Holding Back Rust on Steelies

Just got a set of steelies back from the Powder Coat joint. These are going to be three season set up as I don't wanna use them during road salt season. But I had a similar set of a rims a while back on an old 1964 Dodge D300. They developed an annoying rust band right where the inner rim attaches to the outer rim. This is because of a gap where water gets in and has time to fester. I am wondering what might be the best way to prevent or at least protect against this. I was thinking a bead of white silicone might do the trick. Keep in mind, the powder coat guy warned me about this and recommended a weld to cover this gap, but I didn't have the time to do this. Plus it's not a show truck, just a daily driver. I know rust will eventually take over and am only looking to stave off the beast. Any ideas or opinions?

 

I have some (kind of crappy) FJ steelies and have been experiment on them. What seems to work pretty well is giving that seam a good dousing with Amsoil HDMP once in a while, especially after you wash it (give it time to dry out as much as it can.)

I've been using that HDMP on a bunch of chassis parts and it really holds up well, even in rural VT Salt Hell.

 

Rust treatment?