Corrosion in Transpassive Potential Regime: Effect of Composition and Microstructure of Austenitic Stainless Steel

Khan, Shagufta; Kain, Vivekanand; Reddy, Α. V. R.

doi:10.5006/1066

Cited by 8 publications

(8 citation statements)

References 43 publications

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“…The use of a different approach to study and understand the corrosion behaviour of stainless steels exposed to nitric acid containing different concentration of various oxidizing ions is to apply the final developed potential (in contact with solution containing oxidizing ions) to stainless steel in the nitric acid without any addition of ions. This approach was first reported by Streicher [15] and later used by the authors recently to demonstrate that application of potential to stainless steel sample immersed in near boiling nitric acid for a specified duration resulted in weight loss and form of corrosion was either uniform corrosion or IGC depending on if the potential applied was below a "threshold potential" or above it [14,[43][44]]. This "threshold potential" was established in near boiling 6 M nitric acid for type 304L (NAG).…”

Section: Application Of Potential To Simulate Potential Developed On ...mentioning

confidence: 99%

“…The potential developed is function of the electrolyte, temperature and also the alloy composition and its microstructure. Therefore, in a systematic study to establish if changes of chemical composition of austenitic stainless steels cause a wide variation in the "threshold potential", Shagufta et al showed [43] that there are differences in the threshold potential as well as correlation of the potential to corrosion rate for three different alloys. Taking 6M near boiling nitric acid and applying potentials for 48 h as was done earlier by Shantanu et al [14], they established the correlation of applied potential with corrosion rate in the potential regime that transitions from "passive" potentials to "transpassive" potentials (Fig.…”

Section: Effect Of Alloy Compositionmentioning

confidence: 99%

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Corrosion of Non-Sensitized Austenitic Stainless Steels in Nitric Acid Environment: An Electrochemical Approach

Kain

Khan

Reddy

et al. 2013

AMR

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The austenitic stainless steels are used in nuclear spent fuel reprocessing and waste management plants and the process fluid is nitric acid at temperature up to boiling point. However incorporation of oxidizing ions e.g. fission products as well as corrosion products, in nitric acid stream make the environment highly corrosive to stainless steels. Present work aims to investigate role of process parameters and material parameters (composition and microstructure) on corrosion behaviour of stainless steels. The process parameters studied are temperature, acid concentration and oxidizing ions. It has been shown that the potential attained on stainless steel is a function of acid concentration and temperature and is further strongly affected by addition of oxidizing ions. This developed potential determines the corrosion behaviour of stainless steel. Increasing the temperature and concentration of nitric acid and concentration of oxidizing species increased the developed potential. Potentials were applied to types 304 L (nitric acid grade - NAG), 304 L (commercial purity) and 310 L stainless steels in boiling 6 M nitric acid for a period of 48 h. The corrosion rates measured in such experiments were plotted as a function of applied potential. The form of corrosion was established by microstructural examination. A clear demarcation was observed between uniform corrosion and intergranular corrosion at a potential of 960-980 mVSCE. Above this potential range corrosion rate increased exponentially and the form of corrosion is shown to be intergranular corrosion. Below this potential range, uniform and low rate of corrosion occurred. The influence of microstructure (step, dual and ditch) of type 304 L was also studied and is described in this paper.

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Section: Application Of Potential To Simulate Potential Developed On ...mentioning

confidence: 99%

Section: Effect Of Alloy Compositionmentioning

confidence: 99%

Corrosion of Non-Sensitized Austenitic Stainless Steels in Nitric Acid Environment: An Electrochemical Approach

Kain

Khan

Reddy

et al. 2013

AMR

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“…Austenitic SS alloys are characteristically developed with regulated chemical compositions, which are improved microstructures that eliminate weaker locations for passive film disintegration, dissolution, and increased resistance to trans-passive dissolution, and are also known as nitric acid grade (NAG) austenitic stainless-steel alloys. Many NAG alloys with similar compositions to 304L, 310L, and proprietary alloys are created for use in the reprocessing industry [32][33][34].…”

Section: Introductionmentioning

confidence: 99%

“…Austenitic SS in a sensitised condition is susceptible to intergranular corrosion (IGC) in a boiling HNO 3 atmosphere [1,2,[32][33][34]. Even non-sensitised SS is vulnerable to IGC and end-grain or tunnel corrosion in boiling HNO 3 containing oxidising ions.…”

Section: Introductionmentioning

confidence: 99%

Corrosion Mechanisms of 304L NAG in Boiling 9M HNO3 Containing Cr (VI) Ions

Khan¹,

Saeed

Nazir

et al. 2023

Sustainability

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In this research, the mechanisms of end-grain corrosion of 304L NAG tubes in boiling 9M HNO3-containing Cr (VI) ions are reported to sustainably manage the corrosion of nuclear fuel reprocessing plant components. Specific heat treatments were applied to as-received specimens to produce phosphorus and/or sulphur intergranular segregation. End-grain corrosion on heat-treated specimens and the effect of a Cr (VI) concentration on a 304L NAG tube (as-received) were investigated. It has been reported that an increase in Cr (VI) ions leads to the acceleration of end-grain corrosion due to high electrochemical potential. After systematic heat treatments on the 304L NAG specimens, it is concluded that the primary causes of heat-induced end-grain corrosion are phosphorus or sulphur segregation to the grain boundaries. The key findings of this research are highly significant in terms of understanding the corrosion mechanisms and controlling the end-grain corrosion of NAG steel in boiling HNO3 environments. This research will help to sustainably reduce power plant maintenance costs and will have a significant impact on the delivery of long-term, clean, secure, and tenable energy.

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“…Even in the absence of sensitisation, austenitic SS can still undergo IGC if the operating potentials are in the transpassive regime [14][15][16][17][18][19]. The corrosion potential of SS in nitric acid solution is dictated by the nitric acid concentration, temperature and the cathodic reaction of the reduction-oxidation (redox) process between the alloying elements of steel and the ionic species present in the solution [15].…”

Section: Introductionmentioning

confidence: 99%

Laser surface melting of 304L SS: increase in resistance to transpassive dissolution and pitting corrosion

Ghosal

Gupta

Chandra

et al. 2023

Corrosion Engineering, Science and Technology

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In the present study, laser surface melting (LSM) of 304L stainless steel (SS) was performed using 250 W pulse Nd: YAG laser which resulted in a 250 µm thick melted layer with refined microstructure on the surface. Potentiostatic polarisations at various potentials in the transpassive regime in 6 M HNO 3 solution at 95°C were used to quantify the IGC rate. The transpassive dissolution rate was significantly reduced after LSM. The pitting corrosion susceptibility was assessed by potentiodynamic polarisation in 3.5 wt-% NaCl solution. LSM resulted in an increase in pitting potential. Following electrochemical tests, sample surfaces were examined using optical and scanning electron microscopes besides a 3-D optical profilometer. The depths of IGC attack and pit were significantly reduced after LSM. The improvement in resistance to pitting corrosion and transpassive dissolution was attributed to the elimination of inclusions and impurity segregation at the grain boundaries brought about by LSM.

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Corrosion in Transpassive Potential Regime: Effect of Composition and Microstructure of Austenitic Stainless Steel

Cited by 8 publications

References 43 publications

Corrosion of Non-Sensitized Austenitic Stainless Steels in Nitric Acid Environment: An Electrochemical Approach

Corrosion of Non-Sensitized Austenitic Stainless Steels in Nitric Acid Environment: An Electrochemical Approach

Corrosion Mechanisms of 304L NAG in Boiling 9M HNO3 Containing Cr (VI) Ions

Laser surface melting of 304L SS: increase in resistance to transpassive dissolution and pitting corrosion

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