An early stage of localized corrosion, i.e. pitting and crevice corrosion, of a pure copper and a brass in uncoated and coated conditions in seawater was investigated in situ by a new non-destructive testing (NDT) method. The new method of localized corrosion detection is based on the optical corrosion-meter for measuring the corrosion current density (J) and on a modified electrochemical noise technique for determining the corrosion admittance (A(c)) at the open circuit potential of the alloys in solutions. The observations of localized corrosion were basically interferometric perturbations detected by the optical corrosion-meter only on the uncoated copper and the coated brass at the beginning of the tests. The interferometic perturbations interpreted as a localized corrosion in a form of an early pitting and crevice corrosion, of a depth ranged between 0.3 mum to several micrometers, of the uncoated copper and the coated brass, respectively. Also, the early stage of localized corrosion of the same alloys in same conditions was determined in situ by a modified electrochemical noise (EN) technique, called the modified electrochemical emission spectroscopy (MEES) technique, simultaneously during the optical interferometry measurements. Determinations of localized corrosion by the MEES technique were electrochemical noise spectra detected on corrosion admittance (A(c))-time plots of the alloys in solutions. The corrosion admittance parameter, A(c) = (dJ/dV), which defined the MEES technique, is capable of indicating localized corrosion and uniform corrosion activities. In this investigation, the parameter A, was modified in which that the change of the corrosion current density (dJ) was measured by the optical corrosion-meter rather than by the zero resistance ammeter, which is usually used for measuring the dJ in electrochemical noise technique. Consequently, results of the present work indicate that optical corrosion-meter as an electromagnetic method of measuring the corrosion current density, and MEES technique, as an electronic method for determining the A(c), are very useful techniques as non-destructive methods for detection of localized corrosion at the initiation stage of the phenomenon.