MULTIELECTRODE PENETRATION SENSOR FOR MONITORING LOCALIZED AND GENERAL CORROSION

The concept of multielectrode penetration probes for corrosion monitoring is introduced. A penetration probe that can be used in both open and closed or pressurized systems was fabricated with aluminum foil and tested in simulated seawater and in simulated seawater plus 10 mM ferric chloride solutions. The average penetration rates measured from the multilayer multielectrode penetration probe for the aluminum foil was approximately 0.73 mm/yr (29 mil/yr) in the simulated seawater, and 12.5 mm/yr (490 mil/yr) in the simulated seawater plus ferric chloride solution, respectively. The measured penetration rates in simulated seawater compare well with the maximum localized corrosion rates measured with coupled multielectrode array sensor probes made with Type 3003 aluminum (0.2 to 1.1 mm/yr) and Type 1100 aluminum (0.2 to 0.5 mm/yr). The measured penetration rates in simulated seawater plus 10 mM ferric chloride solution compare well with the maximum localized corrosion rates measured with the coupled multielectrode array sensor probe made with Type 1100 aluminum (7 to 40 mm/yr). The penetration breakthrough times measured with the multilayer penetration probe in the simulated seawater (6.7 to 9 days for one layer of foil) also compare well with the perforation time observed in the immersion test with foil specimens cut from the same foil used in the multilayer penetration probe (6 days)