Occluded solution chemistry control and the role of alloy sulfur on the initiation of crevice corrosion in type 304ss

Brossia, C. Sean; Kelly, Robert G.

doi:10.1016/s0010-938x(98)00084-5

Cited by 85 publications

(36 citation statements)

References 30 publications

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“…Work by different authors has focused on the dependence of E rp and (i ⋅ x) on different factors such metallurgical composition [23][24][25][26][27][28][29][30], temperature [13,[31][32][33][34], bulk electrolyte composition [13,29,[32][33][34][35][36][37][38], and pH [33,34]. In the present work, a systematic study of the dependence of the pit stability product under a salt film and repassivation potential of four stainless steels (304, 316L, 17-4PH, and Custom 465) on bulk chloride concentration and pH using the artificial pit technique is described [20,22].…”

Section: Introductionmentioning

confidence: 99%

Effects of environmental factors on key kinetic parameters relevant to pitting corrosion

Woldemedhin

Srinivasan

Kelly

2015

J Solid State Electrochem

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Experiments using stainless steel artificial pit (leadin-pencil) electrodes in ferric chloride and lithium chloride solutions were performed in order to determine the effects of key environmental factors such as chloride concentration and pH of the bulk solution on the central parameters utilized to characterize the pitting phenomenon-the repassivation potential E rp and the pit stability product under a salt film (i· x) saltfilm . For all the stainless steel alloys studied, a relative independence of the E rp to the pit depth was observed once sufficient anodic charge had been passed. The pit stability product under a salt film was seen to be largely insensitive to the pH of the bulk solution. E rp , on the other hand, was fairly independent of bulk pH only at the lower chloride concentrations of both lithium chloride and ferric chloride solutions. The two parameters were affected differently by variation in the chloride concentration of the bulk solutions. Increasing the chloride concentration resulted in a decrease in the value of (i·x) saltfilm for all alloys in both solutions. In ferric chloride, the value of E rp increased with increasing chloride concentration for Custom 465 and the austenitic steels, whereas it decreased across the same range for 17-4 pH. These trends were explained qualitatively using solution conductivity and alloying composition arguments. Finally, the results obtained from this study allowed for a rationalization of the phenomenology, enabling a method of measurement of the diffusion coefficient and the concentration at saturation of the Bstainless steel cation^within the pit, both of which agreed well with values obtained from the existing literature.

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Section: Introductionmentioning

confidence: 99%

Effects of environmental factors on key kinetic parameters relevant to pitting corrosion

Woldemedhin

Srinivasan

Kelly

2015

J Solid State Electrochem

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“…Due to an increase in pH during the formation of these two species, H 2 S and elemental sulfur can be formed. Hydrogen sulfide was reported to shorten the time to the breakdown of the passive film 35 and to decrease the pitting potential on SS304 in chloride solution. 36 The dissolution of MnS leads to sulfur precipitation on the alloy surface adjacent to the inclusion.…”

Section: ͓6͔mentioning

confidence: 99%

Pitting Corrosion of Bare Stainless Steel 304 under Chloride Solution Droplets

Maier

Frankel

2010

J. Electrochem. Soc.

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Pitting corrosion behavior of stainless steel 304 ͑SS304͒ under droplets of chloride solution was investigated using a Kelvin probe ͑KP͒. Droplets of different volumes of MgCl 2 solution were placed on the steel surface and exposed to a constant low relative humidity ͑RH͒. As the concentration increased during the exposure of the drop to low RH, the open-circuit potential ͑OCP͒ and the shape change of the drop were monitored by the KP. Pit initiation was detected by a sudden decrease in the OCP. Pits initiated earlier under small droplets than under large drops. The chloride concentration at initiation was between 3.0 and 8.4 M for droplets with a starting concentration of 0.88 M Cl − . The initiation concentration increased when the initial concentration of the droplet was higher. The anodic current demand of pits growing at the OCP decreased with time as did the available cathodic current. When the current demand exceeded the available cathodic current, the active pit area decreased. A mechanism for pit formation and growth under droplets of MgCl 2 solution was proposed. © 2010 The Electrochemical Society. ͓DOI: 10.1149/1.3467850͔ All rights reserved. Stainless steels and other corrosion resistant alloys exhibit strong passivity but are susceptible to localized corrosion in the presence of chloride or other aggressive ions.1,2 These alloys are often immune to attack in dilute solutions, but breakdown can occur during atmospheric or alternate immersion conditions by the following scenario. A droplet of salt solution on the surface loses water due to a temperature increase or a decrease in relative humidity ͑RH͒. The chloride concentration thereby increases until pitting corrosion initiates, which is accompanied by a sharp drop in the open-circuit potential ͑OCP͒. 3,4Tsutsumi et al. exposed stainless steel 304 ͑SS304͒ samples to seashore and rural atmospheres.5 No pits were found on samples in the rural area, while pitting initiated between 35 and 75% RH in the marine environment. A humidity of 35% corresponds to a saturated magnesium chloride solution, and 75% RH relates to 3 M MgCl 2 ͑6 M Cl − ͒. According to these results, the chloride concentration for pit initiation under a thin electrolyte layer is around 6 M. This finding agrees with the results of other papers by the same authors.6,7 Tsutsumi et al. determined the onset of pitting, which is associated with a critical chloride concentration, from the sudden drop in the OCP of the stainless steel electrode measured vs an Ag/AgCl reference electrode ͑RE͒.7 The Cl − concentration of the thin electrolyte layer was controlled by varying the RH. The initiation chloride concentration increased with increasing drying rate and with decreasing amount of salt on the surface. The same researchers also studied the influence of electrolyte drop size on the occurrence of the pitting and concluded that pitting is less likely under drops with a small diameter ͑Ͻ5 mm͒ due to a small cathode area. 6,8 The placement of the RE relative to the sample is complicated for a thin-...

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“…While these models proposed several diverging mechanisms for pit initiation at MnS inclusions, central to each of these was the role of S. As it relates to S speciation in the pitting environment, Brossia studied the solutions from artificial crevices of SS 304, using capillary electrophoresis. 9,10 In that work sulfide (S −2 ) was found in the crevice solution at the end of the initiation period. In other work Brossia also showed that the minimum chloride concentration needed to obtain an active to passive transition in the polarization curve for SS 304 decreased with increasing concentration of S −2 .…”

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confidence: 97%

Pit Propagation at the Boundary between Manganese Sulfide Inclusions and Austenitic Stainless Steel 303 and the Role of Copper

Lillard

Kashfipour

Niu

2016

J. Electrochem. Soc.

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Pitting corrosion around manganese sulfide (MnS) inclusions in stainless steel 303 (SS 303) were investigated using in situ Atomic Force Microscopy (AFM), Scanning Kelvin Probe Force Microscopy (SKPFM) and Scanning Electron Microscopy. In situ AFM experiments in 0.1 M sodium chloride solution at voltages near the pitting potential combined with post immersion energy dispersive X-ray spectroscopy (EDS) found copper (Cu) deposition on MnS inclusions but no pitting corrosion. SKPFM images before and after Cu deposition found that Cu ennobled the inclusion. Damage evolution at MnS inclusions was imaged in real-time with AFM at an applied anodic potential. During pit propagation the MnS inclusion remained "passivated" while a trench formed in the bulk SS 303 at the MnS/SS boundary. Focused Ion Beam (FIB) cross sectioning of trenches after this immersion period found no damage to the MnS and Cu deposition on the portion of the inclusion that was inside the trench. FIB images of unexposed samples found preexisting sub-surface trenches at MnS inclusions below the plastic deformation zone at the surface. From these results a proposed mechanism of corrosion propagation at the MnS / SS boundary is described. Over the course of the past century corrosion pits in austenitic stainless steels have been associated with manganese sulfide (MnS) inclusions. An excellent review of the early work in this area has been provided by Wranglen.1 It was proposed that MnS inclusions oxidized preferentially as they were ". . . less noble then the surrounding oxide film, and then [the oxidation] spreads to the active metal below the sulfide inclusions." The model also discussed the sulfur species that may be produced during MnS oxidation including sulfide (S 2− , HS − ), sulfite (SO 3 2− ) and sulfate (SO 4 2− ). As it relates to those species, Wranglen argued that the electrochemical oxidation of sulfur to sulfite produced local acidity. To the contrary, Eklund argued that local acidity was produced from the electrochemical oxidation of sulfide to sulfate. 2More recently, Stewart and Williams, in a metastable pitting study, proposed that MnS dissolution and the corresponding "supply of sulfur to the active pit surface" was a critical step for pit stability.3 They showed that laser re-melting of the surface greatly reduced metastable activity and pitting damage. Thus, larger MnS inclusions could supply sufficient S to maintain pit stability while smaller inclusions could not. Similar conclusions were drawn by Searson and Latanison for rapidly solidified SS 303. 4 Later work by Williams focused on the formation of a critical pitting solution at the site of inclusions as the trigger for pitting corrosion.5 It was proposed that the high dissolution rate of MnS inclusions resulted in the formation of a "sulfur crust" over the inclusion that concentrated chloride underneath it by electromigration. The result was the formation of an occluded environment in which stainless steel depassivates. Early work by Webb and Alkire proposed that the sulfide ...

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Occluded solution chemistry control and the role of alloy sulfur on the initiation of crevice corrosion in type 304ss

Cited by 85 publications

References 30 publications

Effects of environmental factors on key kinetic parameters relevant to pitting corrosion

Effects of environmental factors on key kinetic parameters relevant to pitting corrosion

Pitting Corrosion of Bare Stainless Steel 304 under Chloride Solution Droplets

Pit Propagation at the Boundary between Manganese Sulfide Inclusions and Austenitic Stainless Steel 303 and the Role of Copper

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