Polyurethane Painting

[fryhead]

Hey Guys,
I had my car painted last summer. I bought a polyurethane lip which ended up getting destroyed in a snow storm. I just purchashed the same lip and got the rest of the paint that was used to paint my car. Probably 2 inches worth in a gallon can.

The guy who painted my car said he used a sealer, not a primer. What sealer should I use and how should I prep this?

I also only have an electric spray gun. I know the results wont be the same but I am hoping they will be close. Any tips? I've never used it and only have a small amount of paint left.

It needs to be flexible. I am lowered and when I scraped my lips multiple times the paint never cracked.

Thank You!

 

[TAZ]

Hello,
Welcome to the forum.
It appears that you've already talked to the guy. Can you ask him what sealer he used, or find out what color he used?
If not, then you'll need to decide on which sealer AND what color sealer depending on the color. If it's a real dark metallic, use a black sealer. If it's a medium metallic, use a gray. If it's a red base, use white....

As far as 'what brand', if you can't get any info from the guy, I would suggest going with the same brand as the paint that you will be applying.

 

[fryhead]

Thank You for the welcome and the reply!

He is out of town and has been for quite some time, so I haven't been able to reach him yet. The paint was purchased at Sherwinn-Williams and is Fiji Blue (found on the newer Cvic SI's.)

Here are a couple pics for reference. So what sealer should I use as far as color goes? Do you know where I can get it? The Sherwinn-Williams around here does not sell automotive products, the guy who painted my car got them from about an hour away.

 

[Kong]

Maybe I can help you make some sense of what you've been told and where to go from here. Let me start by saying, use gray.

OK, now to the meat. When the guy told you he used sealer but not primer that was good news, but not particularly relevant to what you need to do. There are some primers that are chemically suitable to adhere to specific surfaces and there are some that are formulated to build thick films and sand easily, and many variations in between. Generally when a painter says they have sealed a job it means that they have used a primer that's main function was to lock down (provide an impermeable barrier) whatever is under it and provide one consistent base color on which you would apply finish coats. Properly the stuff is still called primer, but many times it is refered to as Sealer because that is how its being used. Most, or at least many, jobs require a material that can be sanded be applied to the surface in order to fill sanding scratches and minute lows in the surface. These are primers too, but they are not always needed - or at least some folks think they can get away without them sometimes.

Now, for your air dam, it really doesn't make much difference what the other painter did, because you now have a new part with its own needs. First get yourself a block and some rough (220p or so) paper and block sand the thing. That will tell you if you have any bodywork to do on it, which you most likely will. Fix any lows (its not clear to me if the thing is made of glass or injection molded plastic, but I'm presuming its glass) and then do you final prep work with a good sandable primer. After you've done that then you should seal it with a gray epoxy primer. From there you should be able to shoot your color and clear coat it (I presume you are not shooting a single stage paint on it).

It sounds like your guy felt the

 

[TAZ]

Great detailed answer Kong.
I do agree, that a gray sealer would work the best under that blue.

 

[fryhead]

Thank You very much!
I'll be getting the lip in a few days and will be using the info above! I'll let you know if I have any more questions!

 

[Kong]

Well, if you've got a couple of days before the thing arrives let me give you some tips on how to handle it when it shows up. Once again I'm presuming this thing is glassed, probably with either a gel coat or a primer on it. So here's what you might want to think about doing to clean it up and get it ready to paint.

First off if its in primer get some acetone and a couple of rags and wipe it off. The Acetone should eat right into the stuff and clean it off. If it doesn't come off, so much the better, but normally it will wipe right off. If its gel coat get some harsh unsented dish soap and start washing it. Wash it three or four times, but don't use an abrasive (like Ajax) on it. It is very very important that you clean it before you sand it - I can't emphasize this enough - get it completely clean. If you don't have a wax/degreaser yet go buy yourself a gallon and after you've scrubbed the air dam down meticulously then clean it with the degreaser.

Now you can sand it. The reason I wanted it utterly clean befor you began sanding is that they use wax as a mold release on those parts when they make them and it will remain on top of the gel coat for years - and they generally don't remove it at the factory before they primer over them either. That wax absolutely must be completely removed before you sand. You can not sand wax off of a surface, all you can do is sand the wax into the surface. So if you sand before you scrub and chemically remove that wax you will push it into the substrate and it will come back to bite you - and I mean bite you hard. Ever hear of "fish eyes"?

So, when it comes time to sand just stick some 220p over a sanding block - a hand sized soft block like one of the "Durablocks" or similar will do nicely. Just lightly sand the entire air dam. Because you are using a block you will be knocking down some of whatever orange peel exists in the virgin surface plus giving yourself a good indication if filler materials will be needed or if you'll be able to get away with just shooting some 2k on it then re-blocking it to smooth it out. Either way, just remember, prep is everything. Holler if you have questions, I look at this web page pretty much every evening.

 

[fryhead]

I'll be getting everything I need tomorrow or Thursday. I cleaned it with soap and Simple Green today! I talked to the guy who painted my car and he said just to get the primer from Autozone and to use either a red or gray scuff pad.

Any tips on the actual painting process? All I have access to is an electric spray gun we have. I might check into having some shop paint it if I can prep it and have the paint already.

Is roughly 2 inches in a gallon can of ready to be sprayed paint enough to paint the front lip do you guys think?

 

[fryhead]

I am looking at Advance Auto online and I see two different primers/sealers.

The Primer/Sealer says it seals primered surfaces.

So do I use this first and then the Primer/Sealer?

I don't know how many cans of each to get.

 

[Kong]

I don't know anything about the paints that AutoZone sells but right off hand I would tell you that I would not buy any of their stuff simply because most of what they sell is garbage and there is no reason to think their primers are any different. If you live in a city, or even a small town, you should easily be able to find an auto parts store that specializes in automotive paints if not a true paint store. The products they sell will be of higher quality and cost less than anything you will find at AutoZone or any other big box auto parts store. If you go to a place that sells PPG products you should be able to buy a quart of epoxy primer (MP-170) for a little less than $25 plus the hardener. Be ready for sticker shock on the hardener. Primer and its hardener will cost you about half as much as your clear coat is going to cost you.

Two inches of paint in the bottom of a gallon can will be enough to paint that air dam something between six and ten times, so you're OK there. Do you have an appropriate reducer for the stuff - if not a quart should be plenty. As for your electric spray gun, that might prove tricky but you are going to have to ask someone else how well yours will work because I have very little experience with one. l have to presume though that if you get the paint reduced so it will flow through the gun it should work well enough.

 

[TAZ]

I agree with Kong.
The spray can primers really aren't even worth buying. Most of what's in it is a thinner instead of primer. You'll never get a high-build primer out of a spray can.
Plus you can't put any hardener in it. If you want a good quality job, everything you use will require a hardener except the basecoat.

You may want to check out to see how much a shop would charge to spray it using your base. Possibly $150 or so?
You might find that very close to what you are going to spend on just the materials. Plus you don't even know how well your elec gun will work.
You can figure you'll have possibly $20-$35 or so for the sealer, $40-$50 for the hardener. 1/4 of clearcoat will run you about $40, plus the hardener about $40, plus the reducer (about $46 a gallon).
Some of these you can't buy less than a 1/4...which means a lot of this will be not used.

 

[fryhead]

The paint I have has already been reduced and is ready to go. So will that amount still be enough?

I will reply later but I am late for work!

 

[Kong]

Yeah, you've got plenty of paint, that's not the problem. I have to agree with TAZ completely on his recommendation that you just find someone to shoot your paint on the thing and let them prep it. What will kill you, as TAZ noted, is all the stuff you will have to buy that you just won't be using much of. In truth you'd have more money tied up in primer and reducer/hardener for it than I would charge you to prep and shoot the thing. If you do it yourself you're going to have three quarters of a can of everything you buy left over when you're done and the stuff is quite expensive. A person who paints regularly will already have the stuff you need in small quantities, and you know there's just so many little things; filler, hardeners, degreasers, paint strainers, even the filters for your respirator will run you broke unless you have a lot of jobs to spread the cost over.

 

[fryhead]

Wouldn't hardeners prevent the paint from flexing and therefor cause cracking/chipping?

When I had my lip on it, I would scrape it daily on drives, inclines, and ramps quite often. The paint would scrape off underneath where you couldn't see it, but the paint would not crack even though the lip/airdam would flex alot.

What grit of sandpaper should I use to scuff the bumper?

I am taking your recommendations into consideration, however, because of my small budget it would not be quite some time before I could do such a thing. I may just try a can of Rustoleum primer on the lip to see how it holds up.

 

[TAZ]

Today's paints are much more flexible than previous paints were.
But these are true basecoat/clearcoat paints. I'm not for sure how spray can will hole up. Since these have no hardeners, of course, the paint will scratch pretty easily

I would probably use 180 or 220 for the bumper before priming. Then 320 minimum for the primer before painting.

 

[Kong]

"hardener" is the catylist which caused the chemical reaction that allows the paint to "dry". Paints that require a catylist (hardener) to set up will not set up without it. It is not something that makes the paint hard, or brittle in any way.

As for the spray can stuff, just take a rag with acetone on it and it will wipe any that stuff off - that should tell you how durable it is. Rattle cans are fine for model cars, mail boxes, and lawn furniture*, and not much else.

* actually its not much good for lawn furniture either.

 

[fryhead]

Thanks for all the help guys!

Another friend is going to help me in a couple of weeks or so. He has adhesion promoter and automotive primer so we should be good to go! I'll be getting the lip prepped here shortly.

 

[TAZ]

No problem FH, good luck to you. Be sure and check back to check back and let us know how everything we went.

 

[paxhc]

As for the spray can stuff, just take a rag with acetone on it and it will wipe any that stuff off - that should tell you how durable it is. Rattle cans are fine for model cars, mail boxes, and lawn furniture*, and not much else.

* actually its not much good for lawn furniture either.

I am new here but i don't agree with a lot of the rattle can comments, someone said you can't get high build in a rattle can... SEM makes a very nice high build in a rattle can and as for clears, if you know your way around a rattle can there are a few very nice clears that i have used and can lay flatter than some "pro painters" around here can lay the clear out with their Sata, now as far as long term holdup to UV and whatnot i am not sure

Just my .02 cents

 

[TAZ]

Welcome to the CPF. We appreciate your posts here on the forum. After all, that's what makes a forum a...well, forum!

I would have to guess that you haven't sprayed a true catalyzed hi-build primer through a 1.5 tip spray gun. I think if you could check the mills between 4 coats of the spray gun primer versus the spray can primer, I'm sure you'll see that it builds up quicker and better.
A regular spray gun hi build primer 2.5-3 mils per coat (4 coats = 12 mils max)
The spray can primer you are talking about .75-1 mil per 'wet' coat (4 mils = 4 mils max). If this is not the correct spray can primer you are talking about, feel free to add a link to it :bigokay:
As you can see, you get 3 times the build up of a true primer, plus of course, because it is catalyzed, the hold out will be better.

Hi build should be considered getting the most coverage and millage with a minimal amount of coats (otherwise ALL primers and paints could be considered hi-build).
So if you want to compare one spray can primer to another, then "yes", of course the SEM is thicker than the other spray can primers.
But you wanted to compare against a true primer that can be sprayed through a spray gun...I just wanted to show you the specs on both.

If you're going to buy about 15-20+ cans of clear to paint a car at about $16 a can, I would think it would make more sense to just buy a gallon of HOK at $125 (clear) + $45 (reducer) + $60 (hardener). You may be able to slick it out like the pros (I also find this hard to believe if you do a "full-sized" car)...
compare the paint job 6 months later.

I've been painting 22+ years and never seen or heard of a spray can job outlasting and performing auto body grade type primers/paints.

:yesnod: