Technical Rust prevention

What is recommended for rust arrest/prevention inside of an enclosed window pillar on A pillar?

Id like to spray in something to prevent rust or more rust in sections I cannot readily get to.

Thank you

 

If there is an access hole,or holes. I would use 3M Cavity wax and the appropriate extended wand, which sprays a wide mist of wax in all directions to coat and block air and water from contacting metal. The wax hardens some when dry and works well.
Always spray after paint and bodywork to prevent panel contamination.

 

I used this on the inside of my frame rails. Should work for your purpose as well.

 

If you can get a brush down in there, POR-15 works quite well. I coated the inside of my rocker panels before welding on the top section.

 

Thank you for great suggestions.

The areas I would be wanting to treat would be totally unreachable (except for a probe tube like 1pickup showed.

There would more than likely be a little surface rust within.

Thanks
John