Modified electrochemical emission spectroscopy (MEES) As technique of NDT for detection localized corrosion of copper alloys in seawater

摘要

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 the form of an early pitting and crevice corrosion, of a depth ranging from 0.3 um to several micrometers, of the uncoated copper and the coated brass, respectively.