The effect of sulfate-reducing bacteria (SRB) on electrochemical corrosion behavior of 16Mn steel

and galvanic corrosion behavior of the steels in the juncture area between bacterial and bacteria-free sea mud was studied in laboratory under simulated conditions. Sea mud dense with SRB was taken from the Qingdao beach. Part of the sea mud was sterilized and the rest was kept in the original condition. The sterilized and original sea mud was put respectively into two plastic testing troughs electrically-connected by an agar potassium chloride salt bridge. Galvanic and non-galvanic 16Mn steel samples were put into the trough at the same intervals. The SRB number measured by the MPN tri-tube method was about 2.4×105 per 100 g mud and was kept basically the same during the experimental period. Thep

pH

eH

T

S (salinity) were measured simultaneously. The galvanic current was measured with zero-resistance galvanometer and the corrosion rate was measured with the weight loss method. The results showed that (1) the corrosion rate of 16Mn steel in bacterial sea mud was 4.0 times that in bacteria-free sea mud; (2) galvanic corrosion occurs between steel samples buried in different (bacterial and bacteriafree) sea mud. The steel sample in the bacterial sea mud was the anode of a galvanic couple and had higher corrosion rate than that of the non-galvanic sample. The existence of the galvanic couple increased the corrosion rate of the sample in bacterial sea mud by 4.1%.