Judul: The Optimization of Temperature and Voltage on  Thickness, Hardness, and Corrosion Rate of Hard Chrome Plating
Abstrak: Baja karbon AISI 1045 merupakan jenis baja karbon sedang yang banyak dimanfaatkan diberbagai bidang. Namun, kerentanan sifat logam terhadap korosi mendorong peningkatan kualitas sifat logam. Pelapisan hard chrome merupakan salah satu teknik perlindungan material yang memiliki banyak keunggulan. Selain memberikan perlindungan korosi, pelapisan hard chrome meningkatkan sifat kekerasan material yang berdampak pada meningkatnya ketahanan aus material. Tujuan penelitian ini adalah menentukan kondisi optimum suhu dan tegangan dalam proses pelapisan hard chrome terhadap kekerasan, ketebalan dan laju korosi sampel baja karbon AISI 1045. Pelapisan dilakukan dalam larutan hard chrome dengan kadar CrO3 282,56 g/L dengan ragam suhu, yaitu 45, 55, dan 65 °C serta ragam tegangan 6, 8, dan 12 V. Berdasarkan hasil pengamatan secara visual dan kuantitatif, kondisi optimum diperoleh pada suhu 55 °C tegangan 8 V dengan ketebalan 0,0041 cm, kekerasan 37 HRC, dan laju korosi 0,0412 mm/tahun., AISI 1045 carbon steel is medium carbon steel widely used in various fields. However, the metal susceptibility to corrosion encourages the increase in metal quality. Hard chrome plating is one of the material protection techniques which has a lot of advantages. It does not only protect against corrosion, but it also increases the hardness of material increase of material wear resistance. The study aimed to determine the optimum conditions of temperature and voltage in the hard chrome plating process on thickness, hardness, and corrosion rate of AISI 1045 carbon steel. The plating was conducted in a hard chrome solution containing CrO3 282,56 g/L with temperature variations of 45, 55, and 65 °C as well as voltage variations of 6, 8, and 12V. The result of visual and quantitative observation indicated that the optimum plating condition is obtained at a temperature of 55 °C voltage 8 V with a thickness of 0,0041 cm, hardness of 37 HRC, as well corrosion rate of 0,0412 mm/year.
Keyword: carbon steel 1045, hard chrome plating, optimum condition

Judul: Modifikasi Pelapisan Seng pada Baja dengan Chromating Trivalent menggunakan Bahan Organik Pereduksi
Abstrak: Baja merupakan logam yang banyak digunakan dalam industri perakitan dan konstruksi. Pelapisan seng pada baja diperlukan untuk memenuhi sifat fisik tahan korosi dan ketebalan yang sesuai kebutuhan industri. Perlakuan chromating pada proses pelapisan yang menggunakan kromium heksavalen dapat bersifat toksik sehingga harus direduksi menjadi kromium trivalen menggunakan bahan organik pereduksi. Penelitian ini bertujuan mengetahui pengaruh konsentrasi dan waktu pencelupan pada tahapan chromating terhadap laju korosi dan ketebalan lapisan seng pada baja. Penelitian dilakukan dalam larutan kromium dengan variasi konsentrasi 5; 10; 15 mL/L serta variasi waktu 10 dan 60 detik. Larutan kromium dibuat dari beberapa jenis sumber kromium yang berbeda, yaitu H2CrO4, Na2CrO4, K2Cr2O7. Ketebalan baja diukur dengan mikrometer sekrup digital dan pengukuran laju korosi menggunakan metode kehilangan berat. Hasil modifikasi terbaik ditunjukkan oleh spesimen yang dicelupkan pada larutan kromium trivalen 15 mL/L dari K2Cr2O7 dengan waktu 60 detik. Ketebalan yang dihasilkan adalah 0,0025 mm dengan laju korosi 0,0063 mm/tahun., Steel is a metal that is widely used in the manufacturing and construction industries. Zinc coating on steel is required to fulfill the physical properties of corrosion resistance and thickness suitable for industrial needs. The chromating treatment in the coating process using hexavalent chromium can be toxic, therefore it must be reduced to trivalent chromium by using reducing organic matter to avoid the negative impact. This study aims to determine the effect of concentration and immersion time in the chromating stage on the corrosion rate and the thickness of the zinc layer on the steel. This research was conducted in a chromium solution with concentration variation of 5; 10; 15 mL/L and time variations of 10 and 60 seconds. There are several chromium sources that used in this research, i.e H2CrO4, Na2CrO4, and K2Cr2O7. Thickness was measured with a digital screw micrometer and corrosion rate was measured using the weight loss method. The best modification results were shown by a specimen that was dipped in a 15 mL/L trivalent chromium solution of K2Cr2O7 for a time of 60 seconds. The resulting thickness is 0,0025 mm with a corrosion rate of 0,0063 mm/year.
Keyword: chromating, corrosion, steel, trivalent chrome, zinc plating

Judul: Zero-inflated negative binomial models in small area estimation.
Abstrak: The problem of over-dispersion in Poisson data is usually solved by introducing prior distributions which lead to negative binomial models. Poisson data sometime is also suffered by excess zero problems, a condition when data contains too many zero or exceeds the distribution's expectation. Zero Inflated Negative Binomial (ZINB) method can be utilized to solve such problems. This paper demonstrates the adaption of ZINB methods in Small Area Estimation with excess zero data. It is shown that the excess zero problem has substantially influenced the Empirical Bayes (EB) estimates, and the adaption of ZINB methods has improved the precision and reliability of the estimates. Key Words: Small Area Estimation, Zero-Inflation, Poisson-Gamma, Negative Binomial Regression, Empirical Bayes
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