Effects of biofilms, sunlight, and salinity on corrosion potential and corrosion initiation of stainless alloys
- Delaware Univ., Lewes, DE (USA). Coll. of Marine Studies
This phenomenon of corrosion potential ennoblement on stainless alloys is well known for full strength seawater. This report presents data on the extent to which that process occurs as a function of salinity and sunlight level for: stainless steels S30400 and S31600; stainless alloys S44735 (29-4C), S44660 (Seacure), NO8367 (6XN) and N10276 (C-276); and R50250 (Ti-Gr2). The results showed that natural population biofilms formed from all salinity waters under low light level conditions were capable of ennobling the corrosion potentials of all test alloys, although R50250 was consistently ennobled the least. Both the amount of ennoblement and the highest steady potential reached were maximized in fresh water and decreased for all alloys with increasing salinity. The critical pitting potentials for all test alloys were measured in coastal seawater. In addition, the critical pitting potentials for alloys S30400 and S31600 were measured (or estimated from the literature) as a function of salinity. The effect of ennoblement on the initiation and propagation of crevice corrosion are currently under investigation. The effect of sunlight on corrosion potential ennoblement was examined for the super alloy N10276 (C-276). Mechanisms by which ennoblement may be affected by sunlight were discussed, and it was hypothesized that the phenomenon may be at least partially understood in terms of pH fluctuations within the biofilm under the influence of periodic changes in the rates of photosynthesis and respiration.
- Research Organization:
- Electric Power Research Inst., Palo Alto, CA (USA); Delaware Univ., Lewes, DE (USA). Coll. of Marine Studies
- Sponsoring Organization:
- EPRI; Electric Power Research Inst., Palo Alto, CA (USA)
- OSTI ID:
- 5555070
- Report Number(s):
- EPRI-NP-7275
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360105* -- Metals & Alloys-- Corrosion & Erosion
ALGAE
ALLOYS
BIOLOGICAL FOULING
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CHROMIUM BASE ALLOYS
CHROMIUM STEELS
CHROMIUM-NICKEL STEELS
CORROSION
FOULING
HIGH ALLOY STEELS
HYDROGEN COMPOUNDS
IRON ALLOYS
IRON BASE ALLOYS
MICROORGANISMS
NICKEL ALLOYS
OXYGEN COMPOUNDS
PLANTS
SALINITY
SEAWATER
STAINLESS STEELS
STEELS
TITANIUM ALLOYS
TITANIUM BASE ALLOYS
WATER