Polish it. Looks like you have some pretty bad pitting, possibly from salt; may have to buff it out. Be careful as there are both polished aluminum parts and electroplated (chromed) parts; they take different techniques. Start by hand with something like Mother Aluminum polish.

 

You'll have to remove any "clear coat" first ...

 

 

Wet sand, polish with 1500 or 2000 grit used to put a very high polished finish on forearms, aluminum wheels and fuel tanks with that method.
lots of work tho

 

might try NEVER DULL. it comes in a can and has a treated packing inside. we use this stuff on our steel guitar parts. however, the hd aluminum is a diff animal and to do it best would be to remove them where a low and high speed buffers can be used. they make metal conditioning wheels for heavy marks. a good source but $$$ would be EASTWOODCO.

https://images-na.ssl-images-amazon....YL._SX425_.jpg

 

AGREE
A lot of work, but if needed, this method is fantastic.

 

Never Dull sucks. I tried it twice and threw it in the trash.
Try this
https://www.autogeek.net/wolfgang-me...polishing.html

 

never dull WILL NOT remove heavy marks, it is a FINE abrasive and works with chemically treated wool. if you have heavy marks, metal conditioning wheels will remove them and yes they do have grades so choice in muy importante!!!.
to do it RIGHT, best to remove parts if possible, on machine is crapola!!! never dull works on 3>10k dollar steel guitars but then again not crapola aluminum like hd parts. if you do not have what it takes, farm it out.

 

Quick-Glo found on Amazon. Use it with a foam attachment on a cordless drill. The stuff is magic