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Old 09-22-2018, 06:36 PM   #1
Slowguy
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Prep right before painting frame after sand blasting

So Iím 95% done blasting the frame. Looking really good so far. I have to do my chores in stages so it will inevitably have some light surface rust when I get the time to get it coated. Iím using the pro 15 with chassis black on top of that. I knows it fine to put por15 right on top rust but Iíd really rather wipe the light surface rust off right before I por15. Any recommendations? I used some ďKrud KutterĒ before and that phosphoric acid is like rust magic but I want to be sure thatís ok right before por15íing. Figured spray down with krud kutter then hose it off with water but figured Iíd ask in case someone has a better idea or otherwise thinks thatís not a good plan.
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Old 09-22-2018, 07:00 PM   #2
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Re: Prep right before painting frame after sand blasting

If you remove all the rust, the POR15 will not stick. So be careful how you use it. It will peel if it doesn't adhere to rust.
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Old 09-22-2018, 07:02 PM   #3
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Re: Prep right before painting frame after sand blasting

http://67-72chevytrucks.com/vboard/s...d.php?t=589112

Check this thread out about POR15.
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Old 09-22-2018, 07:05 PM   #4
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Re: Prep right before painting frame after sand blasting

Looking good, I used Phosphoric acid sprayed on with small spray bottle, wipe it also with cloth rag. Let dry to white film, wipe with wax and Grease remover, extra step may not be needed. Then paint...For me, epoxy primer and Hammerite.
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Old 09-22-2018, 07:28 PM   #5
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Re: Prep right before painting frame after sand blasting

Bare metal can be etched with POR metal prep before applying POR
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Old 09-22-2018, 09:24 PM   #6
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Re: Prep right before painting frame after sand blasting

Thanks for the replies guys/gals. So it sounds like either let the surface rust form and hit it then with the basecoat of por15 -or- clean it with phosphoric right before and por15 prep coat -or- clean with phosphoric, wipe clean, then epoxy primer and hammerite. Decisions decisions?
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Old 09-22-2018, 09:44 PM   #7
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Re: Prep right before painting frame after sand blasting

According to the instructions on POR 15, the first step is to clean the metal. Yes, I'm aware you sandblasted, but cleaning the metal will remove all oils and stuff from handling.

Second, you apply metal prep, which etches the metal properly for the POR 15 to bond to. Both of these steps are really helpful to get the proper bond to the metal. Then either spray or brush the POR 15 on. It self levels, and I've used both processes with good results.

I've never used topcoat on a frame. After 10 years, the frame still looks glossy black, although in defense mine does not sit outside. Topcoat will only add another layer of protection.

Lastly, one coat of POR 15 is enough. There is really no value to a second coat, especially if you are going to use topcoat.

Good Luck! I believe this to be an excellent product, superior to powder coat in many respects. I've enjoyed mine, and am likely going to paint the entire underside of the next project with this or KBS coatings Rust Stop!
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Old 09-23-2018, 05:29 PM   #8
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Re: Prep right before painting frame after sand blasting

my frame was clean but still needle scaled the whole thing. washed down with prep sol real good. the por 15 never peeled but the finish looks crappy. and rust was popping thru in places. went back to chassis saver and happy again. to many people around me that build hot rods for a living all so stopped using por 15. i will stick with chassis saver or maybe try KBS. there was a post here couple years ago from some company that made paint for commercial bridges that sounded pretty impressive. if anyone has that link.
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Old 09-23-2018, 05:51 PM   #9
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Re: Prep right before painting frame after sand blasting

Mastercoat silver is the bridge paint, Good stuff. Especially nice over sand blasted steel, top coat with just about anything....I had a bad experience with Por 15, years ago, probably my own fault. But did not want to chance a repeat.
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Old 09-23-2018, 06:22 PM   #10
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Re: Prep right before painting frame after sand blasting

thanks for posting the mastercoat link. bookmarked,,, thanks,,,, will try that next time for sure.
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Old 09-25-2018, 09:12 AM   #11
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Re: Prep right before painting frame after sand blasting

I use a lot of POR-15 as a base coat if I weld up a gate or railing that will be exposed to water like lawn sprinklers. It sticks to new bare metal if wiped first with lacquer thinner.
I put a color coat on almost every application because I've heard POR-15 fades quick with UV exposure. My top coat will not stick to fully cured POR-15 because the surface is too shiny. This means I have to paint POR-15 early and after 3-6 hours when it cures from runny to tacky then I can roll/brush/spray the color coat.
I have white rattle can top coated swamp cooler brackets in my yard that still look great after 15 years in Mr sun. The bonus is how smooth even the top coat flows out and even brush marks disappear with a POR-15 base.
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Old 09-25-2018, 09:36 AM   #12
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Re: Prep right before painting frame after sand blasting

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Mastercoat silver is the bridge paint, Good stuff. Especially nice over sand blasted steel, top coat with just about anything....I had a bad experience with Por 15, years ago, probably my own fault. But did not want to chance a repeat.
Masterseries is an upgrade from POR-15. Company was started my the chemist that worked to develop POR-15 who left and started his own company to sell a better product when POR-15 cheapened their formula. You don't see hiway bridges or other large high dollar projects using POR-15 where the true test is. Bridges get salt and brine dumped on them all winter long, year after year. Classic cars are get done, then babied. Masterseries has a wide line of products to address various situations. I would never apply either straight over rust no matter what they might claim. Do the work and get the best job when it's easiest... a bare frame
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Old 10-15-2018, 07:02 PM   #13
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Re: Prep right before painting frame after sand blasting

Man, this turns out nice. Shame to even paint it with por
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Old 10-15-2018, 10:58 PM   #14
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Re: Prep right before painting frame after sand blasting

nice work
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Old 10-16-2018, 01:02 PM   #15
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Lightbulb Re: Prep right before painting frame after sand blasting

Por15 is a good product. The problem in my experience is that there is no simple prep for topcoating. I too have topcoated it when the Por15 is tacky or still has drag to it but not to a 100% success rate. If you miss that window then you have to hand scuff the Por15 to get the topcoat to adhere. If you provide tooth for the Por15 to grab on to it will stick. Either solid rust (not lose or flaky rust) or acid etched clean steel. Then getting the proper tooth in the Por15 for the topcoat is the key to getting a nice topcoat that lasts.
As far as hot rod builders not using it I would bet it is from an economic standpoint and not from a product failure issue. Using Por15 correctly is a labor intensive project that quite frankly isn't in the budget of many projects. Especially cars that only see the road on dry sunny days. Not to mention the fact that today's standards of street car builds are more than the show cars of 15 years ago. Economics mean that as a builder I will get a new frame from a aftermarket vendor and paint it with a good single stage paint. That will allow me to have a sharp looking product at a good price and it will also allow for easy touch ups that will follow as the owner uses the vehicle. Powder coating and products like Por15 cost me more money to apply and in many circumstances I can't charge more for that extra time. In addition they make invisible touch ups a pain even though I can charge for those.
Now all that being said I have used Por15 extensively on my Burban and my Javelin to good success. It works well on projects that are not being completely disassembled and restored, especially year round driven vehicles.
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Old 10-16-2018, 09:03 PM   #16
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Re: Prep right before painting frame after sand blasting

Now that Iíve actually done my homework (obsessive searches and reading opinions and instructions) and worked with this stuff I can say if itís applied correctly, itís virtually indestructible. I sand blasted and according to por15 instructions, that alone is enough to go ahead and coat. Instead, after blasting, I went ahead and used their prep stuff including the etching. I applied three coats in the method of letting it tack and test with the finger drag. This stuff is like rock. And I think it actually somehow permeates the metal. Like the metal absorbs it somwhat. On top of this Iím using the por15 ďtieĒ coat which is now called ďhigh build primerĒ and can be applied even after the por15 has cured. On top of that primer, I can apply any (most) type of coating I wish and I think Iíll use a two part chassis coat from Eastwood.

Had I known all that would be necessary to do this correctly, I would have opted for another method. Talk about time consuming! Itís too late now, however, and since Iím this far into it I have to complete the process. After seeing the results I find it difficult to imagine anything that would be stronger or better. Research, research then more research. Sandblast, Prep, prep and paint. Bonding tie coat, then top coat. Stuff will be an inch think by the time Iím through!
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Old 10-16-2018, 09:55 PM   #17
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Re: Prep right before painting frame after sand blasting

3 coats of SPI epoxy and the ability to get sockets onto painted fasteners gets my vote but it does look nice with the por on it
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Old 10-16-2018, 10:12 PM   #18
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Re: Prep right before painting frame after sand blasting

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3 coats of SPI epoxy and the ability to get sockets onto painted fasteners gets my vote but it does look nice with the por on it
I do the same. SPI Epoxy. I usually only do 2 coats because it builds up pretty thick.
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Old 10-16-2018, 11:02 PM   #19
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Re: Prep right before painting frame after sand blasting

I'm confused and have done this for years. Etching gives you a bite onto any metal as said.
Sandblasting is the mother of all etching. I believe it's the rough surface after sandblasting that gives this.
I would like to hear from those that have done both. I have and sandblasting is a mechanical way or creating a etch. If I'm all wet then I would like to know why? I will always look at different points of view.
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Old 10-17-2018, 01:12 PM   #20
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Re: Prep right before painting frame after sand blasting

Your not all wet. If your doing the sandblasting and know your grits then all is well. The problem can come from the wrong grit or worn out grit causing the metal surface to resemble a bead blasted surface instead of a sharp toothy surface. So if you are unsure of the surface quality then the acid prep ensures good paint adhesion. There also commercial tests for metal surfaces to ensure that the metal has the correct properties for the paint to adhere.
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Old 10-17-2018, 05:46 PM   #21
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Re: Prep right before painting frame after sand blasting

I have never used POR-15, but I have used Masterseries coatings extensively due to it's better reputation as stated above, and to the best of my knowledge they are similar products with similar prep requirements. The blasting does leave a surface with plenty of profile or "tooth" for the coating to adhere to. However, if the sandblasting has been done with sand, there is a lot of free silica from the sand embedded in the metal, creating adhesion problems for the coating. The cure is to treat with metal prep to remove the silica. For that reason I have switched to crushed glass for blasting, as it supposedly does not leave any silica embedded in the metal, eliminating the metal prep step. So far, so good. Only time will tell. Randy
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Old 10-17-2018, 06:11 PM   #22
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Re: Prep right before painting frame after sand blasting

I blasted my frame with Black Blast from Menards, no silica dust to inhale or get embedded into frame and works very well. Left the frame with a lot of sharp "tooth" and grit to adhere to. Blew off the frame with filtered compressed air and coated with POR. I did not acid etch. POR went on great and I cant even scatch it. So far no adhesion or peeling with assembly of the truck. Did not top coat either but wish I would have while tacky just for extra insurance. Time will tell...
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Old 10-17-2018, 10:27 PM   #23
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Re: Prep right before painting frame after sand blasting

I can tell from test spots that most stuff does not adhere to por15. So I decided to order and try the high build primer. They claim it will bond great to fully cured por and allow a top coat of just about anything. Still have to decide on the actual final top coat. I used por15’s top coat satin black on a few other parts and I do not like it. It is difficult, at least for me, to get a consistent finish. It’s either satin or completely flat. That’s why I figured use the tie coat and finish off with something easier to spray. Anyone have a top coat suggestion that’s easy to spray? I’d like a strong, satin black finish.
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Old 10-17-2018, 10:32 PM   #24
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Re: Prep right before painting frame after sand blasting

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I blasted my frame with Black Blast from Menards, no silica dust to inhale or get embedded into frame and works very well. Left the frame with a lot of sharp "tooth" and grit to adhere to. Blew off the frame with filtered compressed air and coated with POR. I did not acid etch. POR went on great and I cant even scatch it. So far no adhesion or peeling with assembly of the truck. Did not top coat either but wish I would have while tacky just for extra insurance. Time will tell...
I was thinking about the black blast (coal slag) from menards also but the amount I used would have been very expensive. I didnít get much dust (if at all) since I used a wet blast method. Iíve used the slag in my cabinet before and it worked well. The silica actually put a perfect finish for coating and I wonder if much could have embedded in the metal since it was done with very high pressure water as well?

As you can see from the pic above, it cleaned the cross member somwell it looks almost white like it was painted. That is actually the 50 year old steel perfectly cleaned and acid etched.
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Old 10-18-2018, 08:48 AM   #25
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Re: Prep right before painting frame after sand blasting

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I can tell from test spots that most stuff does not adhere to por15. So I decided to order and try the high build primer. They claim it will bond great to fully cured por and allow a top coat of just about anything. Still have to decide on the actual final top coat. I used por15ís top coat satin black on a few other parts and I do not like it. It is difficult, at least for me, to get a consistent finish. Itís either satin or completely flat. Thatís why I figured use the tie coat and finish off with something easier to spray. Anyone have a top coat suggestion thatís easy to spray? Iíd like a strong, satin black finish.
Eastwood chassis satin black was my top coat choice after, blasting /epoxy primer/ slick sand to get the deep pitting out from the rust another coat of epoxy and then eastwoods satin black lots of slick sand left on floor lots of work got the results i wanted..more in my Kim and Doc build thread..........have fun
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