Oxygen and pH microprofiles above corroding mild steel covered with a biofilm

O₂ and pH microprofiles were measured above corroding mild steel covered with a biofilm. The pH in the anodic areas (tubercles) ranged from 5 to 7 and was always 9.45 at the surface of the cathodic areas. After 1 month of biofilm development, O₂ was depleted at the anodic area but could reach the cathodic surface where it was reduced. Consequently, differential O₂ concentration cells were the driving force for corrosion. The O₂ microprofiles indicated that O₂ was consumed in the tubercles, probably by microbial activity, while O₂ was reduced electrochemically in the cathodic areas. It was concluded that O₂ transfer to the cathodic surface was the rate limiting step for the corrosion process.

Key words:

• biofilm
• corrosion
• microelectrode
• tubercle
• mild steel

Notes

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