Studi Numerik Sistem Perlindungan Korosi Internal Menggunakan SACP Pada Bottom Plate Crude Oil Storage Tank Di PT. X

Siahaan, Rizky Monang Dewanto (2026) Studi Numerik Sistem Perlindungan Korosi Internal Menggunakan SACP Pada Bottom Plate Crude Oil Storage Tank Di PT. X. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Korosi internal pada bottom plate tangki penyimpanan minyak mentah dipicu oleh keberadaan lapisan water bottom yang berperan sebagai elektrolit agresif karena mengandung garam terlarut, sedimen, serta senyawa korosif, sehingga meningkatkan risiko terjadinya pitting dan under deposit corrosion. PT. X saat ini menerapkan proteksi katodik hanya pada sisi eksternal, sehingga diperlukan rancangan proteksi internal yang aman dan andal untuk memitigasi degradasi pada bottom plate. Metode Sacrificial Anode Cathodic Protection (SACP) dipilih karena tidak memerlukan sumber arus eksternal, meminimalkan risiko percikan api pada lingkungan hidrokarbon, serta sesuai untuk fluida dengan resistivitas sedang. Penelitian ini merancang sistem SACP internal pada bottom plate tangki minyak mentah PT. X dengan umur desain 10 tahun mengacu pada NACE RP 0169-92 dan DNV-RP-B401. Kebutuhan arus proteksi dihitung dengan mempertimbangkan coating breakdown factor (fc) 5% dan 10%, sehingga diperoleh rapat arus efektif (CDeff) masing-masing 0,002 A/m² dan 0,004 A/m² pada luas bottom plate 6163,953 m², dengan arus desain (Idesain) 12,328 A (fc 5%) dan 24,656 A (fc 10%). Variasi material anoda Al dan Zn dievaluasi berdasarkan kapasitas elektrokimia serta parameter geometrinya untuk menentukan jumlah anoda terpasang, yaitu 12 dan 20 buah untuk Al serta 38 dan 76 buah untuk Zn pada fc 5% dan 10%. Selanjutnya, konfigurasi anoda dan domain elektrolit water bottom dimodelkan pada COMSOL Multiphysics untuk mengevaluasi distribusi arus dan memvalidasi kecukupan arus melalui perbandingan arus simulasi (Isim) terhadap Idesain. Hasil simulasi menunjukkan seluruh variasi memenuhi kriteria kecukupan arus karena Isim berada di atas Idesain, yaitu 13,711 A vs 12,328 A (Al, fc 5%), 24,777 A vs 24,656 A (Al, fc 10%), 12,941 A vs 12,328 A (Zn, fc 5%), serta 25,876 A vs 24,656 A (Zn, fc 10%), sehingga tersedia margin konservatif. Evaluasi cakupan area terlindungi didefinisikan sebagai luas bottom plate dengan magnitudo rapat arus masuk minimal sama dengan CDeff menunjukkan cakupan 99,9–100% dari total luas, sehingga distribusi arus proteksi dinilai merata dan mencukupi. Dengan demikian, rancangan SACP internal yang diusulkan tervalidasi melalui kesesuaian Isim terhadap Idesain, memiliki umur efektif 10 tahun, dan layak dijadikan studi numerik di PT. X.
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Internal corrosion on the crude-oil storage tank bottom plate is triggered by the presence of a water-bottom layer that acts as an aggressive electrolyte because it contains dissolved salts, sediments, and corrosive compounds, thereby increasing the risk of pitting and under deposit corrosion. PT. X currently applies cathodic protection only on the external side; therefore, a safe and reliable internal protection design is required to mitigate degradation of the bottom plate. Sacrificial Anode Cathodic Protection (SACP) was selected because it does not require an external power source, minimizes the risk of sparking in a hydrocarbon environment, and is suitable for fluids with moderate resistivity. This study designs an internal SACP system for the crude-oil tank bottom plate of PT. X with a 10-year design life, referring to NACE RP 0169-92 and DNV-RP-B401. The required protection current was calculated by considering a coating breakdown factor (fc) of 5% and 10%, yielding effective current densities (CDeff) of 0.002 A/m² and 0.004 A/m², respectively, over a bottom-plate area of 6163.953 m², with design currents (Idesign) of 12.328 A (fc 5%) and 24.656 A (fc 10%). Aluminum (Al) and zinc (Zn) anode materials were evaluated based on electrochemical capacity and geometric parameters to determine the number of installed anodes, namely 12 and 20 units for Al and 38 and 76 units for Zn at fc 5% and 10%. Subsequently, the anode configuration and the water-bottom electrolyte domain were modeled in COMSOL Multiphysics to evaluate current distribution and validate current adequacy by comparing the simulated current (Isim) with Idesgin. The simulation results indicate that all variations satisfy the current adequacy criterion because Isim exceeds Idesign, namely 13.711 A vs 12.328 A (Al, fc 5%), 24.777 A vs 24.656 A (Al, fc 10%), 12.941 A vs 12.328 A (Zn, fc 5%), and 25.876 A vs 24.656 A (Zn, fc 10%), thus providing a conservative margin. The protected-area coverage, defined as the bottom-plate area where the magnitude of the incoming current density is at least equal to CDeff, shows a coverage of 99.9–100% of the total area, indicating that the protection-current distribution is uniform and sufficient. Therefore, the proposed internal SACP design is validated through the agreement of Isim with Idesign, has an effective service life of 10 years, and is suitable to serve as an numerical study for PT. X.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Korosi internal, SACP, Bottom plate, COMSOL Multiphysics, Internal corrosion, SACP
Subjects:	Q Science > QA Mathematics > QA141 Numeracy--Problems, exercises, etc. Q Science > QA Mathematics > QA431 Finite differences. Q Science > QD Chemistry > QD553 Electrochemistry. Electrolysis
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Material & Metallurgical Engineering > 28201-(S1) Undergraduate Thesis
Depositing User:	Rizky Monang Dewanto Siahaan
Date Deposited:	26 Jan 2026 09:51
Last Modified:	26 Jan 2026 09:51
URI:	http://repository.its.ac.id/id/eprint/130279

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