Studi Eksperimental dan Komputasional Inhibisi Korosi Baja ASTM A36 Menggunakan Ekstrak Ampas Kopi Robusta (Coffea canephora) dalam Media HCl 1 M

Ramadani, Noer Fitria (2026) Studi Eksperimental dan Komputasional Inhibisi Korosi Baja ASTM A36 Menggunakan Ekstrak Ampas Kopi Robusta (Coffea canephora) dalam Media HCl 1 M. Diploma thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Korosi pada baja karbon rendah ASTM A36 dalam lingkungan asam dapat menurunkan kualitas dan umur pakai material. Salah satu metode pengendalian korosi yang dikembangkan adalah penggunaan green inhibitor berbasis bahan alami yang lebih ramah lingkungan. Penelitian ini bertujuan menganalisis kemampuan ekstrak ampas kopi robusta (Coffea canephora) sebagai inhibitor organik korosi pada baja ASTM A36 dalam media HCl 1 M melalui pendekatan eksperimental dan komputasional, dengan variasi konsentrasi inhibitor 0–5 mL/L. Identifikasi senyawa menggunakan GC-MS menunjukkan tiga senyawa dominan, yaitu kafein (73,27%), 2,3-dihidroksisikloheksanon (18,60%), dan 5-hidroksisiklooktana-1,2-dion (2,30%), yang selanjutnya dianalisis melalui studi komputasional Density Functional Theory (DFT) dan menunjukkan nilai energy gap (ΔE) rendah (1,785–2,909 eV) serta fraksi transfer elektron (ΔN) negatif, menunjukkan mekanisme back-donation elektron pada permukaan logam. Hasil pengujian Potentiodynamic Polarization (PDP) menunjukkan penurunan laju korosi dari 9,3569 mmpy menjadi 3,7592 mmpy dengan efisiensi inhibisi tertinggi 59,82% pada konsentrasi 5 mL/L, sedangkan Electrochemical Impedance Spectroscopy (EIS) menunjukkan peningkatan polarization resistance (Rp) dari 115,21 Ω menjadi 423,35 Ω dengan efisiensi inhibisi hingga 72,79%. Hasil pengujian weight loss memvalidasi temuan tersebut dengan efisiensi inhibisi 51,66%. Berdasarkan nilai pergeseran potensial korosi (ΔEcorr < 85 mV), ekstrak dikategorikan sebagai mixed-type inhibitor. Studi isoterm adsorpsi menunjukkan kesesuaian terbaik dengan model Langmuir (R² = 0,98394) dengan energi bebas Gibbs adsorpsi (ΔG°ads) sebesar −22,26 kJ/mol, menunjukkan mekanisme adsorpsi campuran (fisisorpsi dan kemisorpsi). Karakterisasi permukaan pada konsentrasi optimum melalui SEM dan AFM menunjukkan permukaan baja yang lebih homogen dengan penurunan parameter kekasaran (Sa dari 33,2 nm menjadi 18,1 nm; Sq dari 42,0 nm menjadi 23,9 nm). Hasil penelitian ini membuktikan bahwa ekstrak ampas kopi robusta berpotensi sebagai green corrosion inhibitor yang efektif bagi baja ASTM A36 dalam media HCl 1 M.
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Corrosion of ASTM A36 low carbon steel in acidic environments can reduce material quality and service life. One corrosion control method that has been widely developed is the use of environmentally friendly green inhibitors derived from natural materials. This study aims to analyze the ability of robusta coffee grounds extract (Coffea canephora) as an organic corrosion inhibitor for ASTM A36 steel in 1 M HCl medium through experimental and computational approaches, using inhibitor concentrations ranging from 0 to 5 mL/L. Compound identification using GC-MS revealed three dominant compounds, namely caffeine (73.27%), 2,3-dihydroxycyclohexanone (18.60%), and 5-hydroxycyclooctane-1,2-dione (2.30%), which were further analyzed through Density Functional Theory (DFT) computational studies, showing low energy gap (ΔE) values (1.785–2.909 eV) and negative electron transfer fractions (ΔN), indicating an electron back-donation mechanism at the metal surface. Potentiodynamic Polarization (PDP) testing showed a decrease in corrosion rate from 9.3569 mmpy to 3.7592 mmpy, with a maximum inhibition efficiency of 59.82% at 5 mL/L, while Electrochemical Impedance Spectroscopy (EIS) showed an increase in polarization resistance (Rp) from 115.21 Ω to 423.35 Ω, with inhibition efficiency reaching 72.79%. Weight loss testing validated these findings with an inhibition efficiency of 51.66%. Based on the corrosion potential shift (ΔEcorr < 85 mV), the extract was classified as a mixed-type inhibitor. Adsorption isotherm studies showed the best fit with the Langmuir model (R² = 0.98394), with a Gibbs free energy of adsorption (ΔG°ads) of −22.26 kJ/mol, indicating a mixed adsorption mechanism (physisorption and chemisorption). Surface characterization at the optimum concentration using SEM and AFM revealed a more homogeneous steel surface with reduced roughness parameters (Sa decreased from 33.2 nm to 18.1 nm; Sq from 42.0 nm to 23.9 nm). These findings demonstrate that robusta coffee grounds extract has strong potential as an effective green corrosion inhibitor for ASTM A36 steel in 1 M HCl medium.

Item Type:	Thesis (Diploma)
Uncontrolled Keywords:	Korosi, Inhibitor Organik, Ampas Kopi Robusta, ASTM A36, HCl 1 M, Corrosion, Green Inhibitor, Robusta Coffee Grounds, ASTM A36, 1 M HCl
Subjects:	Q Science > QD Chemistry > QD115 Electrochemical analysis
Divisions:	Faculty of Vocational > Mechanical Industrial Engineering (D4)
Depositing User:	Noer Fitria Ramadani
Date Deposited:	24 Jul 2026 07:50
Last Modified:	24 Jul 2026 07:50
URI:	http://repository.its.ac.id/id/eprint/137305

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