Inhibition Effect of Walnut Green Husk Extract on Steel in NH₂SO₃H Solution

Walnut green husk extract was extracted and prepared by using the extraction solvent of ethanol water solution (volume fraction is 40%). The inhibition effect of walnut green husk extract on the corrosion of cold rolled steel in sulfamic acid (NH₂SO₃H) solution was studied by weight loss method and electrochemical techniques. Scanning electron microscope (SEM) was used to examine the micro-graphs of steel surfaces. The results show that walnut green husk extract exhibits evident inhibitive performance on the corrosion of cold rolled steel in 0.10 mol/L NH₂SO₃H. Inhibition efficiency remarkably increases with the increase of the concentration of walnut green husk extract, and improves with an increase in temperature. Walnut green husk extract can adsorb on steel surface via mainly the mixed-adsorption mode of physisorption and chemisorption, and its adsorption behavior obeys Langmuir adsorption isotherm. The addition of walnut green husk extract drastically inhibits both anodic and cathodic reactions for the corrosion of sulfamic acid on steel, and can be arranged as a mixed-type inhibitor. Nyquist appears an individual depressed capacitive loop, and the charge transfer resistance increases with the increase of walnut green husk extract concentration. Inspection of the SEM micrographs of corroded steel surface reveals that WGHI can efficiently retard the corrosion of steel surface.