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Carbon steel is a metal that is widely used for the construction of industrial and marine applications. Hence, seawater is one of the corrosive mediums due to its Natrium Chloride (NaCl) content as a strong electrolyte. One method to control the corrosion rate is by adding the inhibitor. Chitosan has been chosen as inhibitor corrosion because of non-poisonous and green material. Corrosion inhibition of carbon steel in chitosan inhibitor presence in 3,5% NaCl medium was studied using potentiodynamic polarization technique. This study aims to understand the effect of temperature and inhibitor concentration on carbon steel's corrosion behavior. This study also determined adsorption constant value  of chitosan on the carbon steel surface. The corrosion rate has been analyzed by using potentiodynamic polarization. Firstly, carbon steel is prepared by cutting them in cuboid shape by dimensions 4cmx 1cm x 3mm. Secondly, a 3.5 % sodium chloride solution is prepared by dilute NaCl crystal into demineralized water. The next step is inhibitor preparation by dissolve chitosan powder in the acid solution. The corrosion rate is analyzed in different temperatures, various from 30-70oC, and chitosan concentration varied from 0 to 250mg/l. The results showed that chitosan is a promising corrosion inhibitor in sodium chloride medium. The inhibition efficiency at 30oC reaches 84.92% with a chitosan concentration of 250 mg/L.

Buah naga merupakan tanaman tropis yang dapat berbuah sepanjang tahun. Di Indonesia, buah naga telah dikembangkan di berbagai daerah. Pada musim panen, hasil buah naga sangat melimpah sehingga sbeagian tidka terserap oleh konsumen dan terpaksa dibuang. Disisi lain, daging buah naga merah  memiliki kandungan glukosa sebesar 12% brix sehingga berpotensi menjadi bahan baku pembuatan bioethanol dengan proses fermentasi. Penelitian ini bertujuan untuk membuat bioetanol dari buah naga merah dengan proses fermentasi serta mengetahui pengaruh variabel jumlah yeast dan jumlah nutrisi/NPK terhadap kadar bioetanol yang dihasilkan. Prosedur penelitian dimulai dengan menghaluskan daging buah naga merah sampai lembut. Kemudian menempatkan jus buah naga dalam fermentor sebanyak 300ml lalu melakukan analisa kadar glukosa awal. Tahap selanjutnya adalah penambahan yeast dan nutrisi/NPK sesuai variable yang telah ditentukan. Variabel kadar yeast sebanyak: 1%, 2%, 3%, 4%, dan 5% dari volume jus serta jumlah nutrisi/NPK sebanyak: 2 gr, 4 gr, 6 gr, 8 gr, dan 10 gr. Setelah penambahan yeast dan nutrisi, fermentor ditutup dengan penutup yang dilengkapi  airlock. Proses fermentasi dilakukan selama 4 hari. Selanjutnya jus buah naga hasil fermentasi dianalisa kadar alkoholnya. Dari hasil penelitian diperoleh bahwa kadar alkohol yang dihasilkan dipengaruhi oleh jumlah yeast dan jumlah nutrisi/NPK. kadar ethanol paling tinggi sebesar 26% dengan penambahan yeast sebanyak 15 gram serta nutrisi sebanyak 10 gram.

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