I have been getting all my suspension piece for the '32 ready for paint lately putting in too many man hours for one day haha. I had everything blasted and took it back to the shop to do some body work to it all to get it as close to perfect as I could. I used Evercoat Metalglaze for any deep pitting or smoothing and leveling surfaces, then shot everything with 2 coats of PPG DP40LF epoxy primer, flashed for hour and half then topcoated everything with PPG K38 high build primer. Today I went and blocked out pieces and sanded contours but in a couple SMALL places where I guess I didn't build the epoxy high enough, I went through the epoxy to bare metal, not much at all really but it's there. The spots about size of an eraser head or such, a couple of them. Should I shoot it again with epoxy, or am I just overreacting here? I just want to make sure I'm doing it right and don't want to have to do it a second time. The pieces I'm talking about here are the front and rear bones, the axle, rear axle tubes, etc... all of these pieces are getting shot with PPG DAR9000 black single stage acrylic enamel afterward. I know there are paint guys on here that have more experience than me that know an answer. Thanks in advance!
Its gonna be close here. Most guys are gonna tell ya that it needs to be recoated so no filler or bare metal is showing. Other guys are gonna tell ya that its not a big deal and to just topcoat over it. If you're not in a rush I would take the extra day and recoat it with primer. If you were using a sealer before your topcoat it might be a little easier to swallow, but at this point you might as well make it 100% right.
What I have done in the same situation (bare metal spots etc.) is spot prime with self etching primer using an air brush and then color coat.
wheather needed or not i seal everything before i topcoat it,just in case i have gone through in a spot or two
51 merc got it right, done it like that a hundred times. Most of the time I'll just go and epoxy prime it, wait 45 min. then base & clear like normal.
So after I get all my blocking and finish sanding done, shoot it with another coat of epoxy to seal it all up as well? The spots in question are just hinting at bare metal, where the epoxy is so thin you can see faint bare spots. I need to hit a few more pitted spots with another coat of high build then they'll be done, but I guess what I'm asking is would it be alright to just shoot everything with high build one more time even though there are a couple thin spots of epoxy, then shoot it all with epoxy for a final time? I'm in no hurry, i just want to do it right regardless. I already have epoxy and a high build on it so I can't go over anything with an etch primer. Thanks fellas!
So far everybody has good info on the posts. First of all, I'm not a fan of DPLF for bare steel. It doesn't have much build and or corrosion resistance with only a couple coats, and of course NO etch capability. I prefer etch primer for this type of job. A sealer would be the best, but if your steel was clean and rust free, small spots will be OK with just the DAR9000 black (+hardner). Make sure you give all the parts at least 3.5 to 4.5 mils or probably 3 good coats. Film build/thickness will be important for suspension parts that will be getting rocks and debris hitting them--and DAR9000 touches up easily if you get a nick or two. overspray
You can get etching primer in an aeresol can from eastwood, its a really good grade of etching primer and if you have sand through you can touch it up with this. I learned the trick from a friend and love it. you should be able to get it right off the shelf at your local auto body supply store. Its good stuff try it! I use it after wet sanding also where you really don't want to recoat and resand. Just bust out this rattle can and give the bare spots a couple blasts and paint away... Scot
Good info here guys. I guess people have different opinions of etch primers. Some say use it, others say don't. Why is there so much disagreeing on this? For these parts, I wanted a base that would have good adhesion properties, then have a high build over it. I guess at this point, since I still need to hit it with high build once more I will, then seal it up, then shoot it with DAR9000 and build it like said. I've used DAR9000 before and I love the stuff for touch up characteristics.
-------------------------------------------------------------------------------- Post on primers. http://www.jalopyjournal.com/forum/showthread.php?t=244070&showall=1 (Some excerpts from other primer posts) I used the mild etching primer on my sandblasted steel wheels followed by a single stage urethane. They still look like fresh paint after 5 years. I used the same system on my flathead V8 block with the same good results. Your single stage black urethane should work fine over a mild etch primer. Like Bill posted, when painting wheels it's easy to get runs when you are double and tripple coating nooks and crannies trying to get coverage. There are basically 2 kinds of etch primer. VINYL WASH SELF ETCHING PRIMER: very little film build (fill) and it is slightly more aggressive, acid wise, because it has only a vinyl resin as the film. You can usually see thru it. It is translucent (very thin) and care should be taken not to apply heavy thick coats. THIS etch primer should be coated with either a primer sealer or primer surfacer (filling primer) before a topcoat/paint is applied usually with a wet on wet system after the etch primer has flashed for 1/2 to 2 hours. In industrial/fleet applications this is usually applied to sandblasted steel or aluminum then sealed with a primer sealer and painted. For restorations it is usually applied to bare sandblasted steel or aluminum and primed with a filler primer so it can be blocked sanded or leveled before painting. This type of etch primer should NOT be used over body filler. Some examples---PPG 1791 etch primer or 171-172 etch primer---Sikkens wash primer CR. MILD SELF ETCHING PRIMER: this has some build or fill but is less agressive acidwise because of the solids or filler in the primer. This can be painted over with some single stage paints without other primers (check the tech info for the brand). It is usually applied to sandblasted steel or aluminum and can be coated with primer surfacer (filling primer) or sealer wet on wet after about 30 minutes up to 72 hours (or longer) with some brands. This type of etch primer is OK over body filler (not heavy wet coats). Some examples--Sikkens Wash primer EM---Sherwin Williams GBP---Dupont Variprime Most companies use the same activator/reducer for both etch primers, which is a solvent blend with about 5% phosphoric acid. The phosphoric acid in the reducer is the "etch" and converts iron oxide to iron phosphate. This my preferred primer for sand or media blasted panels. I usually follow it with some 2K urethane high build primer surfacer (wet on wet). I've used this mild etch on bare engine blocks followed by a good quality single stage urethane color with excellent long lasting results and lots of steel or aluminum wheels like Mark does. I'm not sure where the spray can/aerosol etch primers fall in here, but I'm guessing more like a thinner version of the milder etch primer. I like them for small parts or touch up on welds, etc. Automotive panels new from the factory have a phosphate coating on the bare steel. When you sandblast or sand the metal on a car you usually remove all or some of this coating. You can replace this factory corrosion protection (phosphating) with a 2 part metal prep acid wash which is messy and time consuming. Although not quite as good, using an etch primer on old sandblasted or sanded steel panels is the closest you can get to replacing the phosphate coating. If you use the metal prep and converting system to phosphate coat panels, you should NOT use an etch primer. It will probably fail and peel off. Several automotive refinish companies require using an etch primer when repairing new car finishes in order for the paint and repair to be warrantied at the bodyshop. Polyester based primers (featherfill-morton eliminator-etc) usually cannot be applied over etch primers, because the acid will slow down the catalyst (MEKP) in the polyester primer and cause the cure to be longer. I did read in the new Evercoat Easy Sand tech sheet, for that brand of polyester primer surfacer, it can be applied over etch primer but it extends the cure time of the primer. You should not use epoxy primers over self etching primers as the acid does affect the activator of the epoxy and can change it chemically so the epoxy may not cure correctly or at all. Epoxy primers DO NOT etch or convert rust/iron oxide. AS always, read the tech info. Most of these companies have good information available on the web or at their local distributor's store, and you can always email or 1-800 a question to their tech dept. As with all good priming systems (epoxy-etch-urethane-polyester-etc) , if you read the tech info,it always says: "The bare steel should be clean of grease, oil, and dirt and free from rust." A little info on the DP epoxies--1 coat is about .5 mils dry film--which isn't very much protection--even 2 coats isn't enough. There are lots of higher solids epoxy primers, urethane primers, and polyester primers which apply at from 1.5 mils to over 5.0 mils per coat dry film, giving much better film build protection. When you read the tech sheet on primers and paint, always read it thoroughly and see what film build there is per coat (wet and dry) and LBS. per gallon of solids. This is how you find the BANG per BUCK of your primers. Oh yeah--take a test panel with 2 coats of DP epoxy that has dried for 1 day and pour a little water on it and let it stand for a while. It will show discoloring as it soaks up the water. It's not meant to be used as a topcoat for the elements. Also a rag with lacquer thinner will wipe some of it off for quite a while after drying. Everybody that uses DPLF needs to read and understand the "TDS" technical data sheet. Read everything, especially the metal prep required before applying and the film thickness of the dry film. DP products are not bad at all. They are not magic. https://buyat.ppg.com/refinishProduc...c-04551702a5df DPLF---"LF" stands for "Lead Free" not "Looks Fine". When you take the lead out of a coating it is safer, not necessarily better. The old DP had lead. There are other primers that will do a much better job for bare metal protection. Compare product data sheets and see what else is available to protect the metal. Always read the data sheets to help you get the best "Bang for the Buck". overspray
I use epoxy for a sealer over everything. It eliminates any reaction the base may have when shot over areas that are sanded thin or exposed. I used to be an etching prime person, but have since went to epoxy for everything. My 2 cents. Merry Christmas HAMBER'S!!!!
Going off memory DPLF has to be kept at a min of mills which I believe is equal to approx 2 coats. If the parts were rust free and cleaned before I would not worry about it as they are going to be primed or sealed and then top coated. The top coatings are what ultimately seals the surface. Etch primers can cause problems unless you have a tried and true system that works. Otherwise read your tech sheets as there are a lot of primers that can't be used over them. Next time try NCP which is an etch an fill in one and sticks 10x as DPLF. It will feather no problem on bare steel. you are spending big bucks on suspension parts. Just remember the least amount of product will be your best bet. Especially on suspension parts as you do not want a huge chip. That said DPLF can be used as a seal coat. It works great as a seal coat as it locks down everything. I would simply match a color to your top coat and mix as a seal coat. You aren't going to have any problems. EVERYBODY has a break through and to hit it with etch will cause more problems as it will have to be 100% covered before any top coats applied. Good luck and try NCP you can etch, surface and seal with one product. Heck for the cost of all that primer have them powder coated and then seal and top coat.
Hit it with DP reduced, at about 40%, acts as a sealer, lays flat. After shooting two thin coats of DP reduced, wait 45min and shoot your paint. Do not apply paint over bare metal, end of story! good luck
Lots of advice posted. Not a lot of reality though. If they were good clean parts you could have etched them and went right to your enamel. How many of you have seen primer under an OEM black chassis? But now you've surface primed and sanded for a nice smooth look. You say you need to re-prime some stuff for more fill, just spot em in with that. I men, really, are you going to drive it in the ocean? Gonna run it through winter on salty roads? Every product you're using has a durability that's so far beyond just paint you have no worries. My best advice is keep it as thin as possible. Thick acrylic finishes, both primer and paint, will get brittle over time and chip very easily if you have too much build.
NCP is not an etching primer. The tech sheet says: Two step metal treatments or the use of a wash primer coating will improve the adhesion and performance properties of the finished system. · A two step metal treatment or wash primer is required over sanded clean galvanized steel substrate. So they (PPG) reccommends an etch primer or using metal conditioner for better adhesion and performance when using NCP primer system. Catalog page: https://buyat.ppg.com/refinishProdu...roductID=584f4c3a-7a19-4293-afd3-8f950c1f000e
I agree, I'm really over thinking it I believe. Most of the filler primer that went on came off with the blocking in reality, it was more to get a surfacer that I could sand on there. Thanks EVERYONE for their input,overspray, you know your paints it sounds like. Again, appreciate it everyone! Happy Holidays!
I really dislike NCP, no I actually hate it. It might be good for a flawless new panel at best. Not since the days of DZL primers have I seen a product that shrinks like NCP.
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