Studi Eksperimental Pengaruh Variasi Pasangan Material Berbeda terhadap Perilaku Korosi Galvanik pada Turbin Uap Tekanan Rendah

Christofer, Andre Franklin (2026) Studi Eksperimental Pengaruh Variasi Pasangan Material Berbeda terhadap Perilaku Korosi Galvanik pada Turbin Uap Tekanan Rendah. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Turbin uap tekanan rendah (low-pressure steam turbine) merupakan komponen penting pada pembangkit listrik tenaga uap (PLTU) yang beroperasi pada kondisi basah dengan uap jenuh dan ion agresif seperti klorida, sehingga komponen logamnya terutama blade dan rotor disc rentan terhadap korosi galvanik akibat sambungan logam tak sejenis (dissimilar metals). Penelitian ini bertujuan menganalisis pengaruh variasi pasangan material berbeda dan temperatur terhadap perilaku korosi galvanik pada lingkungan yang menyerupai sistem turbin uap tekanan rendah. Pengujian dirancang menggunakan desain faktorial dua faktor (4 × 2) dimana faktor pertama berupa empat kombinasi pasangan material blade (17-4 PH dan ASTM A473 Gr 403) dengan rotor disc (AISI 4340 dan 34CrNi4Mo), dan faktor kedua berupa temperatur (25 °C dan 80 °C), masing-masing dengan tiga replikasi. Karakterisasi korosi dilakukan melalui pengujian open circuit potential (OCP), polarisasi linier, cyclic voltammetry, dan korosi galvanik dalam larutan NaCl, serta didukung analisis morfologi permukaan menggunakan Scanning Electron Microscope dan EDS (SEM/EDS). Data dianalisis secara statistik menggunakan ANOVA dua arah, uji lanjut Tukey HSD, dan fungsi desirability. Hasil penelitian menunjukkan bahwa temperatur merupakan faktor paling dominan dalam mempercepat korosi galvanik (p < 0,001), dengan laju korosi rata-rata meningkat hampir dua kali lipat dari 0,194 mm/year pada 25 °C menjadi 0,397 mm/year pada 80 °C. Variasi pasangan material juga berpengaruh signifikan (p = 0,034), sedangkan interaksi kedua faktor tidak signifikan. Pada setiap pasangan, material rotor disc berbasis baja paduan rendah berperan sebagai anoda dan terkorosi secara preferensial, yang dikonfirmasi oleh morfologi produk korosi pada permukaan anoda hasil SEM/EDS. Pasangan 17-4 PH–34CrNi4Mo menunjukkan ketahanan korosi galvanik terbaik dengan laju korosi terendah (0,254 mm/year; desirability = 1,000), sedangkan pasangan ASTM A473 Gr 403–34CrNi4Mo paling rentan (0,346 mm/year). Temuan ini menegaskan pentingnya pemilihan kombinasi material yang kompatibel secara galvanik serta pengendalian kondisi pada zona kondensasi untuk meningkatkan keandalan dan umur operasi komponen turbin uap tekanan rendah.
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The low-pressure steam turbine is a critical component in steam power plants, operating under wet conditions containing saturated steam and aggressive ions such as chlorides, which make its metallic components, particularly the blades and rotor discs, susceptible to galvanic corrosion arising from dissimilar-metal couples. This study analyzes the effect of different material pairings and temperature on galvanic corrosion behavior under conditions representative of a low-pressure steam turbine environment. A two-factor (4 × 2) factorial design was employed, the first factor comprised four blade–rotor disc pairings (blades of 17-4 PH and ASTM A473 Gr 403 coupled with rotor discs of AISI 4340 and 34CrNi4Mo), and the second factor was temperature (25 °C and 80 °C), each with three replicates. Corrosion behavior was characterized through open circuit potential (OCP), linear polarization, cyclic voltammetry, and galvanic corrosion testing in an NaCl solution, supported by surface morphology analysis using Scanning Electron Microscopy with EDS (SEM/EDS). The data were analyzed using two-way ANOVA, Tukey HSD post-hoc tests, and a desirability function. The results show that temperature is the most dominant factor accelerating galvanic corrosion (p < 0.001), with the mean corrosion rate nearly doubling from 0.194 mm/year at 25 °C to 0.397 mm/year at 80 °C. The material pairing also had a significant effect (p = 0.034), whereas their interaction was not significant. In every couple, the low-alloy-steel rotor disc acted as the anode and corroded preferentially, as supported by the corrosion product morphology observed on the anode surface under SEM/EDS. The 17-4 PH–34CrNi4Mo pair exhibited the best galvanic corrosion resistance with the lowest corrosion rate (0.254 mm/year; desirability = 1.000), while the ASTM A473 Gr 403–34CrNi4Mo pair was the most susceptible (0.346 mm/year). These findings underline the importance of selecting galvanically compatible material combinations and managing condensation-zone conditions to improve the reliability and service life of low-pressure steam turbine components.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	korosi galvanik, turbin uap tekanan rendah, stainless steel, baja paduan rendah, elektrokimia, galvanic corrosion, dissimilar metals, low-pressure steam turbine, low-alloy steel, electrochemistry
Subjects:	T Technology > TJ Mechanical engineering and machinery > TJ164 Power plants--Design and construction T Technology > TJ Mechanical engineering and machinery > TJ266 Turbines. Turbomachines (General) T Technology > TP Chemical technology > TP255 Electrochemistry, Industrial.
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21101-(S2) Master Thesis
Depositing User:	Andre Franklin Christofer
Date Deposited:	29 Jul 2026 08:00
Last Modified:	29 Jul 2026 08:00
URI:	http://repository.its.ac.id/id/eprint/139809

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