No abstract

Penelitian ini bertujuan untuk mempelajari korosi pada baja galvanis setelah diekspos di Sungai Cidaho Wilayah Sukabumi, Jawa Barat. Kehilangan berat baja galvanis diukur dengan metode pengurangan berat setelah diekspos untuk periode waktu tertentu di permukaan air sungai dan kedalaman air 1 meter. Morfologi permukaan dan komposisi produk korosinya dianalisis menggunakan Scanning Electron Microscopy (SEM) -Energy Dispersive Spectroscopy (EDS) dan X-Raya Diffraction (XRD). Setelah diekspos, seluruh permukaan baja galvanis tertutup oleh produk korosi. Hasil berat yang hilang dari baja galvanis setelah diekspos 76 hari adalah 1,37 mg/cm 2 pada permukaan air sungai dan 7,83 mg/cm 2 untuk kedalaman air 1 meter. Peningkatan kerusakan dari baja galvanis ini terjadi karena tidak terbentuk lapisan protektif akibat tergerus arus sungai. Produk korosi yang dominan pada baja galvanis yang diekspos pada kedalaman 1 meter adalah senyawa Zincite (ZnO). Hasil ini mengindikasikan bahwa penggunaan baja galvanis tidak cocok untuk lingkungan di kedalaman air.

Total knee arthroplasty (TKA) implants are becoming an interesting subject in implant design research and development activities due to their complexity. They should be able to facilitate knee movement while supporting body weight during daily usage. Meanwhile, incidents such as hyperflexion in TKA implants outside their designated configuration can lead to subluxation and dislocation in this study, a polyethylene component of a posterior-stabilized right knee joint implant was developed to facilitate a high range of motion (ROM). Finite element analysis (FEA) was used to analyze the contact area on the polyethylene component. FEA was used to simulate weightbearing conditions at 0°, 30°, 60°, 90°, 120°, and 150° of knee flexion. The modified polyethylene component resulted in better performance in terms of contact area, especially at 120° of knee flexion. The two dominant contact areas on the polyethylene component were 733 mm² at 0° of knee flexion and 576 mm² at 120° of knee flexion. Furthermore, the current design of the polyethylene component can maintain a contact area of 65 mm² at 150° of knee flexion. The current design is expected to accommodate deep knee flexion movement in daily activities and reduce the possibility of subluxation and dislocation at the polyethylene component during deep knee flexion. In addition, a large contact area can reduce the potential wear on or fracture of the polyethylene component. Finally, the result of FEA was validated using a simulator of knee kinematic motion; there was no indication of subluxation and dislocation at any degree of knee flexion.

The investigation of atmospheric corrosion of mild carbon steel as representative of offshore infrastructure has been carried out in the marine tropical of Pelabuhan Ratu, West Java, Indonesia. They are exposed up to 76 days of periods, and their corrosion rates are determined according to ASTM G1-03. The surface morphology, the elemental compositions and compounds were observed using a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively.  The environmental parameters of the test site are monitored during exposure, such as air temperature, relative humidity (RH), airborne salinity and dew temperature. Based on the results, the corrosion rates of steels were 2.79 and 2.8 mpy within the 27 and 76 days exposures, respectively. The presence of chloride deposition on the surface of steel can increase the severity of corrosion. Moreover, the detrimental effect of chloride was observed in rust product, which was covered by an oxygen element. The main phases of rust products present were magnetite (Fe3O4) and hematite (α-Fe2O3.H2O). Several cracks were observed in the rust layer, which tended to exfoliate and lose adherence and protectiveness from further corrosion attack. HIGHLIGHTS The presence of chloride deposition on the surface of steel can increase the severity of corrosion. The severity of corrosion attack mainly depends on the exposure time and some climatic parameters, such as relative humidity (RH), air temperature and chloride airborne. The uniform distribution of the chloride tends to increase the production of ferrous chloride in high RH condition and the aqueous layer deposited on carbon steel. There are two phases on corroded carbon steel such as hematite (α-Fe2O3.H2O) and Magnetite (Fe3O4) after exposure GRAPHICAL ABSTRACT

Corrosion is one of the most common problems in water distribution systems. The purpose of this research is to investigate the corrosion rate of carbon steel in synthetic freshwater. The influence of a variety of time exposure that represents the actual conditions in practice was performed. Research conducted by weight loss methods using immersion test. The parameters of water quality were measured by using a multimeter portable (Hach HQ40d). From the experiments obtained that the corrosion rate of carbon steel in freshwater ranged between 0.41 - 0.76 mpy. The results of this study are expected as a first step, as input for prevention, to prevent leakage flow and pipe due to corrosion by the life that has been designed.