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This study analyzed the characteristics of carbon produced from coconut shells and Arabica coffee grounds through a pyrolysis process at a temperature of 1000°C for 1 hour. The SEM test results showed that coconut shells contained 91.87% carbon, while Arabica coffee grounds contained 74.39% carbon, indicating a higher carbon content in coconut shells. Furthermore, this study evaluated the effect of coconut shell carbon and Arabica coffee grounds carbon with temperature variations on the thermal conductivity and corrosion rate of 316L stainless steel plates. The results of the study showed that the highest thermal conductivity values ​​for coconut shell carbon and Arabica coffee grounds were 19.06087 W/m°C and 18.959905 W/m°C, respectively, both achieved at a temperature of 900°C. Increasing the temperature in the pack carburizing process significantly increased the carbon content in 316L stainless steel, which had a positive impact on increasing thermal conductivity. Coconut shell carbon at 900°C showed the lowest corrosion rate of 4.35 mm/year, while Arabica coffee grounds carbon at the same temperature had a corrosion rate of 5.81 mm/year. In conclusion, the effect of adding carbon with temperature variations in the pack carburizing process can increase hardness. The corrosion rate on 316L stainless steel plate will be lower because it contains Cr, Ni, and C which affect strength and high temperature resistance, especially hardness.

ASTM A36 steel has relatively low hardness and corrosion resistance, making surface treatment necessary to improve its material properties. This study aims to determine the effect of temperature and holding time variations in the pack carburizing process on the hardness, corrosion rate, and microstructure of ASTM A36 steel. The pack carburizing process was carried out using coconut shell charcoal as the carburizing medium with temperature variations of 850°C, 900°C, and 950°C and holding times of 20, 40, and 60 minutes, followed by quenching in distilled water. Hardness testing was conducted using the Rockwell B scale (HRB) method, corrosion rate testing was performed according to the ASTM G31 method, and microstructural observations were carried out using Scanning Electron Microscopy (SEM). The results showed that increasing the temperature and holding time improved the hardness and corrosion resistance of ASTM A36 steel. The highest hardness value was obtained at a temperature of 950°C with a holding time of 60 minutes, reaching 114.1 HRB. Microstructural analysis revealed the formation of a martensitic phase on the specimen surface after the carburizing process.

This study investigates the effect of adding onion peel extract as a corrosion inhibitor on the corrosion rate and hardness of radiator pipes. The research employed an experimental method with inhibitor concentrations of 0 ppm, 100 ppm, 200 ppm, and 300 ppm. Corrosion rate testing was conducted using electrochemical methods, while hardness was measured using the Vickers method. The findings reveal that the addition of onion peel extract at a concentration of 300 ppm significantly reduced the corrosion rate to 0.081 mmpy, achieving an inhibition efficiency of 56.45%. Furthermore, the same concentration enhanced the surface hardness of radiator pipes to 255.403 Kgf/mm². These results demonstrate that onion peel extract has strong potential as an eco-friendly organic corrosion inhibitor. Its dual function in reducing corrosion and improving mechanical properties highlights its applicability in radiator pipe protection and sustainable engineering practices. The study contributes to the development of natural inhibitors as alternatives to synthetic chemicals, aligning with environmental preservation efforts and advancing green technology in material protection.

This study aims to analyze the effect of Tungsten Inert Gas (TIG) welding parameter variations on the mechanical and metallurgical properties of AISI 304 austenitic stainless steel, which is widely used in construction and industrial applications due to its excellent corrosion resistance and joint strength. The research focuses on identifying the optimal welding current to minimize welding defects and enhance joint structural integrity. Welding current was varied at three levels, namely 100 A, 125 A, and 135 A, while other parameters such as welding speed, argon shielding gas flow rate, and electrode type were kept constant. Mechanical properties were evaluated through Micro-Vickers hardness testing conducted in the weld metal, Heat Affected Zone (HAZ), and base metal, as well as tensile testing to determine ultimate tensile strength and elongation. In addition, non-destructive testing using the dye penetrant method was performed to detect surface welding discontinuities. Metallographic analysis was carried out using optical microscopy following an etching process to observe grain morphology, grain size, and the formation of microstructural phases. The results are expected to demonstrate a correlation between increased heat input due to higher welding current and changes in mechanical properties and microstructure, particularly in the HAZ. This study provides practical guidance for determining optimal TIG welding parameters for AISI 304 to achieve high tensile strength, homogeneous hardness distribution, and a stable microstructure resistant to intergranular corrosion.

Stainless steel is an alloy steel with corrosion (rust) resistance properties. However, the good corrosion and wear resistance properties of stainless steel also require continuous improvement in its performance and service life, especially in highly aggressive environments. One approach to changing the material structure is by using a mixture based on natural carbon, such as robusta coffee grounds. Robusta coffee grounds will be converted into carbon using a pyrolysis process at a temperature of 1000°C with a holding time of 1 hour. This carbon will be used as a coating material on 316L stainless steel with a variety of pack carburizing and quenching processes and temperatures with a holding time of 1 hour, then it will undergo a testing process that includes: thermal conductivity testing, and corrosion rate testing. In the quenching process, the thermal conductivity value of 900°C has a thermal conductivity value of 20.556 W/m°C, 800°C has a thermal conductivity value of 19.669 W/m°C and a temperature of 700°C with a thermal conductivity value of 18.930 W/m°C. while in the pack carburizing process, the temperature of 900°C has a thermal conductivity value of 20.101 W/m°C, and 800° has a thermal conductivity value of 19.54684 W/m°C, while at 700°C the thermal conductivity value is 18.916 W/m°C. At the raw corrosion rate has a corrosion rate value of 7.614 mm/year, in the quenching process of 700°C has a corrosion rate of 12.781 mm/year, while the temperature of 900°C with a corrosion rate value of 18.401 mm/year, and in the pack carburizing process of 700°C has a corrosion rate value of 9.699 mm/year temperature 900°C with a corrosion rate value of 13.234 mm/year. The better process in thermal conductivity is quenching, because it has a faster time but has a high conductivity value, while for the best corrosion rate is the pack carburizing process because it has a smaller corrosion rate value compared to the quenching process

The Gas and Steam Power Plant (PLTGU) utilizes exhaust heat from gas turbines to produce steam, which is then used to drive steam turbines. One of the critical processes in this system is seawater desalination, which requires reliable measuring instruments to ensure the continuity and quality of the water supply. The Differential Pressure Flow Transmitter type Azbil JTD920S is used to measure fluid flow rates at four main points: Sea Water Flow (feed), Distillate Water Flow, Condensate Water Flow, and Sea Water to Ejector Condenser Flow. A decline in transmitter performance may occur due to environmental factors, corrosion, and high workload, making periodic preventive maintenance (PM) essential. This study aims to analyze the transmitter’s performance by comparing PM data with the manufacturer’s maximum specifications using literature studies, direct observation, and interviews. The calculation results show that the highest performance levels are found in the Distillate Water Flow (73.53%) and Sea Water to Ejector Condenser Flow (73.87%) lines, while the lowest is in the Condensate Water Flow (49.00%). These findings emphasize the importance of close monitoring of high-performance transmitters to prevent premature failure and maintain the efficiency of the desalination process.

The magnesium alloy AZ31B is increasingly used in biomedical applications, particularly as an implant material, due to its relatively low aluminum content and mechanical properties that closely resemble those of bone. Additionally, AZ31B exhibits corrosion resistance that is suitable for biological environments. These properties make it a promising material for bone implants. However, one of the main challenges in using magnesium is its high degradation rate in the body, which can affect the stability and function of the implant. Therefore, surface modification is necessary to control the degradation rate and enhance the material's durability. One effective method to reduce the corrosion rate of AZ31B is the Plasma Electrolytic Oxidation (PEO) technique. PEO can form a hard, protective oxide layer on the surface of the metal, which helps improve its corrosion resistance. This study aims to explore the effect of the mass composition of hydroxyapatite (HAp) and tricalcium phosphate (TCP) on the PEO coating formed on the AZ31B substrate. The compositions used in this study were 70%:30%, 50%:50%, 40%:60%, and 60%:40%, with an electrolyte solution containing Na₂SiO₃ (2.5 g/L) and KOH (2 g/L). Corrosion characteristics of the coating were evaluated using two methods: weight loss and polarization tests. The results showed that the 70%:30% HAp:TCP composition provided the most optimal results. The polarization test recorded a corrosion rate of 0.22 mpy, while the weight loss test showed a corrosion rate of 0.29 mpy. These findings indicate that the PEO coating with the 70%:30% HAp:TCP composition effectively reduces the corrosion rate of AZ31B, enhancing its potential for biomedical implant applications, particularly in environments where corrosion resistance is crucial for long-term performance in the body.

This study investigates the corrosion inhibition potential of a newly synthesized organic compound, (E)-4-hydroxy-3-(phenylamino)pent-3-en-2-one (LASA3), using computational chemistry approaches. Density Functional Theory (DFT) calculations were performed at the B3LYP/6-31G(d) level of theory with the Gaussian09 software package to evaluate several key quantum chemical parameters. These parameters include total energy, the energies of the highest occupied molecular orbital (EHOMO) and lowest unoccupied molecular orbital (ELUMO), the energy gap (ΔEgap), dipole moment, chemical hardness, softness (σ), and the number of electrons transferred (ΔN). The computational results reveal that LASA3 exhibits a higher EHOMO value and a smaller ΔEgap compared to its precursor molecules, referred to as S.M.1 and S.M.2. A higher EHOMO value suggests that LASA3 has a greater electron-donating ability, which enhances its interaction with the metal surface. Likewise, the reduced ΔEgap indicates greater chemical reactivity and a higher likelihood of forming stable coordination bonds with iron atoms on the carbon steel surface. Electrostatic potential (ESP) map analysis further supports these findings by highlighting the distribution of electron density within the LASA3 molecule. The ESP maps show significant electron-rich regions localized around nitrogen and oxygen atoms, which are potential active sites for adsorption onto the steel surface. This adsorption process plays a crucial role in blocking active corrosion sites and reducing the rate of metal degradation. In conclusion, the theoretical analysis confirms that LASA3 has superior electronic properties for corrosion inhibition compared to its starting materials, S.M.1 and S.M.2. Its ability to donate electrons, favorable dipole characteristics, and strategically located electron-rich sites make it a promising candidate for further experimental evaluation as an efficient corrosion inhibitor for carbon steel applications.  

This research explores the engineering and performance evaluation of 17-4 PH stainless steel as a potential material for turbine blades in geothermal power plants (PLTP). To promote renewable energy innovation in industrial engineering, this study focuses on improving material reliability through microstructural optimization and mechanical property control. The material was produced using the investment casting method at PT SPVMB and then subjected to four heat treatment variations: H900, H1025, AVG (average), and as-cast conditions, with reference to ASTM A747 standards. Mechanical and corrosion characterization were performed through hardness and tensile tests, electrochemical corrosion analysis using geothermal water from the Dieng PLTP, and microstructural observation using an optical microscope. The results showed that the H900 condition had the highest hardness and yield strength (48.46 HRC and 939.25 MPa), but its corrosion rate was relatively high. In contrast, the H1025 heat treatment provides balanced mechanical strength (43.88 HRC and 860.91 MPa) with the lowest corrosion rate (0.027 mm/year), supported by a uniform tempered martensite structure. These findings indicate that heat treatment optimization significantly improves the suitability of 17-4 PH stainless steel for sustainable geothermal applications. The H1025 condition meets all the requirements for geothermal turbine blades, including hardness, strength, and corrosion resistance, potentially extending component life and reducing maintenance costs. Furthermore, the results of this study strengthen the agenda for developing durable, environmentally friendly materials to support renewable energy systems. This study also provides practical insights for industry in selecting the optimal heat treatment that combines mechanical performance and corrosion resistance in extreme geothermal environments.

This study aims to analyze the electrical energy consumption of a bench-type drilling machine, RYU RDB 13, by varying machining parameters in the form of spindle speed and feed rate. Electrical energy is a critical aspect of production efficiency in the manufacturing industry, particularly in machining processes that require continuous power consumption throughout the cutting operation. The material used in this study is aluminum 6061, chosen for its lightweight, corrosion resistance, and wide application in the automotive and aerospace industries. The drilling process was carried out using three spindle speed variations: 620 rpm, 920 rpm, and 1280 rpm, along with three feed rate variations: 0.04 mm/rev, 0.08 mm/rev, and 0.1 mm/rev. Current and voltage were measured using a digital wattmeter in real-time, and energy consumption was calculated in wattseconds (Ws) using power calculation formulas. The results indicate that increasing the feed rate and spindle speed leads to higher instantaneous power consumption. However, total energy consumption tends to decrease at higher speed and feed combinations due to shorter machining times. The optimal parameter combination was found at a feed rate of 0.1 mm/rev and a spindle speed of 1280 rpm, which resulted in the lowest energy consumption of 387 Ws and the fastest drilling time. This demonstrates that selecting the right machining parameters not only improves energy efficiency but also maintains or enhances productivity. The observed power consumption pattern typically shows a sharp increase at the beginning of the drilling process, a stable phase during the main cutting stage, and a rapid decrease towards the end of the cut. These findings contribute to a better understanding of the relationship between machining parameters and energy efficiency, serving as a basis for developing sustainable production strategies in the manufacturing sector that prioritize energy savings and cost reduction.

This study aims to describe the application of Internet of Things (IoT) technology in optimizing soil health management through a systematic literature review. This research compares various IoT implementations for monitoring soil moisture, pH, and nutrients based on previous studies, and identifies differences in technological approaches, sensors used, and automation levels. The review results indicate that although IoT technology is proven effective for real-time soil condition monitoring and supporting precision agriculture, its implementation varies significantly between advanced systems with full automation developed internationally and simpler, local monitoring systems in Indonesia. The comparison shows that wireless inductive moisture sensors are superior in accuracy and corrosion resistance compared to conductive sensors. A TDS sensor-based hydroponic nutrient monitoring system demonstrated high accuracy with an average error of 4.7468% , while soil pH monitoring achieved an accuracy with a Mean Absolute Error (MAE) of 0.14. Furthermore, automated watering systems proved to reach a success rate of up to 93.75%. This review concludes that adapting low-cost wireless sensor system models has great potential for improving the efficiency of soil management in Indonesia, despite facing challenges in infrastructure and digital literacy.  

Nickel electroplating on AISI 1020 steel is expected to increase hardness and enhance aesthetic appearance. Nickel plating on AISI 1020 steel is also anticipated to protect the steel surface and reduce the rate of corrosion. In the nickel electroplating process, researchers studied variations in the anode-cathode distance (5 cm, 10 cm, and 15 cm) and the use of an aerator. Data from Vickers hardness tests, corrosion rate tests, and microstructure photos were used as the basis for analyzing corrosion rates. The corrosion rate value without the aerator at an anode-cathode distance of 15 cm is 0.034 mm/year, at 10 cm is 0.019 mm/year, and at 5 cm is 0.015 mm/year. With the use of an aerator, the corrosion rate at an anode-cathode distance of 5 cm is 0.022 mm/year, at 10 cm is 0.011 mm/year, and at 15 cm is 0.008 mm/year. The Vickers hardness values without the aerator for these distances were 337.3 VHN, 190 VHN, and 286 VHN, respectively, while with the aerator, the hardness values were 301.67 VHN, 200.33 VHN, and 339 VHN.

Thermohygrometer is a tool that functions to measure room temperature and humidity. The temperature and humidity in the operating room are set in the temperature range of 19˚C - 24˚C and humidity of 45% - 65%. Therefore, the operating room requires a good temperature and humidity control system to avoid damage to electronic components due to temperatures that are too low and humidity that is too high which causes corrosion. In addition, the influence of high concentrations of medical gas accelerates the rate of corrosion. Because medical gas consisting of CO and CO₂ gas contains oxygen as an oxidant gas. Therefore, a tool such as a Thermohygrometer is needed but equipped with a medical gas reading. This tool aims to read the conditions of temperature, humidity, and medical gas (CO & CO₂) so that it can be analyzed by Electromedics to regulate the air conditioning system. In addition, a Thermohygrometer system is made to allow data access from outside the operating room. The Thermhygrometer tool is made using two sensors, namely DHT22 and MQ-135. DHT22 is used to read temperature and humidity parameters, while the MQ-135 sensor is used to read the concentration of CO and CO₂ gases. The reading results are displayed on the I2C LCD screen. The components are integrated with ESP32 for data processing and as hardware that can be used to create a WiFi connection system. WiFi connectivity is needed to send data to the Blynk application. Testing by calibrating the DHT22 sensor and testing the suitability of the MQ-135 sensor with the gas analyzer. Based on the tests carried out, the temperature error value was obtained at -0.02% and humidity at -0.02%. While the error value was 0.32% for CO gas and -0.16% for CO₂ gas. The error value is still within the tolerance limit