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Deep growth mechanism during pitting corrosion

Deep growth mechanism during pitting corrosion

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Present paper deals with an experimental investigation of pitting corrosion of forged 304 stainless steel. Material is exposed to ferric chloride solution to investigate the effect of pitting corrosion. This material is known to provide structural strength with improved toughness and ductility. A number of experiments were carried out on F304 SS un...

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... The corrosion of A316 stainless steel can be caused by a variety of circumstances, such as Sodium chloride (NaCl) can induce pitting corrosion when present [19] [20]. Environments containing extremely high concentrations of salt (chloride) are prone to pitting corrosion [21] [22]. ...
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... The thickness of the passive film increases over time due to elevated Fe 2 ⁺ levels in the oxide layer with prolonged exposure at elevated temperatures. Increased chloride ion concentration within the typical atmospheric humidity range exacerbates pitting corrosion [88,89]. Given the susceptibility of ASSs to SCC in chloride environments, chloride ions play a critical role in initiating and propagating SCC. ...
... The interaction between chloride ions and sensitized stainless steel surfaces accelerates passive film breakdown, leading to localized corrosion and eventual crack formation under stress. Understanding these mechanisms is crucial for mitigating SCC risks in chloride-rich environments [88,89]. ...
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... In most cases of coating, the coating surface gets damaged due to the presence of pores which then act as pits for corrosion [51]. However, in the present situation, the intactness ...
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... The presence of Cl − in the solution significantly affects the corrosion rate of steel. Under typical conditions, Cl − can disrupt the passive film, making the occurrence of pitting corrosion more likely (Pal et al. 2019). Zhang et al. (2011) studied the pitting behavior of J55 steel in NaCl/NaHCO 3 solution using electrochemical techniques and found that the corrosion rate increased with the addition of Cl − . ...
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... The anode area, located in the deep structure of the material where pitting takes place, is responsible for pitting initiation. On the diffused interface, the cathode zone acts as an electron recapture site, determining the pitting direction and exerting dominance over the anodic region [7,8]. The direction of pitting corrosion depends on passive film stability. ...
... All these aspects pay a key role in the reduction of materials corrosion resistance and increased susceptibility to intergranular SCC [23]. The SCC has been assessed in different testing methods as it has been reported that active corrosion leads to catastrophic failure by the action of [7,6]). residual or applied stress [24]. ...
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... It has a high solubility in water, making it easy to prepare and work with. Additionally, FeCl 3 is particularly corrosive towards 304 stainless steel, making it a suitable solution for testing the effectiveness of various inhibitors in protecting the AISI 304 steel against pitting corrosion [43]. ...
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... The aggressive Cl − ions destabilize the formation of passive film in SS304. It is the Cl − ions that attack the passive film present in SS304 leading to discontinuities in the passive film (surface pitting) [23]. Moreover, these Cl − ions get below the passive surface causing the growth of the pit resulting in the formation of a bigger pit below the surface and finally, the collapse of top surface occurs as shown in Figs. ...
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... The cathode zone forms on the diffused interface, which is a recapture for electron and produces the pitting direction and dominates this anodic area. The passive film becomes more distorted and disruptive when exposed to a chloride aqueous solution [71] then instantly formed chromium enriched passive film. The passive film thickness grows due to Fe 2+ raise in oxide at elevated temperatures and in prolonged exposure time. ...
... In the dissolution-based model, the crack growth rate depends on the rate of repassivation (ROR) and rate of dissolution (ROD). If the ROD is more than ROR, crack growth will be fast because crack tips are free Pitting corrosion growth mechanism [71]. from the passive layer by the anodic solution (Cl − ) and mechanical loading. ...
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Austenitic stainless steels (ASS) are extensively employed in various sectors such as nuclear, power, petrochemical, oil and gas because of their excellent structural strength and resistance to corrosion. SS304 and SS316 are the predominant choices for piping, pressure vessels, heat exchangers, nuclear reactor core components and support structures, but they are susceptible to stress corrosion cracking (SCC) in chloride-rich environments. Over the course of several decades, extensive research efforts have been directed towards evaluating SCC using diverse methodologies and models, albeit some uncertainties persist regarding the precise progression of cracks. This review paper focuses on the application of Acoustic Emission Technique (AET) for assessing SCC damage mechanism by monitoring the dynamic acoustic emissions or inelastic stress waves generated during the initiation and propagation of cracks. AET serves as a valuable non-destructive technique (NDT) for in-service evaluation of the structural integrity within operational conditions and early detection of critical flaws. By leveraging the time domain and time-frequency domain techniques, various Acoustic Emission (AE) parameters can be characterized and correlated with the multi-stage crack damage phenomena. Further theories of the SCC mechanisms are elucidated, with a focus on both the dissolution-based and cleavage-based damage models. Through the comprehensive insights provided here, this review stands to contribute to an enhanced understanding of SCC damage in stainless steels and the potential AET application in nuclear industry.
... Pal et al. examined the surge in pitting corrosion rate with a rise in temperature of 50 °C. It determines appropriate care should be taken while using 304 SS at high temperatures [8]. In the previous laboratory examination, it was found that the initial cracks appeared to start from corrosion pits and later advanced from corrosion pits to surface arbitrarily [9][10][11][12]. ...
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Corrosion pit to crack transition behaviors of forged 304 Stainless steel were investigated in ferric chloride solution. The combined effect of corrosion and stresses were considered. The residual stresses were revealed by XRD analysis. As an outcome, the FESEM and EDX were used to analyze the surface morphology. The high-speed camera was used to detect any changes in the pitting surface. The average pit depth, pit geometry, corrosion rate, and crack at the pit base were briefly summarized. In conclusion, the combined effect of corrosion medium and the residual stresses at pit base leads to the stress corrosion cracking of the stainless steel in ferric chloride solution. Additionally, the three different phases of stress corrosion cracking of 304 SS in ferric chloride solution, such as (i) rapid corrosion action; (ii) nucleation of microcrack and propagation; (iii) active crack growth rate, and plastic deformation zone, were discussed.
... These localised corrosions produce a random distribution of corrosion pits with numerous sizes and shapes, e.g. concentrated on a small area, single pit, and accumulatively produce a larger size (Ansari et al., 2018, Caines et al. 2013, Pal et al. 2019. Moreover, Nugroho et al. (2021a) found the association between pitting severity at a different volumetric change to the corrosion pit geometry, i.e. corrosion pit has shallower form on more significant volumetric change. ...
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The paper presents a procedure for numerically modeling the surface of corroded specimens. A 3D laser scan is utilized to derive surface morphology and corrosion pit depth distribution. This corrosion depth is analyzed with a probability model to assess the morphology difference and the characteristic of the corrosion pit depth at a particular volumetric change. Furthermore, the goodness fit test statistic is carried out to observe the propensity of corrosion depth to a specific distribution, i.e. the Gaussian and non-Gaussian. The corroded specimens that conform to Gaussian distribution are numerically modeled with ANSYS APDL to generate a Gaussian surface. Furthermore, the non-Gaussian surface model is simplified as a single corrosion pit with various geometrical shapes. The mesh convergence is carried out to provide accurate stress distribution. The procedure is adjustable and applicable to the other surface morphology.