Prep for paint
 

Aside from sandblasting, is there a quick way to clean up a frame in prep from paint? Right now I am sanding the thing and it is time consuming and I need to prime it tomorrow. Ideas?

Get some spray-on paint stripper in the paint dept at Walmart or wherever you buy paint. Sanding is torture, with one exception. That exception being if it's a quick and dirty paint job, all you really need to do is rough up the old paint enough that the new paint has something to hold onto.

Stay up late and make a pot of coffee :)

There is no easy way to prep a frame down to the metal. The quality of the finish is dependent on the amount of work put into the undercoating/filler/sanding. Even if you were to sand blast it you would still need several coats of primer to make a smooth base for the top coat. You can still get a nice finish, just sand the pitted and chipped areas down primer sand with 400-600 grit and spray a couple of color coats on sanding with 1200 grit in between. However none of the above will be dry enough by tomorrow to install components.

Good Luck

what are you sanding off? This is a new frame, right? Is there rust?

There are preps based on phosphoric acid, but I don't think I would try it on a frame first.

More info clearly needed. My bad, I did not see that this was the Framebuilder's fora.

Yes, this is a freshly built frame. I was sick for a week and it sat in the garage unprotected and has rust in some hard to get places. Sandblaster would get right to it, but I don't have one to use. Still sick, but am able to stand for 30 minutes at a time and have been sanding the frame at half-times and commercial breaks (I like college football). Was thinking there might be something that can be sprayed on the metal and flushed off with a solvent leaving a nicely prepped surface. Am I dreaming?

I've used phosphoric acid on rust spots to dissolve them. I wasn't aware that a bare steel needed to be prepared before paining, other than removing all the rust and maybe smoothing out rough areas of the welds.

I have never completely sanded a frame. Just cleaned it really well with solvent. Obviously, rust needs to be gone and any cosmetic issues in the surface need to be fixed.

Long, long ago when secondary schools had shop classes we were taught basic metal prep and it included thorough sanding and cleaning of the surface. I like the idea of degrease and paint. The bike is a commuter so perfection is not super important. It's prime time!

I used a final wipe of rubbing alcohol to get rid of oil from my hands off the frame. Would not want to try to paint over that. That was my final step before painting. Did not use primer, with rattlecan paint, what's the point?

paint sticks a lot better with primer, I need all the help I can get

I suppose it does, but when I used it, I had a gray primer underneath, white paint white over it, and when I sanded, I kept sanding through to the primer, and finding spots where the primer showed through, which was extremely irritating.

I'm a pro painter with a major league pressure pot sandblaster and cabinet and other professional painting equipment so I am a bit removed from how to do a rattle can job. However I think about those things for my frame building class students. It doesn't take that long to emery all the tubes with 1" wide 80 grit emery (called production or shop cloth in industry catalogs). The harder to reach areas can be cleaned with some kind of a wire wheel. You can buy big ones for grinders, medium size ones for drills and small ones for a Dremel tool. It is important to wipe down the frame before priming (I can't imagine not priming a frame because of the advantages). I use lacquer thinner because I use a lot of it painting and it is powerful stuff. Be advised to use gloves doing this. An amazing amount of junk will come off. Now it is ready to prime.


There is a spray can product called Spray Max that can be bought at some professional automotive paint stores. They can put in it whatever kind of pro paint you choose. I like to use House of Kolor primers because they come in different colors and I can match the primer color to the top coat color. Thinned out it also works as a sealer. The Spray Max cans are designed that when ready to use, a button on the bottom is pushed and the activator is now mixed with the paint so it will harden by chemical action. Most professional paint works like epoxy and you have a certain time window to spray before it hardens. In other words they don't harden by air drying like house paint. Their spray nozzles are designed to apply paint better than those on a typical rattle can. What to do next is way beyond the scope of this subject thread but If i was somewhere else than at my shop I would buy 3 cans of Spray Max, the primer, the color and clear.

This is one of the reasons pros use a sealer between the primer and color coat. Not only does it make the top coat stick better but it also provides an even undercoat color so the top coat is an even color. This is a time sensitive application. You have to wait a certain amount of time after sealing before color coating but not too much time for maximum adhesion.

As mentioned in my previous post I use House of Kolor primers that come in the primary colors that can be mixed in some combination to get the approximate color of the top coat color. This provides the additional advantage of makes chips less visible. Thinned with the appropriate temperature related reducer they also work well as a sealer.

Doug, I had no clue that pro paint is not just paint. I suppose they paint cars the same way. This morning I rattle canned primer on the frame. It has baked in the truck all day to speed up the cure process. It may or may not make a difference. Shot the bare metal with Rustoleum rusty metal primer, then shot over that with white primer. Color goes on tomorrow morning. Once my daughter sees it and gives thumbs up or down, she will apply the last 2 coats to "make it her own". It is bathroom tile pink. Once it dries she will then take a paint brush to it and do her art stuff on the frame.

Not my car. On a lot of cars these days, even expensive ones, the original paint is so thin you can put a scratch it with your fingernail. Supposedly due to enviro regs.

yes, this is not unexpected. There are online dealers that might sell for less, check ebay. But the way to get the priced down is to buy for more than one bike.

When I painted my frame build I used 2 spray cans of primer, 2 spray cans of color and used the HF gun to spray the 2-3 coats of 2K clear coat at $40 a quart with hardener, I used about 4oz of clear total. As it was my first build I didn't want to invest a lot in the paint until I figured out if I liked the ride or not. The price you were quoted is probably pretty standard for an all automotive quality finish. The finish actually turned out pretty good and more than likely I will not be refinishing it.

If at all possible see if the paint store will sell you the color coat in 1/2 pints. That's usually the smallest amount I have ever been able to purchase. That will be more than enough for one frame and fork. The primer and clear only comes in quarts or gallons so that's going to cost what it costs. A quart will last you a long time should you paint more frames in the future. Unfortunately, automotive paint is quite expensive, it can be a deep rabbit hole. Let's see some pictures when it's done.

Before you use the Harbor Freight gun make sure you clean it throughly. I have heard the guns are not cleaned thouroughly before packing and oil residue remains inside the gun.

I get all of my paint supplies from TCP Global. Paint Colors I've had good results from their Custom Shop line and it is considerably less expensive than my local auto paint shop.

My main ride is about 10 years old and has been drenched in salty sweat without mercy during that time. It was coated with automotive paint (epoxy primer, base coat, urethane clear) but even at that I've had to do a touch-up a few years back due to corrosion around the bottom bracket. Common rattle can paint (not Spraymax) has about 25% of the durability of good automotive paint when it comes to corrosion protection. To each their own, but in my view building a frame and then skimping on the paint is bad juju. I'd rather get the thing powder coated.

BTW, Transtar epoxy primer is good stuff and relatively cheap compared to some of the alternatives. And for my last project I used House of Kolor base coat and USC01 clear. The clear is the low VOC type which isn't my first choice, but that's all that's allowed in my area. It takes three coats to get good film build whereas the older 3.5 VOC clear took two. Wonder if the environmental regulators know this?

the big advantage of rattlecan enamel versus automotive paint is safety. Unless someone is willing to invest in equipment, rattlecan is much safer. I have wondered if my asthma is related to my use of isocyanates under less than perfect conditions. I was probably one of the first people to use urethane clear in the bike industry, the autoparts guy recommended it. Said the local NASCAR team used it over lacquer. That was back when catalyzed acrylic enamel was meant to be a topcoat. You can still get paints like that for a single topcoat application, I have considered it.

Got to thinking about the quality of the air around me when I rattlecanned the frame. Was choking on the fumes and was outside with a slight breeze, too. Seriously considering brush on paint next time around. Likely better for my lungs.

Yeah, but the buzz is not as good, doesn't last as long. I didn't think the stuff was bad when I was spraying it at all, it was the gassing out period where the fumes really got to me, when I left the drying frame in an enclosed area. I just about passed out from those.

a mask good enough for rattlecan paint jobs is not that expensive. 3m sells a really nice mask with many options for filtering. They will work for catalyzed urethane for a while. The fact that they fail silently after some period of use is problematic.

You want a mask that will take filters for VOC, they have activated charcoal

may be too late, I am no expert (I have painted 2 frames one rattle can and one automotive paint) Auto paint is hugely more durable

I did a lot of research and it suggested that an acid etch primer first coat (rattle can from autopaint) will help end result longevity, followed by sandable primer, then color, then clear

I don't use spray paint of any kind without out a basic 40/50 dollar mask with replaceable filters