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The general corrosion (GC) and stress corrosion cracking (SCC) behaviours of three families of stainless steel alloys have been studied in 30% sodium hydroxide solutions with and without chloride and sulphide pollutions. Polarization curves, free corrosion potentials and surface analyses by glow discharge optical spectroscopy have been used. The results show that under reducing conditions, Cr and Ni insure protection while Mo and Fe are detrimental. Under highly oxidizing conditions, Ni and Fe protect the alloys. In this case Cr(III) is oxidized to Cr(VI) and is detrimental. The addition of Mo is detrimental or has no effect depending on the Ni and Cr contents. In pure solutions, superaustenitic grades display the lowest corrosion rates regardless of potential. Ferritic grades are the least resistant and austenitic and superduplex grades intermediate. Chloride additions do not affect austenitic and superaustenitic grades but increase the corrosion rate of others. Sulphide additions affect higher Ni containing alloys while duplex grade are improved. All grade families are susceptible to SCC above the transpassive potential of Cr. Sulphide additions are more aggressive than chlorides. For the former, duplex grades are more resistant. The influence of chlorides increases the susceptibility of all grades only when increasing temperature and concentration. Alloy S31603 is susceptible to SCC in all studied media.

Additional information

Authors: CASSAGNE T, Centre de recherches d'Unieux;GAGNEPAIN J-C, Centre de recherches d'Unieux;VERNEAU M, Centre de recherches d'Unieux;BARTERI M, Centre de recherches d'Unieux
Bibliographic Reference: EUR 16629 EN (1997) 88pp., FS, ECU 15
Availability: Available from the (2)
ISBN: ISBN 92-828-0256-6
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