Yet Another Epoxy Thread

Discussion in 'Body Restoration' started by 71 Camaro, Apr 21, 2011.

  1. 71 Camaro

    71 Camaro Veteran Member

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    It seems nobody has written the definitive article on epoxy primer yet. I've read much conflicting info, here and elsewhere. After literally years of reading up on different types of primer I still am not clear on what to use and under what conditions.

    I swear by Extend and similar products (Rust Fix), but many confuse these with the wash-off phosphoric acid types. It seems that epoxy applied over Extend will cause an adverse chemical reaction. This explains horror stories you've heard. So looks like have a decision to make. Go with what I know works, or try something new, epoxy primer. To help me (and others) make an informed decision I have a question, very simple question:

    Can epoxy primer be applied over factory paint or is it exclusively for bare metal?

    I have been in contact with the manufacturer of Extend and they assure me their product works with everything BUT zinc based coatings, eg: epoxy primer.

    Have also been in contact with SPI which seems to be the preferred epoxy reseller here. Honestly they were of no assistance what-so-ever and never gave me a straight answer to any question. Instead they used scare tactics and some of the stuff they said I know is wrong. If I quoted what they said, you would think I made it up. It was that retarded. It seems they are just salesmen and of course push their own products. How they stack up to other brands is debatable. People who I asked who restore cars have not heard of SPI, so doubt it will be doing any business with them.

    If ever get this all sorted out, maybe I'll write that article which addresses compatibility issues with different restoration coatings since none really exists. I really took offense with SPI insisting that every other product on the market is garbage but theirs. How is that helpful?
     
  2. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    pick an epoxy primer and read the P sheet. It will tell you what substrate it can be applied over. Different manufacturers will have different recommendations. That is probably why there is no universal rule for epoxies in general.

    For your entertainment I have selected Martin Senour Cross/Fire Cp400 Epoxy primer. This is a common, low cost epoxy primer sold in Napa stores. Here is the P sheet.

    http://www.martinsenour-autopaint.com/media/pds/english/9114.pdf
     
  3. Chevrolaine

    Chevrolaine Veteran Member Gold Member

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    Exactly why I never have and probably never will use Epoxy. Prime it, Paint it. KISS!!
    Just another money maker for the mfg's IMO.:rolleyes:
     
  4. NYH1

    NYH1 Veteran Member

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    I've heard a lot of great things about SPI products on this site and some limited info about their products on another site or two.

    My best friend who has been doing all types of body work on cars, trucks, boats, motorcycles ect. for over 15 years from basic collision repair work to as custom as can be. Another guy who has been doing the same type of work for over 30 years and his father for over 50 years. They're probably one of the best body shops in this area. When I asked these guys about SPI's products they had never heard of them. I asked a few other guys that do body and paint work and none of them has heard SPI either. That makes me kind of hesitant to order their products.
     
  5. Paint Fumes

    Paint Fumes Veteran Member

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    Here is my 2 cents. I use epoxy primer over bare metal which has been sandblasted clean of rust, prior to applying primer surfacer or paint. Some use it under plastic filler. I am not one of those people. I don't see any need to do that and never have needed to in the thirty plus years I have been in the trade. I use PPG epoxy primer in both the DP and Shopline variety, both are excellent products and really.. I can't see much of a difference between the two except price. I also use it as a sealer over sanded factory paint and over quality repainted surfaces. It will sometimes attack cheap repaint work and wrinkle it. That's all I use it for, others may (will) have different ideas on the topic.
     
  6. TX79Z28

    TX79Z28 Veteran Member Lifetime Gold Member

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    I guess it's just a matter of preference, SPI does recommend shooting the epoxy before the body work. To ME, it make sense to completely rust-proof everything instead of adding porus filler over bare metal and then cover it. I guess either way it's OK, but for me, it actually seems rather sensible to cover the entire surface prior to filler work. I am using SPI epoxy, and will follow their recommendations. Not saying other ways are wrong.
     
  7. earlysecond

    earlysecond Veteran Member

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    71 Camaro,

    Let us try to approach this logically. I am resisting a knee jerk post here so I will answer your first question.

    All of the epoxy primers that I have use are fine as a beginning point for painting over old paint. I have used several epoxy primers in this function to paint over old lacquer, enamel and urethane single stage and base clear paint. It works just fine as long as the paint is stable AND the surface is properly prepped. As an example, I changed the color of my DD. Factory Acura paint stable but I hated the color. I stripped stone chipped areas to bare metal and scuffed the rest of the car. The adhesion was outstanding. . .EXCEPT for 2 areas I neglected to scuff. In those 2 places, the paint peeled off within a year. I am surprised that the epoxy, SPI in this case stuck at all to what was a non- scuffed waxed surface.

    Walk me through the process that you use so that we might all understand what condition of metal you are starting with AND what products you have used successfully.

    In the meantime, if you want to try your own test but do not want to buy epoxy primer to try it, I will send you a sheetmetal test piece properly prepped and totally sealed in epoxy primer. Take some etch primer and you treat a piece of mild steel sheet metal, apply your next step (acrylic lacquer primer?) Now take both pieces and put a nice scratch on the them that extends to the bare metal. Throw both pieces outside or into a salt bath and wait. I know what will happen. Why, because I have done it. I did not want to rely completely on what other wrote or even worse what marketing departments wrote to sell product.

    One final question, when we are talking about panel painting, do you put a rust prohibiting product on freshly prepped bare metal or would you start with something else.

    On a daily driven suburban are the following tests. I have referenced this before and if it matters I will take pictures and post them BUT only if you really have an open mind and trust that what I am showing are actual results in the real world. On the same vehicle all live Zero Rust, POR-15 and PPG epoxy primer. All surfaces had some rust and I used all steps recommended by the manuractures to properly prep. I recall that I did this stop gap repair to the bottom of some rusted doors and some rusted tow hooks in 2005 when I got the SUV. I treated the door bottoms with the POR products and the cast iron tow hooks with epoxy. All of the products show signs of wear BUT ONLY the epoxy has sealed the metal and survived the many years of use.

    Ulitimately you will need to decide what you will do. Epoxy primer is not as new as you might think. I have no time or reason to allow non-catylized paint products anywhere near anything I own that I expect to last.

    Had I known about epoxy and gotten a bit better advice OR done better reasearch, the chances that I would be restoring my Camaro a second time in 7 years would be greatly diminished. At the end of the day you will probably do what you are comfortable with. If it works and lasts then who cares. There are many ways to skin the same cat.

    I am interested to see how this turns out for you and others who have similar questions or doubts about epoxy.
     
    Last edited: Apr 21, 2011
  8. kawboy

    kawboy Veteran Member

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    To the guys who have asked body and paint guys if they have ever heard of SPI and have not. I sell SPI and yes there are alot of people that have not heard of it. They might even look at the packaging and shy away from it. But when you get through to the guys that normally shoot PPG, DuPont, etc. and they decide to try SPI most of them come back and say that they will never shoot anything else. Especially the Universal Clear(it's awesome). Be open minded and try it. Chances are that you won't regret it.
     
  9. Paint Fumes

    Paint Fumes Veteran Member

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    This article pretty much sums up what I was told by an Evercoat rep when he visited my shop. When I asked his thoughts on the subject, he told me that they recommend applying filler over bare metal roughed up with 36 grit. "You can put filler over epoxy primer if you want.. just don't call us when it peels off". Thats not B.S. those were his words, not mine.
    I found this on the internet:

    Using body filler, by Reed Overson Last updated on January 1, 2010

    Reed Overson lives in Bismarck, North Dakota, and has been a bodyman, painter, sales rep, and technical rep for thirty years.

    Reed used to work as a technical sales rep for the company that makes Rage filler, and knows the chemists that developed the resin for it.

    The following article contains some of Reed's thoughts on using body filler.


    --------------------------------------------------------------------------------
    The resin used in Rage and other body fillers is fiberglass (polyester) resin. Today's resin technology makes the adhesion of these new resins as good as or better than most epoxy adhesives. They are designed to really stick. Also, they are somewhat flexible when used properly.

    Most, or probably all, filler manufacturers design and recommend them to be used over clean and prepped (sanded with coarse 36-grit), rust-free (sandblasted), dry (free from moisture), bare metal. They will stick to epoxy primers with mechanical adhesion. Body fillers do not chemically bond with epoxies. If you put filler over epoxy primer, it has to be fully cured, with no solvents such as thinner or reducer left in the primer, and still should be sanded with a coarse grit and cleaned. In other words, using epoxy primer under filler is a wasted step that may or may not cause adhesion problems later on.

    One of the most critical points is for everything to be clean and moisture-free.

    --------------------------------------------------------------------------------
    Body filler resin is a thermal-set plastic. It cures with heat. The hardener MEK peroxide is a catalyst that produces heat in the resin. It needs to be at 64 degrees Fahrenheit minimum to cure, and the best is between 72 and 80 degrees Fahrenheit. (If you live in a warm climate, read on, but it may not apply to you.)

    If the metal is cold, the filler will cure from the outside in, and could trap some moisture and solvent from the resin underneath, causing adhesion or bubbling problems later. (Styrene is the solvent in resin and produces the smell that we associate with Bondo and fillers). Also, moisture (humidity in the air) will condense on the surface of the cold metal. This is the same effect you get when the mirror in the bathroom fogs up when you shower. The mirror, and the metal of the car, are about 10 to 15 degrees cooler than the air temperature, and the humidity condenses on them. If you warm the mirror or the car's metal to about the air temperature, the moisture won't condense on the surface. Using a heat source to warm up the panel (but not too hot) will eliminate the moisture being trapped under the filler (which can show up as rust under the filler) and help keep the cure temperature even through the filler. This is the way the chemists designed the product to work. You can use extra catalyst to speed the cure, but too much will cause too much heat in the reaction and crystallize the resin which causes it to be brittle and break down, causing more problems later. If you head to the auto body supply store for more hardener you may be using too much and looking at problems down the road. Pre-warming the metal and keeping the shop warm will let it cure more evenly with the correct amount of hardener. Heat lamps or lights should be far enough away so the panel feels warm when you put your bare hand on it (not hot).
     
    Last edited: Apr 21, 2011
  10. 77nomad

    77nomad Veteran Member

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    I never heard of PTFB before coming here. No one i talk to has ever heard of them. Do they make bad products? Just saying, I'm not even at novice level with paint and body, but if five or six guys say give it a go you won't regret it. Sure I'll try it.
     

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