The extract of honeycomb waste was studied as a corrosion inhibitor on 304 stainless steel in H2SO4 solutions. The honeycomb waste was obtained from beekeeping at Lawang-Malang, East Java, Indonesia. Electrochemical and scanning electron microscopy methods were used to investigate the performance of the corrosion inhibition process. The inhibition efficiency of the inhibitor (2000 mg/L) reached 97.29% in 0.5 M H2SO4 and decreased with the acid concentration. Kinetic parameters were calculated to explain the effect of acid concentration on the inhibition process. The study on the adsorption behavior of the extracts followed the Frumkin isotherm model. The adsorption of the inhibitor on the 304 stainless steel surface was confirmed by the negative and lower values of Gibbs free energy. The obtained scanning electron microscopy (SEM) images were confirmed by comparing the surface of the specimens with and without inhibitor after corroding for one week. The results indicated that the extract acted as a good inhibitor for 304 stainless steel in acid corrosion.

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Tannin isolated from Psidiumguajava leaves are developed to enhance the corrosion protection of austenitic stainless steel. It is used as a green inhibitor, extracted from Psidium guajava which grow in East java, Indonesia. In the present work, the corrosion inhibition properties of the tannin inhibitors were investigated in 3M HCl by polarization potentiodynamic measurements. The result reveals that tannin 1g/L could enhance the inhibition efficiency up to 91.81%.

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A binder is any material used to strengthen the bonding of moulding sand grains. The primary function of the binder is to hold the moulding sand and other materialstogether to produce high-quality casts. In this study, there were four binder compositions being tested, i.e. 5% bentonite + 5% Portland cement, 4% bentonite + 6% Portland cement, 6% bentonite + 4% Portland cement, and 7% bentonite + 3% Portland cement. Each specimen was measured for its compressive strength, shear strength, tensile strength and permeability. The highest compressive strength was obtained fromthe specimen composed of 6% bentonite+ 4% Portland cement. The highest shear strength was obtained from the moulding sand with 7% bentonite+ 3%Portland cement. The highest tensile strength was obtained fromthe specimen contained 5% bentonite+ 5% Portland cement. The specimen composed of 5% bentonite + 5% Portland cement had the lowest permeability of 131 ml/min, while that of 6% bentonite + 4% Portland cement had the highest permeability of 176 ml/min..

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