Baja ASTM A36 umum digunakan sebagai kerangka dan badan kapal, serta jembatan yang sering berkontak dengan larutan garam yang dapat menyebabkan korosi. Korosi adalah kerusakan bahan, biasanya logam, yang dihasilkan dari reaksi dengan lingkungannya. Untuk mencegah korosi maka dibutuhkan inhibitor korosi. Alternatif Inhibitor korosi yang murah dan ramah lingkungan dapat menggunakan inhibitor korosi organik alami. Korosi baja ASTM A36 dalam medium larutan garam NaCl 3% dapat dihambat dengan menggunakan ekstrak metanol daun Ashitaba (Angelica keiskei) karena kandungan metabolit sekundernya sebagai inhibitor korosi organik alami.Tujuan dari penelitian ini yaitu mendeskripsikan pengaruh penambahan konsentrasi inhibitor ekstrak metanol daun Ashitaba terhadap laju korosi pada baja ASTM A36, menjelaskan mekanisme penghambatan korosi oleh ekstrak metanol daun Ashitaba terhadap laju korosi pada baja ASTM A36, dan menentukan efisiensi inhibisi ekstrak metanol daun Ashitaba terhadap laju korosi pada baja ASTM A36. Metode penelitian uji korosi ini secara elektrokimia yaitu dengan polarisasi potensiodinamik dan Electrochemical Impedence Spectroscopy (EIS). Setelah itu, data hasil uji akan dianalisis secara statistika. Hasil penelitian ini yaitu penambahan ekstrak metanol daun Ashitaba berpengaruh terhadap laju korosi baja tipe ASTM A36 yaitu semakin tinggi konsentrasi ekstrak yang ditambahkan hingga titik optimum maka semakin rendah laju korosinya, mekanisme inhibisi korosi dengan cara adsropsi senyawa ekstrak pada permukaan material baja sehingga menghalangi transfer elektron dari Fe terhadap oksigen dan air, dan efisiensi inhibisi korosi dari ekstreak metanol daun Ashitaba yaitu 99,51670444 % pada konsentrasi ekstrak 2000 ppm dengan laju korosi terrendah adalah 0.024737 mm / years. Jenis inhibitor korosi dari ekstrak metanol daun Ashitaba yaitu inhibitor katodik organik alami dengan menggunakan prinsip adsorpsi isotermal jenis adsorpsi isotermal Langmuir.
Kata Kunci: Ashitaba, Baja ASTM A36, inhibitor korosi, ekstrak metanol, elektrokimia
ASTM A36 steel is commonly used as a frame and hull, as well as bridges that often contact with salt solutions that can cause corrosion. Corrosion is damage to materials, usually metals, that results from reactions with the environment. To prevent corrosion, corrosion inhibitors are needed. Alternative inexpensive and environmentally friendly corrosion inhibitors can use natural organic corrosion inhibitors. ASTM A36 steel corrosion in 3% NaCl salt solution medium could be inhibited by using methanol extract Ashitaba leaves (Angelica keiskei) because of secondary metabolites in them as natural organic corrosion inhibitors. The purpose of this study was to describe the effect of increasing the concentration of Ashitaba leaf methanol extract inhibitors on the corrosion rate of ASTM A36 steel, explained the corrosion inhibition mechanism of Ashitaba leaf methanol extract on the corrosion rate of ASTM A36 steel, and determined the efficiency of Ashitaba leaf methanol extract to corrosion rate on ASTM A36 steel. The research method for this corrosion test was electrochemically by using potentiodynamic polarization and Electrochemical Impedence Spectroscopy (EIS). After that, the data would be analyzed statistically. The results of this study were that there was the effect of adding methanol extract of Ashitaba leaves to corrosion rate of ASTM A36 steel, the higher of extract concentration added up until the optimum point, the lower of corrosion rate, the corrosion inhibition mechanism was the extract compound adsorbed on the surface of steel material and so it could prevent electron transfer from Fe to oxygen and water, and the corrosion inhibition efficiency of Ashitaba leaf methanol extract was 99.51670444% at an extract concentration was 2000 ppm with the lowest corrosion rate was 0.024737 mm / years. The type of corrosion inhibitor from Ashitaba leaf methanol extract was natural organic cathodic inhibitor using the principle of isothermal adsorption, with Langmuir isothermal adsorption type.
Keywords: Ashitaba, ASTM A36 Steel, corrosion inhibitor, methanol extract, electrochemical