Occurrence of Salt Films during Repassivation of Newly Generated Metal Surfaces

Abstract

A mathematical model is developed to describe the processes by which transient appearance of salt films occurs during initial stages of corrosion of oxide-free metal surfaces. The model describes transport-controlled processes which lead to supersaturation by anodic dissolution, to precipitation of a salt film, and eventually to dissolulion of the salt film after oxide passivation of the substrate material. Experimental observations on iron repassivation in ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 155.69.4.4 Downloaded on 2015-06-05 to IP Vol. I25, No. 9

In-situ Synchrotron Studies of the Effect of Nitrate on Iron Artificial Pits in Chloride Solutions

“…This is the first reported crystal structure of ferrous nitrate. The salt layer is also found to give an anisotropic diffraction pattern, consistent formation of platelets with (0 2 0) It is well known that salt layers can form at the bottom of growing corrosion pits due to supersaturation of metal salts, [1][2][3][4] and that the presence of salt layers is important for continued pit growth.…”

“…It is well known that salt layers can form at the bottom of growing corrosion pits due to supersaturation of metal salts, [1][2][3][4] and that the presence of salt layers is important for continued pit growth. 5 This information is significant both in the field of electrochemical machining (ECM), where nitrate solutions are often used, [6][7][8] and in corrosion of steel in radioactive waste solutions.…”

On the onset of current oscillations at the limiting current region emerged during iron electrodissolution in sulfuric acid solutions

“…Therefore, the overall anodic dissolution reaction in the active state, and the overall passivation reaction at higher potentials may be represented as It is the formation of this salt film that leads to the partial passivation of the Fe electrode resulting in the emergence of the LCR between the active and passive states. Both the salt film formation and the LCR have been studied extensively because of the significance of the salt film on the iron passivation, pit repassivation during pitting corrosion and electropolishing [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52]. Supersaturation of metal salt solutions close to the Fe surface was found to occur prior to the salt precipitation [41][42][43].…”

“…Both the salt film formation and the LCR have been studied extensively because of the significance of the salt film on the iron passivation, pit repassivation during pitting corrosion and electropolishing [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52]. Supersaturation of metal salt solutions close to the Fe surface was found to occur prior to the salt precipitation [41][42][43]. Alkire et al [42] developed a model that describes transport-controlled processes to lead to supersaturation by anodic dissolution, to precipitation of a salt film and to dissolution of the salt film after the oxide formation and passivation of the Fe electrode.…”

The Effect of Nitrate on Salt Layers in Pitting Corrosion of 304L Stainless Steel

“…8,[18][19][20][21][22] When the rate of metal ion generation at the dissolving metal surface exceeds the rate of metal ion diffusion out of the pit, a salt layer can nucleate. [23][24][25] The * Electrochemical Society Student Member. * * Electrochemical Society Active Member.…”