We like jeeps, jeeps don't like to rust, but jeeps rust. Every time you sneeze, a Jeep gets a hole in it somewhere. I've been looking at converters mainly as the majority of my jeeps rust aside from floor boards is surface rust. I've been doing some research on the subject trying to determine the best course of action that doesn't involve me taking the jeep to a body shop and shelling out several thousand bucks. Now, I'm not endorsing any product, but I've found what I think to be the path I'm going to take based on this info.
I saw a thread on POR-15, but in reading it doesn't recommend application on unrusted metal or paint. It states that it doesn't provide protection against rusting specifically. Also after reading, it appears that POR-15 is identical to GrizzlyGrip minus the rubber chunks. Bear in mind that this is speculative based on information provided on both sites and is an inference rather than bona fide scientific according-to-Hoyle definition of identical. Both are moisture dry materials that are prone to UV Breakdown (without additive treatment).
There are several ways of applying a rust converter, and these will be the focus of my research in the interim. Rust converters use a chemical process to convert iron oxide (Rust) to another, stable, material. The 2 main ones that I found are Tannic Acid (Tea & molasses!) and Phosphoric Acid. Another product converts to magnetite, http://store.roddapaint.com/corroseal-r ... erter.html. Corroseal uses Gallic Acid as it's catalyst. There is a 4th called Oxalic Acid, but it performs rather bad in comparison to Tannic in particular.
http://corrosion-doctors.org/Experiment ... oducts.htm is some information on the types of rust. Corroseals Gallic acid makes 'another' form of rust found on iron skillets called Magnetite. Also called black rust, if you have iron skillets in your home you should be familiar with it. It is protective rather than infective and is formed in nature by the absence of breathable air, such as iron submerged in standing water.
Phosphoric acid is the longest standing rust converter. Ospho http://www.ospho.com/ has been around for a long time and it works well. My 'beef' with it is that it is a thin media and runs off fairly quickly. Would probably be better served as a bath rather than a spray. It does appear to work quickly, but is outperformed in many cases by the slower acting Tannic Acid.
Tannic acid is the first I came across in my research. Who knew that it was in molasses and tea? There are videos about that show the 'miraculous' conversion of stripped rusted panels that have been submerged for several weeks in a bath of molasses and water then sprayed off. Blew me away personally because I'd never thought of chemically converting rust even though I knew it should be possible. Rust-oleum's 'Reformer' product line uses this in it's mix, and actually outperforms a whole slue of competitors (http://www.slideshare.net/ChurchJ/churc ... dy#btnLast, slides 21 and 22). There is another product from Orison called Rust Bomb that looked awesome, but I can't find it. Giant thick blue gel, kinda like Naval Jelly, but faster. Found here http://www.hotrod.com/techarticles/body ... val_guide/
The bonus of my Jeep is that I could really care less about dings and waves in the body. I just want said body to last until. Baseline I'll be using some of the POR-15 system along with Eastwoods (http://www.eastwood.com/eastwood-rust-converter.html/) and topping it off with a rough coat of 2 part epoxy primer and concluding with the GrizzlyGrip. POR-15 Silver for the brackets and such, Eastwoods or Reformer for all over general coverage. Many/most of my body brackets are pitted with rust and will require a bit of filler that the POR-15 Silver provides.
So, I hope this kinda helps and gives you some resources that you can view on your own when considering what tools to use on your rust. I know rust converters aren't every ones cup of tea, but I dig the possibilities. Bear in mind to read the manufacturers surface recommendations. Some are not recommended for existing painted surfaces, others encourage use on already painted yet rusty areas.