Effectiveness of Red Dragon Fruit Peel Extract as an Eco-Friendly Corrosion Inhibitor for API 5L Steel

Mechanical Engineering Department, Faculty Engineering, Udayana University, Bali. Indonesia

^* Corresponding author: nyoman.budiarsa@unud.ac.id

Abstract

The development of organic or natural inhibitors is essential due to their cost-effectiveness and eco-friendliness. In this study, an organic inhibitor derived from red dragon fruit peel waste is employed. The material of interest is heat-treated API 5L Grade B steel. The research assesses the inhibitor’s efficiency in corrosive environments, namely 3.5‰ NaCl solution and pH 3 HCl solution, with varying inhibitor concentrations (5 ppm, 10 ppm, 15 ppm, 20 ppm). Using Tafel analysis and Electrochemical Impedance Spectroscopy (EIS), it is found that the addition of red dragon fruit peel extract substantially reduces the corrosion rate. The highest efficiency is observed in the 3.5‰ NaCl solution (62.4%) and pH 3 HCl solution (87.73%), accompanied by charge transfer resistances of 2.47 x 106 Ω and 1.79 x 103 Ω, respectively. Immersion tests reveal corrosion products, subsequently examined using X-ray Diffraction (XRD) to identify lepidocrocite phases in the 3.5‰ NaCl solution and magnetite phases in the pH 3 HCl solution. This research supports the development of environmentally friendly and effective natural corrosion inhibitors for protecting steel materials in corrosive conditions.