TR2/3/3A sections meet on the apron

Does anyone have any suggestions on what to do with the lap joint of the sheet metal where the up and lower sections meet on the apron? I am starting to get rust coming out and was looking for a quick fix. . I noticed the rust when I was color sanding. The proper way would to have drill out the spot welds and sand blasted the 2 pieces and then re-weld them. But I am think about doing it an easier way. Perhaps put some acid in crack to etch the metal and paint it, or maybe some seem sealer. The connection ends up behind the grill, so people really do not see it. I usually try and do things the correct way, but this car is taking too long and I have done the body work and painted the apron.

steve

The problem with acid is it must be completely removed, or it will continue to react with the metal and cause as much damage as the rust would cause. Once the seam is completely dried out, the outer layer of rust will help preserve the under metal. But then you must seal the seam from water and salts from getting in. On the underside a thick coat of primer will seal it. Primer tends to remain more flexible to reduce it from cracking. On the outside seam...more color. I’m not above using tiny touch-up brushes to re-coat very small areas like that.

I might try a phosphoric acid based product, like PPG DX579 or Naval Jelly. Phosphoric acid is relatively harmless to healthy steel, and chemically converts any rust to a protective coating.
Not very pretty, but I painted the foot rest on my tractor with "Prep and Etch" two years ago, never found time to sand it down and paint it properly, and it still has only a few small spots even being outdoors for over a year now.

I used one of Johns earlier suggestions and turned the fan screw way in and shot a stream of paint into the crack after I open it between the spot welds and clean it with air and some emery cloth. I might leave it or perhaps put some seem sealer in and repaint when and or if I get the colors matching better. Truly incidentally, when the fan gets way smaller the air should be turned down also or the paint shoots out to fast.