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51316-7193-Influence of Magnesium on SCC Susceptibility of Duplex Stainless Steels in Boiling Solutions

This paper deals with some problems associated with stress corrosion cracking assessment of duplex stainless steels in boiling concentrated solutions.

Product Number: 51316-7193-SG
ISBN: 7193 2016 CP
Author: Fiona Ruel
Publication Date: 2016
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This paper deals with some problems associated with stress corrosion cracking assessment of duplex stainless steels in boiling concentrated solutions. Electrochemical polarization experiments conducted on UNS(1) S32304 lean duplex stainless steel in NaCl, CaCl2 and MgCl2 boiling solution indicate that the presence of Mg2+ cations has a strong impact on its passive layer properties. This influence has been attributed to a possible incorporation of Mg into the passive film, as evidenced by depth profile analysis using glow discharge optical emission spectroscopy. These findings contrast with those obtained on standard S32205 duplex stainless steel where Mo alloying content appears to prevent Mg insertion behavior and this is supported by theoretical calculations of substitution energies of Mg in Cr2O3 oxide film. This specific interaction between Mo and Mg is regarded to be a good explanation of the negative influence of Mo in boiling concentrated solutions of MgCl2, and suggests that the standard 45 % MgCl2 155 °C boiling solution is unfortunately unsuitable for stress corrosion cracking resistance assessments of stainless steels with different Mo alloying level.

Key words: Downloadable, Duplex stainless steel, Stress Corrosion cracking, ab initio calculations, GD-OES, SCC

This paper deals with some problems associated with stress corrosion cracking assessment of duplex stainless steels in boiling concentrated solutions. Electrochemical polarization experiments conducted on UNS(1) S32304 lean duplex stainless steel in NaCl, CaCl2 and MgCl2 boiling solution indicate that the presence of Mg2+ cations has a strong impact on its passive layer properties. This influence has been attributed to a possible incorporation of Mg into the passive film, as evidenced by depth profile analysis using glow discharge optical emission spectroscopy. These findings contrast with those obtained on standard S32205 duplex stainless steel where Mo alloying content appears to prevent Mg insertion behavior and this is supported by theoretical calculations of substitution energies of Mg in Cr2O3 oxide film. This specific interaction between Mo and Mg is regarded to be a good explanation of the negative influence of Mo in boiling concentrated solutions of MgCl2, and suggests that the standard 45 % MgCl2 155 °C boiling solution is unfortunately unsuitable for stress corrosion cracking resistance assessments of stainless steels with different Mo alloying level.

Key words: Downloadable, Duplex stainless steel, Stress Corrosion cracking, ab initio calculations, GD-OES, SCC

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