The corrosion behavior of two different high-strength Al-Zn-Mg-Cu alloys (AA7010-T76 and AA7349-T76) in overaged temper condition was investigated using potentiodynamic and potentiostatic polarization techniques. Optical and scanning electron microscopy were used to describe the corrosion morphology. The composition of intermetallic phases was determined by energy dispersive X-ray spectroscopy. Because the susceptibility to localized corrosion is strongly affected by intermetallic phases present in the alloy's microstructure, the influence of various individual cathodic and anodic intermetallic phases was investigated by using a microelectrochemical setup. Microscopic and macroscopic electrochemical data were compared leading to elucidation of specific macroscopic effects from a microscopic point of view. Thereby, the electrochemical behavior of intermetallic Mg2Si and Al7Cu2Fe particles in the two alloys was studied in detail. The influence of the chloride ion concentration on the onset of pitting corrosion was investigated and a "size-effect" of the probing area could be seen. Furthermore, we show that the experimental conditions have a huge influence on the pitting potential. (c) 2007 The Electrochemical Society.