Kulit buah manggis mengandung senyawa tanin yang cukup besar sehingga berpotensi sebagai inhibitor organik yang dapat mengahambat laju korosi. Tujuan dari penelitian ini adalah untuk mengetahui pengaruh penambahan inhibitor ekstrak kulit buah manggis terhadap laju korosi, dan untuk mengetahui efisiensi inhibitor ekstrak kulit buah manggis terhadap laju korosi pada material baja stainless steel - 304. Penelitian ini menggunakan metode pengujian laju korosi dan pengujian FTIR untuk mengetahui jenis senyawa yang terdapat pada inhibitor estrak kulit buah manggis dan spesimen stainless steel – 304. Penelitian ini menghasilkan nilai laju korosi pada perendaman selama 30 hari yaitu 130,256 mpy tanpa inhibitor, 121,690 mpy dengan penambahan inhibitor sebanyak 200 ppm dan 137,012 mpy dengan penambahan inhibitor sebanyak 400 ppm. Berdasarkan hasil tersebut diperoleh nilai efisiensi sebesar 6,576% dan (-5,187) %. Pada pengujian FTIR inhibitor estrak kulit buah manggis menghasilkan jenis senyawa utama yaitu senyawa Hydroxide, senyawa Methyl, senyawa β-amino ketones dan senyawa yang cukup lemah yaitu Satured acid chlorides sedangkan pada spesimen stainless steel – 304 menghasilkan jenis senyawa utama yaitu senyawa Hydroxide, senyawa Carboxlie acid, dan senyawa Cyano and nitrile complexes.

Kata Kunci: Inhibitor, Laju korosi, Pengujian FTIR, Stainless steel - 304.

Mangosteen peel contains a large adequate tannin compound that has the potential as an organic inhibitor that can inhibit the corrosion rate. The purpose of this study aims to determine the effect of the addition of mangosteen peel extract inhibitor on the corrosion rate, and to determine the efficiency of the mangosteen peel extract inhibitor on the corrosion rate of 304 stainless steel. This study used the corrosion rate test method and FTIR test to determine the type compounds contained in the inhibitors of mangosteen rind extract and 304 stainless steel specimens. This study yielded corrosion rate values for 30 days of immersion, namely 130.256 mpy without inhibitors, 121.690 mpy with the addition of 200 ppen inhibitor and 137.012 mpy with the addition of 400 ppm inhibitor. Based on these results, an efficiency value of 6.576% and (5.187) % was obtained. In the FTIR inhibitor test, the mangosteen peel extract produced the main types of compounds, namely Hydroxide compounds, Methyl compounds, ß-amino ketones compounds and relatively weak compounds, namely Saturated acid chlorides, while in the 304 stainless steel specimens, the main types of compounds were Hydroxide, Carboxylic acid, and Cyano and nitrile complexes compounds. Keywords: Inhibitor, Corrosion rate, FTIR Test, 304 Stainless steel