Corrosion behavior of pure iron beneath a micro-droplet of sulfuric acid solution investigated by atomic force microscopy

A micro-droplet of H2SO4 solution with a diameter of 1–10 μm is put on a pre-assigned target micro-zone of pure iron and the corrosion behavior investigated using an atomic force microscope. During the initial 0.6 ks, the average corrosion rate of the specimen decreases with the decrease of the droplet size. The drying of the droplet to a solid corrosion product in 25–30% relative humidity condition is faster than that in 50–70% relative humidity condition.