PENGARUH WAKTU KONTAK AIR LINDI DAN UDARA TERHADAP LAJU KOROSI BAJA ST-41 DAN ST-60

The use of metals in the environment is especially important in environments such rubbish in heavy equipment or trucks, especially those of the tailgate is a tool to bring a variety of organic waste and inorganic bring the matter dissolved through a liquid called leachate and make contact or direct contact with the steel so that corrosion occurs due to leachate or wastewater flow contains many corrosive compounds that make part tailgate become quickly corroded. This study aims to determine the bias steel resist corrosion rate. The steel used is steel steel ST-41 and ST-60 is a low carbon steel and medium carbon steel. The methods used in research in the methods of losing weight and observe the types of corrosion that occurs by means of immersion with ASTM G31-72 which vary contact time for 3 weeks. Based on research conducted showed the corrosion rate of the fastest occur in steel ST-60 with a contact time of 1 week soaked the leachate and 2 weeks in contact with the air due to differences in the composition of the steel ST-60 and steel ST-41 which has a chromium content so high that steel ST-41 is superior in resisting corrosion rate while the type of corrosion that occurs is evenly corrosion and atmospheric corrosion.

Risk Mitigation and Mapping on Tubular System During Microbial Huff and Puff Injection Coupled with Lean Six Sigma Approach at Field X

Increasing demand of oil in Indonesia is in contrast with the decreasing oil production every year. Enhanced oil recovery (EOR) has become one of the most favorable method in maximizing the production of mature fields with various applications and research has been done on each type, especially microbial EOR (MEOR). “X” field is a mature oil field located in South Sumatra that has been actively producing for more than 80 years and currently implementing MEOR using huff and puff injection. However, there are some potential risks regarding MEOR processes that may inhibit the production by damaging the well’s tubular system, particularly microbially induced corrosion (MIC). This study reviews the risk mitigation and mapping to prevent corrosion on tubular system during MEOR huff and puff processes, equipped with the approach of Lean Six Sigma.The mitigation and mapping process follow the framework of define, measure, analyze, improve, and control (DMAIC). It starts with defining the problem using supplier-input-process-output-customer (SIPOC) diagram after all the field data necessary has already been collected, then measuring the corrosion rate model using ECE™ software as well as conducting sensitivity analysis of the fluid rates. The analyze phase involves constructing fishbone diagram to identify the root causes, comparison with industry’s specification and standard, and analysis of chromium effect on corrosion rates. Further simulation is conducted to support the analysis and to ensure the improvements and sustainability of the design selection.Based on the simulation results, the normal corrosion rate ranging from 0.0348 – 0.039 mm/year and the pH is around 4.03 – 5.25, while the ±30% fluid rate sensitivity results shown that the change of water flowrate is more sensitive than oil flowrate with the corrosion rate approximately 0.0275 – 0.048 mm/year. The fishbone diagram identifies that material selection and environmental condition as the main root causes, then corrosion resistant alloy (CRA) is used in the tubing string to prevent corrosion in the future by using super 13Cr martensitic steel (modified 2Ni-5Mo-13Cr) as the most suitable material. Further simulation on chromium content supports the selection that corrosion rate can be reduced by adding the chromium content in the steel. The completion design is then capped with choosing the Aflas® 100S/100H fluoro-elastomer as the optimum material for packer and sealing. Overall, the Lean Six Sigma approach has been successfully applied to help the analysis in this study.

Kinetic Monte Carlo Modelling of Dissolution and Passive Film Formation in Fe-Cr Alloys

<p>Stainless steels differ from iron in that chromium content allows for the formation of a passive iron-chromium oxide film which is only nanometres in thickness, offering protection from the environment. While the composition of this oxide layer has been established, the mechanism of its formation is not well understood. In particular, the threshold level of chromium for oxide formation is significantly lower then the chromium content of the alloy itself. We present a Cahn Hilliard type analytical model that relates the onset of passivation to an instability which leads to a phase segregating current above 17% Cr in a bulk alloy. Proposing that this current could lead to Cr enrichment at a surface, we compare atomistic simulations with and without a surface driven Cr current. We implemented a kinetic Monte Carlo algorithm with extensions to allow for vacancy assisted nearest neighbour migration in a body centered cubic alloy, tracking a surface, dissolution and surface passivation. We compare the time evolution of Fe dissolution rates, Cr surface enrichment and the threshold for passive film formation and find that the Cr current has a significant impact on each of these properties.</p>

Kinetic Monte Carlo Modelling of Dissolution and Passive Film Formation in Fe-Cr Alloys

<p>Stainless steels differ from iron in that chromium content allows for the formation of a passive iron-chromium oxide film which is only nanometres in thickness, offering protection from the environment. While the composition of this oxide layer has been established, the mechanism of its formation is not well understood. In particular, the threshold level of chromium for oxide formation is significantly lower then the chromium content of the alloy itself. We present a Cahn Hilliard type analytical model that relates the onset of passivation to an instability which leads to a phase segregating current above 17% Cr in a bulk alloy. Proposing that this current could lead to Cr enrichment at a surface, we compare atomistic simulations with and without a surface driven Cr current. We implemented a kinetic Monte Carlo algorithm with extensions to allow for vacancy assisted nearest neighbour migration in a body centered cubic alloy, tracking a surface, dissolution and surface passivation. We compare the time evolution of Fe dissolution rates, Cr surface enrichment and the threshold for passive film formation and find that the Cr current has a significant impact on each of these properties.</p>

Typical Defects of Natural Phospholipid Fatliquors in Leather Industry and Their Solutions

Leather made with soybean phospholipid fatliquors is prone to problems such as yellowing, elevated hexavalent chromium content, and undesirable odor. In this study, the aforementioned typical defects of soybean phospholipid fatliquors were investigated in respect to the main components, the antioxidants and the unsaturation degree of the natural soybean phospholipid. The results showed that the oxidation of soybean phospholipid is the primary source for its yellowing, elevated hexavalent chromium content, and undesirable odor. The volatile aldehydes produced by lipid oxidative rancidity are the main components of the undesirable odor. The purification of natural soybean phospholipid through removing the non-phospholipid components cannot solve the problems caused by oxidation of phospholipid. Furthermore, as a typical natural antioxidant existing in natural soybean phospholipid, tocopherols can restrain the oxidation of phospholipid to a certain degree, however, the dissolving out and destruction of tocopherols at high temperature in the phospholipid purification process can lead to more obviously oxidation of phospholipids. Additionally, the oxidation defects of phospholipid cannot be completely resolved by adding extra tocopherols, even at high dosages. The research finds that the defects of soybean phospholipid fatliquors can be thoroughly solved by increasing the saturation degree of lipid through addition reaction, the suggested iodine value of phospholipid products is lower than 20 g I2/100 g.

Formation of a Cr-Zr surface alloy using a low-energy high-current electron beam

The paper investigates the regularities of the formation of Cr-Zr surface alloy using a low-energy high-current electron beam (LEHCEB). The influence of the electron-beam processing parameters and the magnetron deposition parameters on the elemental composition of the formed Cr-Zr surface alloy is estimated. It is shown that, for all considered modes, there is a general tendency to a decrease in the chromium content in the surface alloy with an increase in the energy density or the LEHCEB processing pulse number. The thickness increasement of the chromium film applied in one cycle or the surface alloy total thickness increasement leads to an increase in the chromium content in the surface alloy. The LEHCEB processing parameters, namely the energy density and the number of pulses, have a greater effect on the chromium content during the formation of the Cr-Zr surface alloy in comparison to the magnetron sputtering parameters, namely the deposited film thickness and the formed surface alloy thickness. A linear regression model that describes the chromium content in the surface alloy depending on the film thickness, the surface alloy total thickness, the number of pulses and the pulse energy density is proposed.

The Effects of Preparation Conditions And Chemical Composition On CMAS Glass Ceramics With One Step Process

Based on the composition of Cr-doped solid waste, other oxides were added to adjust the composition to prepare glass-ceramics with on step composition, and the effect of heat treatment system (including temperature and holding time), chromium content, MnO and Fe2O3 doped on the crystallization and physical properties of glass-ceramics was studied. The samples were characterized by X-ray diffraction, differential thermal analysis and scanning electron microscopy. The results show that the best treatment conditions are 1090 ℃ for 4h, and the amount of dissolved chromium reaches 5%. The main crystallization phase is diopside and anorthite. The hardness and chemical stability of the material were measured. The doping of MnO and Fe2O3 increases the crystallization activation energy of glass ceramics, and makes the crystal phase more uniform as the SEM results. This experiment provides a theoretical basis for the preparation of CMAS glass ceramics from chromium containing solid waste.

Evaluation of the Heat Resistance of the Fe-Cr-Al System Coatings

The influence of the chemical composition of aluminide coatings of the Fe-Cr-Al system on their heat resistance at 1100 °C was investigated. It is shown that the lowest oxidation rate is possessed by the coating obtained by aluminizing the Cr15Al5 alloy in the silumin melt, for which the depth of corrosion penetration after 500 h at 1100 °C did not exceed 2.5 μm. The depth of corrosion penetration after 500 h at 1100 °C in coatings with a higher chromium content (23 at.%) reaches 8.9 μm. A decrease in the content of chromium (up to 5 at.%) or aluminum (up to 10 at.%) in the surface layer is accompanied by a critical increase in the corrosion rate. The longest time of retention of heat-resistant properties at 1100 °C is possessed by the coating obtained by aluminizing the Cr23Al5 alloy in an aluminum melt.