Optical visualization of concentration field of Zn2+ during galvanic corrosion of a Zn/steel couple

We applied shadowgraphy and Mach–Zehnder interferometry to investigate concentration field of Zn2+ above a Zn/steel couple in 0.01 M NaCl. During galvanic corrosion, the marked changes in the concentration of Zn2+ were visualized in a thin solution layer less than 0.5 mm thick above zinc. The concentration profile of Zn2+ was also obtained by analyzing the deflection of interference fringes. The obtained concentration profile was in good agreement with that obtained by our group with a scanning probe technique. The formation of zinc corrosion products was also visualized, which occurring on the steel surface a certain distance away from zinc.