haighter

Hi all. I've been researching the following for quite some time to no avail. Perhaps someone on the forum can lend advice from personal experience.

Basically, I have a 1987 Cannondale road bike that was originally a dark gray. I had to get a new fork and rather than try and match it to the frame, I decided to repaint the bike.

Now, before I go any further, I am aware that I shouldn't do this. I should go get it powder coated so it'll be durable, long-lasting, and professional. Well, I don't have the cash to do that (unless you know someone in San Francisco that'll do it for $50 or less...), so I figured this a great time to not only learn how to paint a bike, but how to take it apart and put it back together.

The Cannondale is aluminum, which I hear requires some special prep work to ensure a proper adhesion with paint. I've already stripped and sanded the frame to bare metal. My next step (according to other posts on the board and online tutorials) is to lay down a few coats of primer, do some wet sanding, and then lay down color and clear (with obligatory wet sanding in-between).

However, I fear that some of the tutorials I'm reading are in regards to steel bikes, because I've seen some (very basic) articles that say if you don't prepare aluminum correctly, the paint will start peeling off in a matter of weeks. So, my question is this: now that I have the bike stripped down to metal (stripped using chemical paint stripper and 80 grit sand paper), what next? Do I start with the primer or is there another step before I start applying it? I appreciate any and all help. Thanks everyone!

lusterwand

You need a primer specific to aluminum. In an industrial application Ive used Vinyl Wash primer on Aluminum and galvanized steel.
Its kind of a transparent yellow color when applied, maybe you saw it when you stripped the frame.

LarDasse74

In your opinion, how durable is a home paint-job on aluminum, done with primer as you suggested, compared to factory paint? Compared with a rattlecan paint job on aluminum.

I am also considering painting my alu bike, so I would like to hear your experience.

I have painted a couple of steel frames - strip all the paint off with nasty chemicals then do several light coats with Home Hardware rust paint - and I have had decent results - no massive chipping, no peeling. I have seen other rattlecan jobs where all the paint starts falling off after a month.

lusterwand

Hi LarDasse, of course in terms of durability and adhesion a factory 'baked" finish is best.
IMO the best rattle can job, (air-dry) in terms of adhesion and durability would be an automotive base -coat and compatible clear-coat, (two separate applications). and if your not making a drastic color change, dark to light, then roughing up the frames original finish with 600 or 800 grit and smoothing out spot repairs,( a shot of primer on the bare spots), is probably a better surface prep than removing that original baked paint.
I know people spend alot of time and effort stripping frames but its really not necessary unless the frame has got corrosion or parts fit, paint thickness issues.
When you take a car in for a respray they don't strip off the old paint first .
If your aluminum is unpainted then use a primer, if not ,after you rough up the old paint you can just apply base color of choice and clear-coat as described above.
Hope this helps

haighter

Interesting.

When I went to the paint shop I asked the cat working there specifically if they had any primers that would properly adhere to aluminum. He pointed me to some "Painters Touch" brand (I think) that said it was safe for all metals, but made no specific mention of aluminum. I bought it anyways, but have yet to use it. I read somewhere (can't find the link now, will track it down) that you need to apply a special coat to prep aluminum. THEN you can lay down the coats of primer, color, and clear as you would on a steel.

The reason I'm getting confused is that there seems to be conflicting reports on this process. Some say just strip it, sand it, prime it, color it, clear it as you would any other bike. Others say to get a special primer (which BTW, the yellowish base as mentioned above was NOT on my C-dale). And still some say get a special product to prep the aluminum.

Don't wanna beat a dead horse here, but is anyone else confounded by all this?

DannoXYZ 

It really comes down the quality and longevity you want from your paint-job. Different people have different standards and implicit in their suggestions is that their recommendation will give you the paint-job that THEY want; not necessarily what YOU want.

For $50, you can do a very high-quality job... depending upon how you amortize your expenses. Rattle-cans are the highest-price, lowest-quality paint you can get on volume/area-covered to price ratio. It does have the benefit of low buy-in cost, but for the quality you get, I don't think it's worth it.

Automotive paints such as the PPG OmniAU line offers much better quality for roughly the same price. About $30-40 will get you a quart of this with activator & reducers and be good enough for about 15-20 bikes. It will give you a final-finish somewhere in between a GM product and BMW/Mercedes.

Aside from the actual paints used, the process is perhaps even more important. Aluminium requires different levels of treatment depending upon the corrosion-resistance you want as well as paint-adhesion. The best technique is a multi-stage aqueous conversion-process that leaves a corrosion-resistant surface ready to accept paint. This is prohibitively costly except for mass-production lines with thousands of items.

Next best thing is to use a zinc chromate primer after you've done your final sanding. You'll want to use a finer final-grit as well, go down to about 400 wet to give a smoother finish. Then apply the zinc chromate primer. This is a chemical process that etches into the aluminium. This primer is a very thin layer, typically in yellow or green. Only after you've done this etching primer, would you then apply the traditional thick sanding primer. Wet-sand that with 400-600 grit to give a perfect surface for paint.

Then apply your automotive finish according to instructions and follow up with clear-coat. You don't need pro-quality paint-booth and equipment. You can get re-fillable bottles that can be pressurized with a floor-pump from Harbour Freight. Basically a rechargeable rattle-can that you can fill with just the right kinds of paint you want.

haighter

Nice, thanks a lot. Exactly what I'm looking for. I feel this'll take a while to get done, but I'll post pictures for everyone once it's done.

Joshua A.C. New

Hey, Danno, thanks for the actual breakdown.

Haighter, post pics!

Lennysody

I currently painted an old Schwinn World rattle can style and it seems to be holding up just fine (given that I wasn't throwing it around ect.).
I just sanded the original paint down with sandpaper- then primered it with a gray- then a layer of white- then white circular stickers- then gloss black- then peeled back the stickers for a "black with white" polka dot effect. Then I tossed on a heavy amount of clear-coats... it was a jolly time and it's pretty radical- So I'd say that rattle can isn't your worst alternative given the price and what you're using the bike for

noglider 

Damn, DannoXYZ, you're a wealth of information!

Lennysody, post pictures!

GreenPurgatory

I am about to do this rattle can style, also on an aluminum Cannondale. I am almost done stripping all the paint. I will rough the metal up a tiny bit, apply rattle can primer (let it sit for 24 hours, wet sand, respray if necessary), apply color and wet sand after 24 hours (repeat for 5-6 coats), and then give it the clear (2-3 coats). Wash, wax, buff and done! Atleast, that is the plan. I may go for the flat black, and stop after the color phase, unless I find some matte clear.