Presentation Title

Microbiologically Influenced Corrosion in Marine Environment – Surface Roughness Effects

Faculty Mentor

Dr. Vilupanur Ravi, Chemical and Materials Engineering, Cal Poly Pomona

Start Date

17-11-2018 1:45 PM

End Date

17-11-2018 2:00 PM

Location

C301

Session

Oral 3

Type of Presentation

Oral Talk

Subject Area

engineering_computer_science

Abstract

Microorganisms can influence the corrosion rate of metallic materials through a phenomenon known as microbiologically influenced corrosion (MIC). MIC can increase corrosion rates of metallic alloys utilized in corrosive environments, e.g., salt water corrosion experienced in marine infrastructures, thereby reducing the service life of these alloys. The objective of the current study was to determine whether the surface roughness of an alloy has a significant effect on its corrosion resistance in the presence of microorganisms. Three test coupons each (N = 3) of marine grade carbon steels and stainless steels (UNS G10180, UNS S30400 and UNS S31603) were ground to multiple finishes (80 grit, 600 grit and 0.05 µm) to achieve various surface roughnesses. The cylindrical test coupons, each 6.0 ± 0.2 mm long and with a diameter of 13 ± 0.1 mm, were immersed in biologically active seawater in the vicinity of the port of Los Angeles. The mass differences between pre-and post-corroded coupons were recorded and the corrosion rates were determined using an equation per the ASTM G102 standard. Post-test coupons were examined using optical and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). The overall trend was that corrosion rates decreased with increasing exposure time possibly due to the formation of a biofilm inhibiting further corrosion. The surface roughness effects were more nuanced with different trends being exhibited by the different alloys.

Summary of research results to be presented

Corrosion rates were calculated for each of the alloy coupons for 24 and 48 hour exposures as well as 7 and 14 day exposures in natural seawater. The overall trend was that corrosion rates decreased with increasing exposure time. For example, UNS31603 coupons with an 80 grit surface finish had average corrosion rates of 135 ± 6 µm per year for 7 days and 62 ± 3 µm per year at 14 days relative to the 24 and 48 hours test coupons, i.e., 1011 ± 51 µm per year for 24 hours and 589 ± 30 µm per year for 48 hours. For UNS S30400 and UNS S31603 coupons, this decrease in the corrosion rates with increasing exposure times can be attributed to the formation of a protective passive film. However, the same trend was seen in the UNS G10180, a material that does not form a protective oxide film. One possible explanation for the latter may be the formation of a biofilm inhibiting further corrosion. The surface roughness effects were more nuanced with different trends being exhibited by the different alloys.

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Nov 17th, 1:45 PM Nov 17th, 2:00 PM

Microbiologically Influenced Corrosion in Marine Environment – Surface Roughness Effects

C301

Microorganisms can influence the corrosion rate of metallic materials through a phenomenon known as microbiologically influenced corrosion (MIC). MIC can increase corrosion rates of metallic alloys utilized in corrosive environments, e.g., salt water corrosion experienced in marine infrastructures, thereby reducing the service life of these alloys. The objective of the current study was to determine whether the surface roughness of an alloy has a significant effect on its corrosion resistance in the presence of microorganisms. Three test coupons each (N = 3) of marine grade carbon steels and stainless steels (UNS G10180, UNS S30400 and UNS S31603) were ground to multiple finishes (80 grit, 600 grit and 0.05 µm) to achieve various surface roughnesses. The cylindrical test coupons, each 6.0 ± 0.2 mm long and with a diameter of 13 ± 0.1 mm, were immersed in biologically active seawater in the vicinity of the port of Los Angeles. The mass differences between pre-and post-corroded coupons were recorded and the corrosion rates were determined using an equation per the ASTM G102 standard. Post-test coupons were examined using optical and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). The overall trend was that corrosion rates decreased with increasing exposure time possibly due to the formation of a biofilm inhibiting further corrosion. The surface roughness effects were more nuanced with different trends being exhibited by the different alloys.