ABSTRAK
Penelitian ini dilakukan untuk menganalisa pengaruh inhibisi ekstrak cair daunBeluntas (Pluchea Indica Less.) terhadap korosi pada baja karbon rendah dilingkungan 3,5% NaCl. Penelitian dilakukan menggunakan pengujian weight loss,polarisasi, dan Fourier transform infrared spectroscopy (FTIR). Pengujian weightloss menunjukkan bahwa perendaman selama 9 hari dengan penambahan ekstraksebanyak 3 mL memberikan nilai rata-rata efisiensi paling maksimum sebesar75,97% dengan rata-rata laju korosi paling minimum sebesar 0,89 mpy. Pengujianpolarisasi menunjukkan terjadi pergeseran kurva ke arah anodik pada penambahanekstrak sebanyak 1,2,3 mL, dan bergeser ke arah katodik pada penambahansebanyak 4 mL. Penambahan ekstrak berpengaruh terhadap penurunan laju korosiyaitu dari 24,8 µA.cm-2 menjadi 5,04 µA.cm-2, sehingga memperkuat hasilpengujian weight loss bahwa ekstrak daun Beluntas dapat menghambat korosibaja karbon rendah di larutan 3,5% NaCl. Pengujian polarisasi menunjukkanbahwa ekstrak daun Beluntas memiliki tipe inhibisi campuran (mixed) dengankecenderungan lebih dominan kearah anodik berdasarkan nilai potensial korosiyang berubah secara acak. Pengujian FTIR menunjukkan bahwa estrak daunBeluntas teradsorpsi pada permukaan baja karbon rendah dan proses adsorpsinyaterjadi melalui gugus fungsi yang dimiliki ekstrak. Mekanisme adsorpsi ekstrakdaun Beluntas sesuai dengan Langmuir adsorption isotherm yang menunjukkanbahwa telah terjadi pembentukan lapisan monolayer di permukaan baja karbonrendah.

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ABSTRACT
The study was conducted to analyze the inhibition effect of Beluntas (Plucheaindica Less.) leaves extract on the corrosion of low carbon steel in 3.5% NaClenvironment. The study was invetigated by weight loss, polarization, and Fouriertransform infrared spectroscopy (FTIR) methods. Weight loss showed that soakingfor 9 days with the addition of 3 mL of the extract gave an average value of themaximum efficiency of 75.97% with an average of the minimum corrosion rate of0.89 mpy. Polarization shows the polarization curve shifts to the anodic directionin addition of 1,2,3 mL extract, and shifted toward the cathodic curve to theaddition of 4 mL. The presence of inhibitor causes decrease in the corrosion ratefrom 24.8 to 5.04 μA.cm-2, thus confirm the results of weight loss that Beluntasleaves extract can inhibit the corrosion of low carbon steel in 3.5% NaCl solution .The polarization showed that the Beluntas leaves extract acts through mixed modeof inhibition, as evident from the values of Ecorr, which do not increase or decreasein a regular manner from the blank value. FTIR showed that the Beluntas leavesextract adsorbed on the surface of low carbon steel and the process of adsorptionoccurs through a functional group extract. Beluntas leaves extract showsLangmuir adsorptions isotherm that indicated the monolayer formation on the lowcarbon steel surface.