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Abstrak :
Inhibition is one of the mechanisms used for mitigating the metallic corrosion, particularly in an acid environment. The present work aims to investigate the inhibiting effect of N-benzyl-N/-phenyl thiourea (BPTU) on the corrosion of low carbon steel in a 0.1 M hydrochloric acid (HCl) solution using a Tafel extrapolation and linear polarization techniques. The study reveals that BPTU acts as an excellent anodic inhibitor for low carbon steel in a HCl solution. The protective efficiency of the compound was found to be more than 97% even at higher temperatures. The study demonstrated that BPTU gets adsorbed on the steel surface, following Temkin?s adsorption isotherm and the inhibition is controlled by a chemisorption mechanism. The investigation shows that the results obtained from the Tafel extrapolation and linear polarization techniques for the corrosion of mild steel in HCl medium were in good agreement. The influence of temperatures and concentrations of BPTU on the corrosion of low carbon steel are also examined in the present work.

Abstrak :
Inhibition is one of the mechanisms used for mitigating the metallic corrosion, particularly in an acid environment. The present work aims to investigate the inhibiting effect of N-benzyl-N/-phenyl thiourea (BPTU) on the corrosion of low carbon steel in a 0.1 M hydrochloric acid (HCl) solution using a Tafel extrapolation and linear polarization techniques. The study reveals that BPTU acts as an excellent anodic inhibitor for low carbon steel in a HCl solution. The protective efficiency of the compound was found to be more than 97% even at higher temperatures. The study demonstrated that BPTU gets adsorbed on the steel surface, following Temkin’s adsorption isotherm and the inhibition is controlled by a chemisorption mechanism. The investigation shows that the results obtained from the Tafel extrapolation and linear polarization techniques for the corrosion of mild steel in HCl medium were in good agreement. The influence of temperatures and concentrations of BPTU on the corrosion of low carbon steel are also examined in the present work.

Abstrak :
Imidazolin merupakan senyawa heterosiklik yang telah banyak dikenal dalam industri perminyakan sebagai inhibitor korosi pada kilang minyak baja di perairan laut. Pada penelitian ini telah dilakukan sintesis senyawa turunan imidazolin menggunakan metode MAOS (Microwave Assisted Organic Synthesis) dengan mereaksikan tetraetilenpentamina (TEPA) dan asam oleat (AO) pada perbandingan ekivalen reaksi 1:1 membentuk imidazolin TEPA-AO dan 1:2 membentuk bis-imidazolin TEPA-AO dengan variasi waktu reaksi 7, 9, 11, dan 13 menit. Persen yield optimum senyawa imidazolin TEPA-AO diperoleh pada waktu sintesis 9 menit (82,62%) dan senyawa bis-imidazolin TEPA-AO pada 11 menit (88,56%). Kedua senyawa hasil sintesis kemudian dimurnikan dengan metode ekstraksi cair-cair dan dianalisis menggunakan kromatografi lapis tipis (KLT). Struktur kedua senyawa hasil sintesis telah dikonfirmasi berdasarkan data spektrum UV-Vis, FTIR, dan 1H-NMR. Penentuan aktivitas kedua senyawa hasil sintesis sebagai inhibitor korosi dilakukan pada baja karbon dalam larutan 1% NaCl dengan variasi konsentrasi (100, 200, 300, 400, dan 500 ppm) menggunakan metode polarisasi Tafel. Persen efisiensi inhibisi (%EI) tertinggi untuk kedua senyawa diperoleh pada penambahan konsentrasi 500 ppm berturut-turut sebesar 86,37% dan 89,70% untuk senyawa imidazolin TEPA-AO dan bis-imidazolin TEPA-AO. Untuk mengetahui mode inhibisi korosi pada baja karbon, ada tidaknya perubahan struktur senyawa setelah uji inhibisi korosi dianalisis menggunakan FTIR. Berdasarkan spektrum FTIR diperoleh bahwa masih terdapat puncak-puncak khas cincin senyawa imidazolin dan juga ditemukan perubahan struktur dari kedua senyawa hasil sintesis setelah dilakukan uji inhibisi korosi, sehingga dapat dikatakan mode inhibisi korosi dari kedua senyawa tersebut terjadi secara adsorpsi fisik dengan sedikit adsorpsi kimia. Dari penelitian ini dapat disimpulkan bahwa senyawa imidazolin TEPA-AO dan bis-imidazolin TEPA-AO dapat digunakan sebagai inhibitor korosi terhadap baja karbon dalam larutan 1% NaCl.

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Imidazoline is a heterocyclic compound which has been widely known in the oilfields industry as corrosion inhibitor for oil refineries in sea environment. In this research, imidazoline derivatives was successfully synthesized by reacting tetraethylenepentamine (TEPA) and oleic acid (OA) using MAOS (Microwave Assisted Organic Synthesis) method at equivalent ratio of 1:1 to yield TEPA-OA imidazoline and 1:2 to yield TEPA-OA bis-imidazoline in various reaction times (7, 9, 11, and 13 minuntes). The optimum yield of TEPA-OA imidazoline was obtained at 9 minutes reaction time (82.62%) and TEPA-OA bis-imidazoline at 11 minutes (88.56%). Both of synthesized compounds then was purified by liquid-liquid extraction method and analyzed by thin layer chromatography (TLC). The structure of all synthesized compounds was confirmed based on UV-Vis, FTIR, and 1H-NMR spectral data. Corrosion inhibition activity of all synthesized compounds was determined towards carbon steel in 1% NaCl solution with variation of imidazoline concentration (100, 200, 300, 400, and 500 ppm) using Tafel polarization method. The highest percentage of inhibition efficiency (%IE) was obtained at 500 ppm with 86.37% dan 89.70% for TEPA-OA imidazoline and TEPA-AO bis-imidazoline, respectively. To analyze corrosion inhibition mode towards carbon steel, the structure of synthesized compound after corrosion inhibition test was analyzed using FTIR. Based on FTIR spectra, the structure of both synthesized compounds still had imidazolines ring-peaks characteristics and were slightly altered after corrosion inhibition test, therefore corrosion inhibition mode of synthesized compounds were physic- and slightly chemisorption. From this research, it can be concluded that TEPA-OA imidazoline and TEPA-OA bis-imidazoline compounds can be used as a corrosion inhibitor towards carbon steel in 1% NaCl solution.

Abstrak :
Pada penelitian ini dilakukan studi terhadap molekul Catechin pada teh Putih (Camellia sinensis) sebagai inhibitor ramah lingkungan (IRL). Penggunaan metoda spektroskopi Elektrokimia Impedansi (EIS), Fourier transform infrared (FTIR) dan Raman, digunakan untuk mempelajari interaksi antara atom-atom/gugus fenol dengan lingkungannya. Sedangkan Scanning Electronic Microscope (SEM)/Energy X-Ray Dispersive (EDX) dan Atomic Force Microscope digunakan untuk mempelajari permukaan substrat. Selain itu, Wettability test digunakan untuk mempelajari sifat hidrofobik dari lapisan film pada permukaan logam. Data eksperimen akan dibandingkan dengan hasil kimia komputasi untuk mendapatkan prediksi efisiensi inhibisi dan orientasi molekul inhibitor. Untuk itu, digunakan metoda Density Functional Theory (DFT) dan Simulasi Monte Carlo. Hasil yang didapat yaitu pengukuran efisiensi inhibisi secara eksperimen dengan komputasi menunjukkan kesesuain. Hasil pemanasan larutan inhibitor pada suhu 25-600C menunjukkan bahwa inhibitor teradsorpsi lebih banyak pada suhu tinggi. Hasil karakterisasi gugus fungsi menunjukkan bahwa gugus -OH, C=O, Aril C=C, C-O-C teradsorpsi dari larutan inhibitor ke permukaan logam. Hal ini diperkuat dari hasil studi permukaan yang menunjukkan terjadinya pengurangan jumlah korosi sumuran dan menurunnya root mean square (RMS) height. Nilai fitting R2 mendekati 1 berkorelasi dengan Langmuir Isotherm Adsorption dan penambahan inhibitor mampu menurunkan energi aktifasi hingga 70%. Kenaikan suhu 600C dan konsentrasi hingga 80 ppm menyebabkan penurunan nilai laju korosi sebesar 0.016 mpy sedangkan nilai potensial passivasinya mengalami kenaikan hingga -103.7 mV. Sedangkan hasil prediksi komputasi menunjukkan molekul penyusun catechin terikat secara parallel pada bidang (110) atom besi dan memudahkan terjadinya ikatan kimia antara inhibitor dengan logam. Data pengujian dan hasil penelitian ini diharapkan dapat digunakan sebagai guideline pada penelitian di masa akan datang dalam hal pengembangan inhibitor ramah lingkungan baik secara eksperimen maupun pendekatan komputasi.

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This work covers the comprehensive studies on the catechin molecule in White tea (Camellia sinensis) as a green corrosion inhibitor. To achieve this aim, the spectroscopic technique such as Electrochemical Impedance (EIS), Fourier transform infrared (FTIR) and Raman was used to studying the interaction between the atom(s)/phenolic group and the environment. Surface analysis of Scanning Electronic Microscope (SEM)/Energy X-Ray Dispersive (EDX) and Atomic Force Microscope was used to study the surface of the substrate. A Wettability test was used to study the hydrophobic nature of pasif film on the surface of the metal. The experimental results will be compared to computational outcomes. The elevating temperatur at 25-600C extends a stable and thicker layer of the inhibitor. Several functional groups accountable to adsorption were -OH, C=O, Aryl C=C , and C-O-C. As a result, the reduction of pitting corrosion and root-mean-square height of the damaged surface. The fitting value of R2 close to 1 incorporates to Langmuir Isotherm Adsorption and decreases the activation energy of inhibition nearly to 70%. Rising temperatur and concentration at 600C and 80 ppm lowers the corrosion rate at 0.016 mpy and increases the passivation potential at -103.7 mV. The computational prediction on the catechin molecule shows that the molecule is oriented at the flat orientation of (110) surface and eases the formation of the Chemiadsorbed reaction. I expect our results are expected to provide a guideline to facilitate prospective research in White tea as a green corrosion inhibitor both experimentally and computationally.