Modified electrochemical emission spectroscopy (MEES) of detection of crevice corrosion of metallic alloys

An early stage of crevice corrosion of an epoxy coated sample of a pure aluminium, a stainless steel and a low carbon steel in 1 M KCl, 1 M NaCl and 1 M NaOH solutions, respectively, was investigated in situ by a new method. The new method of crevice 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 (Ac) at the open circuit potential of the alloys in solutions. The observations of crevice corrosion were basically interferometric perturbations detected by the optical corrosion-meter only on the coated steel and the stainless steel samples in 1 M NaOH and 1 M NaCl solutions, respectively. The interferometric perturbations interpreted as localized corrosion underneath the coating in a form of an early crevice corrosion, of a depth ranged between 0.3 μm to several micrometers. Also, the early stage of crevice corrosion of the same alloys in same solutions was det...