Chemical etching behaviour of titanium in bromine-methanol electrolyte

An air-formed or anodic oxide film was detached from titanium by chemical etching in bromine-methanol electrolyte, exposing the bare titanium substrate and grain boundaries with defects at specific regions. Without the protective air-formed TiO2 film, pitting corrosion occurred on the bare titanium substrate due to the attack of bromine. The corrosion pits propagated with etching time from 10 to 300 s and were displayed using white light interferometry. Increased surface roughness was identified with etching time due to the increase of pitting corrosion attack. TiBr4 compounds were detected by EDS and X-ray diffraction patterns, indicating that the dissolution of the titanium substrate was induced in each etching treatment.