On the Cl− breakdown of passive films on mildsteel

Ashworth, V.; Boden, P. J.; Leach, Joan; Nehru, A.Y.

doi:10.1016/s0010-938x(70)80033-6

Cited by 18 publications

(15 citation statements)

References 6 publications

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“…12, where the From this result together with other results at different potentials, we obtain (7) where ks is the rate of pit growth in area of the pit mouth. This is in agreement with the result reported by Rosenfeld and Danilor (12) who made measurements with artificial pits.…”

Section: Pit Growthsupporting

confidence: 93%

“…Furthermore, the material balance with respect to the metal ion gives (11) where the first term represents the rate of metal dissolution inside the pits and the second the rate of accumulation of metal ion in the pit, CM being the concentration of metal ion in the pit and V the volume of pit. Since (12) density of the metal, respectively. Note that we have here assumed that the concentration of metal ion in the pit, CM, is unchanged during the pitting dissolution; CM would be very large and close to the saturated concentration for metal salts.…”

Section: Pitting Dissolution Currentmentioning

confidence: 99%

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Generation and Propagation of Chloride-Pits on Rotating Stainless Steel Electrode in Acid Solution

et al. 1972

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Anodic pit generation and pit growth of stainless steel at constant potential in a sulphuric acid solutlutturic acid solutphuric acid solutttd soluttution containing chloride ion have been investigated by use of a rotating electrode. The electrode rotation makes the generation and growth of pits very stable and enables the pit generation frequency and the pitting current from a single pit to be measured potentiostatically. The pits break out at constant frequency and the rate of pit generation is a linear function of the potential, suggesting that the pit generation proceeds electromechanically rather than electrochemically. An incubation time, probably associated with the initial adsorption of chloride ion, is found before the linear pit generation commences, which differs from the induction time for opening an initial pit.The pitting current is in proportion to the area of pit mouth with the current density (8A/cm2) which is independent of the potential, indicating that the mass transfer is rate-limiting. The pit grows following a parabolic law and the rate constant is an exponential function of the potential, from which a pit model is proposed in which the transpassive film continuously forming and breaking down on the inner pit surface assumes a high electric field.

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Section: Pit Growthsupporting

confidence: 93%

Section: Pitting Dissolution Currentmentioning

confidence: 99%

Generation and Propagation of Chloride-Pits on Rotating Stainless Steel Electrode in Acid Solution

et al. 1972

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“…3. These variations are probably a result of the statistical variations in the number and growth of pits (14). Comparison of the shape of this curve with that in Fig.…”

Section: Resultsmentioning

confidence: 69%

“…The initiation of breakdown has been investigated in detail in pitting experiments (6,14,15), but there is little knowledge of the subsequent undermining of passivity as the composition of the solution changes within the cavity. During the first stage the steel surface is passive.…”

Section: Discussionmentioning

confidence: 99%

The Behavior of Resistive Layers in the Localized Corrosion of Stainless Steel

Isaacs

1973

J. Electrochem. Soc.

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The dissolution of austenitic stainless steels in artificial crevices has been studied as a function of potential and chloride ion activity. Impedance measurements have shown the presence of a resistive layer on the steel which limited the rate of the electrode reaction in the localized corrosion of stainless steels. The potential across the layer, equal to the product of the direct current and layer resistance, varied linearly with the electrode potential indicating ohmic ionic conduction across the layer. The growth of the layer was limited by its solubility and the diffusion of metal cations in the aqueous phase in the cavity. The layer had the properties of a metal chloride with a given solubility product. Increased chloride activity decreased the saturation concentration of the metal cation, its concentration gradient, and gave decreased dissolution rates or currents.

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“…This finding cannot be explained by traditional models. Ashworth [40] suggested that the breakdown of passivity followed by corrosion was stifled by the formation of corrosion products that would cover corrosion pits. Duffo [41] found that rust of steel reinforcement in concrete is the mixture of a-Fe 2 O 3 , c-Fe 2 O 3 , Fe 3 O 4 , a-FeOOH, c-FeOOH, b-FeOOH, and FeO.…”

Section: Introductionmentioning

confidence: 99%