Bad rust or ok?

That's looks fine, but still wouldn't hurt to tap all along with a hammer to insure there are no thin areas.
I'd rather see surface rust like that then where it's been painted over to just cover it up.

 

So true! Id be worried about fresh paint!
Funny thing is, such things as flash rust is also a protectant!

 

This ^ BUT make sure you check the entire frame yourself with a small ball peen hammer BEFORE you buy it.

 

So, here is some basic information on different metals and why you should be selective in what you attach directly to your frame in the future.
One of the big issues we had in the military (and on our own vehicles) is the use of antennas. The electric current running through the base and antenna created a galvanic corrosion since most bases for the antenna were mild steel and the antenna was aluminum (or any different combo). So, basically....the base would rust like crazy and fast no matter what you did. The solution to that came in a gasket with a metal mesh inserted between. This allowed the separation of the 2 metals, but still allowed connection. Basically, we use this type of gasket (only since 2008) across every platform we can.
Here is a chart of what metals sacrifice for others (if you're like what!?!? this is for real??) then yes, I was the same way when I first was educated on this. Most boats you will notice have a sacrificial bar of zinc near the motor. Here is a chart to help understand just pulled from the internet.

As far as using inorganic/organic zinc powder in paint, you would be surprised to find that many paints come this way, but doing it yourself is an option. the mix and application really depend on your abilities and preference. I would say get some off the shelf stuff (s a primer) and then look to put a topcoat on it once it cures on the frame. Believe it or not (and I'm not a fan of rustoleum) but they have a cold galvanizing spray you can use (zinc rish spray) that you can get from home depot.


"Zinc powder is used in zinc rich paint to protect steel surfaces from corrosion. Zinc-rich paint is an essential component of most heavy duty coatings, as used in the protection of major structures such as offshore oil rigs, steel bridges, petrochemical and powder industries. Other applications include the painting of sea containers and in the construction and maintenance of ships and marine equipment."

 

what ratio would you use? any special paint you'd recommend or just any exterior paint for steel?

 

You sir deserve a cookie. I work in collision and you would be surprised how few people grasp this.

 

I am saying for the average person (like us taco users) this would work fine for at home application (see below). Although I just noticed it states it provides cathodic protection (which it definitely does not). I haven't used this product, but I might get a can to test out.

Then, you could use a POR15 or something like that as a top coat (since this is for the frame) you don't have to worry about UV protection and the like. I'm not even opposed to rustoleum top coat after you lay the primer. From your military background, you probably have seen that most systems we have, paint coatings is the cheapest investment to make, but CARC is by it's very purpose not a corrosion protectant. Although different variants of CARC are now available.

 

yeah, you would see this all day long I bet. It's basic properties that want to go back to their original form...iron ore. We'll never stop it, but we can prolong, delay, and control it.

 

Thanks for the info, this is really useful.

Would you consider this a good option on a bare metal part of the frame (think CMC), and then top coat it with whatever you want?

$17 Rust-Oleum Corporation V2100 Cold Galvanizing FLAT 15 OZ. SPRAY, Gray

https://www.amazon.com/Rust-Oleum-V...dp/B000LET8DA/ref=psdc_13399701_t1_B00106H68W

 

Its all i did to my 2001 tundra and after 19 years the frame was still good. I guess if you plan to keep the truck to eternity you need to do more prep work. Fluid film basically encapsulates any rust so the air can't get at it for awhile.

 

This particular spray seems to work, but it looks like you cannot do a top coat. I haven't tried it, but if the content is as they say, it should work as a single spray application upon cleaning up the surface. Note of caution though, surface prep is key (but) I think you should be good to go with frame application considering it's a used vehicle. This or fluid film application will take care of your situation. Might I suggest Fluid Film spray with straw nozzle in any open gaps of the frame and a cold spray on the outer....protect what you can on both inside and out. My FJ had areas where I could do that (screw holes, etc).