Electronic Theses and Dissertation

Korosi merupakan kerusakan material logam akibat reaksi kimia atau elektrokimia
dengan lingkungan yang menimbulkan kerugian ekonomi signifikan, sehingga
diperlukan metode pengendalian yang efektif dan ramah lingkungan melalui
penggunaan inhibitor alami. Penelitian ini bertujuan untuk menganalisis
kemampuan ekstrak daun temiki (Melastoma candidum) sebagai inhibitor organik
dalam menghambat laju korosi baja karbon dalam medium NaCl 3,5% dengan
meninjau pengaruh variasi konsentrasi (0, 200, 400, 600, 800, dan 1000 ppm) dan
temperatur (25, 35, 45, dan 55°C). Hasil karakterisasi Fourier Transfer Infrared
Spectroscopy (FTIR) mengkonfirmasi keberadaan gugus fungsi hidroksil, karbonil,
dan aromatik yang berasal dari senyawa aktif tanin, saponin, dan fenolik yang
berperan dalam pembentukan lapisan pelindung pada permukaan logam.
Berdasarkan pengujian kehilangan berat (weight loss), efisiensi inhibitor
menunjukkan nilai optimal pada rentang waktu menengah dengan efisiensi tertinggi
mencapai 88,24% pada konsentrasi 1000 ppm setelah perendaman 216 jam.
Sementara itu, hasil potensiodinamik polarisasi (PDP) menunjukkan efisiensi
tertinggi sebesar 83,88% pada konsentrasi 1000 ppm dan mengklasifikasikan
ekstrak ini sebagai inhibitor tipe campuran (mixed-type inhibitor) karena
pergerakan Ecorr berada di bawah ambang batas 85 mV. Analisis isoterm adsorpsi
menunjukkan mekanisme inhibisi paling sesuai dengan model isotherm Frumkin
(R2 = 0,97) dengan nilai energi bebas Gibbs (ΔGads) sebesar -19,57 kJ/mol yang
mengindikasikan proses adsorpsi berlangsung secara spontan melalui fisisorpsi,
oleh gaya-gaya lemah seperti ikatan hidrogen dan interaksi van der waals. Analisis
morfologi melalui Scanning Electron Microscopy (SEM) membuktikan secara
visual bahwa penambahan inhibitor mampu membentuk lapisan pelindung merata
yang melindungi permukaan baja dari serangan ion klorida.

Corrosion is the degradation of metallic materials due to chemical or electrochemical reactions with the environment, leading to significant economic losses; therefore, effective and environmentally friendly control methods are required through the use of natural inhibitors. This study aims to analyze the capability of temiki leaf extract (Melastoma candidum) as an organic inhibitor in reducing the corrosion rate of carbon steel in a 3.5% NaCl medium by examining the effects of concentration variations (0, 200, 400, 600, 800, and 1000 ppm) and temperature (25, 35, 45, and 55°C). Fourier Transform Infrared Spectroscopy (FTIR) characterization confirmed the presence of hydroxyl, carbonyl, and aromatic functional groups derived from active compounds such as tannins, saponins, and phenolics, which contribute to the formation of a protective layer on the metal surface. Based on weight loss testing, the inhibitor efficiency showed optimal performance at intermediate exposure times, with the highest efficiency reaching 88.24% at a concentration of 1000 ppm after 216 hours of immersion. Meanwhile, potentiodynamic polarization (PDP) results indicated a maximum efficiency of 83.88% at 1000 ppm and classified the extract as a mixed-type inhibitor, as the Ecorr shift was below the 85 mV threshold. Adsorption isotherm analysis revealed that the inhibition mechanism best fits the Frumkin isotherm model (R² = 0.97), with a Gibbs free energy of adsorption (ΔGads) of −19.57 kJ/mol, indicating a spontaneous adsorption process dominated by physisorption through weak interactions such as hydrogen bonding and van der Waals forces. Morphological analysis using Scanning Electron Microscopy (SEM) visually confirmed that the addition of the inhibitor forms a uniform protective layer that effectively shields the steel surface from chloride ion attack.