I have some light rusty spots in some hard to reach areas on my truck, under the bed, around the rad support corners and so on. Id like to address the issue before it gets worse but its really not feasible to fix these spots properly (ie sanding and repainting) so I'm wondering if these rust converter products actually work? I found some VHT spray on rust converter that says you can just spray it directly on rust and it turns the rust into a black coating. What are your thoughts on this? Waste of time and money or worth giving it a shot?

 

A heavy duty rust converter will/should take any near by paint off so you really need to be careful with it.

Phosphoric acid is the active ingredient in most rust dissolvers/converters, it changes rust to an inert metal that can hold primer.

Many products use Phosphoric acid, like coke a cola, which can be used as mild rust remover/converter, have to clean off the sticky stuff with soap and water after, lol.

You would clean any areas first, then apply Phosphoric acid and mix it around with brush or ?? and let it sit a few minutes then mix it around again, you have to give it time to react with the rust, then rinse and repeat as you see fit.
Mini wire brushes are good for tight places, even tooth brushes

Navel Jelly has a higher concentration of Phosphoric acid, its a jelly form so it can stick to non-flat surfaces, but it WILL take off paint, so use carefully.

After any treatment clean the area with soap and water and then use a degreaser or oil remover if it needs it.
Wait until area is DRY, and that's dry as a bone, a dinosaur bone, lol.
Then primer it and then after it drys paint it.

Primer can stick to metal, paint can not stick very well
Primer doesn't wear well, light, water and other things cause it to breakdown
Paint does wear well, and paint can stick to primer and holds very well

So Prime and then paint.............always

 

I like navel jelly my self, but I leave it over night and apply until the rust is gone, scraping off any excess rust as I apply more jelly.

 

I have used Corroseal and brushed it on rust. It does work well. It converts the rust to a hard black substance.

 

And just a heads up
Rust is the same oxidation that occurs when you burn wood, or anything else with fire.
Oxygen is corrosive, which is why bare metal rusts/"burns", and it does release heat like a fire does, just can't roast marshmallows on it, lol.

And like a fire, to put it out completely you must get ALL the smoldering embers.
Primer and paint cut off the oxygen, which is how it protects from rust.

Oxidation occurs faster if there are salts and water, water is H2O so 2 parts OXYGEN
Salts, any minerals really, speed up rusting, which is why areas with salted roads or areas near an ocean will have faster rusting of unpainted metal.
And why Navel ships rusted so fast, lol.


You can cover rust with a thick paint to cut off its oxygen, air and water proof, and it will, for sure, slow it down.
But getting a rust spot down to bare metal, put out ALL the embers, is the only way to stop it