Corrosion of Stainless Steel by Urea at High Temperature

The corrosion mechanism of stainless steel caused by high temperature decomposition of aqueous urea solution has been investigated. The relationship between aqueous urea solution, its thermal decomposition products and the corrosion mechanism of stainless steel is studied by FTIR spectroscopy, SEM and stereo microscopy. The corroded steel samples, together with deposits, were obtained from the injection of aqueous urea solution on the steel plate at high temperatures. Uniform corrosion underneath the deposits was proposed as the main driver for corrosion of the steel samples. At the crevices, corrosion due to the used geometry and due to high temperature cycling could play an acceleration role as well.

A Comparative Study on the Effect of Temperature and Concentration on Density, Sound Velocity and their Derived Properties for Diclofenac Potassium in Aqueous Urea Media

The present study has undertaken experimental measurements of ultrasonic velocity (U) and density (d) of solutions of Diclofenac potassium in water and in aqueous urea media of different molar concentrations. Computation of physico-chemical parameters like apparent molar volume (V_Φ), limiting apparent molar volume (V_Φ^0 ), apparent molar expansibility (E_Φ), limiting apparent molar expansibility (E_Φ^0 ), molar isentropic compressibility (K_s), apparent molar isentropic compressibility(K_(s,ɸ) ),molar adiabatic compressibility (W), molar isothermal compressibility (K_T), acoustic impedance (Z), free volume (V_f ), internal pressure (π_i), relative association (R_A), coefficient of thermal expansion (α) and van der Waals constant (b) was done by using the experimentally obtained values. The influence of varying concentrations of Diclofenac potassium as well as of urea in solutions and the variation of the investigating temperatures on the above mentioned parameters are expected to reveal the nature of different molecular interactions existing in the drug solutions.