Lubricant and tribological properties of zinc compound in palm oil

Purpose This paper aims to investigate the composition of lubricant and the enhancement of tribological properties using palm oil as a parent base oil mixed with an organo-zinc compound as an additive. Design/methodology/approach The oil samples were prepared by mixing organo-zinc compound additive, zinc dioctyldithiophosphate (ZnDoDP) and zinc diamyldithiocarbamate (ZDDC), at 0 to 3.0 Wt.% concentrations with commercialised palm oil which were then homogenised using an ultrasonic homogeniser. The oil samples were then tested for their oil properties through elemental analysis, their viscosity index, flashpoint and acid number. Next, the friction test was performed using a four-ball tribometer, and the worn surfaces of the balls were observed using a digital microscope. Findings The results showed that commercialised palm oil with 2.0 Wt.% of ZnDoDP had excellent characteristics regarding its lubricant properties, such as its viscosity index, coefficient of friction and wear compared to commercialised palm oil with the addition of 2.0 Wt.% of ZDDC. Originality/value To the best of the authors’ knowledge, this is the first study to compare the effect of the concentration of ZnDoDP and ZDDC on the lubricant and triological properties of vegetable oil (palm).

Effects of TiO2 Nanofluid on the Surface State of Brass

The surface states of brass in simulated cooling water (SCW) containing or free of sodium dodecyl benzene sulfonate (SDBS) and TiO2 nanofluid were analyzed by means of scanning electron microscope (SEM), energy spectrum analysis (EDS) and X-ray diffraction (XRD). The concentrations of Cu and Zn ions in the solution after brass immersion were analyzed using a plasma emission spectrometer. The relationship between the surface states and corrosion resistance of brass was investigated by electrochemical impedance spectroscopy (EIS). The results showed that the brass surface was mainly covered with zinc compound Zn5(OH)6(CO3)2 as corrosion product in SCW. In SCW containing SDBS, a large amount of SDBS was adsorbed on the brass surface. In TiO2 nanofluid, the brass surface was relatively bare and mainly contained cuprous oxide. There was no obvious adhesion of SDBS aggregates and no accumulation of zinc compound on brass surface in TiO2 nanofluid. TiO2 nanoparticles inhibit the adsorption of SDBS on brass surface. Solution analysis results showed that the concentrations of Cu and Zn ions in TiO2 nanofluid was obviously higher than that in SCW and SCW containing SDBS, indicating that most of corrosion products of brass dissolved into the nanofluid. The EIS results illustrated the brass electrode had a larger reaction resistance in SCW containing SDBS, indicating the good protective performance of the adsorbed SDBS film on brass surface. The reaction resistance of the brass electrode was the smallest in TiO2 nanofluid, which illustrated that TiO2 nanoparticles in solution promoted the corrosion of brass.