The degradation of most of metals, with the exception of gold is a universal reaction. It is a constant and on-going problems, make it often difficult to eliminate completely causing either industrial or heritage conservation losing a lot of money. One way and most practical for corrosion protection are using green inhibitor. Therefore it is widely use either industry or heritage conservation. Unfortunately, the inhibitors used in conservation are frequently hazardous to conservator, either through inhaler or touch with skin. Responding to this, several researches has been conducted to look into environmental friendly inhibitors or green inhibitors. This paper will review current practice use of inhibitor in metal preservation before propose a new inhibitor which been used a long time ago in Malay traditional practice in Keris preservation.
This present paper is aims to study the influence of cold rolling process on the microstructure and corrosion behaviors of 316L stainless steel using potentiodynamics polarization testing techniques. The steel with initial thickness of 2.0 mm was unidirectional cold rolled to 10%, 30% and 50% reduction in thickness. The corrosion behaviors of the cold rolled steels were evaluated in phosphate buffered saline (PBS) as their simulated body fluids environment. The pH and temperature of the solution was maintained at 7.31 and 37°C and took approximately 5 hours for each individual test. The microstructure observations of the steels were studied using optical microscope and scanning electron microscopy (SEM). The results showed that the cold rolling process has modified the microstructure of 316L stainless steel by producing extensive surface defects. The microstructure modifications of the cold-rolled steel caused to enhance the corrosion resistance by lowering its corrosion rate to 23% and reduce the pitting resistance by lowering its breakdown potential to 61%. The pit corrosion was extensively appeared after reaching the breakdown potential.
Coal blending technique in electric generating power plant has been widely used to reduce coal consumption cost. However, due to various coals from different places blended together, it had caused problems. Slagging formed during the operations can reduced boiler efficiency, resulting high costs for maintenance caused by blockage, corrosion and erosion. Many empirical indices and predictive method have been developed to minimize these problems but most are unreliable for coals from different places and many predictive methods are carried out in different environment. In this research, the method starts from fabricating the pre-blended and in furnace blend techniques at a local coal pulverized power plant. After feeding the coal blends for coal trial burn, the resulting ash deposition are collected at the burner where slagging usually occurs. The raw coals in used and the slagging samples are then characterized and determine their crystalline phase and compositions by using X-Ray Diffraction (XRD) and Sacnning Electron Microscope Energy Dispersive Xray (SEM/EDX). From XRD analysis, compounds such as quartz, cristobalite low and manganosite were found as main species in ash deposition at all location of collected slagging. However, there are also some compound exist at specific location with specific technique being used. In the burner area for pre blended technique, compound Al2SiO5, Mg2Al4Si5, KNO2 and FeO was found, whereas in furnace blend K2Mn2(SO4)3 was found. At bottom part of the furnace, pre-blended graphite was presence and in furnace yield MnO2 and Al2SiO5. At top part where superheater reside, the existence of mullite, Al2(Al2.5Si1.5)9.75 was found for pre-blended technique and microcline, KAlSiO3O8 is observed from in furnace blend technique. From the EDX analysis, in furnace technique shows more complete combustion and feasible for less slagging inside the furnace compared to pre-blended technique.
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.
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