Thanks for the info, I wonder why on some other threads I read once you sand and polished up the crank, you will have to repolish it every couple of the months or it will look really bad.
it is because un-anodized aluminum has open pores that readily loses its luster. I have full polished rims on my bike and if I ride on wet roads I get water spots and dirt that begs for a touch up to bring back the bling:
The water spots are visible on a clean rim and might take 2 rounds of being rubbed with Mother’s mag wheel polish to buff fully out.