NOPR Collection:

A simple and fast reaction of 3-substituted4- amino-5-mercapto-s-triazoles with substituted aldehydes without solvent under microwave irradiation: An environment co- friendly synthesis

1998-07-01T00:00:00Z

Title: A simple and fast reaction of 3-substituted4- amino-5-mercapto-s-triazoles with substituted aldehydes without solvent under microwave irradiation: An environment co- friendly synthesis Authors: Paul, Satya; Gupta, Rajive Abstract: A simple and high yielding environment co-friendly method has been developed for the dry condensation of 3-substituted-4-amino-5-mercapto-s-triazoles with substituted aldehydes without solvent using inorganic solid supports coupled with microwave irradiation. Page(s): 263-266

Inhibition of corrosion of Al and aluminium alloys in basic solutions

1998-07-01T00:00:00Z

Title: Inhibition of corrosion of Al and aluminium alloys in basic solutions Authors: Badawy, W A; AI-Kharafi, F M; Azab, A S EI Abstract: The technological importance and wide range of application of aluminium and its alloys have led to an extensive investigation on these materials. The corrosion behaviour of AI, AI-6061 and Al-Cu in basic aqueous solutions and the effect of three corrosion inhibitors were studied by EIS and polarization techniques. X-ray photoelectron spectroscopic (XPS) investigation of these materials revealed the presence of Cu in the AI-Cu alloy surface just below the surface of a thin film of hydrated aluminium oxide. EIS studies indicated the effectiveness of dichromate and molybdate in inhibiting corrosion of aluminium and its alloys. XPS studies of these materials after immersion of each in basic solutions containing separately 0.01 M dichromate, molybdate and sulphate ions respectively did not show the presence of chromium, molybdenum or sulphur on the surface film of these metals. SEM investigation of the electrode surface before and after immersion in the basic solution showed that the corrosion process is occurring in the flawed regions of the metal surface. Page(s): 251-262

Inhibition effect of some aniline compounds on corrosion of mild steel in 3% HF

1998-07-01T00:00:00Z

Title: Inhibition effect of some aniline compounds on corrosion of mild steel in 3% HF Authors: Vishwanatham, S; Emranuzzaman Abstract: The corrosion inhibition efficiencies(IE%) of aniline(AL), p-toluidine(PTD), p-anisidine (PAD), p-phenitidine ( PPD) and N,N-dimethyl aniline(DMA) have been evaluated in 3% HF by weight loss and potentiostatic polarization methods. PAD is the best inhibitor and IE% can be classified in the following order: PAD> PPD > PTD > DMA > AL. The effect of temperature (range 303-333 K) on the corrosion behaviour of mild steel in plain HF solution and inhibited acid was also studied. The corrosion rate increased with increasing temperature both in uninhibited and inhibited acid and the values of IE% of all the inhibitors depend on temperature. The inhibitors act as mixed adsorption type inhibitors. Adsorption of AL, DMA and PTD on mild steel in 3% HF interface corresponds to Langmuir adsorption isotherm model while PAD and PPD appear to adsorb on the metal surface according to Temkin adsorption isotherm. Page(s): 246-250

An investigation on dissolution and passivation behaviour of Ti-6AI-4V in sulphuric acid

1998-07-01T00:00:00Z

Title: An investigation on dissolution and passivation behaviour of Ti-6AI-4V in sulphuric acid Authors: Singh, V B; Hosseini, SMA Abstract: Potentiostatic technique has been employed to investigate the polarization behaviour of a titanium alloy (Ti6A14V) in a wide concentration range (1-17 M) of sulphuric acid, at 30°C and 40°C. Effect of temperature variation of the experimental solution has been studied in selected concentrations (5M and 9M) of the acid. The cathodic current density increased in accordance with increasing acid concentration, temperature and applied potential. Anodic polarization studies showed active-passive transition and broad passivity range of potential available for the stability of alloy. The critical current density and passivity current density.(i_c and i_p) increased with an increase in the concentration and temperature of the solution. However, these values decreased in solution above 11M sulphuric acid. The passivated specimen revealed formation of uniform and stable anodic film during longer exposure time. Apparent activation energy, obtained from Arrhenius plots, corresponding to critical current densities is of order for the chemical reaction. Impedance measurements indicate that the passive film has the characteristics of valve metal in respect of capacitance and formation potential, and consists of two types of grains on the surface. Page(s): 241-245