ABSTRAK
Inhibisi merupakan salah satu metode penghambatan laju korosi, salah satu jenis dari inhibitor adalah inhibitor organik yang memiliki sifat biodegradable sehingga bersifat lebih ramah lingkungandan relatif lebih murah dibandingkan inhibitor anorganik.Penelitian ini dilakukan untuk mempelajari perilaku inhibisi dari campuran ekstrak ubi ungu (Ipomea batatas) dan kunyit (Curcuma longa) pada pipa baja API-5L di lingkungan NaCl 3,5% dengan menggunakan metode kehilangan berat dan polarisasi. Dalam penelitian ini variasi kadar ekstrak ubi ungu dan kunyit yang dicampur berbanding terbalik. Efisiensi tertinggi ada pada kadar 16 mL ekstrak kunyit dan 2 mL ekstrak ubi ungu dengan efisiensi 82,54% sedangkan kadar optimal yang didapat adalah 8 mL ekstrak kunyit dan 6 mL ekstrak ubi ungu dengan efisiensi 74,2%.

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ABSTRACT
Inhibition is one of corrosion protection method, one kind of corrosion inhibitor is organic inhibitor which has biodegradable characteristic thus the inhibitor is environmental friendlier than conventional inorganic inhibitor. This research was done to study the inhibition activity of combination between purple sweet potato (Ipomea batatas) and turmeric (Curcuma longa) extract for API-5L steel pipe in NaCl 3,5% environment. Weight loss and polarization method were used to measure the inhibitor efficiency. In this study concentration variation between purple sweet potato extract and turmeric extract.It was found that the highest efficiency achieved by 16 mL turmeric extract and 2 mL purple sweet potato extract with 82.54% inhibitor efficiency while the optimum concentration achieved by 8 mL of turmeric extract and 6 mL purple sweet potato extract with 74.2% inhibitor efficiency.