Acid etches were used on production lines for many decades and I don't recall ever seeing paint bubbling from those seams. The acid only etches the metal to allow the solder to bond to it.
Unless you leave open pockets of flux residue there will be no problem and the nature of working with body solder (in that the solder creates a molecular bond with the steel) makes the possibility of voids or pockets nil... unless the work is very sloppy.
