"Long-Term
Performance of an
Organic Corrosion
Inhibitor"
"Corrosion Inhibition
Properties of a
Complex Inhibitor -
Mechanism of
Inhibition"
"The Effects of
Calcium Nitrite and
Mix Design on the
Corrosion Resistance
of Steel in Concrete"
"Modelling Chloride
Diffusion in Concrete.
Effect of Fly Ash and
Slag"
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"Corrosion Inhibition Properties of a Complex Inhibitor - Mechanism of Inhibition", Violetta F. Munteanu and Frederick D. Kinney, CANMET 2000, pp 255-269 (2000).
This paper focuses on an examination of the inhibitive action of a commercially available complex inhibitor containing 15% nitrite and an aminoalcohol. The result was a synergistic effect, combining the ferric ion-precipitation effect of nitrite with the known film-forming properties of hydroxyalkylamines. Stainless steel electrodes (type 304, ASTM G-61) were immersed in limewater solutions with and without sodium chloride (3%), at pH=12.67 and at pH=9.37 for up to 72 hours. A potentiostat was used to determine corrosion potential, corrosion current, polarization resistance and Tafel slopes. Several half-reactions involving nitrite ion are considered, and inhibition by oxidizing agents such as nitrite is related to alkalization which occurs near the anode, rather than acidification, which occurs during pitting corrosion. Nitrite ions stabilize a passive iron oxide layer in the presence of chloride ion even up to a chloride to nitrite ratio of 1.0 to 1.5. Aminoalcohols adsorb on the metal surface at both anodic and cathodic sites. The corrosion current of the stainless steel specimens in limewater with 3% NaCl was reduced by the complex corrosion inhibitor at pH 12.67 by a factor of 2.5 and at pH 9.37 by a factor of 5.4 compared to stainless steel in limewater + 3% NaCl without corrosion inhibitor. The corrosion reduction for the complex inhibitor was significantly better than for either component alone. |
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