Papers by Keyword: Seawater

Abstract: SS316L material exhibits superior corrosion resistance. The two grade compositions, comprising nickel and molybdenum, enable the alloy to resist acids and chlorides without degradation. Due to its exceptional corrosion resistance, both metals are among the few classified as "marine grade stainless steels." Gas Tungsten Arc Welding (GTAW) is executed to guarantee sufficient corrosion resistance during installation. This study analyzes the outcomes of welding ER316LSi as a filler material with SS316L base metal, focusing on microstructure, EDAX analysis, and corrosion rate. This study did not perform hardness testing. This study will indicate welding variables for future research on specific applications, utilizing various weld blades and current parameters. Corrosion testing, encompassing Tafel and Electrochemical Impedance Spectroscopy, indicates that the SS316LSi weld metal will yield a higher degree of ferrite development in the weld region. The welding temperature significantly influences the ferrite structures. The corrosion rates for each electrolyte solution are as follows: for the seawater electrolyte solution, a current of 110A yields a rate of 8.39857 x 10^-6 mpy, 120A results in 7.09315 x 10^-6 mpy, and 130A produces a rate of 7.85427 x 10^-6 mpy. The MgCl₂ electrolyte solution exhibits a concentration of 110A = 7.2195 × 10^-6 mpy, a current of 120A = 7.2156 × 10^-6 mpy, and a current of 130A = 7.1406 × 10^-6 mpy. The corrosion resistance at a current of 120 amperes is greater in seawater conditions than at a current of 130 amperes in MgCl2 solutions. The corrosion rate and reductions in Fe, Mo, Cr, and Mn following 14 days of immersion testing in sewage and MgCl2 are the reasons that low-heat-input or solid-phase bonding techniques can significantly enhance pitting resistance compromised by welding.

Abstract: Water sources in coastal areas are highly susceptible to seawater intrusion, leading to significant environmental and economic losses. Therefore, advanced treatment methods are required to make seawater suitable for clean water production, particularly in addressing water scarcity in coastal regions. One promising approach is seawater desalination using calcium alginate/graphene oxide (GO) beads. In this study, waste coral skeletons were utilized as a calcium source due to their high calcium content. X-ray fluorescence (XRF) analysis revealed that the calcium content in the coral skeletons was 93.4% before calcination and increased to 94.9% after calcination. These findings suggest that coral skeleton waste has potential as an adsorbent for Na⁺ and Cl⁻ ion removal. The synthesis of calcium alginate/GO was conducted using a droplet method and characterized using Fourier-transform infrared spectroscopy (FTIR). The adsorption process for Na⁺ and Cl⁻ ions was investigated at varying CaCl₂ concentrations (0.5 M, 1 M, and 2 M) to determine the optimal conditions for ion removal. Na⁺ ion analysis was performed using atomic absorption spectroscopy (AAS), while Cl⁻ ion concentration was determined via argentometric titration. The optimal Cl⁻ adsorption was observed at a CaCl₂ concentration of 0.5 M with a contact time of 30 minutes, achieving an adsorption efficiency of 99.8% in a standard NaCl solution and 35.9% in seawater. For Na⁺ ion removal, the highest adsorption efficiency was achieved at a CaCl₂ concentration of 2 M with a 30-minute contact time, resulting in 97.3% adsorption in a standard NaCl solution and 61.9% in seawater. These results highlight the potential of calcium alginate/GO composites, derived from waste coral skeletons, as effective adsorbents for seawater desalination.

Abstract: Water shortage is a major global issue affecting the construction industry. One possible solution is to use seawater instead of tap water in cement-based materials. However, this raises concerns about the impact on material properties. In addition, it is known that the use of volcanic pumice powder in cement mortar can improve its properties, but the combined effects of seawater and volcanic pumice powder have not been thoroughly investigated. This study aims to fill this gap by investigating the synergistic effects of seawater and volcanic pumice powder on the slump flow, compressive and flexural strengths, water absorption, and fracture toughness of cement mortar. The main variables in this study are the type of water (Mediterranean water and tap water) and the percentage of volcanic pumice powder (VPP). The volcanic pumice powder content is 0%, 10%, 20%, and 30%, replacing cement by mass. Based on investigation results, it was shown that the combination of seawater and volcanic pumice powder leads to less fluid and more viscous mortars compared to those made with tap water (TW). However, in the hardened state, seawater promoted the early precipitation of cement hydration, resulting in an increase in compressive strength from the second day until 28-days, along with an improvement in the transport properties of mortar at 28 days. Meanwhile, a noticeable decline in both strength and fracture toughness was recorded for ages more than 28 days and up to 90 days, compared to mortars cast and cured with tap water.

Abstract: The chloride concentration (Cs) on the concrete surface is an indispensable metric for designing resilience and estimating the lifespan of concrete structures in aquatic settings. Consequently, due to Chloride action, many reinforced concrete constructions cannot reach their intended or planned life span and experience early degradation. This study utilizes three independent machine learning techniques, Extreme Gradient Boosting (XGBoost), Multi Expression Programming (MEP), and Decision Tree (DT), to forecast the concrete’s surface chloride concentration (Cs). To achieve this objective, a comprehensive database consisting of 642 observations of Cs exposure data in the marine field, including the applicable mixture quantity of constraints, conditions of the environment, and exposure time, has been created through a thorough investigation of relevant literature. This database covers tidal, splash, and water-logged zones in numerous locations across the globe. The database trains three independent machine learning models: XGBoost, MEP, and DT. These models are then employed to compare their prediction performances with each other and with previous modeling techniques. Diverse statistical criteria evaluated the model's accuracy and suitability. During the validation process, the XGBoost, MEP, and DT models demonstrated enhanced accuracy with coefficients of correlation (R) 0.98, 0.97, 0.95 for training and 0.97 for validation. Additionally, these models' mean absolute errors (MAE) were correspondingly 0.020, 0.021, and 0.09. The SHapley Additive exPlanations (SHAP) technique has found the chloride binder content as a crucial component in determining the concentration of Cs. The SHAP method provides a thorough understanding of the links between various input variables and their effects on the concrete’s surface concentration of chloride, both on a global and local scale. The results indicate that by including more diverse datasets and considering new variables, the predicted accuracy of standard models may be improved. The XGBoost machine learning model, trained on a vast database, can effectively include 14 key characteristics that pose challenges for conventional models. It exhibits superior predicted accuracy and enhanced time efficiency compared to conventional models. However, to lessen the problem of overfitting, it is advisable to use a more extensive dataset, including synthetic or genuine experimental data.

Abstract: One of the significant problems to be solved is the availability of clean water for public consumption. As the population increases, the clean water needs will also increase. Some areas are at risk of shortages of clean water. One of them is in coastal areas. One of the methods used is to convert seawater into freshwater to provide clean water in coastal areas. With the distillation process, water can be separated from salt. In this research, the heat source used is induction electrical energy. The induction heater is chosen because of its efficiency. A method to change seawater into pure water is to boil the seawater. In this research, the level of electricity power is 600 W, 800 W and 1000 W. The airspeed over the condenser was varied in three level of speed. The result shows that the highest freshwater product is at 1000 W at level 1 airspeed with freshwater product is 632 grams. The most effective result is at 900 W induction heater with power consumption of 1.295 W/g.

Abstract: Fly ash is a material suitable for making concrete because of its silica, alumina, and calcium contents, which can improve the compressive strength of concrete. In this study, the researcher tried to renew a mixture that is resistant to corrosion using fly ash and calculating the powder in an oven at 200°C for 60 min to change the nature of the shell powder to become reactive in a concrete mixture. Using experimental methods and supported by previous studies. In this experiment, normal concrete (Fc' = 30 MPa. In this study using 6 formulations, with Fly ash 10%, 10%, 15%, 10%, 5%, and 13% of cement and clamshell power 10%, 20%, 20%, 20%, 20%, and 17%, respectively) from sand. The influence of seawater on salty materials, such as shells, and pozzolanic materials, such as fly ash, during drying affects the compressive strength of concrete. The addition of 20% shellfish powder as a substitute for river sand and a combination of 15% fly ash as a substitute for cement (code. C3-SC) greatly affected the performance of concrete for application in marine areas, with the result that the compressive strength of this composition did not decrease. With a curing experiment using seawater, the compressive strength results at the age of 7 days were 23.93 MPa, at the age of 14 days were 33.55 MPa, and at the age of 28 days were 34.02 MPa. These results indicate that the compressive strength of concrete with this mixture does not decrease. From the research results, it can be concluded that calcined shellfish and fly ash powder materials can be applied to concrete in seawater areas.

Abstract: Seawater has the potential to replace fresh water in the production of concrete. Given the restricted availability of freshwater sources and the high cost of transportation, it is crucial to optimize this scenario. On the other hand, agricultural residue is a potential material that can replace cement-based materials, thereby reducing CO2 emissions. Sustainability in the concrete sector is important, hence, research on using alternative renewable resources such as palm oil fuel ash (POFA) for concrete production is necessary. POFA is an agricultural byproduct and industrial waste that is potentially used as a partial substitution for cement due to the presence of pozzolan. The objective of this study is to examine the impact of icluding POFA (Palm Oil Fuel Ash) as a substitute in the paving block, while also considering the influence of seawater mixing and curing water. Further, POFA is used as a supplementary binder for paving blocks at 0%, 10%, 20%, 30%, 40%, and 50% for Portland Composite Cement replacement. The paving blocks properties, such as workability, density, compressive strength, water absorption, and resistance to sulfate attack, were evaluated. The results of the tests confirmed that 10% POFA mixed with seawater and cured with freshwater met the minimum necessity for Class B, as specified by the Indonesian National Standard for parking park applications. As a result of incorporating POFA as a cement replacement, a more environmentally friendly paving block could be established.

Abstract: This study investigates the corrosion inhibition performance of Anthocleista grandiflora leaf (AGL) extract on carbon steel in seawater, considering the effects of temperature, immersion time, and inhibitor concentration. Predictive modeling, adsorption behavior, and the kinetics and thermodynamics of the inhibition process were examined. The weight loss technique,characterization techniques combined with response surface methodology (RSM), revealed that the AGL extract follows the Langmuir adsorption model, exhibiting physical adsorption with ΔG values between −16.24 to −15.49kJ/mol, indicating spontaneous and endothermic inhibition. The thermodynamic parameters entropy (−198.87 to −52.58 J/mol), enthalpy (20.42 to 53.42 kJ/mol), and activation energy (13.68 to 56.32 kJ/mol further support this. The corrosion reaction follows first-order kinetics, with the half-life decreasing as the rate constant and extract concentration increase.The SEM images revealed that the AGL extract formed a protective surface layer on the mild steel, effectively preventing pitting. This protective effect became more pronounced as the concentration of the extract increased. RSM optimization identified optimal conditions for maximum inhibition efficiency (98.70%) and corrosion rate (0.058 mm/y) at 800 ppm, 303 K, and 45 days, with a prediction accuracy of 95%, making it suitable for application in the oil and gas industry.

Abstract: In this research, a hydrophobic surface has been successfully created using a mixture of silica sand and methyltrimethoxysilane (MTMS) precursor. This research aims to determine the effect of varying the volume of MTMS on the hydrophobic surface. The MTMS as silica precursor was synthesized with Stöber method. The variation used is the volume of the MTMS precursor, while the silica from silica sand is made constant. The volume variation of the MTMS precursor is 9.5 ml, 19 ml, 28.5 ml and 38 ml. The MTMS/SiO2 composite which has been synthesized then get mixed with steel ship paint and coated on the steel plate surface as a topcoat. The MTMS/SiO2 composite was further characterized by X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), Water Contact Angle (WCA), and Atomic Force Microscope (AFM) which were employed to investigate crystal structure, morphology of particle, hydrophobicity on a surface, and topography of the three-dimensional surface layer respectively. The type of liquid used in the WCA characterization is seawater. XRD characterization results show that silica sand has a quartz phase, MTMS has an amorphous phase and MTMS/SiO2 composite tends to have an amorphous phase. SEM characterization show that the particle size of silica sand that has been mixed with MTMS is around 8 – 20 μm. WCA characterization show that the addition of silica powder on the topcoat increase surface roughness and WCA, so that the steel plate surface has good hydrophobic properties. The highest water contact angle obtained in this research was 109o by seawater.

Abstract: The hybridization of carbon fiber (CFRP) and glass fiber (GFRP) composites is required to overcome the disadvantages of GFRP composites and their commercial feasibility for marine applications. This study was conducted on a hybrid glass/carbon composite with a vinyl ester matrix made by vacuum-assisted resin infusion process with a stacking sequence of [GCG₂CG₂C] s. Composites are immersed in natural seawater for up to 6 months. The maximum weight gain of e-glass/carbon hybrid composite is 0.79%. The results showed that the tensile, shear and compressive strengths of the glass/carbon hybrid composite after immersion in natural seawater decreased to 19%, 13%, and 50%, respectively. The decrease in compressive strength is the highest compared to others. It indicates that compressive strength should be of more significant concern for marine environmental applications. SEM analysis exhibited that seawater absorption causes the matrix, fiber, and fiber/matrix interface degradation. It is indicated by the absence of a firm matrix fracture surface, the number of fractures in the thread, the presence of fiber/matrix debonding, and fiber pull-out in the specimen after immersion in seawater. It is the cause of the decrease in the mechanical properties of the hybrid composite.