Etch primer and sun baked 'surface rust'

[Khayward]

Planning on starting to clean up my roof - lots of bald spots with sun baked surface rust. I have some self-etching primer and am wondering if it's the right product, seeing as there is still paint around the bald spots, and, if it is, how far should it be prepped? Does the bald spot need to be shiny, or just cleaned up? Should I avoid getting the primer on the existing paint? (I read that the acid can make paint bubble or pickle)

 

[Ricko1966]

Planning on starting to clean up my roof - lots of bald spots with sun baked surface rust. I have some self-etching primer and am wondering if it's the right product, seeing as there is still paint around the bald spots, and, if it is, how far should it be prepped? Does the bald spot need to be shiny, or just cleaned up? Should I avoid getting the primer on the existing paint? (I read that the acid can make paint bubble or pickle)

Unless you are planning on painting your work immediately, you have the wrong primer. Most primers are porous and meant to promote adhesion,not protect bare metal. Epoxy primer you can shoot,and as long as you shoot a primer surface over it in the recoat window you can leave it for years without water penetrating the primer. That said,you can use that primer if it's getting a topcoat immediately. I'm not going to go into any detail as how much prep etc. That just opens the door for 4 pages ofvresponses on how everyone else would do it. Check with the manufacturer,they know their product better than anyone.

 

[Khayward]

Unless you are planning on painting your work immediately, you have the wrong primer. Most primers are porous and meant to promote adhesion,not protect bare metal. Epoxy primer you can shoot,and as long as you shoot a primer surface over it in the recoat window you can leave it for years without water penetrating the primer. That said,you can use that primer if it's getting a topcoat immediately. I'm not going to go into any detail as how much prep etc. That just opens the door for 4 pages ofvresponses on how everyone else would do it. Check with the manufacturer,they know their product better than anyone.

Thanks for the reply! I am going to rattle can over it. It'll look goofy as I'm going to put black over it but, at this point, I have to do bits and pieces as I have time and money so at least each patch will be protected until I can afford to have the whole thing done.

 

[Camar068]

scuff off the little, wire brush big chunks. Then I spray a rust convertor on it per directions, prime and paint....of course this is spray paint and not auto paint. The rustoleum line of 2x Ultra Cover painters touch is a primer/paint all in one.....if your gonna spray paint it.

Then again, it's the roof. If your on a budget, skip the rust convertor.

 

[Ricko1966]

Idk what color your truck is now but white hides flaws better than any color and the icing on the cake some squares came with white roofs so it won't look goofy.

 

[Grit dog]

Looks like the non rusty parts of your roof are a dead match for gray primer color.
If you’re not going all in and painting the truck then don’t waste your time doing something you may have more time involved in removing later.
Wire wheel the rusty spots, clean off the roof, hang a curtain around the rest of the truck and spray it with a good direct to metal primer and call it a day. It’ll hold up for a while. Years likely.
I sprayed some primer on some old stuff sitting outside a couple years ago when I started prepping parts on the 86. Ad hoc test I suppose. Literally wiped an old paint/rusty wheelbarrow and squirted 2 coats of quality filler primer/sealer.
It’s still gray and not rusty after 2 years outdoors in western Washington. Don’t overthink it.

 

[Khayward]

Don’t overthink it.

Best advice so far. I did a brief stint in a body shop just south of Astoria many years ago and I think that experience is clouding my thinking on this. How exactly can I make it worse? )

Not sure where you are in WA but I've seen what happens to cars on the WA coast and we're in the mountains of ID, so yes, overthinking for sure!

 

[Grit dog]

Best advice so far. I did a brief stint in a body shop just south of Astoria many years ago and I think that experience is clouding my thinking on this. How exactly can I make it worse? )

Not sure where you are in WA but I've seen what happens to cars on the WA coast and we're in the mountains of ID, so yes, overthinking for sure!

bottom line you want to seal it up. And ideally you want something good that you don’t need to remove prior to permanent priming and painting.
I’m about as shade tree as it gets when it comes to paint and body but there are many primers whether epoxy or urethane that are designed to bond to bare metal (not all primers are even though that’s the basic function of a “primer” by definition) or even to bond to lightly rusted surfaces. Think flash rust or the little specs you can’t “get” when de-rustifying or even possibly what your roof looks like now.
The other good thing is most all automotive paint basically lasts forever if you seal the can up. Heck I just used some clear from over 20 years ago and I still use 20-30 year old single stage and basecoat leftover from vehicles long since gone. So whatever you buy won’t go to waste and you can use the remainder next month, next year or 10 years from now.

 

[Ricko1966]

bottom line you want to seal it up. And ideally you want something good that you don’t need to remove prior to permanent priming and painting.
I’m about as shade tree as it gets when it comes to paint and body but there are many primers whether epoxy or urethane that are designed to bond to bare metal (not all primers are even though that’s the basic function of a “primer” by definition) or even to bond to lightly rusted surfaces. Think flash rust or the little specs you can’t “get” when de-rustifying or even possibly what your roof looks like now.
The other good thing is most all automotive paint basically lasts forever if you seal the can up. Heck I just used some clear from over 20 years ago and I still use 20-30 year old single stage and basecoat leftover from vehicles long since gone. So whatever you buy won’t go to waste and you can use the remainder next month, next year or 10 years from now.

And to make it all more fun,many primers are porous and will allow metal to rust underneath the primer. Unless I'm using epoxy primer I always topcoat it with something just to be safe. Yea I know primer sealer should be sufficient. Something I learned from ditzler was if you shoot epoxy primer,and then primer surface during the recoat window,you can walk away for years,come back clean it scuff it and shoot paint.

 

[Ricko1966]

I apologize I didn't look at your pic,I assumed you had a c or k not a burb,a burb with a white roof would look cool,kinda k5 like. But with a burb I think Grit dogs right,don't make extra work. Sand it epoxy prime it,hit it with grey primer

 

[Khayward]

I did a bit of tinkering between Sunday things today. The primer I have is self etching probably should have spent more time getting scratches out of the steel, took the surface rust off with 120.
Did note that the silver basecoat is barely attached to the primer where it's not obviously peeling, so a bit of scraping before wasting sandpaper.

 

[Grit dog]

I apologize I didn't look at your pic,I assumed you had a c or k not a burb,a burb with a white roof would look cool,kinda k5 like. But with a burb I think Grit dogs right,don't make extra work. Sand it epoxy prime it,hit it with grey primer

And there are plenty of primers that will do all 3 functions. Bond to bare steel, high build and a sealer.
No need in todays paint world, imo, to do an etching or epoxy first.
But looks like the OP is rattle canning something on there. In that case, just turn it gray, and it will be better than just rusting.
Or in less words, if you plan on painting it for reals in the near future then don’t do much if you’re just going to have to remove it later.

 

[Khayward]

I apologize I didn't look at your pic,I assumed you had a c or k not a burb,a burb with a white roof would look cool,kinda k5 like. But with a burb I think Grit dogs right,don't make extra work. Sand it epoxy prime it,hit it with grey primer

I think the previous generation burb looks great in green with a white roof. For mine I'm just trying to treat problem areas while I save for a full paint job or equipment to do it myself - the few shops I've talked to said they'd want 30k to paint it.
I'm as allergic to paint and bodywork as most people - it looks for all the world to be a form of voodoo, but for thirty grand I can buy a trailer queen already done so I think I'm going to roll up my sleeves, tell myself that I can't really make it worse and try to enjoy the process.
The reason for the original post was that I read that self etching primer would make paint it landed on bubble, and so far my test patch isn't exhibiting that problem.
I think next I will take a weekend and grind the bare spots and loose paint, hit the bare metal with the etching primer and, once complete, scuff/sand the whole roof and put primer on the whole thing.
I did try out a paint prep aerosol cleaning spray; works good but smells like the soap cake things in truckstop urinals.
Eventually I want the truck to go from silver with a black stripe to black with a silver or gunmetal stripe.

 

[Wumbo]

Skip the etching primer. Clean up the rust best you can, then treat it with Ospho. You can get a gallon of Ospho at most hardware stores for around $30.00.

Ospho pickles clean steel, converts rust, and it does a really good job.

After that, seal it up with an epoxy primer, then a sandable primer.

 

[Ricko1966]

Ospho is great stuff,I use it a lot. The thing about ospho,you can let it dry and it will protect metal and turn rust into iron phosphate,just like the rust converters. But if you want to shoot epoxy over it, you have to rewet it with more ospho and while it's wet you need to wash it off with water. The reason I said shoot epoxy then primer surfaces was to extend your topcoat time,most sealers and epoxies have a prime to paint window of 7 days. If you epoxy prime then shoot primer surfacer,you extend your topcoat window indefinitely,making your life easier when you are ready to paint.gritdog brought up a great point,last time I worked in a body shop was 20 years ago,there be new better stuff. Something I did read about was real deal,roll on/brush on Automotive primers and rollers etc. for body shops to save time and money,the article I read was pretty interesting. I'll see if I can find it have a great day.