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The inhibition efficiency of an aqueous extract of garlic in controlling corrosion of aluminium immersed in sodium hydroxide solution at pH 11 and 12, in the absence and presence of Zn 2z , was evaluated by the weight loss method. At pH 11, the extract accelerated corrosion of aluminium in the absence and presence of Zn 2z . The influences of N-cetyl-N,N,N-trimethylammonium bromide (CATB) (a biocide and a cationic surfactant) and immersion period on the inhibition efficiency were investigated. The influence of sodium sulphite, an oxygen scavenger, on the inhibition efficiency of the inhibitor system revealed that transport of inhibitor towards the metal surface plays a greater role than the removal of oxygen from the aqueous solution in determining the inhibition efficiency of the system. The protective film was analysed with the use of Fourier transform infrared spectra.

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Nanofluids are tailored nano- colloidal suspensions of nanoparticles in a suitable base fluid. This present work investigates the absorption spectrum in TiO2-water nanofluids to identify the potential application of nanofluids in Direct Absorption Solar Collectors (DASC). Nanoparticles of Titanium dioxide (TiO2) are prepared by sol gel and characterized by X Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). TiO2-water nanofluids with weight fraction of 0.1% are prepared by a two-step process with sonication. The prepared nanofluids are investigated for their stability by a gravity sedimentation method and for their optical property by UV-Vis spectroscopy. Stability of nanofluid is essential for the applications of nanofluid in DASC. TiO2 nanoparticles with a crystallite size of 43nm are obtained .The SEM image reveals the agglomerated state of TiO2 nanoparticles and the stability of TiO2 nanofluid is reported as 9-10days. UV results indicate the decrease in absorption from 440-500nm, complete absorption from 500-700nm and increase in absorption from 700-900nm.TiO2 nanofluids are recommended as potential candidates for DASC in UV and IR regions.

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