Search

Corrosion or oxidation attacks on carbon steel pipelines can be prevented by producing aluminum slurry coating. Observations of the optimal slurry composition containing aluminum scrap powder as a load agent in the binder solution with a certain mass ratio were studied to obtain good quality aluminum coating on ST37 carbon steel. Several variation compositions of Al content and binder ratio were evaluated by viscosity test and optical microscope (OM), then showed a slurry coating of 43 wt.% Al content and binder ratio of 1:40 possessed good consistency, stable shear-thinning behavior, and the lowest surface roughness. Therefore, further analysis of microstructure was performed on this sample. A surface morphological structure showed moderate roughness with some particle characteristics observed on the slurry coating sample. A cross-sectional structure showed the presence of an internal oxide layer with a thickness of about 129 µm. In addition, a protective oxide Al2O3 layer with a thickness of about 173 µm was observed on the top of the internal oxide layer. Phase identification by XRD analysis showed the formation of Fe3O4 as the internal oxide layer and α-Al2O3 as the protective oxide layer with a small amount of unstable Al2O3, α-Fe, and Fe3Si phases. [ABSTRACT FROM AUTHOR]

The influence of alkali chlorides such as NaCl and KCl on 75Cr3C2−25NiCr coating and A516 steel was studied. The effect of alkali chloride is carried out by vapor-condense salt (45%NaCl+55%KCl) test at 900°C on bare and coated steel under cyclic conditions. Rusting and damage on specimens were visually evaluated. The mass changes were performed each cycle consisting of 20 hours to establish the corrosion rate. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) equipped with an energy dispersive X-ray analysis (EDS) were used to characterize the phase and microstructure analysis, respectively. Severe damage was observed on specimens after exposure on alkali salt environment, especially on A516 steel. After 20 hours of exposure, the mass change of A516 steel was almost seventeen times higher than the Cr3C2−NiCr coating which was approximately of 177.05 mg/cm2 and 10.64 mg/cm2, respectively. The severe damage on corroded specimens is due to chlorides penetrated the substrate and formed Fe2O3 oxide. The corrosion mechanisms of bare and 75Cr3C2−25NiCr coated steel were performed in this study. [ABSTRACT FROM AUTHOR]

In this research, we investigate the effect of weight percentage alteration for magnesium to the thermal behavior and flash quality of orange pyrotechnic composition. These parameters will determine what application type is suitable for composition that is created. We combined Sr(NO3)2 and NaNO3 as color source to generate orange spectrum, in which the orange spectrum was usually produced from calcium compound. This composition was synthesized using mechanical alloying with planetary ball mill equipment with rate of 50 rpm for 15 minutes. We find that this combination can generate orange spectrum, in which the composition of 30 wt.% Mg - 0.5 wt.% Sn – 33 wt.% Sr(NO3)2 – 33 wt.% NaNO3 − 3.5 wt.% Paraffin Wax (X1) produced flash higher than 18 wt.% Mg - 0.5 wt.% Sn – 39 wt.% Sr(NO3)2 – 39 wt.% NaNO3 − 3.5 wt.% Paraffin Wax (X2). This finding is also supported by spectrometer and heat of reaction data. The spectrum data of 30 wt.% Mg can't be captured completely, because it emits color with so high intensity. Chromaticity diagram also shows that 30 wt.% Mg composition emits spectrum in white area, while the 18 wt.% Mg generates medium-dark orange. Further, the composition with the 30 wt.% magnesium has calorific value two times bigger than composition with 18 wt.%. To observe the ignition temperature of each composition, differential thermal analysis (DTA) test is executed, while XRD test is applied to reveal produced compound after combustion process. Based on their character, the composition with 18 wt.% magnesium can be developed for orange flare and tracer applications, while another composition can be initiated for flash bomb application. [ABSTRACT FROM AUTHOR]

In this research, corrosion properties of assorted types of PTFE were examined under concentrated strong acid and high temperature condition. The most optimum type from the test results will then be used as a coating material for high temperature reactors using the hot press method, which are intended to be used as a coating on tin sulfate production reactor. PTFE was examined using sulfuric acid 96% by immersion and steam method at 250°C. The result shows that the PTFE sheet possesses the least affected by concentrated sulfuric acid corrosion, with 0.0116% corrosion per hour. In addition, PTFE sheet has been successfully coated on high temperature reactor. [ABSTRACT FROM AUTHOR]

75Cr3C2-25NiCr coating was deposited on A516 steel by flame spray process to enhance high temperature corrosion resistance. Corrosion studies were investigated on bare and flame spray-coated steel after exposure at 600°C under cyclic condition in a molten salt environment (45% NaCl+55% KCl). The mass change measurements were performed after each cycle that consisted of 20 hours to establish the corrosion rate. Field emission scanning electron microscopy (FESEM) equipped with an energy dispersive X-ray analysis (EDS), X-ray diffraction (XRD), micro-vickers hardness, and 3D optical microscope (OM) were used to characterize the microstructure, elemental analysis, phase, mechanical properties, and surface roughness of the coatings, respectively. The spallation occurred on A516 steel without coating after corrosion test due to the formation of unprotective Fe2O3 oxide scales. On the contrary, Cr3C2-NiCr coating was found to be more protective by the formation of oxide scale consisted of Cr2O3 and spinels. The results showed that the corrosion rate and the surface roughness of Cr3C2-NiCr coating having lower value than that of A156 steel without coating which were approximately of 11.49 mm/y and 25.02 µm, respectively. However, the mechanical properties from vickers hardness measurement showed that Cr3C2−NiCr coating reached the highest value of about 364.77 HV. [ABSTRACT FROM AUTHOR]

This paper reports the effect of aluminium corrosion reaction on the density, porosity, and thermal insulation capability of porous fire bricks. The reaction between aluminium and alkaline solution produces hydrogen and other sediment products. The test specimens of fire bricks were made from the mixture of castable cement, aluminium powder of 325 mesh in size (0, 0.1, 1, and 2 wt% with respect to castable cement), and 0.185 M KOH solution. The structural examination of the specimens shows the increase of porosity to 22.7 - 30.6% and the decrease of density in the range of 1.135-1.503 g/mL. In addition, the samples possess average pore size of 0.001-0.003 cm3 with the thermal insulation in the range of 47-78%. [ABSTRACT FROM AUTHOR]

The aims of this research were to study the leaching process of manganese ore which originated from Sumbawa, Indonesia and its characterization. A high grade Indonesian manganese ore from Sumbawa, West of Nusa Tenggara was characterized by X-Ray Fluorescence (XRF). The result showed composition of 78.8 % Mn, 17.77% Fe and the rest were trace elements such as Si, Co, Ti, Zn, V and Zr contents. X-Ray Diffraction analysis showed that the manganese ore was consisted of pyrolusite (MnO2), rhodonite (MnSiO3), rhodochrosite (MnCO3) and hematite (Fe2O3). Manganese ore was also analyzed by thermal analysis to observe their thermal decomposition character. In this study, sulphuric acid (H2SO4, 6 M) was deployed as leaching agent. The leaching process was performed at 90 °C for two hours with the addition of NH4OH to control pH. Recovery percentage of leaching process yielded of 87 % Mn extracted. The crystallization process result at heating temperature of 200 °C was confirmed by XRD as manganese sulfate. [ABSTRACT FROM AUTHOR]