Lewis_Moon

I'm building a "rat racer" (old steel frame, parts bin chimera gruppo, all used and abused) and I'd like the frame to be a requisite primer grey. Are any of the rattlecan primers better than the others? Can you apply them over lightly sanded original paint and have it stick?
OK, I might put a clear coat over it, but you didn't hear it from me.

bobotech

From what I remember years ago, primer isn't really supposed to be used as a weather protecting coating, back when I painted a couple of cars, it was rather porous. I just would make sure and clear coat it when you were done painting it if it were me.

Primer should stick well to lightly sanded original paint. Primer tends to not stick as well to aftermarket paint jobs.

No advice on the primer paints themselves, sorry.

2manybikes

I gave a friend an old steel frame, he primed it, and left it in primer. He built in into a nice bike. He never rode it in the rain, it was stored in the garage. The top tube is very rusted right through the primer.

It will rust if there is exposed steel under the primer. I have done a couple of frames myself, and coated the primer with finish coat. They're fine a decade later. They do get ridden in the rain, but always completely dried off before being put away. They look the same.

ironwood

Cover the primer with either an enamel o ra laquer before clearcoating. I don't think clearcoat will protect the metal from the elements.

fietsbob

once all apart, remove all grease everywhere,
so paint won't flake off remaining grease
do a frame saver treatment inside too.

decades ago I did black undercoat, transparent color coat,
made a color patina of black finish.

Retro Grouch 

I've painted a lot of bikes with spray cans. Whenever I've taken the time to strip the frame down to bare metal I've gotten good results. When I've tried to cheap out by scuff sanding and spraying over the original finish, the result has chipped easily.

Booger1

Use epoxy primer,it won't rust underneath......

Clem von Jones

Spray Max makes a really good 2 part epoxy primer but it's light yellow. You could top it with silver or black appliance epoxy. $25 + $8

The 2 part epoxy primer will have really strong adhesion to bare metal and the top coat will bond with the primer coat if you do them a couple hours apart whereas the grey lacquer or enamel primers from the auto parts or hardware store will likely scratch or chip off eventually.

Use a chemical paint stripper to take off the old paint first but only do it outside, use eye protection, thick rubber gloves, and stay upwind of the fumes.

nymtber

find a flat grey to match the primer, then find a flat clear coat to add protection.

I paited up an old Schwinn mountain bike (steel) with 2 different colors primer (brown then grey), full can of each, then a full can of gloss black followed by a full can of clear.

Its a bit orange peel looking, but its got a good coat of paint on it.

DCB0

Spraying over the old paint is almost guaranteed to look bad after a few months. YMMV.

kevbo

What works for me:

Strip to bare steel. Degrease with MEK or acetone.

Now the wierd thing: wipe down with WD-40, and wipe off as much as I can with dry rag or paper towel.

Spray 3-4 light coats rustolium protective enamel, paying attention to what it says on can for time between coats. Note this is the slow drying fish oil stuff. Rustolium has several quicker drying paints that stick as poorly as other brands IME.

Let dry overnight, then place inside car parked in sun for a couple days. This will bake the enamal into a hard tough finish... Not imron, but pretty good for a rattle can job.

I only do the wd40 thing with this particular paint. It was a discovery by a friend. He was trying to prevent the paint from sticking to a hard to mask area, and found wiping it down with WD40 to have exactly opposite the expected effect...the paint sticks really well.

I think you can get this in light gray, but it will be glossier than primer.

SlimRider

If you want an urban-stealth-Ninja type look that's chip-resistant, you might want to check this out:

www.bikeforums.net/showthread.php/795210-anyone-ever-have-a-bike-painted

I like the idea of stripping the frame down to bare metal. Cleaning it. Then spraying the surface with rust-converting-primer. Afterwards, you spray a final coat of Krylon truckbed enamel, that's somewhat textured.

Sounds pretty cool, eh!

- Slim

PS.

Myosmith, the Lover of Old Chrome Moly, also seems to have the idea that you can make numerous undectable touch-ups. That sounds fairly appealing to me, as well.

rawhite1969

I've done a couple of bikes with a primer designed to cover rust. I disassemble, clean, prime, then paint. did a cruiser in flat black, no clear coat and it has held up fine. Current bike same thing, but a metalic blue with a clear coat, but haven't assembled it yet. I did see a "primer grey" color at the HD the other day....

bud16415

Sanding primer will offer zero protection over bare metal. Its purpose is much like body filler to spray on sand off and slowly block out slight imperfections it is porous and will let moisture right thru. Better to go to an auto parts store and select a car paint made in the shade of gray and flat finish if that’s what you want. I have had great luck with auto paint in spray cans on bikes with the original finish scuffed up to give the surface a tooth for the new paint. I got the semi flat finish I wanted with this GMC blue by dusting the coats on.

2manybikes

Nice....