In situ high-resolution photoelectrochemical imaging of precursor sites for pitting in polycrystalline titanium

Photoelectrochemical microscopy (PEM) was used to locate pitting precursor sites on polycrystalline titanium immersed in sulfuric acid and in ferrocyanide solutions. PEM imaging was done with both a conventional method and a new shear-force feedback method. The resolution of the PEM images obtained are highly dependent upon the size and preparation procedure of the optical fiber used for the test. 1 μm diam etched tips yield higher lateral resolution images compared to commercially available `pulled' tips. PEM with simultaneous independent topography (using the tuning fork method) resolved submicron features at precursor sites at inclusions and grain boundaries. Both PEM and topographic images were obtained in situ with high lateral resolution by using specially fabricated tips with 100 nm aperture.