An electrochemical sensing technique based on nanocapillaries is presented. Corrosion tests can be performed on exposed areas with a diameter below 500 nm. The high current resolution of less than 1 fA (10-15A) allows the detection of early pit initiation processes and the characterization of smallest features in complex material structures. The technique was applied to track corrosion initiation processes at reinforcing particles on lead-free solder alloys and to evaluate the corrosion behavior of single phases on WC-Co hardmetals. The results showed that it would be beneficial to use Cu6Sn5 and not pure Cu- particles as reinforcing particles for lead free Sn Ag Cu solder alloys. Furthermore it was found that WC-Co hardmetals with an improved corrosion resistance should contain a tungsten carbide phase with a cobalt concentration of more than 3 atomic percent and cobalt phase with a tungsten concentration of more than 10 atomic percent.