I'm in the process of derusting, cleaning, priming & painting my '92 Talon's underbody, e.g. control & trailing arms, knuckles, strut towers, diff carrier, subframe, etc., and was hoping for some advice on rust prevention once I'm done removing the rust and cleaning the parts.

I've more or less figured out how to remove the rust and clean everything, mainly wire and abrasive brushes, the occasional drill or rotary tool grinding wheel for tough spots, sandpaper, Scotchbrite, Evaporust, Krud Kutter, Rustoleum Gel, etc., and then some Purple Power, a washdown, then brake cleaner or isopropyl alcohol before priming and painting.

Using these methods I'm able to get most of the rust off down to the bare metal, but there are a few spots here and there where there's still some rust, especially in hard to reach areas. So I'm wondering what to prime and paint it with to either convert or seal what rust remains and prevent future rust.

So far I've used Rustoleum Rust Reformer (auto version) as a converter/primer/sealer and Rustoleum Stops Rust Enamel Semi-Gloss paint as a topcoat (no need for a clear coat under the car although I may apply rubberized underbody spray paint to parts close to the ground).

But I've found out that Rust Reformer is really for completely rusted metal, not lightly rusted metal. Am I better off using Rusty Metal Primer, or perhaps even Clean Metal Primer for where there's very little rust? And is the paint I've been using ok as a top coat?

I know about POR-15, and some will suggest it instead as a superior alternative. But it seems pretty involved and kind of nasty and hard to apply, so I'd rather not mess with it if possible.

There are many threads on here asking the same question, and the answer depends on where the rust is, and how much there is. You did a good job describing your process and it should be fairly successful, if you can keep the rust from coming back.

There are 3 ways to chemically deal with rust: 1) Smother the remaining rust with a good quality enamel, like Rustoleum, and try to prevent moisture from reactivating the rust. 2) Neutralize the rust with a chemical that converts the rust to an oxide, like Rustoleum Restorer, or 3) Stop the rust ‘growth’ by sucking the moisture (water) out of the rust to stop it using POR-15.

We’ve had good success wire brushing as much of the rust as possible, applying POR-15, and top coating with Rustoleum. POR-15 can break down in UV light, so it cannot be left as a top coat.

I like the neutralize rust option, but am wondering which product to use for that. Apparently Rustoleum has several, that contain tannic acid, that neutralizes the rust. But it's a bit confusing as to which one is best for what can best be described as spotty rust, i.e. brushed down to mostly metal but spots of tough rust distributed throughout, sort of like metal rust freckles, where the rust pitted the metal more than elsewhere. It's a pain to get it all out, especially in hard to reach areas.

Apparently Rust Reformer, which I've used so far, is too heavy-duty for that, being intended for where rust coverage is complete. But the next step down, Rusty Metal Primer, also says it's for heavily rusted metal. The next step down from that is Clean Metal Primer, but it's for clean metal with little to no rust. Nothing in-between the Rusty and Clean Metal Primers.

Also, I wonder how effective any rust converter/neutralizer is when applied to the sort of cruddy, "baked-on" rust that's so hard to take off. I'm guessing that this is surface or scale rust mixed with oil, grease or brake fluid, that's heated up and "baked" into this hardened scab-like rust deposit.

If I scrape or grind it, it breaks apart into this fine rusty dust that's strangely satisfying to see, since it confirms that I'm removing rust. But if I wire brush or abrasive wheel it, it just glazes the surface. I wonder if rust neutralizer can actually get in there and convert this kind of rust. It would have to be pretty strong acid to do that. I try to scrape or grind it off, but that's not always possible. I'm guessing that this sort of rust is self-encapsulating, and you can just prime and paint over it. But I'm not sure.

DogWhistle said:

There are many threads on here asking the same question, and the answer depends on where the rust is, and how much there is. You did a good job describing your process and it should be fairly successful, if you can keep the rust from coming back.

There are 3 ways to chemically deal with rust: 1) Smother the remaining rust with a good quality enamel, like Rustoleum, and try to prevent moisture from reactivating the rust. 2) Neutralize the rust with a chemical that converts the rust to an oxide, like Rustoleum Restorer, or 3) Stop the rust ‘growth’ by sucking the moisture (water) out of the rust to stop it using POR-15.

We’ve had good success wire brushing as much of the rust as possible, applying POR-15, and top coating with Rustoleum. POR-15 can break down in UV light, so it cannot be left as a top coat.

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This
I was into muscle cars years ago and por15 is tough stuff. You do have to top coat it. I did all the control arms on a gm a body cutlass. I could hit them with a ball peen hammer when it was dry.

XC92 said:

I like the neutralize rust option, but am wondering which product to use for that. Apparently Rustoleum has several, that contain tannic acid, that neutralizes the rust. But it's a bit confusing as to which one is best for what can best be described as spotty rust, i.e. brushed down to mostly metal but spots of tough rust distributed throughout, sort of like metal rust freckles, where the rust pitted the metal more than elsewhere. It's a pain to get it all out, especially in hard to reach areas.

Apparently Rust Reformer, which I've used so far, is too heavy-duty for that, being intended for where rust coverage is complete. But the next step down, Rusty Metal Primer, also says it's for heavily rusted metal. The next step down from that is Clean Metal Primer, but it's for clean metal with little to no rust. Nothing in-between the Rusty and Clean Metal Primers.

Also, I wonder how effective any rust converter/neutralizer is when applied to the sort of cruddy, "baked-on" rust that's so hard to take off. I'm guessing that this is surface or scale rust mixed with oil, grease or brake fluid, that's heated up and "baked" into this hardened scab-like rust deposit.

If I scrape or grind it, it breaks apart into this fine rusty dust that's strangely satisfying to see, since it confirms that I'm removing rust. But if I wire brush or abrasive wheel it, it just glazes the surface. I wonder if rust neutralizer can actually get in there and convert this kind of rust. It would have to be pretty strong acid to do that. I try to scrape or grind it off, but that's not always possible. I'm guessing that this sort of rust is self-encapsulating, and you can just prime and paint over it. But I'm not sure.

Click to expand...

Again check out por15. My control arms were not bare metal. Not crusty. I cleaned them off but still had plenty of surface rust. Worth reading up on the product.

I have, and it's widely considered to be the best, but I keep reading about how nasty it is to work with. I appreciate the feedback, which is all I asked for, and will decide how to proceed.

I take it you're not a fan of Rustoleum primers, at least with rusty underbody parts?

Would phosphoric acid-based reformer like Krud Kutter or Rustoleum Gel Rust Dissolver, allowed to convert the rust and dry, maybe sanded down so it doesn't look lumpy, primed, then painted, accomplish much the same thing? It's just that I already have all of these.

IVe used por 15 two years ago until i can cut out the old rust and weld in some new metal its, a really great product. I enjoy using it and its easy to do.

Well, then POR-15 it is! Thanks.

Eastwood's Rust encapsulator is good stuff. Better than rustoleum but not quite as tough as Por15. Much, much easier to work with than Por15.

Doesn't phosphoric acid-based rust converter basically "encapsulate" what rust it can't convert, since they all come with some sort of resin in the formula as well? This is so confusing!

I have no opinion on rustoleum as I've not used it. Por15 applies easily it just doesn't come off and its thin so it drips easily. Its kinda nice because no brush strokes because its thin. I put this stuff up in an industrial environment. Metal diamond plate on a wall that sees a lot of abrasion.. 3 years and nothing. it was a UPS hub if you're interested. You don't want to get it on anything, the floor etc as it does not come off. This includes your hands. No joke it doesn't come off with anything. As stated it does not like UV rays.

Man wear gloves its really nasty ive gotten it on the floor had the garage a mess, so wear gloves and i did mine in a dark garage with limited lights when i used it.

That's exactly my concern. I'm working on the car in the driveway of a kindly old neighbor who just passed away, so not only do I have to get this done fairly soon as her family is probably going to sell the property, but I don't want to risk getting stains on the driveway. I suppose that I could put a tarp and weightit down with bricks, but one false move and I've got some splainin' to do.

Yes POR15 is real nasty black stuff that drips all over you and is permanent. I mean you'll never get it out of whatever it touches so plan accordingly. Clothes that you can throw away, tarp under car, gloves, hat, etc. It works great but what a mess to apply.

In case anyone's still following this thread, after completing the rear I took apart the front and am in the process of derusting, cleaning and painting the front. I mean the calipers (including a complete rebuild with new seals and boots), knuckle, control arm, other suspension components, etc. It's really cruddy and rusty and it would be a shame to not take the opportunity to do it right.

And, since I have to pull the CV axles to drop the trans to replace the clutch (and try to fix a separate trans issue that I addressed in a separate thread, 1st gear popping out under load), I was thinking of completely removing the lower control arm and knuckle (with the hub still installed as the bearings appear to be ok and don't need replacing at this point) and cleaning them outside the car. It would make it a lot easier and I would be assured of doing a thorough job.

Here's what it looks like now:



I can do it with everything on, but pulling these out just seems like the right way to do it. I can get loaner tools from local auto stores to do it right. The challenging part will likely be taking the CV axle out of the hub. I bet it's never been removed and is rusted seized (the axle nut looks terrible). In which case I'll either leave it on or have a shop press it out and if necessary replace it.

If I do do this, some of these are locking nuts and need to be replaced. Any idea what their specs are and where to buy them? They're self-locking, right, the kind with a rubbery insert above the threads?

Is this the one: https://www.rockauto.com/en/moreinfo.php?pk=6336729&jsn=7444

Also, the bottom of the strut assembly looks pretty rusty. How bad does it look, and should I get new struts for this reason alone (it might be time to replace them anyway)?

And, while I'm at it, here are the front brake caliper pistons, left and right, respectively:





The left one needs to be replaced, I assume. How about the right one? When I rub my finger along the rough-looking part near the boot, I can just barely feel a very light roughness. It's more obvious when I try to scratch my fingernail across it.

I ended up ordering a new one from Amazon. However, it's Dorman, not OEM, at $9:

https://www.amazon.com/gp/product/B004Y3HSHW

I found the OEM part # and turns out that Amazon's got it too, cheaper than other places at $19:

https://www.amazon.com/Mb699692-Cylinder-Piston-Mitsubishi-Febest/dp/B00DMA3W96

Should I cancel the Dorman and get the OEM?

IMHO yes. Dorman is junk quality IMHO. Things where you don't need quality they are ok.

Does it look like both need replacing or just the left one?

Also, RockAuto sells a Raybestos version for $15 that lists the OEM part # as an alternate part #, so it may actually be OEM:

https://www.rockauto.com/en/moreinfo.php?pk=307261&cc=1103094&jsn=58328&jsn=58328

...Ok never mind about the RockAuto version. With shipping it's more than the OEM.