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The tribological performance of commercially used tire rubber was evaluated at ambient conditions under dry, wet and 3.5% NaCl corrosive environment. A pin-on-disc apparatus was used for the experiment. Applied load of 2.5N at sliding velocity of 0.246 ms-1 distance ranging from 75m-2650m were used for this study. The results showed that the nature of the wear rate was similar in all environments as initially increases afterwards decreases to more or less a constant value. Moreover, the wear rate in dry environment was significantly higher than that of wet and corrosive environment. Water tends to lubricate the contact, reduce the heat generation as well as for sealing effects thus the wear rate is reduced. Coefficient of friction in wet and corrosive environment showed the lower value due to sealing and lubricating effect between the particles. The damage behaviors of worn surfaces were analyzed by optical microscope and SEM. At dry sliding condition greater voids and holes are observed.

In this proposal the mechanical properties of natural and synthetic rubbers are studied under different temperatures both real and ageing heat treatment conditions. For this purpose, tire rubber and bearing pad rubber are considered as they are most governed in natural and synthetic rubber respectively. The experimental results confirm that the impact of real temperature is higher on the mechanical properties than that of ageing temperature because of ambient temperature aggravate thermal motion and changes the molecular arrangement of rubber other than the ageing samples recovers the mechanical properties during breezy. Except hardness, all the cases in terms of mechanical properties like tensile strength, elongation, Young's modulus and Poisson's ratio of bearing pad rubber provide the higher performance than the tire rubber. Under ageing treatment condition the degraded mechanical properties recover well by the natural rubber since extremely ordered long chain of the molecular structure. The significant differences in the micrographs of the two rubbers suggest that tire rubber consists of uniform grains because of its highly controlled molecular arrangement. Under heat treatment the microstructure turned rougher and the size of the voids became larger as temperature increases the secondary cross linking reaction which initiate to cracks.

Chemical and physical behavior including corrosion performance, thermal conductivity and visual color change of the copper-based alloys brass and bronze have been studied prior and after corrosion in acidic, alkaline and saline media. The concentrations of 0.5 M H2SO4, 0.5 M NaOH and 0.5 M NaCl were used in which copper and copper-alloy samples were immersed and left to corrode at room temperature for 28 days. The experiments were performed prior and after corrosion, using conventional gravimetric measurements accompanied with measurements of thermal conductivity, microstructure and optical properties. The color change of different samples was also studied through tristimulus color parameter (L*, a* and b*) values. It is concluded that the corrosion rate of copper and copper alloys is greater in acidic than in salt and alkaline media. This is due to the extent of disruption of the passive film formed on the surfaces. In the cases of alkaline and salt media, the passive films on the surface remain stable to a large extent. Small increase of thermal conductivity takes place due to formation of a very thin film of oxide and hydroxide bonded to the surface. The environment also affects the color of copper and copper alloys by chemical changes like oxidation and formation of different intermetallics on the surfaces. A microstructural study of experimental materials confirms that corrosion after 28 days results in formation of pores on the surfaces in acidic environment, and passive film that grows thicker on the surfaces in alkaline and saline environments. Aluminum oxide that is more stable than zinc oxide causes better anti-corrosion performance and minimal color variation of bronze compared to brass, especially in acidic environment.

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