rust repair

[74.5 347Z]

hey everybody,

 

i am new to z's, kinda. i was in japan for a couple years and owned a '84 fairlady. anyway, about a month ago i bought a '74 that looks pretty solid underneath but has a bit of rust on the rear quarter panels and rocker panels. my question is if i sand blast rusted areas how should i treat the metal? also, if i plan to replace rocker panels with ones from victoria british how would i treat the area inside the panels?

[Georgia Flash]

I sand blasted the rear taillight panel of my z and will be doing a lot of blasting under the hood once the inliner comes out. I am relatively new to painting so when I went to pick up sand for the blaster at the local Dupont paint store ((go Jeff Gordon)) I told the guy that I was going to need a primer for bare metel. He sold me some etching primer. It goes on nice and is a puke green color. Now I have no idea what "etching primer" does but I used it like he said. There are some great guys here who know a lot about painting so maybe one of them will help out. Good Luck.

[Owen]

My opinion is that etching primer isn't really necessary at all since the quality of well known epoxy primers is so good. Also, the metal will already be etched by the sandblasting.

 

I just finished sandblasting my car and am coating with PPG DP90LF, no etching primer.

 

Etch primer can't hurt but you also can't put filler over some brands. I think there is less compatibility with brand x etch and brand y primers too.

 

The worst it can do is increase the mils of paint on your car, which is not always a bad thing.

 

Owen

[74.5 347Z]

owen,

 

so a good expoxy primer on top of a blasted area will prevent further rust? how long do i have to primer the exposed bare metal before any chance of rust returning, minutes, hours or days? this por-15 that members are talking about is for areas of rust that cannot or have not been fully "derusted"? the more i look at this car the more rust i find. soon i am buying a sand blaster and declaring war on rust. just looking for the best way to treat the surface before painting. i appreciate your inputs.

 

mark

[Georgia Flash]

Ok once again I am confused! When I first got my Z it had a lot of surface rust. I quickly sanded the rusty areas to bare metal and having good common sense, I primered the areas using grey primer. It didn't take long till the surface rust started coming back through the primer!

Now at the time I was taking an auto mech class at the local vo-tech school and all the folks there said never to just paint over bare metal with primer. Yes even the paint and body shop teacher said this. They all said that regualar primer is porus and that you should use an etching primer.

Even the guy who works in an automotive paint store for a living did not hesitate when I ask him about painting over bare metal, he grabbed a can of etching primer. Also I have since removed all the rubber sound deadening material on the floor pans, tranny tunnel, and rear hatch area. What did I find?

Looks like that puke green etching primer that the Datsun factory sprayed on way back in 1975!

Just my 2cents worth.

ps.

Racer x I have long be a fan of yours since coming to this site, so I do not mean to offend, I am just a confused little old man right now when it comes to this etching primer thing

[Guest Anonymous]

Owen, PPG DP90 has an etching agent in it according to my PPG rep. The green Dupont stuff is a vinyl-wash etching primer similiar to zinc chromate primer developed for the military eons ago.

[Sumo]

Now you got me confused So should you repair the panel with bondo then use etching primer or etching primer first then bondo since bondo is prone to moisture absorption?

[Georgia Flash]

I think everybody is confused LOL

[74.5 347Z]

i didn't mean to get anyone confused. owen and racer x, i now have an idea of what you are talking about. i live in maine and right now we have a bit of moisture, so it is a good idea to do small sections. does this procedure of metal prep, rinse, dry, wipe w/thinner, sand, wipe w/thinner, and then expoxy primer work both on bare metal that has been derusted and metal that has had no rust? if so i think i can handle that. "PPG", is that a brand name? i plan to cut the areas around the rusted spots, so hopefully the metal will be rust free. is there any other considerations i nood to take into account while i am doing these things?

[Georgia Flash]

Racer X you da man One quick question. I have sprayed most of the rear of my Z in the puke green stuff and it has been on there for a couple of weeks. Now since you say that you should spray on the regular primer when the green stuff "flashes" what do I do now? Can I sand the green stuff when I get ready to use the regular primer? Or will this not work?

Oh by the way you can now see my car as I found it er uh...in the ruff so to speak

[74.5 347Z]

i read up on the por15 stuff you mentioned. so you think this would be better? it sounds like it is a simpler process. they have the metal-ready that goes on before the por15, what should you use after the por15, a primer surfacer or their tie-coat primer? they say the tie-coat is sandable. the por15 only sticks to bare metal or rust, correct? they advertise that "TIE-COAT Primer™ is a tough-yet-sandable single-component polyurethane primer, with special adhesion characteristics that make it perfect for most painted surfaces... Especially POR-15®." so after the metal prep, por15/well sanded old paint, tie-coat primer i should be ready for paint, right? what about the fine line where the bare metal area meets the old paint? should i use bondo or something else in needed areas on top of the por15 before the tie-coat or after the primer?

 

monday i will call "RestoMotive Laboratories/POR-15, Inc. P.O. Box 1235, Morristown, NJ 07962 Phone: 1-(800)-457-6715" to talk to their techs.

 

your advice is very helpful. i agree with Georgia Flash 75V8, you definately are the man.

[Guest Anonymous]

I have found POR15 works fairly well for small area problem surfaces but is very tempermental on larger surfaces. I would suggest that you treat only the rust areas directly with the metal prep and POR15 with the use of a sponge type paint "brush" followed by the tie coat and then finish with regular primer and paint.This paint and it's chemical surfacer is specifically made to cover and seal metallic rust (the silver has a lot of metallic particles to fill areas in). I also found that POR15 does not like it's solvent/thinner in large doses which tends to cause blistering or orange peel.The paint is allergic to sun light and fades fairly fast. I painted the engine bay of my project (2X) and it looks like I will be sanding it down the second time to cover with tie coat for regular paint. It cures fast and is easy to sand. I have been writing about my trials and tribulations with POR15 in this Body and Paint section and my biggest problem was expecting too much out of the product. > I should have prepped only the area under the battery tray with POR15 and finished the rest of the engine compartment with regular paint.(and would have been totally finished last week). POR 15 is not cheap.

[Owen]

Good advice on those blue tarps! Glad I never did this.

 

I went through this really quick so I hope I don't repeat anyone's answers. I don't know if POr-15 is compatible with most of the automotive paints. Better check first instead of getting lifting and blistering later. There's also a thing called Zero Rust which is basically the same thing but widely used by the people I've been talking to for automotive prep.

 

I've also had problems with POR-15 on large areas, especially the underside of the floors which flexes a little. In my case, the POR-15 started to crack and eventually peel off. Then again, this metal was new so there probably wasn't enough tooth in the metal for the POR-15 to bite to.

 

And the rust prep, I used some on my rear quarters and it really ate the rust away! But what I don't like about it is that you have to clean every bit of it off later or you'll get adhesion problems. I gave up on it and went straight to sandblasting. One little missed spot of that rust prep could cause havoc.

 

Regarding the DA, I use 40grit on bare metal, but that's for areas that need filler.

 

Owen

[74.5 347Z]

please don't appoligize about the lengthy replys! i am just glad there is someone that has the patience to explain this to me. a friend and i done a little rust repair on a bronco that i had and then primered and painted it. a few months later the rust was back, definately didn't do something right. as far as the primer we used had two parts and the paint had three parts, i think. he said this is what we are using, so we did. it was my first experience with a paint gun it turned out pretty well considering. the only bad part was the rust. now the bronco is sold and i bought this z. i hope to have better results this time thanks to the help that all of you are giving me. ok,ok.

 

now i will blast the rust, weld in the new panels (rockers, lower quarters, and a bad spot above the tail light on the quarter panel) then treat the bare metal. rinse,dry,wipe w/thinner,sand,wipe w/thinner, and then spray w/expoxy primer. then comes the body filler, a diffrent kind of primer, and paint, this of course that will be later. this is what i gather from what you are saying. and then the por15 deal will take care of hidden areas inside and underside. am i getting close? what are good brands besides ppg and rustmort? i will take some pictures before i get to far into it.

 

once again, thanks for your paitence and your help.

[Guest Anonymous]

One other thing. You said you were going to weld in panels. If you are going to have any over lapping seams, not butt welded, then pick up some weld through primer at the automotive paint store.

 

I also have done $10,000.00 plus paint jobs and frame off restorations and I personally would never leave out the etching primer step. When you purchase any sheet metal from any manufacturer especially GM they are coated in black etching primer and I feel there is a reason. If I charge that much money I feel I owe it to the customer to provide the best foundation for their paint job that money and technology can buy.

 

I rely on the millions of dollars in research that is provided for free by the paint manufacturers. Most all of them will guarantee in writing material and labor reimbursement if you follow their procedure and their paint fails.

[Owen]

RacerX,

Thanks for the suggestion, I don't take it as criticism cuz I don't know anything at all!

 

This procedure, you mentioned, is this for bare metal followed by the high build instead of epoxy?

My car is already fully covered in DP90LF, gotta sand some runs out though. Next comes the K36!

Owen

[74.5 347Z]

bbbowtie,

 

what is weld through primer? how should i treat the metal that is inside the overlap? do i even have to?

[Guest Anonymous]

Weld through primer is something relatively new on the market. There are so many times when a body man has to re-spotweld uni-body panels back together of course at the seams. These seams will trap moisture and most seams where a panel has been removed because of damage has to be worked (hammer and dollied and ground) back into shape. So now to the point. The auto paint industry needed a primer, sealer that could with-stand a lot of heat and protect the rust prone seam. I'm pretty sure it comes in a spray can from 3M or SEM just ask your auto-paint dealer. It's been a year or so since I used any. Anyway I feel it's a necessary prevention thing.

[Owen]

RacerX,

The reason? Cuz I don't know anything else

I've researched a couple of paint lines but was really limited to what my local shop stocked the most.

 

Owen

[Guest Craig280z]

Holy Cow.

 

I read this whole thread. Lots of good information.

 

I know its a little old but I wanted to add a question.

 

Is this a feasible plan?

 

I want to do the body work on my car and I plan to take it down to bare metal and primer it with the epoxy primer as racerx suggested. Since this primer is non-pourus, is it ok to prime with this primer and then continue to drive the car?

 

I will be working in small sections at a time so it may take me awhile to finish but I still want to drive my new LT-1 powered Z (when I get it running )

 

What is the best way to do this work in stages but still be able to use the car?

 

Thanks everyone on this thread for all this great info. I always wondered what the self etching primer was and how it was used. My friend was priming some parts yesterday and he held up the can of primer, it was self etching, and said that this is what the sales guy told him to use. He said, I don't know what it is but he said it was the best. I'll have to let him know that it is porous and if he doesn't seal it like he is suppossed to, he is asking for trouble....

 

Thanks

Craig