Corrosion detector using an array of planar Cu electrodes is demonstrated. The planar Cu electrodes are patterned from commercially available single-sided printed circuit board (PCB). The ten electrodes exhibit anodic and cathodic characteristics by producing anodic and cathodic currents when they are immersed in 3 wt sea salt solution. The corrosion rate deduced from the maximum anodic current and from the three times standard deviation of anodic currents agrees reasonably well with corrosion rate published in the literature. ©2009 IEEE.