Nickel tends to be corrosion resistant. Oxidation is a probabilistic sort of thing. The higher the surface area, the higher chance of corrosive cascades. A meta

Nickel tends to be corrosion resistant. Oxidation is a probabilistic sort of thing. The higher the surface area, the higher chance of corrosive cascades. A metal sponge has significantly higher surface area than the equivalent mass of polished bar stock. I bet if they did the same thing with iron, a drop of peracetic acid on it would make it go "FOOF!". Actually that might still work on the nickel.