automotive primer in a can

[G_Body_Enthusiast]

so what do people use for a primer?

i picked up some rustoleum auto primer. i got it because its dark grey and flat. it should help give my body the protection it needs until i can afford to get the body work done whenever...as i have no clue when i'll get it done.

aside from like 3-4 bad spots the rest of the body is very good and still has little rust but...i'm gonna have fun with my car and murder it out with this flat dark grey. i'm gonna take the bad spots down to bare metal and maybe look for a zinc wash of some sort and then spray em with the primer i got.

i'm just trying to figure out how many cans im gonna need to do the whole car. i'm not doing body filler as it's going to absorb moisture if its not sealed properly and that will only make the rust problem worse.

you have any favorite primer for your car/parts? i'm really liking this flat look and may stick with it.

 

[StreetDogg316]

Rustoleum is decent, I have used it before. I heard that POR-15 is pretty good too, I'm going to get some when I get the chance to coat the rust spots and the frame. And body filler sucks, I won't use the stuff, Even if you have it done by a shop, After awhile it usually breaks up and falls off.

 

[Ribbedroof]

Primer is porous, so it'll absorb moisture. Better to use a satin black or something of the sort over a regular rattlecan paint if flat is the look you need.

StreetDogg....As for filler...you do realize that it's been in the roof seams of vinyl top GM cars since the very early 70's, right? Hardtops got lead, vinyl top cars got plastic. Filler gets a bad rap for failing, when it's almost always the substrate that fails. Put filler over holes, or rusty metal, or other substrates with poor adhesion, it's going to fail.

I've read somewhere on here about somebody that has stated that filler wicks moisture in from a welded seam...it's actually the weld that's failing. Either through not cleaning all the contaminants (slag/spatter, burnt coatings, etc) off before applying the filler, OR (and here's the biggie) failing to treat the backside of the welded area. Heat starts rust, just like water or salt do. Don't clean and protect the backside of a patch panel seam, it's going to fail. If the weld has no defects (pinholes), is cleaned properly, and treated ON BOTH SIDES, there won't be problems with adhesion of the filler.

Most people have poor habits when it comes to using filler. They rub the bare metal to see if it's pretty straight, then spread it on. Bare hands will cause all sorts of issues with poor adhesion, but I see it done every day in the shop I work in. Personally, if I touch the bare steel, it gets wiped with wax/grease remover before it gets filler.

 

[oldscutlass350]

POR-15 is really good. my doors are rotted at the bottom of my 02 grand am. i wire wheeled the bottom where the door skin folds over and brushed some of that on there before winter. winters almost over and i see no signs of it getting worse.

also vari-prime from dupont is really good. it is made for bare metal applications and works really well. i know a guy who sand blasted the frame on his 67 buick GS convertible and that was 20 years ago. its been sitting in his garage ever since and has not started rusting at all. you can also get some etch primer in a can from dupont that we use at work. its good stuff and the rattle can stuff is not too expensive for what it does.

 

[custom442]

To begin your question you have to decide what your primer is to be used for--if it's going to be used for a cover until the real bodywork is finished, then you can use any color or build as long as it isn't too porous. You should be fine with even a primer sealer until you begin the real body work.

Unless you decide to paint soon, the primer is going to collect moisture and decay, no matter how expensive or high of quality. If you want to do it right, first decide what type of paint you want to spray. If it's old style lacquer (which is not a good choice of paint unless it's a trailer queen) then you need an acrylic lacquer primer. If you are using acrylic enamel (which is what I always paint with) then you need an enamel primer - you could use an epoxy or polyester primer in this case. Epoxy primers usually come in two stages, these are the 'fancy' types, if it's labeled epoxy and doesn't have 2 stages - it isn't of good quality and should be avoided. Polyester primer, or high-build polyester primer, is my most favorite of all because it is simply bondo in a spray can. It allows you to build on top of tiny bubbles in body filler and fill in cracks in metal from coarse sand paper - this is the best stuff and you can buy high build primers from most auto spray can companies. If you decide on urethane paint (which is most common today) then they require special urethane top coats, or primer sealer. From my experience primer sealer holds up to the weather and moisture much longer than any other type and forms a good base for paints other than just urethane.

I would stay away from metal etching primers. These types once were very effective because they had acid which bonded into the metal for a more secure paint base. Nowadays the toxic chemicals have been taken out of the formulas and they don't perform like they used to. I've had metal etching primers and noticed no difference between them and high build primers as a base.

Another factor is what color do you need the primer to be. Black may look cool, but the primer is just base for the paint. If you want the flat look, spray flat black over the primer because it will decay in time if there's no paint. You can either contrast the top level of primer so it's easier to see where you've painted and where you haven't (light gray primer - black paint, dark primer - white paint). Or if youre getting professional paint or know how to paint well, you should use the primer as a tint, if you're using a dark blue paint you might want a black or dark gray primer. Or if you wanted the paint a shade lighter you could use a white primer. This really is getting into paint details because it makes very little difference - I just contrast the primer/paint so it's easier to paint the first few coats.

The formula I like is duplicolor high build primer (red), then contrast a primer sealer (white or dark gray) depending on what color I paint. Just make sure to use the same company for all your paint - use all duplicolor primer and paints, or all tasco, or all maaco, etc. This is also getting particular, but some paints by certain companies don't work well with primers from other companies.

By the way, you're looking at about 2 cans for the roof for each type of primer (ex - 2 cans for base, 2 cans for sealer). Use that formula to guestimate how many cans you might need for the whole car. It's also a good idea to buy a bunch of cans first and use full ones to paint all the flat (top) surfaces of the car, then set them aside after you've used half a can. Use the half filled cans for the sides of the car, since that's how spray cans were designed to be used (upright).

 

[Blake442]

I won't put paint on top of old spray can primer. Might be fun to black it out for a bit, but there's no way I'll lay down a new finish on top of it, let alone when that cheap rattle can primer is on top of cracking old laquer paint. Reciepe for problems. Auto body supplies are expencive enough, I don't need to buy the stuff twice cause I have to redo it cause it lifted.

Filler gets a bad wrap from mis-use. Body filler should never be thicker than a nickel. If it is, than the metal wasn't properly straightened. How many times have you seen chunks peeling off a car that are half an inch thick or more? Too many.

You can do a satin rattle paint job for now if it floats your boat. But if you're looking for a quality finish down the line, the only way to do it is to completely strip the car for the best results. Remember that the finished result is only as nice as that first layer. Spraying on top of shitty paint is a huge gamble that I certainly wouldn't be willing to take.

 

[StreetDogg316]

Primer is porous, so it'll absorb moisture. Better to use a satin black or something of the sort over a regular rattlecan paint if flat is the look you need.

StreetDogg....As for filler...you do realize that it's been in the roof seams of vinyl top GM cars since the very early 70's, right? Hardtops got lead, vinyl top cars got plastic. Filler gets a bad rap for failing, when it's almost always the substrate that fails. Put filler over holes, or rusty metal, or other substrates with poor adhesion, it's going to fail.

I've read somewhere on here about somebody that has stated that filler wicks moisture in from a welded seam...it's actually the weld that's failing. Either through not cleaning all the contaminants (slag/spatter, burnt coatings, etc) off before applying the filler, OR (and here's the biggie) failing to treat the backside of the welded area. Heat starts rust, just like water or salt do. Don't clean and protect the backside of a patch panel seam, it's going to fail. If the weld has no defects (pinholes), is cleaned properly, and treated ON BOTH SIDES, there won't be problems with adhesion of the filler.

Most people have poor habits when it comes to using filler. They rub the bare metal to see if it's pretty straight, then spread it on. Bare hands will cause all sorts of issues with poor adhesion, but I see it done every day in the shop I work in. Personally, if I touch the bare steel, it gets wiped with wax/grease remover before it gets filler.

I've never really used the stuff myself, But I'm just going on what I've seen and people has told me. I've seen people that have had body work done by a professional and within a year it has failed and chipped away, They paid alot of money to have it done right, And that is the result. I would not bother with body filler if you are going to paint your car and get it nice looking, I would just get some patch panels and weld them on, grind down the seams so they are nice and flush with the body and then paint. And I would not know about GM cars, As this is my first one. I have had Ford(NEVER AGAIN), Honda, Nissan Etc. But no GM's.

 

[Ribbedroof]

If it needs patch panels, filler was not the answer to begin with. That's the kind of failure I was talking about.

Grinding down flush and painting is virtually impossible on anything built in the last 40 years, especially wavy patch panels of questionable steel content. A skim coat is going to be needed, if you want it straight. Some people use lots and lots of primer/surfacer to accomplish this, but that can lead to cracking as well.

It's like most anything else in the world...used correctly, as designed, with attention to what you're doing, filler works fine and lasts for decades. Slather it on over holes with no regard for how it's intended to be used, guaranteed failure. If it failed in a year, I have to question their definition of professional. Sadly, many will do whatever the customer wants regardless of whether or not it will last..and there are plenty of fast-buck artists? out there that know you won't be able to tell how it was done if it looks good on the outside. At least until the rot comes back, and by then, they already have your money.

And before the old schoolers start going on about lead, every old lead repair I've ever seen had considerable rust under it, from the heat of the torch, presumably.

 

[78gp]

Not all fillers are plastic you can buy a metal filler from a body shop this stuff has metal in it and when it dries it is so hard you have to use a grinder on it also it seals the metal from moisture oh yea a magnet will stick to this stuff, thi stuff is the only way to go for patch work.

 

[pontiacgp]

when you prime your vehicle you should tint the primer so that the color of the paint will neutralize the primer