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Abstrak :
Korosi CO2 merupakan salah satu jenis korosi yang umum ditemukan pada industri geotermal dari hulu hingga hilir. Korosi CO2 memiliki karakteristik yang berbeda dari korosi akibat elektrolit pada umumnya. Hal ini karena CO2 dapat bereaksi dengan air dan menghasilkan asam karbonat (H2CO3) yang bersifat asam lemah dan dapat mempengaruhi kinetika korosi logam yang digunakan dalam sumur dan sistem perpipaan geotermal seperti baja AISI 4140. Peristiwa korosi di lingkungan CO2 belum banyak dibahas pada kondisi pH rendah, sebagai contoh pada saat dilakukan operasi acidizing sumur geotermal. Penelitian ini mengeksplorasi pengaruh CO2 terlarut dengan metode bubbling pada tekanan atmosfer terhadap perilaku korosi baja AISI 4140 dalam fluida geotermal artifisial dengan pH rendah. Fluida yang dimaksud terdiri atas KCl (5,960 g/L), NaCl (28,548 g/L), dan CaCl2 (2,664 g/L) yang disintesis berdasarkan modifikasi komposisi brine dari salah satu lapangan geotermal, lalu larutan diberi HCl (37%, 2 mL) dengan tujuan untuk menyimulasikan kondisi acidizing. Pengujian cyclic voltammetry (CV) menunjukkan bahwa penambahan CO2 pada larutan uji meningkatkan laju korosi hingga 25,62%, peristiwa ini dikonfirmasi hasil uji perendaman. Hal ini disebabkan oleh penurunan pH larutan setelah mengalami bubbling CO2. Lapisan protektif tidak terbentuk setelah pengujian CV, yang ditunjukkan dari adanya peningkatan arus korosi pada sweep ke-2 uji CV, dan didukung hasil karakterisasi XRD, di mana ditemukan lapisan produk korosi non-protektif setelah sampel terkorosi larutan uji non-CO2 maupun CO2, namun fasa nya tidak dapat diidentifikasi. Observasi dengan mikroskop optik menunjukkan bahwa sampel terkorosi secara seragam, dan densitas pori-pori sampel yang telah terkorosi larutan uji non-CO2 adalah 3,28 × 10-3 /μm2 , dan 3,64 × 10-3 /μm2 untuk larutan uji CO2. Ukuran pori-pori pada larutan non-CO2 dan CO2 tidak memiliki perbedaan median yang signifikan, menandakan tidak ada endapan produk korosi dalam pori-pori. ......CO2 corrosion is one of the types of corrosion commonly found in the geothermal industry. CO2 corrosion has a different characteristic from common electrolyte corrosion, this is due to the CO2 reacting with water which then generates carbonic acid (H2CO3), that is known to be a weak acid. The presence of H2CO3 could influence the corrosion kinetics of the AISI 4140 steel. The CO2 corrosion phenomenon has not been extensively observed under acidic brine condition, for instance on acidizing operations carried on geothermal wells. This research is aimed to explore influence of dissolved CO2 presence in acidic brine to the corrosion behavior of AISI 4140 steel utilized in geothermal wells and piping system at atmospheric pressure. The brine consists of KCl (5,960 g/L), NaCl (28,548 g/L), and CaCl2 (2,664 g/L) that was synthetized in reference to a geothermal brine and 2 mL of 37% HCl were added to simulate the acidizing condition. The cyclic voltammetry (CV) test shows that the CO2 brine has greater corrosion rate by 25.62% compared with the non-CO2 brine. The increase of corrosion rate by adding CO2 to the brine has been confirmed by the immersion test, that shows similar result, due to pH reduction after CO2 bubbling. The protective layer has not been established throughout the CV test for both non-CO2 and CO2 brines, which is evident by the result of the secondsweep of the CV test that has an increased corrosion current density, and also confirmed by the XRD characterization that shows a formation of corrosion product but could not identify the phase. The obeservation through optical microscope suggested that both nonCO2 and CO2 brines had caused uniform corrosion and generates pores with the density of 3.28 × 10-3 /μm2 for non-CO2 brine and had increased to 3.64 × 10-3 /μm2 for the CO2 brine. The pore size difference of the corroded steel on by both non-CO2 and CO2 brine are insignificant, indicating that no corrosion product is accumulated within the pores.

Abstrak :
Korosi yang disebabkan oleh karbondioksida (CO2) pada pipa baja karbon dan peralatan di pengolahan minyak dan gas sangat umum terjadi. CO2 larut dalam air menghasilkan asam karbonat (H2CO3) yang mempunyai sifat yang lebih korosif dibanding asam klorida (HCL) pada pH yang sama. Electrochemical impedance spectroscopy dan linear polarization resistance digunakan untuk mengetahui fenomena proses yang terjadi selama proses adsorbsi inhibitor di permukaan logam. Variasi temperature dan konsentrasi dari inhibitor dilakukan untuk mengetahui kemampuan inhibisi inhibitor dan mekanisme inhibisi. Penelitian ini dilakukan pada baja karbon A106 grB di dalam lingkungan 3% NaCl. Konsentrasi inhibitor bervariasi dari 0,5,15, dan 40 ppm dan dengan variasi temperature di 40 0C dan 90 0C. Pada temperature 40 0C laju korosi menunjukan 213,9 MPY pada lingkungan tanpa penambahan inhibitor , dan akan turun drastis ke 22,4 MPY ketika 5 ppm inhibitor ditambahkan ke lingkungan, dengan effisiensi inhibisi 90%. Penambahan konsentrasi inhibitor sampai 40 ppm meningkatkan effisiensi inhibisi sampai 98%. Penambahan konsentrasi inhibitor berbasis Imidazoline dari dari 0 ppm sampai 5 ppm pada temperature 90 0C dapat menghasilkan penurunan laju korosi yang signifikan yaitu dari 173,3 MPY menjadi 31,67 MPY, dengan effisiensi inhibisi 82%. Dengan penambahan konsentrasi inhibitor sebanyak 40 ppm akan menaikan effisiensi inhibisi sampai 99,99 %. Mekanisme penghambatan laju korosi terjadi sebagai akibat terbentuknya ikatan polar (O-H dan N-H) yang berikatan dengan permukaan logam melalui proses chemisorption.

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Corrosion caused by carbon dioxide (CO2) in carbon steel pipes and equipment in oil and gas processing is very common. Water soluble CO2 produces carbonic acid (H2CO3) which has more corrosive properties than hydrochloric acid (HCL) at the same pH. Electrochemical impedance spectroscopy and linear polarization resistance are used to determine the processes that occur during the adsorbs inhibitor process on the metal surface. Variation of concentration of the inhibitor is conducted to determine the ability of inhibitor inhibition and inhibition mechanism. This research was conducted on A106 gr. B carbon steel in an environment of 3% NaCl. The inhibitor concentration varies from 0,5,15, and 40 ppm at 40 0C. At temperatures of 400C the corrosion rate shows 213.9 MPY in the environment without the addition of inhibitors, and will drop dramatically to 22.4 MPY when 5 ppm inhibitors are added to the environment. Electrochemical Impedance Spectroscopy is used to study inhibition mechanism. Increasing the concentration of Imidazoline based inhibitors from 0 ppm to 5 ppm at 90 0C can produce a significant decrease in corrosion rate from 173.3 MPY to 31.67 MPY, with 82% inhibition efficiency. With the addition of inhibitor concentrations up to 40 ppm will increase inhibition efficiency to 99,99 %. The mechanism of inhibition of corrosion rate occurs as a result of the formation of polar bonds (O-H and N-H) that bind to the metal surface through a chemisorption process.

Abstrak :
[ABSTRAK
Korosi memiliki dampak yang sangat besar terhadap ekonomi dan lingkungan pada berbagai infrastruktur, terkait dengan kegagalan operasi dan aset. Masalah yang umum terjadi pada jaringan pipa minyak dan gas saat ini adalah korosi internal yang disebabkan oleh media korosif yang umumnya mengandung karbon dioksida (CO2) dalam larutan aqueous. Karenanya, diperlukan cara untuk mengevaluasi korosi CO2 pada baja karbon terkait laju korosi agar dapat memenuhi umur operasi. Dalam penelitian ini, model Norsok yang telah dimodifikasi digunakan untuk memprediksi laju korosi pada lingkungan CO2, dan mempertimbangkan data parameter seperti suhu, tekanan parsial CO2, dan laju aliran untuk menghitung shear stress dan laju korosi. Software ini dibuat dengan menggunakan bahasa pemrograman visual basic (Microsoft Visual Studio ? VB), kemudian dengan menggabungkan basis pengetahuan mekanisme korosi CO2 dan aturan tertentu maka akan dihasilkan suatu sistem pakar. Berdasarkan perhitungan shear stress dan laju koros, kemudian rekomendasi dapat diajukan untuk mempertimbangkan, apakah baja karbon masih dapat digunakan atau penggunaan baja karbon dengan memberikan inhibitor atau penggantian baja karbon dengan Corrosion Resistance Alloys. Hasil perhitungan modifikasi model Norsok menunjukkan bahwa hasil perhitungan laju korosi tampak lebih realistis dibandingkan dengan model Norsok asli, dan dapat digunakan untuk mengevaluasi baja karbon yang mengalami korosi CO2 dengan tingkat kepercayaan lebih tinggi.

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ABSTRACT
Corrosion has a great detrimental effect to economy and environment in almost all infrastructures, in regards of operations shutdown and asset facilities failure. A common problem in oil and gas process piping and transport pipeline nowadays is internal corrosion caused by corrosive media containing mainly carbon dioxide (CO2) in aqueous solutions. Therefore, there is a need to evaluate CO2 corrosion of carbon steel in terms of corrosion rate in order to meet its life expectancy in such environment. In this paper, a modified Norsok model was used to predict corrosion rate in CO2 environment, and consider typical data parameter used such as temperature, CO2 partial pressure, and flow rate or fluid velocity to calculate shear stress and corrosion rate. By combining knowledge base related to CO2 corrosion mechanism and its logic algorithm with certain rules resulted in such expert system which utilize visual basic (Microsoft Visual Studio-VB) programming language to develope a software. Based on calculated shear stress and corrosion rate, then recommendations can be proposed whether carbon steel still can be used or carbon steel with inhibitor injection or carbon steel replaced by Corrosion Resistance Alloys. The modified Norsok calculation model results show that the calculated corrosion rates are likely more realistic compared to the original Norsok model, and can be used to evaluate carbon steel which suffered CO2 corrosion with highly confident.;Corrosion has a great detrimental effect to economy and environment in almost all infrastructures, in regards of operations shutdown and asset facilities failure. A common problem in oil and gas process piping and transport pipeline nowadays is internal corrosion caused by corrosive media containing mainly carbon dioxide (CO2) in aqueous solutions. Therefore, there is a need to evaluate CO2 corrosion of carbon steel in terms of corrosion rate in order to meet its life expectancy in such environment. In this paper, a modified Norsok model was used to predict corrosion rate in CO2 environment, and consider typical data parameter used such as temperature, CO2 partial pressure, and flow rate or fluid velocity to calculate shear stress and corrosion rate. By combining knowledge base related to CO2 corrosion mechanism and its logic algorithm with certain rules resulted in such expert system which utilize visual basic (Microsoft Visual Studio-VB) programming language to develope a software. Based on calculated shear stress and corrosion rate, then recommendations can be proposed whether carbon steel still can be used or carbon steel with inhibitor injection or carbon steel replaced by Corrosion Resistance Alloys. The modified Norsok calculation model results show that the calculated corrosion rates are likely more realistic compared to the original Norsok model, and can be used to evaluate carbon steel which suffered CO2 corrosion with highly confident., Corrosion has a great detrimental effect to economy and environment in almost all infrastructures, in regards of operations shutdown and asset facilities failure. A common problem in oil and gas process piping and transport pipeline nowadays is internal corrosion caused by corrosive media containing mainly carbon dioxide (CO2) in aqueous solutions. Therefore, there is a need to evaluate CO2 corrosion of carbon steel in terms of corrosion rate in order to meet its life expectancy in such environment. In this paper, a modified Norsok model was used to predict corrosion rate in CO2 environment, and consider typical data parameter used such as temperature, CO2 partial pressure, and flow rate or fluid velocity to calculate shear stress and corrosion rate. By combining knowledge base related to CO2 corrosion mechanism and its logic algorithm with certain rules resulted in such expert system which utilize visual basic (Microsoft Visual Studio-VB) programming language to develope a software. Based on calculated shear stress and corrosion rate, then recommendations can be proposed whether carbon steel still can be used or carbon steel with inhibitor injection or carbon steel replaced by Corrosion Resistance Alloys. The modified Norsok calculation model results show that the calculated corrosion rates are likely more realistic compared to the original Norsok model, and can be used to evaluate carbon steel which suffered CO2 corrosion with highly confident.]