You can use Dupont 244S to etch bare metal and put any primer you like on. Self etching primer etches the metal for you. Think of it like wood stain on wood, it soaks in. self etching primer does this on a smaller scale. You should always have a good mechanical bond, it wont substitute for that. Most self etching primers do not have any filling or very little filling qualities. You should use a two or three part urethanebased primer over it.