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).