Effect of a mixture of paint and Rhizophora mucronata leaves extract as a natural inhibitor of marine steel in 3.5% NaCl solution

• Wajilan¹, A. Fernandes² and A. Wahyudianto¹

¹ Politeknik Negeri Samarinda, Jl. DR Ciptomangunkusumo, Kampus Gunung Lipan, Samarinda, East Kalimantan, Indonesia
² Dipterocarps Research Center, Jl. A W Syahranie no. 68, Sempaja, Samarinda, East Kalimantan, Indonesia

Abstract: Marine steel is steel used in marine environments, such as steel for offshore construction and ships. Marine steel is easily corroded. To increase the corrosion resistance of marine steel, paints can be mixed with natural inhibitors, such as Rhizophora mucronata leaves extract. This study aimed at determining the effect of a mixture of paint and Rhizophora mucronata leaves extract as a corrosion inhibitor on marine steel. The GC-MS test was performed to determine the content of chemical compounds in Rhizophora mucronata leaves extract. Emission spectroscopy testing was carried out to determine marine steel elements. The corrosion inhibitor was prepared by making a mixture of paint and concentrated Rhizophora mucronata leaves extract with concentrations of 10, 20, 30, and 40% by volume. A potentiostat/galvanostat (PGSTAT101) was utilized to acquire anodic and cathodic polarization curves for marine steel in 3.5% NaCl solution. Based on GC-MS test results, Rhizophora mucronata leaves extract contain chemical compounds that can coat and inhibit the surface oxidation process of marine steel. Based on emission spectroscopy, marine steel specimen contained 98.56% Fe, 0.316% C, 0.26 Si and 0.655 Mn. The paint mixture with Rhizophora mucronata leaves extract could reduce the corrosion rate to 0.000112485 mm/year in 3.5% NaCl solution. The paint-coated specimens with all the concentrations of Rhizophora mucronata leaf extract had almost the same percentage increase in inhibitor efficiency (%IE), 97.86–98.96%. Therefore, the use of a mixture of the paint with 20% Rhizophora mucronata leaves extract was taken as the optimal composition.

Keywords: Rhizophora mucronata leaves extract, marine steel, inhibitor, corrosion

Int. J. Corros. Scale Inhib., 2021, 10, no. 4, 1441-1453
doi: 10.17675/2305-6894-2021-10-4-5

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