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bodywork/paint query

Discussion in 'The Hokey Ass Message Board' started by airnwater, May 14, 2007.

  1. airnwater
    Joined: Dec 31, 2006
    Posts: 40

    airnwater
    Member

    Looking from some advice from experts on here..........

    Car bodywork down to clean bare metal (steel & aluminium)
    When using polyester spray filler /bondo(Sikkens) whats best for adhesion ?
    - good coat 2 component etch primer ,let dry hour or so then spray filler?
    -or is adhesion equally good if metal abraded (180 ?) then spray filler ?
    -or epoxy primer onto metal ,let it cure, scuff with scotchbrite then spray filler ?
    ( Incidentally car is in small room with dehumidifier, so no moisture )
    - Once sprayfiller sanded ,is there any benefit in spraying whole car with
    etch primer for better adhesion of next coats, or just do the bare metal spots, prior to high build 2pk regular primer ?

    Thanks in advance for any advice
     
  2. overspray
    Joined: Jan 14, 2003
    Posts: 1,417

    overspray
    ALLIANCE MEMBER

    Welcome!!

    Grab a couple pints, then read through this. Then ask some questions. Some of your european products (Sikkens) are the same here in the U.S., and some are a little different. We are mostly on the same technology page on both sides of the Atlantic.


    http://www.jalopyjournal.com/forum/showthread.php?t=8318&showall=1

    overspray

    PS--introduce yourself, it's good manners, and fill out your profile. Check out the Tech Archive and search functions.
     
  3. mikhett
    Joined: Jan 22, 2005
    Posts: 1,516

    mikhett
    Member
    from jackson nj

    Forget etch primer! Most polyester products including body filler wont adhere were etch primer is used due to the acid in the product(Phosphorus).Use epoxy primer then poly.Why polyester primer?Is the bodywork that wavy?I use a one step product HOK kp2cf which is a hybrid epoxy- which can be sanded and gives good build.Most epoxies you cant sand.Dont put poly over bare metal! uSE EPOXY FIRST.i HOPE THAT HELPS! .mIKE
     
  4. An epoxy zinc based primer is a necessary step that should not be omitted especially on aluminum. Sometimes referred to as etching primer, they are available with or without the self etching properties . Primer that is not adhereing to a metal substrate is usuallly the result of an improperly cleaned and prepared surface.You will sometimes get information that may be contradictory. Please check with the paint manufacturors website for the proper materials and application procedures . Remember they engineered and designed the products . Their answers are the ones to follow.
    Zinc based primers have adhesion and rust inhibiting properties that are not found in other primers and are one of the secrets to a long lasting paint job. Most other primer/surfacers are basically used as a filler and do not possess these qualities. Again check the data sheets as some primersurfacers are not to be watersanded , since they are pourous and moisture can get trapped in sanded material.
    Overspray makes a good suggestion. Please read the thread and do a search and lets us know of any questions.
     

  5. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 10,245

    theHIGHLANDER
    ALLIANCE MEMBER


    Ditto. Can't do that. I'd acid etch with metal prep or alodine, whichever applies, rinse with distilled water, then go to the epoxy. I hate polyester primers...too heavy.
     
  6. overspray
    Joined: Jan 14, 2003
    Posts: 1,417

    overspray
    ALLIANCE MEMBER


    Very well put, Larry.
    Zinc, Chromate, and lead. These toxious beauties are all composed of large dense molecules which add to the protection from UV, Salts, and other corrosive elements that can penetrate a coating-primer/paint. They are essential for the best protection, but due to health and environmental concerns they are dissappearing from the good old primers and paints. So our new products must rely on better resins to try and protect the metal from corrosion. I'm not sure we are getting adequate replacements for the old products, but there are some real good ones out there.

    As a restorer, (I read your profile) Larry, you know that most of us in this hobby usually don't have the luxury of a nice new "Brookville" body that is nice clean unrusted steel, that we can scuff, apply a nice coat of highbuild epoxy primer, and sand and prep for paint.

    Almost every tech sheet I've read for bare metal primers starts with: The surface must be clean, and free of wax, oil, grease and RUST. Wax, oil and grease can be cleaned off the surface with detergents or solvents. Rust has to be chemically removed to get it all. Even abrasive blasting won't get it all. Using metal prep (usually phosphoric acid) is messy and time consuming. "Dipping" a body in solution to remove rust usually leaves corrosive material in crevices and seams that is impossible to remove completely.

    Most steel body panels from way back to present have a phosphate coating (part of the 2 step metal conditioner process) applied from the factory, to inhibit corrosion under the primer. Good quality products from the phosphate coating to the color increase the longevity and durability of the coating.

    In Europe, Polyester based primers have been very popular for a long time. The polyester resin technology we have in the U.S. today, came from Europe. Most polyester primers and fillers (bondo) have much greater adhesion with todays formulas that equal or exceed epoxy based products. We probably have a thought of "glue" when we hear the term epoxy. It is more a term of a different type of resin that is the carrier for the primer filler material. Acids, like in metal prep, can affect the hardners in both epoxy and polyester resins, causing incomplete or slowed cures of the resins. A thourough reading of the technical information for a primer and system is a must.

    Urethane resin is another system usually using a hardner or catalyst. Etching primers can usually be used under urethane high build primer surfacers as a system to provide extra corrosion protection. The acid in self etching primers is an accepted process in many automotive paint companies warranty requirements to replace the factory phosphate coating after grinding the bare metal in a repaired area.

    I don't like to spend the time and deal with the mess involved with removing rust with acid. On old rusty bodies I abrasive blast the steel, sand with a DA sander to reduce the texture from the blasting, solvent clean the metal, then apply self etching primer, followed by highbuild urethane primer. I prefer to use the milder etching primer which has a slight build and less acid and follow the tech instructions for applying the urethane primer. I feel I'm getting more corrosion protection with this system over blasted rusty steel than using polyester or epoxy high build direct to metal. Good products and good techniques will give good results.

    overspray
     
  7. SlowandLow63
    Joined: Sep 18, 2004
    Posts: 5,958

    SlowandLow63
    Member
    from Central NJ

    ^^^ Damn man you're like a walking tech sheet. I just go about doing what I do because thats the way to do it. I never stopped to think of why thats the way to do it, I just know the way. Don't get me wrong, I understand when to use which products, but the chemical formula type stuff is foreign to me.

    This should have more than answered the questions, kudos.
     
  8. overspray
    Joined: Jan 14, 2003
    Posts: 1,417

    overspray
    ALLIANCE MEMBER

    Well Bill, I wanted to put some "why" into the info pile because too many guys swear by one thing or another without knowing "why". The point is to follow the tech sheets, but all of the instructions need to be read and understood in order to have the best results with the products. That is part of quality workmanship. I had questions about these same things and spent the extra time to learn "why". I was fortunate to ask a lot of the right people and get some real good answers. All the systems I described are real good when used correctly. I see some guys going the epoxy route because a lot of times it is preached to be a "sand it and shoot it product". Also, there is a lot of misunderstanding about using the self etching primers which leads to improper use and film "failures".

    Read all the tech information and be a more informed craftsman about all types of products. This will help pick the proper coating for the job.

    overspray
     
  9. Its good to hear your response. Its right on target.
     
  10. chopolds
    Joined: Oct 22, 2001
    Posts: 6,208

    chopolds
    Member
    from howell, nj
    1. Kustom Painters

    Overspray, you and I almost always have a similar opinion about bodywork. But I have to disagree with your opinion of epoxy. Perhaps it is that I exclusively use HOK's epoxy. I know it is different than the more common brands.
    \I've been using it for over 20 years, with great success. On bare metal, fiberglass, aluminum, even "scuffed" chrome. I use it under, and over bodyfiller. I use it right to the point of painting, as it works well as a sealer, as well as a surfacer, and primer. Excellent adhesion, good filling (tech sheets say it will fill 36 grit scratches!!!), relatively easy sanding, and seals as well.
    It's a great all in one product.
    I do work on lots of car parts that others would throw out, and can't remember a failure due to this product. Rusty, pitted, wavy parts, all repaired correctly and still looking good after all these years!
    When Kosmoski still owned HOK, he recommended it, and I believe him. How can you not trust a product recommended for putting under over $1000 worth of Candy paint?
    Again, though, HOK's epoxy is NOT like the other brands!
     
  11. overspray
    Joined: Jan 14, 2003
    Posts: 1,417

    overspray
    ALLIANCE MEMBER

    We are NOT in disagreement. You are using one of the finer epoxies available. My point was about understanding the prep involved before applying the coating, whatever the type. A good quality, high solids, primer of any type, applied correctly, should perform as intended. There are lots of epoxy primers on the market that vary in resin properties and solids. There are big differences on how they perform. There are industrial epoxy primers and coatings that make the automotive stuff we use look like kindergarden fingerpaint. They protect bridges, oil storage tanks, and other structures for years from weather and corrosion. I used to use an epoxy, similar to the HOK, that was originally an industrial primer that was crossed over to the automotive lines. It was fantastic for filling, adhesion, color holdout, and with a remarkably fast thru cure. One of the main reasons it is not around is misuse from the technicians not following the product information sheet.

    I'm getting better at finding information on the internet and I can find the tech sheets for most of the automotive refinish primers and paints available to us today. I read the tech on the HOK and was impressed. It does have a little bit of information I mentioned earlier-- the little letters= cf = on the end of the part number of the one version of the primer. Chromate Free. It is safer, but there has to be something else in the primer to replace the chromate to make it perform. The tech sheet on the other version says Chromate Free in the text, but it is not noted as "cf" in the part number. The tech sheets also say, that if you have to remove rust with acid, that it should be thouroughly flushed or a loss of adhesion could occur.

    The main type of adhesion of all primers is mechanical. There is probably some chemical adhesion in etch primers as the phosphoric acid bonds with the iron and forms iron phosphate. Mechanical adhesion is enhanced by having a clean and sanded surface.

    Clean and sand and use good product. Understand the application. No disagreement here.

    overspray
     
  12. SlowandLow63
    Joined: Sep 18, 2004
    Posts: 5,958

    SlowandLow63
    Member
    from Central NJ

    I'm glad you did, I'm always eager to learn more. The more I learn, the more insight I can provide to my customers. I consider myself by no means an expert, but I do know my way around a spray gun. I read tech sheets until there is no tomorrow, I'm always overthinking jobs and I'd rather be overprepared than lost. The tech sheets don't include how the product works exactly down to the chemicals involved. They only say spray this over this and do this. Just like Mark, I spray mostly HOK products when I'm doing complete jobs. For the rest, I'll use PPG products as I've had good luck with them as well.
     

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