Persistent mildew

I have a brace of freezers sitting in open air on my back porch, both of them get 6 + hrs of sunlight and the only moisture they get is condensation and frost.
Even after cleaning with Clorox and frequent spray downs with Lysol they develop mould and mildew starting as black or green spots on the broad painted surfaces and green mould on the exterior of the seals.

Is there any thing the leaves a long term mildewcidal film that would eliminate this growth over a protracted (year plus) period?

You could try colloidal silver, copper sulfate, or borax solution, but I doubt it would work. It sounds like you have the perfect environment for that stuff to grow. I know the feeling.

what would happen if you sprayed a pretty strong concentration of baking soda on the gaskets and let it dry?
It sounds loony, but we have a mildewy bathroom and my husband and I have a competition going in terms of who can keep the mildew down. He is a bleach guy and my office is right next to the bathroom and I enjoy my respiratory ability. I read something saying that mold needs a specific pH to grow and if you can keep it skewed for long enough, you will discourage it. So far regular cleaning with baking soda (spray, scrub and rinse, and then spray again as a preventative every so often) is winning. It costs next to nothing, can't hurt.

I also do Tereza's baking soda thing. It works well for me too!

Also anything you can do to increase air flow in the area will help to keep things dry and mildew from settling in. Our furniture is kept a few inches from the walls or moved often to keep the walls and furniture backs from getting mildewy. We run a fan on musty days. Someday, I want to set up a solar chimney of some kind to keep air flowing.