The image below shows a sample of an electropolished aluminum product.
Similar to stainless steel, aluminum has a directional crystal structure when it is rolled into a round bar. As a result, the crystal structure differs greatly between the side and cross section of the bar material. Due to the electro polishing process, you can see the difference in the photo [after treatment], the side has gloss finish, cross section has satin finish as shown.
[Before EP treatment]
[After EP treatment]