Muhtadi, Handi (2019) Pengaruh Perubahan pH dalam 9 wt. % NaCl akibat Penambahan Asam Sitrat Terhadap Perilaku Korosi Baja Karbon Rendah dan Austenitic Stainless Steel 316L. Other thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Asam sitrat merupakan senyawa yang kerap digunakan dalam industri makanan minuman dalam kemasan dan berbagai produk sanitasi. Asam sitrat digunakan dengan berbagai konsentrasi yang berbeda dalam larutan yang berbeda pula. Asam sitrat dapat digunakan bersamaan dengan berbagai larutan, misalnya garam dapur (NaCl). Penambahan asam sitrat merubah nilai pH dari larutan dan merubah perilaku korosi material secara berbeda. Baja karbon rendah dan austenitic stainless steel yang merupakan material yang kerap digunakan pada permesinan industri tidak lepas dari serangan korosi dari larutan yang telah dicampur dengan asam sitrat. Penelitian ini dilakukan untuk mengetahui pengaruh perubahan pH dalam 9 wt. % NaCl yang terlarut dalam air akibat penambahan asam sitrat terhadap perilaku korosi dari baja karbon rendah dan austenitic stainless steel 316L. Perilaku korosi baja karbon rendah dan austenitic stainless steel diuji dengan dua metode yaitu hilang massa dan pengukuran polarisasi. Pengujian hilang massa untuk kedua material dilakukan dengan variasi nilai pH 2, pH 4, dan pH 7. Setiap variasi diuji dengan tiga replikasi secara bersamaan dalam satu larutan yang sama. Baja karbon rendah diuji dalam metode hilang massa selama dua jam, sedangkan austenitic stainless steel direndam selama dua belas jam. Perendaman dilakukan sebanyak lima kali untuk mengamati pengaruh perulangan penggunaan. Pengukuran polarisasi baja karbon rendah dilakukan dalam larutan pH 2, pH 4, dan pH 7 dengan rentang potensial ±0.1 V dari Open Circuit Potential. Laju penambahan potensial selama pengujian ini sebesar 1 mV/detik. Pengukuran polarisasi austenitic stainless steel dilakukan dalam larutan pH 2, pH 3, pH 4, pH 5, pH 6, dan pH 7. Austenitic stainless steel dipolarisasi dengan rentang antara -0.4 V hingga +0.6 V dari Open Circuit Potential. Laju penambahan potensial polarisasi selama pengujian ini sebesar 1 mV/detik. Dari pengukuran polarisasi didapatkan kurva nilai polarisasi sebagai fungsi logaritmik arus. Ekstrapolasi Tafel dilakukan untuk menentukan nilai potensial korosi (Ecorr), arus korosi (Icorr), dan laju korosi. Hasil penelitian menunjukkan laju korosi baja karbon rendah semakin tinggi seiring menurunnya nilai pH. Korosi menyerang baja karbon rendah secara merata pada seluruh permukaan. Pada pH 2 tampak laju korosi baja karbon rendah sangat dipengaruhi oleh kekasaran permukaan. Hasil pengujian untuk austenitic stainless steel menunjukkan bahwa risiko korosi akibat pitting lebih mengancam dibanding serangan korosi secara umum. Stainless steel 316L terserang pitting paling parah pada pH 7 dibanding variasi pH lainnya. Tidak ditemukan indikasi terbentuknya lapisan pasif pada permukaan pada pH 7. Penambahan asam sitrat hingga pH 4 menurunkan serangan korosi pada stainless steel. Tampak ada pergeseran sifat elektrokimia dari aktif menjadi pasif pada pH 4. Baik pada pH 4 dan pH 7 tidak ditemukan adanya korosi general yang terjadi. Pada pH 2 perilaku korosi yang terjadi menyerupai korosi general dan tidak tampak adanya pembentukan pitting.
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Citric acid is a versatile organic complex often used as an additive in sanitation, food and beverages industries. Citric acid in the industries is mixed in many different kind of solution mixtures with wide range of concentration. One of the most often solution used along citric acid is NaCl. The addition of citric acid in solution, however, change the pH level of the solution and bring about different corrosion behaviour from the material. Low carbon steel and austenitic stainless steel is one of the most widely used alloys in industries is also affected by this pH level changes. This study is then conducted to illuminate how pH level change resulted from addition of citric acid influence the corrosion behaviour of low carbon steel and stainless steel 316L. Corrosion behaviour of these alloys is studied through two different methods, which are immersion test and polarization measurement. Immersion was conducted by directly observing the loss of mass that became apparent as the materials is exposed to corrosive environment. The environment of the test is conditioned as the working environment of the alloys. Both alloys is immersed in three different pH level, which are pH 2, pH 4, and pH 7. For each solutions there were triplicate specimens immersed paralelly in the exact same solutions. The low carbon steel is immersed for 2 hours and the stainless steel 316 L is immersed for 12 hours. The latter method is performed by observing the electrochemical properties of the alloys to determine the behaviour of the corrosion system in a rather short time. The low carbon steel is polarized from -0.1 V to +0.1 V of its respective open circuit potential. The austenitic stainless steel 316 L is polarized with wider range of voltage, ranging from -0.4 V to + 0.6 V of its open circuit potential. The experiment result shown that the corrosion rate of the low carbon steel alloys increased as the pH value decreased. Corrosion will attack the low carbon steel specimens uniformly at any site in all the pH level tested. In pH 2 the roughness of the surface is greatly affect the corrosion rate. The corrosion attack on austenitic stainless steel 316L is dominated by pitting at pH 7 and pH 4. There most severe pitting attack is found in pH 7. There were no passive region apparent in the polarization curve of the stainless steel in pH 7. At pH 2 the corrosion will attack with the form almost just like general corrosion. The passive region of the stainless steel in pH 2 has increasing value of current density as polarization increased, shown that the passive layer is not in passive state and still reacted with the solutions.
| Item Type: | Thesis (Other) |
|---|---|
| Uncontrolled Keywords: | citric acid, austenitic stainless steel 316L, low carbon steel, mass loss, corrosion, polarization, pitting |
| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) > TA418.74 Corrosion and anti-corrosives |
| Divisions: | Faculty of Industrial Technology > Mechanical Engineering > 21201-(S1) Undergraduate Thesis |
| Depositing User: | Handi Muhtadi |
| Date Deposited: | 21 Jul 2026 04:43 |
| Last Modified: | 21 Jul 2026 04:43 |
| URI: | http://repository.its.ac.id/id/eprint/68284 |
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