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Old 04-13-13, 11:33 PM   #1
acoustic
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Painting issue: New (DIY) paint flaking off

Hi everyone, hope this section is the best place to post this.

I had my old road bike laying around (it's a cheap bike) and I decided to make a city cruiser kinda thing out of it for my girlfriend. And as the title says, I'm having problems with my paint flaking off. I'm new to painting and tried to do as much reading as I could through what I did find on google before I started.

Looks like this might be a problem of the surface not being prepared properly for painting and since I want to learn from this mistake I'd appreciate some feedback.

Here are the order of steps I took:

(Step 1 - Took 2-3 days)
1. Strip the paint down to the metal using detailed sander and sand paper, paint stripper in some places.

2. Wipe clean the frame with some rags.

3. Wipe the frame with thinner to remove any grease, oil.

4. Apply primer until the frame is covered fully (see the photo for the type of primer: new link bottom of the post)

(Step 2 - Which was actually a few weeks after I applied primer, due to rain-I don't have access to a closed garage and don't have the work space in my apartment)
5. Sand the primer with 400 grit sandpaper (dry), apply primer to areas which were sanded too much.

(Step 3 - 3 days after sanding and re-applying primer)
6. Sand the remaining primer to make a smooth surface overall (400 grit, dry).

7. Wipe clean the frame with rags.

8. Apply the color in light coats, waiting 20 mins between each coat until the whole frame is covered (I had some runs due to getting too close- it was windy! here is the paint I used: new link bottom of the post )

Today, after waiting 8 days for the paint to dry, I decided to put on the wheels and the fork to take the bike somewhere and realized the paint has started to flake off in places, I didn't accidentally hit it with something solid as I was being really careful however I know they didn't happen until today either because I was inspecting the frame every day. So maybe the flaking is happening in places which I touch. Obviously the paint around the bolts which hold the wheels came off too.

The magnet test revealed that the body is aluminum and the forks steel (actually the spots I touched on the forks with the magnet flaked off too).

You can see from the photos that the flaking is down to the primer, not all the way to the metal.

What do you think I did wrong? Wrong type of paint? Perhaps waited too much between primer and paint? Didn't clean it enough after sanding the primer?

Any feedback is welcome.

Cheers

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UPDATE: Sorry for the login issue guys, try this: PHOTOS
**************************************

Last edited by acoustic; 04-14-13 at 06:26 PM. Reason: updated photo links
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Old 04-14-13, 12:02 AM   #2
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Your photos are asking for a login, so they're no help. There's probably a setting you need to change.
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Old 04-14-13, 02:54 AM   #3
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[edited to correct all the errors made trying to post through a tablet] If the paint is flaking off the primer, but primer is solid, you probably didn't clean the primer. IF (big if) the primer is correct for paint. I always use a product made for final clean, sold in paint shops. Very volatile stuff. Dont know if mineral spirits is right for that, but I use that cleaner and have never had flaking problems.

Last edited by Camilo; 04-15-13 at 11:00 AM.
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Old 04-14-13, 05:12 AM   #4
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None of your links work for me. Lots of possibilities as to what went wrong.

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Old 04-14-13, 05:51 AM   #5
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That sounds like paint/primer incompatibility. I always use paint and primer made by the same manufacturer and explicitly stated to work together. If you didn't do that here you might just as well strip the paint off and start over correctly.
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Old 04-14-13, 06:27 AM   #6
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Nothing wrong with the primer. Those paints are intended to be used as a system and are industrial grade.

But thats the only link I can open. What did you use as a color top coat?

Last edited by Burton; 04-14-13 at 06:31 AM.
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Old 04-14-13, 08:51 AM   #7
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Why not just get it powder coated? It's relatively cheap (~$75 here for a single color) and more durable than paint, especially rattle-can.
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Old 04-14-13, 02:09 PM   #8
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Aluminum needs to be primed with self etching primer (Wallmart auto) then once you apply paint set the can in hot water for 20 seconds, much better spray, sand lightly 800 or 1000 grit between, , finally after last coat of paint ( 3 or 4 layers extremely thin) sand very very light then apply a automotive clear coat. That process will work, stick with Krylon paints or go with more expensive auto spary paints.
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Old 04-14-13, 06:42 PM   #9
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Updated the links for the images guys, don't know what went wrong in there.

@Burton - The paint I used is an 'all purpose gloss enamel' and the primer is an etch primer which can be used on aluminum and steel (at least that's what's written on the can)

@JohnDThompson - I wanted to work on it myself because I wanted to learn a bit, but you are right I think powder coating would be more reliable and more durable.

@Pistard - Putting the spray can in hot water for better spray sounds like a hell of a tip, thank you (as even though I shaked it like a maniac the whole time, I had some issues). So you CAN actually sand the colour coats? What do you do, wait for the colour coat to dry (2-3 days), then sand it, then apply more coats?
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Old 04-14-13, 09:26 PM   #10
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OK - so I Googled dulux spraypak paint and some of the reviews also claimed flaking as a problem.

Suggest you go with any polyurethane spray paint as a top coat. You'll probably have to start from scratch because that Dulux will make a poor base and I doubt you can remove it without damaging the primer.
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Old 04-14-13, 09:47 PM   #11
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Add clear coat at the end.
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Old 04-15-13, 11:06 PM   #12
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That paint is general purpose stuff, and not particularly durable anyway. I've used similar, and it ends up dinged and scratched no matter how carefully you handle the bike.

I strongly recommend powder-coat. I had a bike done by Brooker Enterprises: http://bikeportland.org/2009/02/04/b...ke-video-14335
and it came out beautiful.
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Old 05-01-13, 06:38 AM   #13
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I don't know about the particular paint that OP refers to, but here is something I'll throw in anyway. If you live in a first-world country, the only spray paints you can buy nowadays ,,,,,,, all suck. Every last one of them is crap.

Environmental and health laws in most first-world essentially banned lead from paints sold through retain channels (to ordinary people like you and me) and the paints don't work nearly as well without them.

Even if they are not made there, a LOT of manufactured goods are sent to places like China for painting, because the old formulas of paint are still widely obtainable there.
This is why it was so---$&*#ing---difficult to sand the old paint OFF a part, but yet the brand-new-paint you tried to put on........ won't stay on.

http://www.nytimes.com/2007/09/11/bu...pagewanted=all

Adding lead greatly boosts the adhesiveness and durability of many kinds of paints:
http://en.wikipedia.org/wiki/Lead_paint
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