Effect of microstructure on corrosion behavior of 9% chromium-1% molybdenum steel
- Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Metallurgy Div.
The corrosion behavior of 9% Cr-1% Mo ferritic steel was studied using potentiodynamic polarization measurements in 0.5 M sulfuric acid with ad without addition of chloride and arsenic oxide. The influence of various heat treatments and microstructure on the electrochemical parameters and corrosion rate was investigated. The steel showed characteristic features of active, passive, secondary passive, and transpassive regions. The open-circuit potential, primary passive potential, primary and secondary passive ranges, and transpassive potential were about the same for all microstructures studied. Because of the inhibiting action of As{sub 2}O{sub 3}, the critical current density (i{sub crit}), Flade potential, and primary and secondary passive current densities were lower in H{sub 2}SO{sub 4} containing As{sub 2}O{sub 3} than in H{sub 2}SO{sub 4} alone. In the presence of Cl{sup {minus}}, this steel was susceptible to pitting attack from localized breakdown of passivity. Passive behavior was observed in NaCl solution up to a concentration of 0.005 M, while passivity could be sustained to a much higher limit in the H{sub 2}SO{sub 4} medium. When the normalized materials were tempered, pitting resistance decreased during the initial stages of tempering. With further tempering, pitting resistance was restored. The fully tempered material was more resistant to aqueous corrosion. During cathodic polarization, the material was susceptible to hydrogen blistering. Severity of attack was highly dependent upon microstructure. Material that was austenitized and furnace-cooled (annealed) was more prone to failure by blistering. The difference in corrosion behavior and susceptibility to blistering of various heat-treated materials was correlated to microstructural differences arising from heat treatments.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 260673
- Journal Information:
- Corrosion, Journal Name: Corrosion Journal Issue: 7 Vol. 52; ISSN 0010-9312; ISSN CORRAK
- Country of Publication:
- United States
- Language:
- English
Similar Records
Irradiation effects on the electrochemistry and corrosion resistance of stainless steel
Dissolution of glassy Ni-P alloys in H/sub 2/SO/sub 4/ and HCl electrolytes