Investigation of intergranular corrosion welded joint of austenitic stainless steel by electrochemical methods

Sensitization degree of the austenitic stainless steel welded joints was investigated by electrochemical methods: the double loop electrochemical potentiokinetic reactivation (DL EPR) in H2SO4 + KSCN solution and by of the corrosion potentials measurement of the steel in the solution drop of HNO3 + FeCl3 6H2O + HCl. The welded joints, by an X-ray radiographic method on possible presence of the weld defects, were tested. Grain size of the base metal and the welded joints, by applying an optical microscopy were determined. The existence of compatibility between the results for different electrochemical methods is shown. Heat affected zone (HAZ) of the austenitic stainless steel welded joints has shown significant degree of sensitization. The corrosion potentials measurement method is simple, nondestructive method, that gives qualitative informations about degree of the sensitizations of the stainless steel. The double loop electrochemical potentiokinetic method gives quantitative evidence about susceptibility of the stainless steel to intergranular corrosion. This method can be applied with some adaptation in field environments

DETERMINATION OF THERMAL CONDUCTIVITY OF THE INSULATION MATERIALS USING NUMERICAL CALCULATION OF THE PRESSURE INCREASE

In the paper is presented the possibility of determination thermal conductivity for the insulation materials, which are used in the tanks for liquid carbon dioxide, in situ. For this purpose, was developed the mathematical model for description of the pressure changes in function of the ambient conditions and storage time. The application software was developed also for computation of the pressure increase two-phase mixture in tank, relating to the time, and the thermal conductivity determination of the insulating material. Verification of the program was done in function of exploitation incoming data. The numerical simulations of the pressure increase are done for various degrease of tank compliance. The influence of the ambient conditions is expressed by the heat transfer fluid in tank and the environment. Used incoming data are the temperature profile and sun heat flux characteristic for Serbia, in summer time