Why do we see much Corrosoin on the rim of a spade than other parts of it?

Question

I know what is the cause of corrosion but I don't know what is the relationship between the surface of iron and corrosion?

Answer 1

I always thought it was because the rim was a raw edge.......

Answer 2

The rim is the part of the spade that bears the brunt of the impact. When you drive a spade into the ground, the part that hits is the tip of the rim, then the rim itself is the part that first has to cut into the rock and debris, thus causing the finish of the metal to wear off. When the pressure of this causes the paint and/or finish to wear away, it exposes the raw metal, which then rusts and corrodes.