The corrosion behavior of three steels in high temperature water was compared: a low-alloy steel (ASTM A-508), a cast martensitic steel (CA-6NM, UNS J91540) and 403 stainless steel (UNS S40300). Test specimens were exposed to mildly alkaline solution at 260 °C for up to 5,000 hours. Several surface conditions were used, including chemically passivated and electropolished surfaces. The corrosion films consisted of ferrite spinel crystals (AFe2O4) with some basal chromite spinel (ACr2O4) for the steels with higher Cr content. Total corrosion and corrosion product release were also quantified using chemical descaling. The corrosion rates were more than an order of magnitude greater than those of Ni-based alloys tested previously, and greater than that of 304 stainless steel. Relative comparisons of the rates are interpreted in terms of the base alloy composition and surface treatment.

Subject
Scanning electron microscopy, Films, Materials, Corrosion rate, Oxide films, Surface treatments, Corrosion products, Electropolishing, Sputter deposition, Corrosion data, Corrosion coupons, Stainless steel, Test specimen
Keywords:
corrosion, film, stainless steel, passivation, electropolishing
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2012
Association for Materials Protection and Performance (AMPP)
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