Microbiological Influenced Corrosion Behavior of Full-coated and Nicked-coated Specimens

The microbiological influenced corrosion (MIC) behavior of the low alloy steel with Zn-rich epoxy coating and micaceous iron oxide epoxy coating in the sterilized medium and sulfate-reducing bacteria (SRB) solution was investigated by using both full-coated and nicked-coated specimens. Results show that for steel coated with Zn-rich epoxy, the corrosion resistance of both full-coated and nicked-coated specimens was improved obviously. The Zn-rich epoxy coating protected the test steel effectively in the microbial environment with the cathodic protection in the earlier period and physical barrier protection in the later period. For steel coated with micaceous iron oxide epoxy coating, the corrosion resistance of full coated specimens was improved greatly. However, for nicked-coated specimens, corrosion was aggravated because the small anodic area around the nick accelerated the corrosion. It is concluded that the basic low alloy steel may be effectively protected by the micaceous iron oxide epoxy coating only when the steel is perfectly coated with the coating, breakage must be avoided.