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Primer, Rust, and related...

Discussion in 'The Hokey Ass Message Board' started by Bort62, Mar 31, 2008.

  1. Bort62
    Joined: Jan 11, 2007
    Posts: 594


    I've done a search and read a lot - but it's still fairly ambiguous. I am hoping that, for my own information and others on this site, someone can help me lay out a fool-proof method for dealing with rust.

    I am currently dealing with some very serious rust on my Ranchero. The easy answer that people will give you is "cut it out and replace the metal"

    That's great... but we all know that in some circumstances that is not a realistic approach.

    What I am looking for is some constructive information on dealing with rust in two circumstances.

    1.) Surface rust on sheet metal.

    I sandblasted my fenders down to bare metal, and then primered them with rustoleum. It's been a few months (and it's been out in the weather) and I can already see rust coming up through the primer. Is the rustoleum primer I used not waterproof, or did I just not get all the rust before I painted (altho it sure looked rust-free after blasting). What primer should I use if I figure on it sitting a while before getting to paint? (specific, please)

    2.) Cancer.

    It's a unibody car, and suffers from typical cancer. I am not worried about the structural aspect - I feel comfortable fixing that issue. What I am worried about is stopping the existing rust and keeping the cancer from spreading.

    Short of cutting it out and using new metal (which is not an option for many parts of it) What approach is best for accomplishing this?

    And please don't say "use a rust neutralizer". Tell me WHICH neutralizer to use as there are about 200 different ones on the market and I am sure they don't all perform the same.

    Thank You.
  2. The Hop Walla
    Joined: Aug 19, 2007
    Posts: 427

    The Hop Walla
    from Dallas

    Not to be a prick, but I don't understand 'not an option' when referring to cut/replace. How else do you deal with a big honkin' rust hole?
  3. Gas Huffer
    Joined: Feb 26, 2007
    Posts: 272

    Gas Huffer

    "cut it out and replace the metal"
  4. Bort62
    Joined: Jan 11, 2007
    Posts: 594


    OKay, the front leafspring mount on the passenger side is rusted badly and not structurally sound.

    So I cut it out and fixed it. I ran subframe connectors and essentially put a frame under the car rear half.

    Back where the leafspring mount is there is some rusted out remainds of the subframe and various other sheetmetal. It is no longer structural. I would like to seal it off rather than cut it all out and have a bigass hole
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  5. Fifty5C-Gas
    Joined: Sep 1, 2003
    Posts: 1,428


    Cut it out an replace it....If not it will ALWAYS come back, much much sooner than later.
  6. Bort62
    Joined: Jan 11, 2007
    Posts: 594


    I guess I asked too much. There are plenty of chemical reactions that remove rust from steel. When its done, you have bare steel.

    You can then paint it and protect it from re-rusting. What I wanted to know is what products people have used with success. However, apparantly, everyone on the HAMB has spent 1000's of man hours cutting out, fabricating, and welding in replacement metal for EVERY rusty spot on their car.

  7. JDHolmes
    Joined: Nov 25, 2006
    Posts: 918

    from Spring TX

    I use KB coatings system and Bill Hirsch rust preventive products. KB is POR-15 under a different name (same guy who developed POR is now working at KB). The system uses degreasing, converter, cover coat in both of these system and most others.

    I also like Picklex after degreasing/grinding/whatever because it doesn't have to be washed off. You can paint right over it with whatever encapsulator you choose. So....clean the area, convert it, encapsulate it.
  8. Slide
    Joined: May 11, 2004
    Posts: 3,026


    You'll get plenty other answers on the other questions (mostly ones you don't want to hear, but....), but regarding the primer you used:

    Primers are [usually] a porous coating, especially non-catalyzed (no separate hardener you hafta mix in). Thusly they actually hold moisture next to the metal, so leaving it out in the weather didn't do much except marginally slow the rusting process. You need to seal it off if you're gonna leave it out like that. Even finding some cheap mis-mixed single-stage paint from the automotive paint store and squirting it on there would be better. Looks like you prolly ought to at least run an aggressive (40-80 grit) paper on a DA over the parts again... or get them re-sandblasted (better)... and re-primed... and then either topcoated or stored indoors.
  9. rcnut223
    Joined: Oct 12, 2006
    Posts: 1,230

    from wisconsin

    I see your not getting a lot of action on your question so here goes.

    Primer is not waterproof, it adheres well to the metal and paint adheres well to it. Once primed a good self ecthing primer should hold off rust if top coated with paint. The best primer for holding off rust is a zinc chromte primer, but it is nasty dangerous to spray (very carsinogenic). I don't think you will find a primer that will deal with be left out in the eliments for any period of time. Best store them in a dry place.

    On your second point, it's best to cut and replace where possible. When you can't you do need to neutrilize the rust. Typical removing any scale and loose rust , and using a metal conditioner like "Right Stuff" or "Eevapo Rust". Follow the directions!!!!

    POR-15 works for this as well.:)
  10. Bort62
    Joined: Jan 11, 2007
    Posts: 594


    Alright, thank you for some useful answers. I had suspected that primer wasnt waterproof, but now I know. Re-blasting it isn't a big deal... should I just leave it until I am in a position to do the entire process, start to finish, in a reasonable period of time?

    As for the rust neutralizers, thanks for the suggestions.
  11. 29Jay
    Joined: Aug 9, 2007
    Posts: 1,101

    from Ft Worth

    "And please don't say "use a rust neutralizer". Tell me WHICH neutralizer to use as there are about 200 different ones on the market and I am sure they don't all perform the same"

    Send a PM to Scootermcrad... He did a post on his project... (can't seem to find it for ya) he used a de-ruster call "A-Must-For-Rust" Look at his post and you see what it did... I am using somthing from Home Depot that is getting the surface rust off too...

    Agree with the others about the primer...
  12. SlowandLow63
    Joined: Sep 18, 2004
    Posts: 5,953

    from Central NJ

    For light surface rust, Picklex 20 works well. Spray it on, wait 2 min and wire brush the surface rust off. It cleans pits and most lightly rusted areas in one or two applications. It then gives the metal a phosphate coating which will protect the bare metal shortly until its primed. For primers, I would reccomend an epoxy. The Picklex isn't compatible with any self etch primers because of the acid in them. I use epoxy primers and surfacers pretty much exclusively and have had good results with them. Good luck.

  13. I'm going to break my response down into two sections... First the corrosion process and what to do to stop it... Second how to do a repair without cutting and welding.. AKA... the chemical fix...

    Corrosion is an electrochemical process. The following things are needed... Eliminate any one of these things and you stop the corrosion. Think of a wet acid battery.

    A cathode
    An anode
    A metallic pathway
    An electrolyte

    When you have all of these things you have a corrosion cell. This can happen at the molecular level. Meaning a single molecule of water on the bare steel surface and the result is corrosion.


    What we have with a bare sheet of steel that is covered with moisture is called a corrosion cell... The steel plate has areas that are anodic and cathodic that are connected by the metallic pathway (the steel itself)... Add the moisture and the corrosion process starts. Just like the plates in a battery. The area of the plate that is anodic sacrifices itself to area that is cathodic and the byproduct is iron oxide. RUST.

    A piece of steel has the first three things when it is rolled into a sheet. So we obviously can't remove one of the first three.

    The only thing that can be dealt with is the electrolyte.

    Water in its purest form (no dissolved ions) isn't the greatest electrolyte. It has relative low electrical conductivity on the steel surface.

    Add salts (dissolved ions) and the electrical potential goes up dramatically. (This is the reason cars in salty environment rot faster than those in other places.) Dirt will contain salts and other ions that will dissolve in the water. So when dirt collects in those hard to get to areas they rot with little moisture added.

    So we eliminate the electrolyte on the surface by using a barrier coating. The coating will have to have a very low permeability rate in order to keep the water molecules away from the surface.

    A sanding primer is highly filled with mineral fillers that make the coating very permeable and the minerals themselves have some solubility in water. Are our minds working here???? An epoxy, like the DP primers that are a very low solids content and are applied in a thin layer are also porous (thinner evaporation) and will not keep the water molecules away from the surface. An oil base primer like Rustoleum is better that the above only if it is applied properly resulting in a thicker dry film thickness. Fast drying paints will be more porous than a slower drying material.

    It takes multiple coats of paint to seal the steel surface and stop the water molecules from reaching the surface. Cars are formed of many panels welded together... the welding process damages the applied coatings giving RUST a place to start… usually in hard to reach areas. Especially true with a unibody constructon.

    PAINT = It's all good stuff in the can.... It takes people to put in on.

    Rust = IRON OXIDE = It ain’t as bad as people think… Have you used an Iron Oxide Primer? Chlorides are the real Demon… Chlorides mixed with water = CANCER. Abrasive blasting helps remove the chlorides from the surface. A product called ChloRid can remove almost all of the salts.

    Anything you do to stop the moisture from getting to the bare metal areas will help. Multiple coats of Rustoleum with a good top coat will work… Multiple coats of surface tolerant epoxy will work. Even if you don’t get all the rust off. Make new sheet metal covers for the rusted out areas and screw them on and then caulk all the edges… It will slow down the process if the rusted areas stay dry. Think about the Corrosion Cell.



    Works great if done properly... Stronger than the original panel..

    HOW TO:

    Backup the panel with some type of releasable mold... This can be as simple as a piece of cardboard with some PVC film (Saran Wrap) over it. On a large curved panel a piece of plywood pressed to match the curvature works. Clean the remaining steel the best you can, as in grind to bare metal and the rougher the better (24 grit disk). Get some good laminating resin such as an Isophthalic Polyester or even better a Vinyl Ester Resin... these can be obtained at TAP Plastics or a local boat repair shop. A cheap Orthophthalic will not last long. Get some 1.5 oz Chopped Strand Mat. Enough to cover the area to be repaired times 4 or more... that is.. four or more layers of mat. DO NOT try to use fiberglass cloth... Lay up 2 or more layers of mat on the outside of the panel and let it cure... remove the back up panel/mold... grind/clean the other side of the panel as best you can... make sure to rough up the fiberglass laminate and apply two more layers of mat to create a fiberglass sandwich with the steel as the meat... A little Bondo and wall-ah!! Repaired without welding…

    Does this work... Yes it works and if done properly I will dare you to find it without tapping on the panel...

    Have I done it... yes... on occasion... when I found it necessary... Usually a time issue.

    I have a rear fender on a 55 Dodge truck that was repaired this way 30 + years ago and it still looks just like it did the day I did it.

    I have welders... I like metal... So I DON'T make a practice of it.

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