Take it from someone that has "Been there done that"...
My 1964 converted aluminum Lone Star flats boat still
looks good from a Dupont Centari paint job 20 years ago!
Sand blasted then acid washed and primered with zinc chromate. Make sure you zinc the chit out of your bracket
to prevent the corrosion factor.
A little more effort up front pays off in the long run..
See ya, Ken