Microbially Influenced Corrosion (MIC) on Valve Body
4/17/2019
Flanged 3" valve body after cross sectioning.
Observations
Pitting corrosion typical of microbiologically induced corrosion (MIC) was localized on one side of the valve body. It appears that most of the corrosion pits were inactive and filled with adherent oxide scale. The valve may have been closed for an extended time period, creating a localized stagnate low oxygen environment optimal for growth of sulfite reducing bacteria (SBR) resulting in severe MIC attack.
Material
ASTM A216 WCB
Chemistry
Carbon (max): .30
Manganese: 1 max
Phosphorus (max): .04
Sulfur (max): .05
Silicon: .10 – .35
Nickel (max): .40
Chromium (max): .30
Copper (max): .40
Columbium (max): .02
Vanadium (max): .08
Application
Upstream oil and gas process water transport lines.
Product
Cast steel valve body
Properties
Tensile Strength (ksi, min): 70 – 95
Yield Strength (ksi, min): 36
Elongation 2″ (% min): 22
Reduction Area (% min): 30
Hardness (HB, max): 187
Microstructures
Pearlitic and ferritic grain structured carbon steel