The inhibition of pit growth on an iron surface in a borate buffer solution containing chloride ion by inhibitors classified as soft bases in the HSAB principle

López

2012

J. Electrochem. Soc.

This work deals with the effect of nitrite ions on the breakdown of passive films formed on steel in simulating pore concrete solutions with a high content in carbonate ions. The solutions contain 0.015 mol l −1 Na 2 CO 3 and 0.3 mol l −1 NaHCO 3 and may incorporate 0.05 or 0.1 mol l −1 NaCl. The inhibition efficiency is evaluated recording cyclic voltammograms, polarization curves, polarization resistance, impedance and Raman spectra. Weight-loss measurements were also performed. High CO 3 −2 concentrations favor the development of a passive film that becomes more compact when nitrite ions are added. As the [NO 2 − ]/[Cl − ] increases, the films become more resistant to pitting attack. A linear relationship was established between E pit and log ([NO 2 − ]*([HCO 3 − ] + [CO 3 = ])/[Cl − ]). It is shown that the [NO 2 − ]/[Cl − ] ratio cannot be taken as an appropriate parameter to evaluate the inhibitor efficiency for different pH values and different carbonate and chloride ions concentrations. Instead, the results showed that exceeding [NO 2− ] = 0.2 mol l −1 can be taken as a better criterion for the level needed for adequate protection in the various electrolytes studied.

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Section: Resultsmentioning

confidence: 99%

The Role of Chloride, Nitrite and Carbonate Ions on Carbon Steel Passivity Studied in Simulating Concrete Pore Solutions

López

2012

J. Electrochem. Soc.

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“…Due to the presence of adequate dosages of nitrite ions in the electrolyte, repassivation starts as soon as the potential sweep is reverted. The hard and soft acids and bases principle (HSAB) can be used to explain the inhibition of pit growth [36]. In this context, NO 2 − is acting as a soft base by chemisorpting on the bare iron substrate, displacing chloride ions inside of the pit.…”

Section: Resultsmentioning

confidence: 99%

Carbon steel passivity examined in solutions with a low degree of carbonation: The effect of chloride and nitrite ions

Materials Chemistry and Physics

2009

114

“…After 90 days of ageing, the anodic polarization curve showed pitting at potentials positive to 0.60 V. Due to the presence of nitrite ions in the electrolyte, repassivation starts as soon as the potential sweep is reverted. The inhibition of pit growth has been explained in terms of hard and soft acids and bases principle (HSAB) [43]. Within this framework, NO 2 − is acting as a soft base by chemisorpting on the bare iron substrate, displacing chloride ions inside the pit.…”

Section: Effect Of Incorporating Chloride Ions As Contaminants Togethmentioning

confidence: 99%

Carbon steel passivity examined in alkaline solutions: The effect of chloride and nitrite ions

2008

Electrochimica Acta

170

103