This research aims at investigating the corrosion behavior and hardness of AISI Stainless Steel 304 (AISI SS 304) in corrosive hydrochloric acid solution and temperature variation treatment. In this study, the samples of AISI SS 304 are immersed for six (6) days in the corrosive acid solution at the temperature of 30°C and 50°C. The solution used as the corrosive media are HCl, FeCl3, and NaCl in the concentration of 5%, 10% and 15%. The results show that the higher the concentration of the solution, the higher the corrosion rate of AISI SS 304 will be, and the higher the temperature, the higher corrosion rate will also occur in all corrosion media. The corrosion that occurs in AISI SS 304 is mostly in the form of uniform corrosion and some pitting corrosion, and the value of hardness decreases after corrosion.

MgB2 superconductor is a superconductor with a critical temperature of around 39K and has the potential to replace Nb3Sn and NbTi as superconducting coils to produce high magnetic fields. In this study, monofilament wires have been made to analyze the doping effect of SiC and Carbon Nanotubes (CNT) in its manufacture using Powder-In-Tube (PIT) method. Stainless Steel (SS-316) tube was used as a tube filled with powders of starting materials of Mg, B, SiC and CNT. A total of 8 samples were prepared with variations in the addition of SiC, and CNT as much as 5, 10, and 15 wt %, and also the variations in the addition of Mg composition by 0 and 10 mol % from normal stoichiometric values. The samples were rolled and sintered at 800°C for 3 hours. The samples then were analyzed using SEM (Scanning Electron Microscopy) to analyze the surface morphology, XRD (X-Ray Diffractometer) to analyze the formed phases and crystal structures, and then resistivity versus temperature using cryogenic systems to analyze their superconductivity properties. Based on the results of the XRD analysis, the MgB2 phase is the major phase in the samples and the SiC doping causes the formation of minor phases of Mg2Si and Fe3C. The addition of SiC causes a decrease in crystalline properties of the MgB2 phase due to reaction with SiC, while the addition of CNT does not cause the formation of a new phase. Based on the results of the analysis of resistance versus temperature, it is seen that the addition of SiC causes a decrease in TC value. While the addition of CNT causes the improvement in the nature of superconductivity, but it also causes the decrease of its TC values.

Cast iron is a high-carbon iron-carbon alloy. Cast iron is difficult to weld because of the high carbon concentration. A good connection necessitates the application of specific strategies and processes. This study investigates the effect of current strength on the mechanical properties of tensile strength and impact toughness of cast iron welded joints. The main materials used are gray cast iron and CIN 3 filler.The welding process uses an AC TIG welding machine. The welding seam is made of a single V with an angle of 70 o , and the electric current variations are 80A, 90A, and 100A, respectively. Tensile testing is carried out with a UTM machine referring to ASTM E8M, while the Charpy impact test refers to ASTM E23. From the study results, it was found that the higher the use of electric current resulted in the mechanical properties of the tensile strength and impact toughness of the weld being also higher, which occurred at 100A electric current, reaching 181.05 MPa and 0.22 J/mm 2 .

Using inhibitors becomes an alternative way to reduce the level of corrosion. One type of the inhibitors proven effective is inorganic or chemical inhibitors. Regarding this, the purpose of this study is to determine the effectiveness of chemical inhibitors in reducing the level of corrosion. This study showed that the addition of natrium acetate and natrium was proven effective in reducing the corrosion, with the level of inhibitor efficiency of 75%. The result also showed that the inhibitors gave good performance to inhibit corrosion attack in natrium chloride acid medium, the form of corrosion that occurs in API 5L material is uniform corrosion.

Penggunaan baja pada saat ini telah berkembang pesat dan digunakan dalam teknologi industri sebagai salah satu material penunjang. Ada beberapa penggunaan baja yang digunakan pada industri sepeda motor, kereta api, mobil, kapal laut, serta kontruksi lainnya. Namun dalam penggunaan baja, banyak faktor yang menyebabkan daya guna baja ini menurun. Salah satu penyebabnya yaitu fenomena korosi pada baja. Penelitian ini bertujuan untuk mengetahui pengaruh konsentrasi inhibitor ekstrak daun teh terhadap laju korosi pada baja API 5L dan menghambat laju korosi pada baja API 5L. Metode yang digunakan adalah kehilangan berat. Medium korosif yang digunakan adalah NaCl dan HCl. Lama perendaman yaitu 10 hari untuk melihat kemampuan inhibitor menghambat laju korosi. Metode pembuatan inihibitor ekstrak daun teh menggunakan ultrasonic bath. Konsentrasi inhibitor yang dibuat pada penelitian ini adalah 1%, 3%, 5%, 7%, dan 9%. Sebelum baja direndam dalam larutan korosif, larutan korosif dicampur terlebih dahulu dengan larutan inhibitor sesuai dengan konsentrasinya. Hasil penelitian menunjukkan bahwa efisiensi inhibisi korosi yang paling besar terjadi pada larutan korosif NaCl dengan konsentrasi 9% pada perendaman selama 10 hari yaitu sebesar 95% dan pada larutan korosif HCl dengan konsentrasi 9% sebesar 45%. Morfologi permukaan yang diperoleh menggunakan Scanning Electron Microscope dari baja API 5L memperlihatkan permukaan baja yang dilapisi dengan ekstrak daun teh mengalami korosi lebih sedikit. Hal ini menunjukkan bahwa inhibitor ekstrak daun teh baik dalam menghambat laju korosi yang terjadi pada baja API 5L.