The rate of iron corrosion for different organic carbon sources during biofilm formation

The effects of total organic carbon and biofilm on microbial corrosion were quantified using serum bottles in a 2 x 2 factorial design. Both organic carbon and biofilm bacteria had a significant effect on the iron corrosion rate, irrespective of the levels of the other variable (p = 0.05). There was no evidence of interaction between organic carbon and biofilm bacteria. Within the tested levels, the addition of exogenous organic carbon increased the corrosion rate by an average of 3.838 mg dm(-2) day(-1) (mdd), but the presence of biofilm bacteria decreased the rate by an average of 2.305 mdd. More iron was released from the coupon in response to organic carbon. Powder x-ray diffractometry indicated that the scales deposited on the corroded iron surface consisted primarily of lepidocrocite (gamma-FeOOH), magnetite (Fe3O4) and hematite (alpha-Fe203). Corrosion rates by different organic carbon sources, i.e. acetate, glucose and humic substances, were compared using an annular biofilm reactor. One-way ANOVA suggested that the effect of each carbon source on corrosion was not the same, with the iron corrosion rate highest for glucose, followed by acetate, humic substances and the control. Magnetite was a major constituent of the corrosion products scraped from iron slides. Examination of community-level physiological profile patterns on the biofilms indicated that acetate was a carbon source that could promote the metabolic and functional potentials of biofilm communities.