Does treating rust cause it to accelrate?

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I have a 2002 Eclipse and the passenger rocker panel has a weld that is starting to rust. Normally I would just treat it with POR-15 but over the weekend I happened to see my old 2006 Mazda 6 that I sold in 2012. That car had a bad pinch weld on the passenger rear wheel well and dogleg that I had touched up with POR 15 in the spring of 2012. 2 years later the whole wheel arch and dogleg was a rusty mess with a hole about the size of a golf ball in the dogleg. Does trying to treat the rust cause it to accelrate? We had 1 mild winter and 1 severe winter between Spring 2012 and now. I dont want to treat the rust on the Mitsubishi if I am only going to accelrate it into a major body rot issue in the near future. Has anyone had a similar experience? I completed the 3 step clean, prep, paint process with the POR-15 on the Mazda and then top coated the POR-15 with black automotive paint.
 
I think it does!!

Never had external rocker panel rust visible and the Winter before I sprayed Amsoil HDMP on. Drove the Sierra "just some" last Winter.

Last Spring, there was A LOT of external rust after the treatment!!

Never before! It went up exponentially.

NO WAY am I using that stuff again.
 
It all depends on how you pre-treat the rust.

If you use the Phosphoric acid/Zinc oxide "pre-treatment" and keep the rust wet for several hours, it will help "kill" the rust. If you just scrape the loose stuff off and POR-15 over it, I don't see how the rust could stop.
 
Originally Posted By: carguy996
Does trying to treat the rust cause it to accelrate?

It depends on the "treatment".

If you wind up encapsulating active rust and moisture you'll make it worse in the long run. A good example would be the "rubberized undercoating" sprayed over existing rusted areas. You'll be able to rip the coating off in a few months and find water under it.

On the other hand if eliminate the moisture and create either a strong bond impermeable barrier or a sacrificial coating of some sort, you may reduce or stop the rust.

Your description of the Mazda sounds like the POR surface-coated something that was working from the inside out. You would have been better finding the source of the moisture fueling the rust, fixing that, and then after drying it coating the inside of the wheel arch and dogleg with something along the lines of a waxy oil.
 
Originally Posted By: Wilhelm_D
Originally Posted By: carguy996
Does trying to treat the rust cause it to accelrate?

It depends on the "treatment".

If you wind up encapsulating active rust and moisture you'll make it worse in the long run. A good example would be the "rubberized undercoating" sprayed over existing rusted areas. You'll be able to rip the coating off in a few months and find water under it.

On the other hand if eliminate the moisture and create either a strong bond impermeable barrier or a sacrificial coating of some sort, you may reduce or stop the rust.

Your description of the Mazda sounds like the POR surface-coated something that was working from the inside out. You would have been better finding the source of the moisture fueling the rust, fixing that, and then after drying it coating the inside of the wheel arch and dogleg with something along the lines of a waxy oil.











Agree!
 
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Originally Posted By: Turk
I think it does!!

Never had external rocker panel rust visible and the Winter before I sprayed Amsoil HDMP on. Drove the Sierra "just some" last Winter.

Last Spring, there was A LOT of external rust after the treatment!!

Never before! It went up exponentially.

NO WAY am I using that stuff again.



That scares me. I touched up a cleaned up small rust spot under my Buick with Amsoil HDMP in the fall. I'm going to have to take a look. My experiences with products that use some form of oil slow rust down. Maybe over the weekend if I remember I'll have a look.
 
Once it starts it's my belief nothing will stop it...I have a couple vehicles now that have rust around the rear wheel wells...every spring and fall I grind off as much of the rust as I can get off, spray the areas with a Rustolium primer, then cover with the factory color...it of course comes back, but this at least seems to slow it down a bit...
 
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I've had very mixed results with rust converters and if you research the internet, you will find out the same (military tests). It is not the silver bullet the marketing claims to be.

Surface rust can be stopped. Rust starting from the inside of the pinch weld seams is another story. Applying a topical treatment of POR-15 or anything to this internally started rust will just seal in the moisture and and allow the rust to continue developing.

The oil products like Krown claim that they penetrate these seams and drive/seal out the moisture and oxygen.

Moisture and salt in the red area......a topical surface treatment on the outside will not stop the rust.
honda-steel-aluminum-02.jpg
 
The only successful rust repair that I had good luck so far with is to repair and paint the area as usual, and then treat it with oil rustproofing compound. Preferably annually.

For hard to reach areas or just general repairs where the rust cannot be guaranteed to be 100% removed, forget POR15, rubber undercoating or any other such product. Oil or grease coating that penetrates all crevices and repels water is the only solution that is long term and cost effective. It's a perfect solution for fender well and pinch weld rust.
 
Doesn't it matter how the metal was prepped initially? Seems like the better method is to use some sort of zinc underlayer, or similar. I noticed on my Jetta that initially a paint chip would leave unrusted metal. It would take a long time (like a year plus) before it would start rusting. I did some grinding on a fender, and I swear the rust on that metal is vastly worse than the rust on the hood. BUT then again the rust I'm looking at likely dries much slower than the hood.

I happened to look at the wheelwheel on my truck this weekend, and noticed rust! on the frame. I don't know if the FF dried out, washed off or I just missed it (or some combo). I think though the problem was poor paint adhesion: it was a weld point, long bead for a suspension bracket.
 
Sounds like I would have been better off leaving the pinch weld alone versus trying to repair it on my old Mazda. I think I will just live with the bubble on the rocker, I dont want to treat it only to have no rocker panel left in the spring. Is there any successful product to use for pinch weld rust? A friend of mine has a pristine 2001 model year vehicle where the pinch weld is starting to rust on the right rear. The previous owner sprayed caliper paint over the rust. Is there a neutralizer/product that could be sprayed into the pinch weld to attempt to stop the rust or at least slow it down? This particular vehicle is way to nice to start rusting and would like to help my friend out if possible.
 
There are different approaches.

POR 15 cures to a hard shell in the presence of moisture. However it is UV sensitive, and its only as good as its bonding and interface. There can be poor contact points where moisture can enter in and continue the oxidation.

I too have seen with HDMP the rust underneath. I believe the issue is that any place where the film is potentially peturbed, moisture can get underneath and stay trapped. Ditto for any that is under there before. And, regardless of how "self healing" it may be claimed, I have my doubts.

I personally feel that waxy coatings are only to be used in enclosed spaces, like inside door skins or inside rockers. Anyplace where there is the potential for damage should get a high tack oil, like Krown.

Applications may differ for certain things, like the cast iron suspension parts that wont necessarily rust away that bad under the car. But for sheet metal and similar components, no waxy coatings, IMO, only stuff that truly will creep and self-heal. Fluid film is an intermediate product that is likely OK too.

For the OP, I'd use a product like Krown or Carwell or corrosion x standard (HD is waxy). Both can be ordered online. These will drip, travel, and move into the rust and the weld, fully wetting the surface with the oil and inhibitor.
 
Originally Posted By: JHZR2
There are different approaches.

POR 15 cures to a hard shell in the presence of moisture. However it is UV sensitive, and its only as good as its bonding and interface. There can be poor contact points where moisture can enter in and continue the oxidation.

I too have seen with HDMP the rust underneath. I believe the issue is that any place where the film is potentially peturbed, moisture can get underneath and stay trapped. Ditto for any that is under there before. And, regardless of how "self healing" it may be claimed, I have my doubts.

I personally feel that waxy coatings are only to be used in enclosed spaces, like inside door skins or inside rockers. Anyplace where there is the potential for damage should get a high tack oil, like Krown.

Applications may differ for certain things, like the cast iron suspension parts that wont necessarily rust away that bad under the car. But for sheet metal and similar components, no waxy coatings, IMO, only stuff that truly will creep and self-heal. Fluid film is an intermediate product that is likely OK too.

For the OP, I'd use a product like Krown or Carwell or corrosion x standard (HD is waxy). Both can be ordered online. These will drip, travel, and move into the rust and the weld, fully wetting the surface with the oil and inhibitor.


Again I agree.

I have also had success with a Wire rope lube* applied inside to pinch welds and seams.

* the type that sprays on thin to penetrate, but sets like a viscus Tar.
 
the best you can do is slow rust down so your vehicle is all worn out before the rust gets to be a big issue. I just touch up the areas with rustoleum and krown or fluid film throughout the year and it makes a huge difference. it just doesn't get much worse. usually by the time you notice the rust, it is because sand and water are trapped in areas. when the holes appear, powerwash them clean and apply the spray paint and then the krown. most often it is wheel arches, cab corners and rocker panels
 
I would treat it.. We are talking about a Mazda here, nothing else rusts as fast as a Mazda, and this is well known in areas where we get road salt.

I applied Fluid Film all over the rear fender wells of my folks car a few years ago and the rust barely got worse as long as I kept treating it every few months.

I can't imagine that not doing anything is better than at least trying.

At least keep the car washed, if nothing else.
 
I would definitely look at Fluid Film if you are worried about sheet metal seams rusting. Would hold up to washoff during bad weather but let it creep around and get into the nooks and crannies and it should help.
 
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