Effect of tannic acid on corrosion behavior of carbon steel in NaCl solution

A Novel Environmentally Friendly Synergistic Mixture for Steel Corrosion Inhibition in 0.51 M NaCl

“…Except for tannin, single components show <30% inhibitive action both in the inhibitor solutions and quiescent 0.51 M NaCl with a formed layer. As expected, 15 the solution of tannin as a chelating agent significantly increases corrosion rate of steel to 1.6 mmpy, but at the same time forms the most protective modified rust layer suppressing the corrosion rate in 0.51 M NaCl to 0.06 mmpy. Addition of benzoate to tannin solution decreases the corrosion rate to 0.11 mmpy but at the same time hinders the formation of protective tannin modified rust layer, increasing the corrosion rate in 0.51 M NaCl to 0.2 mmpy.…”

“…The morphology of the tannate layer is close to the one recently reported for tannic acid on Q235 carbon steel in 3.5% NaCl. 15 Similarly, due to inhibitor presence, the carbon content of the layer is much higher in the inhibitor-modified rust layer at locations #2, #4, #5 and #8 (16-25 %wt) than in the rust layer at locations #1, #3 and #7 (<6 %wt). Low carbon content is also observed at the location of the crack in the inhibitor layer protruding to the metal surface at position #6, and in the area of the damaged layer where the substrate is clearly visible at position #9.…”

“…14 Recent investigation of low carbon steel inhibition by 1-5% tannic acid solution in 3.5% NaCl shows that efficiencies up to 51% can be obtained. 15 Concentrations of the same order are needed for efficient steel corrosion inhibition in chloride media by starch 16 and sodium benzoate. 17 In the present study, minimal quantities of individual components that would be effective, based on the above literature references, were chosen for the inhibitor mixture composition.…”

“…Since polyphenols are weak organic acids known to decrease pH of neutral solutions, 14 along with the inhibitive effect of the tannate layer, iron dissolution enhancing effect may be expected. 15 Increased release of iron ions form steel, on the other hand, is favourable for ferric tannate formation. Hence, sodium benzoate 17 has been added to the mixture for controlled iron release, until the protective surface layer is fully formed.…”

New polymer-based treatments for the prevention of damage by salt crystallization in stone

“…Its main applications are as antioxidant, hemostatic and antibacterial agent [35]. Tannic acid was selected for its interaction with gypsum [21], SO 4 2ions [36] and aragonite [37] due to the large numbers of carboxylic functional groups and to its ability to form a large amount of H-bonds.…”