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I have a real issue with rust because my car already has it and I have heard that once it is there, it has to be cut and replaced with fresh meat, er metal.





Rust is indeed the cancer that slowly eats away at our cars until the day they finally go to that great smelter in the sky.

In my book there are really two types of rust. There is surface rust and there is 'advanced rust'.

Surface rust is the easiest to deal with. The intergrity of the metal itself has not yet been compromised. So to deal with it you just have to sand off the surface particles and apply 'something' over the formerly rusty surface that will cheat it from having access to OXYGEN and moisture ( don't forget that H20 is one part hydrogen and two parts oxygen ). IF you can starve that rust area of oxygen and moisture, it is darn near impossible for the rust to rally again.

This is the difference between a car that has lived in a super dry and hot climate and one that lives near the ocean or in any of the moderate temperature climates.

So just keep that principle in mind when looking at surface rust. You simply want to starve it.

The more difficult rust to deal with is the advanced rust that has eaten its way through the sheet metal - or that has begun or completed the conversion of the formerly flexible metal into the more shale or rock like rust. This is the stuff that has to be cut out and replaced with new metal. Because once the metal hits this advanced stage of rust there is NO CHEMICAL known to mankind that can return the shale or rock like rust back to the flexible metal that once existed there.

Now... there are some chemicals out there that promise to kill in its tracks any of this advanced rusting and freeze it so that there is no further advancing of the rust. This is absolutely true. BUT you are still left with an area that has the flexibility of shale or a rock. You would be able to do surface preparation over such a chemically treated area and get primed and painted. But nonetheless that area will have zero flesibility and would be destined to crack the paint if that area is flexed ( because it would stay rigid while the surrounding area would flex ).

Another factor would be the rate of expansion during temperature changes of the metal area versus the chemically treat shale and rock rust area. Different rates of expansion gurantee future cracks in the paint. A crack in the paint gives oxygen and moisture a pathway back to the chemically treated area. Eventually it will reach the surrounding areas that do not have the chemical treatment through a process called papillary action - where it seeps and travels between the subsurface of the body and the paint skin.

The key principle to remember here is that if you have holes that are all the way through.. or the rust has converted the former flexible metal to shale or rock... you have to remove it and replace it.

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Since none of the rust is structural, and the car isn't likely to be worth much in the future, I was looking for a DIY solution in the spirit of the $50 paint job.





The best place for most of these 'freezes rust in its tracks' compounds is the undercarriage of the car. These are ideal spots to be using that type of chemical because undercarriage and subframe rust is ultimately what will send your car to the wrecker ( barring an accident or fire first ).

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I have used por on a variety of small rust repair jobs where finish quality wasn't important, and it works. I was under the impression that its sucess was due to its ability to lock out air and moisture from the surface of the metal.





Exactly right. It chokes off the access of oxygen and moisture from the metal surface.

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Are you saying that a smooth finish on a large scale with por is perhaps beyond the skillset of a beginning roller?





I believe anyone can get the stuff on to a cars body. But some problems arise. To do the roller method properly you need to thin the paint. This helps with the self-spreading / self-leveling. By adding thinner to POR you are chemically changing it or altering the way it was designed by the manufacturer to be used. You also may be altering its effectiveness at doing what it was designed to do. The other difference will rest on how the subsequent surface sanding or adhesion of the later paint layers may turn out.

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I did not understand the single stage urethane reference.





Think of a polyurathane as simply being a liquid plastic type paint. A single stage polyurathane is a self-contained paint... in that its ability to dry and harden is all in that ONE can. You slap that one stage paint on and it dries on its own merits based on the evaporation of the 'carrier' that the paint comes with.

But as in everything in the world, people always want faster and quicker... So the paint industry came up with a TWO stage paint... where you basically get one can with paint and one can with the catalyst or drying/hardening agent. Prior to using the TWO stage polyurathane, you have to blend the two cans together.

In body work, this would be like saying that glazing putty is a one stage chemical ( since you usually just squirt it out of the tube to appy it ) and comparing it against Bondo as being a two stage chemical ( since you have to combine the Bondo with its hardening creme to get it to harden and dry ).

All this having been said... Rustoleum painted over a prepared surface rust area will do the job of choking off the oxygen and moisture to that metal surface. This is what it was chemically designed to do in the first place. So it is a safe bet for achieving what you want for surface rust.

Brightside on the other hand was originally designed to be use on boats - the majority of which are fiberglass. But to Brightside's advantage it is basically a liquid plastic. And as such its polymers do provide an excellent seal against penetration from oxygen and moisture from reaching the subsurface. Combined with the polyurathane's better adhesion qualities I think you can safely consider it as a safe bet for painting over prepared surface rust areas.


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On another note, with proper surface preparation, Do you think por-15 (or silver bullet)is unnecessary with the rustoleum paint?





I believe you can go either way on this. You can either treat the POR as the surface primer and than lay Rustoleum/Tremclad or Brightside over it... OR you can bypass the POR stage and go straight to the Rustoleum/Tremclad or Brightside painting. The deciding factor will be your confidence leval at which way will ultimately give you the longest lasting effect.


Tee hee... I must sleep at Best Western Hotels and Motels quite a bit to be writing so much on Christmas day.

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