Frame... Just had an idea..!!

Don't leave it as it is.....oil it or get underneath and paint wheel bearing grease with a foam brush on suspect areas.

 

It is not a full boxed frame like a lot of trucks so no way with adding to seal it up.

There are a few small sections boxed but not enough to deal with.

 

The last thing you want, is to seal any thing. You need drain holes. Even box frames have faily large side entry holes. Remember, rust starts at the welds which break down any protective coating. Theoretically, a box form which has more welds in it and fewer places to drain, should be more, not less prone to rust.
Remember too, in the majority of the country, rust is not a problem. If you live in the salt belt, you listen intently to any suggestion made. If you live in Teaxs or Florida, you're more concerned about keeping a good finish then rust.

 

My '12 Tacoma was starting to show so pretty nasty scale on the frame after just two MI winters, so the problem still exists. My '10 Xterra (just purchased) still looks like new after 5 winters, so it's something to do with Toyota QC. Fully boxed or not makes little difference if the frame itself is properly coated.

 

What did the previous owner do and where did he drive it. I have a friend who hoses his cars underneath EVERTIME he drives in bad weather. He has cars thirty years old with no rust. He keeps them til they become antiques.....literally in the rust belt. Nothing beats cleanliness and oil.

 

I have a 2012 and crawl under mine every couple of months and spray any rust with the rust converter spray and then spray again with Rust Resist paint. Trading for 2016 and will do the same.

 

Of course if you just painted wheel bearing grease on it every year it would last a life time too. Even spots that have started to rust..will stop with grease on it. The O2 is shut off.

I had an 04 Runner I did the grease and oil thing. It's frame looked great after 11 years. Grease treatments will make your car last decades. Reprainting does not show the rust under the paint until five years later and it starts flaking off with a hole underneath. Permanent paints are temporary solutions. Paint is porous, grease is not. Now, if you wax your frame over any paint, if might work better.