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All Journal Journal of Materials Exploration and Findings Makara Journal of Science
Pragitta, Riene Kaelamanda
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Carbon dioxide-Induced Corrosion of AISI 4140 Steel in Acidified Artificial Geothermal Brine Anawati, Anawati; Izzat, Rayhan; Pragitta, Riene Kaelamanda; Hernandi, Rafli Ihsan
Makara Journal of Science Vol. 27, No. 1
Publisher : UI Scholars Hub

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Carbon dioxide (CO2)-induced corrosion often occurs in the structural materials of geothermal industry. The presence of CO2 influences the formation of various corrosion products. This research investigates the effect of dissolved CO2 in acidic brines on the corrosion behavior of AISI 4140 steel at atmospheric pressure. The brines were the standard brine, Ca-free brine, and high-salinity brine. The corrosion behavior was studied using electrochemical and immersion tests. A cyclic polarization test showed that the corrosion rate was higher in dissolved CO2 brine than in non-CO2 brine, and an immersion test demonstrated a similar result. In the absence of CO2, the presence of Ca ions in the brine reduced the corrosion rate of the alloy from 26.8 to 24.6 mmpy and further to 20.7 mmpy in the high-salinity brine. A similar trend was demonstrated during immersion in the CO2-containing brine, with higher rates of 37.1, 30.9, and 24.9 mmpy for the Ca-free, standard, and high-salinity brines, respectively. However, the Ca ions and high-salinity brines induced a more localized corrosion as pit and filiform. A surface analysis using an optical microscope revealed that immersion in CO2 brines generated 4–10-fold higher surface roughness than the non-CO2 brines. In all specimens, a protective layer was not established during the tests. No new phase was detected using X-Ray diffractometer after the immersion test. Moreover, no tendency of passivation was observed in the reverse scan of the cyclic polarization test.
Assessment of H2S-Induced Cracking Susceptibility in Steam Line Pipes and Weld Zones During Geothermal Well Construction Pragitta, Riene Kaelamanda; Pratesa, Yudha
Journal of Materials Exploration and Findings Vol. 4, No. 1
Publisher : UI Scholars Hub

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The susceptibility of steam line pipes, especially in the HAZ (heat-affected zone) and weldment areas, to hydrogen sulfide in the geothermal industry is crucial to understand from the early stages, particularly during construction. The combination of tensile stress from residual stresses after welding and metallurgical phase transformation makes the joint areas vulnerable to sulfide stress cracking. This condition becomes even more extreme when the equipment operates during the well stimulation phase. This research assesses the severity of H₂S-induced cracking using NACE MR0175 and ISO 15156-1 standards, focusing on the effects of pH and partial pressure of H₂S (pH₂S). The findings aim to provide insights into critical factors influencing H₂S cracking susceptibility and to enhance material integrity in geothermal systems. The result shows that while A106 Gr B steel generally meets sour service requirements, certain nodes within the geothermal facility exhibit a moderate risk of cracking under transient conditions. These results emphasize the importance of controlling fluid composition and implementing proper welding procedures to mitigate sulfide stress cracking (SSC).
Co-Authors Anawati, Anawati Hernandi, Rafli Ihsan Izzat, Rayhan Yudha Pratesa