives, such as oleic acid, which physically adsorbs on the electrodes, the resistance and capacitance of the electrode-lu...

An Etch-stop Utilizing Selective Etching Of N-type Silicon By Pulsed Potential Anodization

A new dopant selective etching technique, which uses pulsed anodizing voltages applied to silicon samples in KOH: H/sub 2/O solutions, has been developed. The use of pulsed anodization causes passivation of p4ype silicon while n-type silicon continues to etch, making It possible to selectively etch-stop on p-type material. These results are consistent with a process which Is rate limited by holes in the semiconductor. To demonstrate this technique, a 12-.spl mu/m-thick p-type inembrant was formed. This method differs from the conventional p-n junction etch-stop in that the performance of the etch-stop does not depend on the rectifying characteristics of the diode or on the magnitude of Its leakage current. This paper presents data on the passivation of p-type and n-type silicon under pulsed anodization conditions for a broad range of KOH concentra tions and temperatures. Additionally. the application for etch stepping is presented.

Using Electrochemical and Spectroscopic Techniques as Probes for Investigating Metal-Lubricant Interactions

The interactions between three representative lubricant additives and iron are characterized using AC impedance and surface infrared spectroscopies, fast-scan cyclic voltammetry, and laboratory friction measurements. The experimental results provide an increased understanding of the mechanisms by which each additive reduces friction. At 50°C, oleic acid adsorbs on iron to form a friction-reducing layer. This friction-reducing layer becomes less effective at elevated temperatures (100° and 150°C) due to de-sorption of the oleic acid molecules. A mixed acid phosphate is characterized by a relatively high electrochemical reactivity as compared to that for oleic acid and fatty amine, which correlates with its ability to form a reaction film on iron. The formation of this reaction film is accelerated by increasing the temperature from 50° to 150°C. Therefore, an acid phosphate is more effective in reducing friction at elevated temperatures. A fatty amine is characterized by intermediate electrochemical reactiv...