Development of the new generation of Ultra Supercritical (USC) power plant that has successfully achieved the targeted working temperature of 970 K. Nonetheless, increasing the operating temperature will further accelerate the high temperature oxidation of ferritic alloys of the boiler. Furthermore, water vapour in humid environment will make it easier for the alloy to further oxidize at high temperature. It is hypothesized that water vapour provides hydrogen that dissolves into the ferritic alloy susbstrate, hence altering their electronic state at the metal-semiconductor (oxide) interface. This study aims to measure Schottky Barrier Height (SBH) in dry and wet environment and relates it with acclerated oxidation behaviour. The Schottky Barrier was prepared by sputtering Cr2O3 onto the T91 boiler tube in high vacuum condition of 0.4 Pa, RF power 150W for an hour. The existance of Cr2O3 / Fe junction was confirmed by XRD analysis. The junction was then connected with platinum wire to act as the electrode for the current-voltage, I-V and capacitance-voltage, C-V test at high temperature. From the I-V graph, the reversed saturated current, Io was estimated and the SBH was calculated from the results. The SBH increased as the conductivity increased with the increment of temperature. From the C-V plots the value of Vbi was determined and used to calculate the SBH. The SBH increased with the increased of built in voltage. The result obtained from the two method agrees with one another. SBH value in wet condition is higher than that in dry condition. This is explained by the formation of space charge layer at metal/oxide interface due to dissolved hydrogen in metal, thus may change the transport property and accelerate the oxidation rate in water vapor.

Power plant industry extensively using ferritic Fe-Cr alloys as boiler materials due to its good resistant to creep, low in thermal shock and thermal expansion. However, the development of new generation of Ultra Supercritical (USC) power plant requires boiler materials to be operate at higher temperature and pressure, thus make it susceptible to high temperature oxidation. The USC power plant successfully reaching the target of working temperature at temperature more than 873K (600°C). By increasing the operating temperature, the efficiency of power plant also increases at the expense of acceleration of high temperature oxidation. This project explored the application of impressed current cathidic protection (ICCP) at 1073 K. At high temperature, gas may dissociates into charged ions that make it possible to conduct electrons. Typical boiler material of T91 was used in high temperature oxidation at 1073K, under Ar-20%O2 mixed gas. The sample is connected to potentiostat with Pt wire to measure the value of corrosion potential (Ecorr), and Icorr. Blank experiment is conducted to determine the presence of reaction by the presence of current conductivity at high temperature in oxygen condition. The weight gain is following parabolic’s rate law, which shows that diffusion is the rate determing step. Blank test shows that as potential induced, current flows from one Pt terminal to another Pt terminal through intermediate mixed gas. Corrosion potential (Ecorr) of the sample show the value is greater than value at room temperature. It is concluded that ICCP is feasible to be conducted for controlling corrosion at high temperature.