Location of corrosion on iron and carbon steel surfaces with crevices

Corrosion of iron and carbon steel surfaces within crevices formed by a thin piece of glass, was assessed using a Video microscope, current density mapping, and corrosion potential measurements. Corrosion initiated adjacent to the glass and spread slowly to other parts of the freely exposed areas. For many days, no corrosion was found under the glass in simulated tap water, NaCl, and Na2SO4 solutions. An explanation for the protection oi the crevice has been suggested whereby alkalization with partial reduction of the passive oxide protects the surface under the glass from corrosion.