It is a oxidized brushed aluminum plate with dirt. The oxidation reduces the reflectiveness of the metal, so the surface has uneven glossiness.

Besides oxidation, dirt also affects the colors and reflectivity of aluminum.

This highly oxidized metal plate is full of round cap nails, but well aligned. It is usually used as covers for containers.

Dirt has accumulated around round caps as those are good places to hide debris.

Oxidation has different degrees too. It can be proved by different reflectivity.

Of course, scratches cannot be omitted for oxidized iron metals.

It is a galvanized metal sheet with different sizes of scratches and pitting.

The crystallized pattern defines the signature of galvanized iron.

Galvanized metal is commonly used for covering wooden structure. Usually, construction workers simply nail them on wooden parts.

It is also used to make water tanks.

It is a cobalt or nickel like metal plate. The surface has been hammered, so it is very uneven and bumpy. The surface is also oxidized affecting the reflection.