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Abstract. The corrosion behavior of mild steel in seawater was investigated using an immersion test and energy-dispersive X-ray spectroscopy in solutions from the sites of Muara Baru, Suramadu and Tol Mandara. As reference, solutions of 3.5% and 5% NaCl were prepared. Dissolved oxygen, salinity, conductivity, and total dissolved solids (TDS) were measured. It was found that uniform corrosion occurred on the mild steel during the immersion test. The corrosion resistance of the steel decreased with increasing exposure time. Since the magnitudes of conductivity, salinity and TDS of all test solutions were similar, it was concluded that dissolved oxygen (DO) and chloride ions play an essential role in inducing the corrosion risk of mild steel. Both parameters hinder the formation of a stable passive film on the surface of corroded mild steel.

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This work covers the effectiveness of the White tea extract as a green corrosion inhibitor and is correlated to the strength and stability bonding between the phenolic molecule and the Fe atoms in mild steel and how this interaction can be studied by altering the concentration and temperature. White tea has received considerable attention due to its capability as a corrosion inhibitor and has been extensively studied using electrochemical techniques. However, accurate and systematic functional group identification and surface modification have been missing. Our study sought to demonstrate the quantitative measurement of electrochemical impedance spectroscopy (EIS) complemented by the FTIR (Fourier transform infrared spectroscopy), Total Phenolic Test, and Raman Spectroscopy. The SEM (Scanning Electronic Microscope)/EDX (Energy-Dispersive X-Ray Spectroscopy), and AFM (Atomic Force Microscope) were used to study the surface modification. The EIS results show that the optimum inhibition efficiency was 96 % in a solution of 80 ppm at 60 °C. Acetone 70 % was used to extract White tea and gives 14.17±0.25 % phenolic compound. Spectroscopic studies show -OH, Aromatic C=C, C=O and C-O-C become major contributors in the adsorption process and are found on the surface of metals as corrosion protection. Meanwhile, the thermodynamic calculation shows the White tea was adsorbed chemically. The nearness of R2 to 1 shows the adsorption agrees with the Langmuir adsorption isotherm. Eventually, the surface modification revealed that phenol molecules are responsible to reduce the corrosion rate at 16.38×10-3 mpy. Our results are expected to provide a guideline for future research in White tea as a green corrosion inhibitor