If they look chrome, then they are always chrome plated, most often on late model wheels the chrome is over aluminum. Some older wheels might have been over steel. You will never see all chrome, it will always be plated. It's properties make it unusable for much else.
Some 03/04 Cobras came with plain machined aluminum wheels that are also painted in spots and then clear coated over all. Those versions are obviously going to be the lightest.
They use chrome because it's "more purdy".
The chipping has not been a problem on my car but brake dust corrosion is a valid concern. That is why I have switched to Carbotech Bobcat 1521 brake pads for my street pads.