Hey. I have a few sheet metal parts removed from my project that I want to paint soon. Some of the parts have unique shape, size, nooks, crannies, etc, so they were media blasted instead of sanded. They are now down to bare metal. Measures have been taken to completely prevent rust. None of the parts require any work - no body filler or anything. They just need to be painted. I want to shoot some type of primer on the bare metal, then shoot my single stage acrylic enamel (DuPont Centari) on top of the primer, all in one session. Which type and/or brand of primer should I use for this application? Deluxe
For bare metal I would use an Epoxy primer like PPG's DP series primers.. I've had good luck with it and use it all the time on customer cars.
I would clean with metal prep first then use self etching primer. As for the brand I would try to use the same paint system for primer and paint. I like Sikkens, It seems to hold up well for me, but there are a lot of great paint suppliers these days, so it's what you feel he most comfortable with.
I agree with this suggestion,,,that's what we do in the shop. Oh yeah,,,and another thing,,when ya metal prep don't touch it! HRP
Ditto,you HAVE to use a etch primer to prevent the steel rusting and you can use bondo right over the top of it . Ordinary primer regardless of the paint system will not prevent rust because it's porous and needs the etch primer to adhere properly. i use etch all the time and sometimes a job may sit for a year or so before being finished and it's fine for keeping rust away.
Sorry, but no. Etch primers have acid in them which reacts with fillers and epoxies causing them to lift and peel. Etch primer is just as pourous as any other primer. No primer on the market is not pourous. You've been brutally misinformed. Epoxy primer is the way to go. I personally would use HOK Epoxy KP2CF. It is by far the best and I'm sure many others will agree.
You are correct... I only use etch primers on stuff that i cant really sand the way i want but i get the stuff clean then etch prime.. For body panels and stuff like frames that have been blasted sanded etc epoxy is the way to go.. The shit sticks to everything so cover your motorcycle and stuff and dont ask me how i found this out years ago.. I epoxy first then after the proper time frame i spray hi fill over the epoxy.. then you can use filler over the hi fill primer.. Just try not to sand thru but if you do get to the epoxy no biggie. the etch primers or at least most of them can be a problem when you sand thru.. Also the stuff im talking about like brake brackets and spindles and shit I use SEM etch from a spray can.. Works fine.. Dave
Im a metal fabrication guy and in no way a painter. I thought the question was what to spray on sand blasted parts, so thats why I threw my 2 cents in. I spray all my parts with self etching primer after they are media blasted, will this work, or should I use epoxy primer.
Alright. Now it's time to get REEAALLY technical (sarcasm). I've seen epoxy primer/sealer that specifies using the primer and hardener when used as a primer, and the primer, hardener, and reducer when used as a sealer. The sealer mix should probably produce a much finer and less thick application because of the reducer. I like that. Can the sealer mix be used as a primer, even though that particular mix is specified for use as a sealer? Your just adding in a reducer for the sealer. Deluxe
For a high volume shop that turns stuff out on a daily/weekly basis, the etch primer makes sense as the top coat is normally on there before there is a chance for any moisture getting past the primer. For the home enthusiast that may spray some parts (like you described) and then set them on a shelf for a month, two, maybe more, while getting the rest of the car ready, then epoxy primer is your best choice for longer term exposure and prevention of moisture passing thru. I also use the House of Kolor KP2CF and have had very good results with it, as it has stood up to being splashed with MEK when I was cleaning out some m/c tanks. It does have its limitations, however. The H/K epoxy primer is not compatible with some of the ospho-type rust conversions, it will react and cause lifting issues. Had this problem on a Model A I had painted, and the H/K tech line confirmed it. Bare, shiny steel only, no rust conversion coating. So if you need a rust conversion process on your metal, there are also some other good epoxies available, like the PPG line that was mentioned, is compatible with the rust conversion products.
Yes. The terms primer and sealer are merely technical terms in this case. By reducing the product more, you are merely enhacing the sprayability to lay down a smoother coat with less build than an unreduced coat. If you are confident in the straightness of these pieces/panels, then go with it. If you think they might be alittle wavy and need some sanding, go for some build.
Not all sealers are primers, and not all primers are sealers. And to make it more confusing, neither of these need to be surfacers, and vice versa! That's why I like HOK epoxy. It's all three!
I'm the opposite, so you can probably show me a thing or two. You aren't wrong. But theres 2 sides to every story. Self etching primer has a limit to what it can go over and limits what can go on top of it and when. Epoxy primer is way more versatile and adheres just as good, if not better, to bare metal which makes it my choice. Self-etch depends more on the application, whereas epoxy primer is more universal.
If the parts are freshly blasted, you SHOULD NOT use metal conditioner if you are going to put a self etching primer on. The acid in the metal prep will nuetralize any minute corrosion and most etch primers will not have anything to convert with and can peel. Refer to the tech sheet for the primer. Just blast, etch prime, fill prime (if needed), then color (centari) I believe is what he wanted. Another thing about color over self etching primer. Some etching primers will bleed into or discolor the paint (usually lighter colors). Check with the tech info to see if it is reccommended to paint directly over the self etching primer. Vinyl wash self etching primers (very thin see thru) need to be primed (wet on wet-OK) before color. On the freshly blasted parts he is referring to, a milder self etching primer is better, one that has some fill and not just a transparent film (vinyl wash primer). Sherwin Williams, Sikkens and several others make a good mild etch primer with some fill quality. They are usually mixed 1:1 with a wash hardner (reducer with about 5% phosphoric acid). Some have up to a 2 week nonsanding recoat window. These primers are nice for the project pieces he is describing. A good epoxy primer should work also, as well as a urethane primer, or a polyester based primer. There are a lot of good undercoats available. Don't use self etch under epoxy or polyester primers (although Evercoats tech sheet says it's OK to shoot their easy sand over self etch, but it will extend the dry/cure time.) overspray
Now Im really confused, what is the benefit of self etching primer and should I use epoxy primer on blasted metal instead?
The main benefit of a self etch primer is the acid reacting with the metal and any slight corrosion left in the blasting texture. Most factory steel parts have a phosphate coating on the surface for corrosion protection. This is removed by blasting , sanding or grinding. You can replace this coating by using a 2 part metal prep (acid wash) or the next best (easier) solution is to use the self etching primer. The phosphate coating helps keep rust from creeping under the paint/primer finish if it is broken, like a chip or scratch. Self etching primer kind of goes into the surface of the metal (chemical bond) and protects similar to the phosphate coating. The benefit to an epoxy primer is the resin and the solids that make up the film build. If you have a good quality epoxy with a chemical/moisture resistant resin and good solids it will protect the metal from corrosion. It will not chemically bond with the metal surface, only mechanical bonding is present. If the epoxy is durable enough it can still resist rust creeping under a chip or scratch. It really depends on the product. DP epoxies are very thin and not the best choice for this type of protection. Of course you would get better corrosion protection using the 2 part acid wash and then an good quality epoxy. (More work.) Good clean rust/corrosion free metal will be protected with most good quality primer and paint systems by following the tech info. You still need to have some kind of film thickness in both the primer and paint to get good results. overspray
I've heard Picklex is an extremely effective metal wash. Mark (chopolds) has started using it and I'm waiting on my first go-round to come in the mail.
I posted a question a couple days ago about DuPont Centari acrylic enamel paint and received many incredibly valuable responses from experienced paint people here on the HAMB. Now I have more invaluable responses from many of the same folks about my primer on bare metal concern. With all of the info I received from you in the past few days I now consider myself an automotive paint expert. So if you have any paint questions you can ask me, cuz I'm a flippin' expert. Just kidding. Thanks for the help!!!!! Deluxe
Nobody else asked, so I will, Centari? I didn't think they even made that stuff anymore. At least use a urethane based single-stage as opposed to acrylic, you'll be alot happier with the results. Just my 2 cents and I paint alot. As for the primer, you can't beat PPG's DP90, excellent product!
It's a long story, but I believe it is really good stuff. I'm using it for my current project and I'll be open to other paints for future projects. I've been hearing for years about potential for Centari to be discontinued and it hasn't happened. Maybe Centari will be discontinued but I doubt acrylic enamel will be. Deluxe
To do what you describe, what you are looking for is Dupont Velvaseal 1986S. First treat the metal with metal-prep/conditioner. (we're talking acid here, follow instructions carefully) You'll love the velvaseal. Use strait out of the can, easiest thing there ever was to spray. I'm a little concerned that you are talking sheet metal here. A lot of the necessity of working down primer is in the way it enables you to find imperfections that are very difficult to find on bare metal by sight and sense of feel. I personally always confirm a sheet metal surface with guide coat and blocking, and almost always find something that needs some attention. Good luck! (ps: I'm really looking forward to your next project, where you use a modern basecoat/clearcoat system. I'm placing my bet that you will be telling everyone on the HAMB what a joy it was to use compared to acrylic enamel)
Epoxy is the way to go, as far as brand I use may hyde but Im sure I doesnt really matter too much as long as you dont buy the super super cheap stuff get a name brand.
30...clean the freshly blasted metal with a cleaner, something that has no oils in it and will remove all oils to prep the metal. You can use urethane thinner or I use stuff I sell that's non-hazardous for the same purpose. preferably non-water based. (Not selling it to you, just mentioning it). After it's clean and dry, use Epoxy primer. Brand and color of your choice. I use PPG stuff but I hear HoK is as good or better (as others have recommended). If you are going to need build, use 2k primer or if repairs, then bondo or whatever then 2k. Block out if needed. SEAL it. I use Epoxy because by reducing it, you can use the same as a sealer over previous. Then finally, top coat it.
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