Transformation Kinetics of Oxide Formed on Noble Metal-Treated Type 304 Stainless Steel in 288°C Water

• Published in: Corrosion (Houston, Tex.) Vol. 59; no. 6; pp. 511 - 519
• Main Authors: Kim, Y.-J., Andresen, P.L.
• Format: Journal Article
• Language: English
• Published: Houston, TX NACE International 01.06.2003; NACE
• Subjects: Analytical methods; Applied sciences; Austenitic stainless steels; Chromium; Corrosion; Corrosion mechanisms; Corrosion potential; Electrochemical corrosion; Electrochemistry; Electron microscopes; Electron microscopy; Exact sciences and technology; Ferric oxide; Heat resistant steels; Heavy metals; High temperature; Iron oxides; Kinetics; Metals; Metals. Metallurgy; Noble metals; Reaction kinetics; Spectroscopy; Stainless steel; Transmission electron microscopy; Water chemistry; Water temperature; Zinc; Platinum addition; Water corrosion; Austenitic stainless steel; Corrosion mechanism; Electrochemical corrosion; Corrosion potential; Type 304 stainless steel; Oxide layer; Electron diffraction; Rhodium addition; Steel; Experimental study; Dispersive spectrometry; Hot water; noble metal; electrochemical corrosion potential; high- temperature water; Transmission electron microscopy; Stainless steel-304; oxide
• ISSN: 0010-9312; 1938-159X
• DOI: 10.5006/1.3277582

ABSTRACTCharacterization of oxide films formed on metals and alloys has been the subject of study for many years because the chemical and physical properties of oxide films can alter the mechanism and kinetics of the corrosion processes.1-3 Particularly, the characteristics of oxide films formed on Type 304 (UNS S30400)(1) stainless steel (SS) and carbon steel as nuclear power plant materials have been the subject of investigations to understand environment-related materials failure problems. Intergranular stress corrosion cracking (IGSCC) of Type 304 SS has been a major concern in boiling water reactors (BWR) under normal water chemistry (NWC) conditions containing 100 ppb to 300 ppb of oxygen, 200 ppb to 500 ppb of hydrogen peroxide (H2O2), and <10 ppb of hydrogen. The IGSCC susceptibility is attributed to the oxidizing water chemistry that consequently alters the oxide film composition and structure. The electrochemical corrosion potential (ECP) of SS is being used as a diagnostic parameter for the IGSCC susceptibility of sensitized austenitic SS in BWR. The ECP behavior is known to be controlled by the dissolved O2, H2, and H2O2 concentrations and water flow rate in high-temperature water.4-7 Typically 1 ppm to 2 ppm of hydrogen is now being added to the feedwater of many BWR to mitigate the IGSCC problem. This process is referred to as hydrogen water chemistry (HWC). The primary purpose of the hydrogen addition is to reduce the dissolved oxygen levels of the coolant water and thereby lower the ECP below a critical value (­230 mV vs standard hydrogen electrode [SHE]) at which the IGSCC susceptibility is markedly reduced.8-9 It was also suggested that the Cr-enriched oxide formed under the HWC condition might decrease SCC susceptibility.10 However, some HWC plants have reported increases