sandblasting help
 

I plan on sandblasting my bike frame.

I have an aluminum trek 1420, and the frame is bonded so I do not want to use any chemical strippers. Nor do i want to hand sand the frame. I dont mind doing the small areas that i might not be able to reach with the blaster.
I will use acrylic beads as opposed to actual sand as it is less abrasive. And I found a place near by my house that rents out blasting booths for 1.50 a minute. Im thinking I will use gorilla tape to mask all the sensitive areas down.

Does this add up to you guys? Any thoughts? thx



oh the paintjob is ugly but i love the frame

Try not to blast your BB or where the headset goes in the head tube. Make sure you use a media that will not damage the aluminum.

How much would it cost to just pay them to do it with the appropriate media? May not be worth your time and they may actually get better results if you are not familiar with media blasting.

Yes, agreed. But I think blasting is not a good idea on an aluminium frame.

Personally, I would sand the surface lightly (you don't need to take off the original paint and get down to the bare metal -- usually, there is a thin clear top coat), apply the proper aluminium primer, then apply the top coats.

I hope you are prepared to work at this for several weeks (even if you sandblast -- and here I have to say, this is a bad, bad idea if you do it yourself). It's not so much the sanding with a fine-grit paper, but if you want a decent finish, you will need to apply five or six coats, of top finish, leaving it to cure for several days in between, then sanding off each one except the last to remove bits, runs, and fill flaws, and apply a key for the next coat.

Each coat has to be light, and there is a definite technique in using the spray to avoid runs.

And pick a colour slightly darker than what you want on the frame. Yellows are really bad for that, but so can be reds.

If you want to get the frame powder coated, blasting is part of the prep and is included in the price. I wouldn't worry about blasting aluminum. Nothing much bad can happen as long as you stop when the paint is gone.

Blasting an aluminum frame is fine, but it would be best to have someone that knows what they are doing and using the correct blast media do it. Which is why I suggested he look into that.

I thought the same about having it powder coated, but he says it is a bonded aluminum frame. Not sure how the bonding adhesive would hold up to the heat involved in powder coating. I would stick to painting for this reason.

It is hard to say what temperature was used to cure the epoxy resin, but it could have been around 150 deg C. Powder coating baking temperatures can be a little higher, say 200 deg C. Hard to say whether there is anything to worry about. One thing for sure is that a lot of powder coating is done on aluminum with a bead blast prep so it is safe to blast the frame. How to coat it afterwards is another matter. Maybe the powder coater could advise OP about his temperatures. If less than or equal to 150 C, I wouldn't worry.

We're talking about an amateur using equipment for the first time. It's all well and good to say it's fine if you know what you are doing.

A simple run over with a fine grade of sandpaper will provide the key for the primer and the top coats. The fact that the guy says he doesn't want to use sandpaper suggests to me the finish is going to be less than desirable because he simply won't have the patience to do the proper prep work.

I have used a sandblaster. It's not as simple as it looks.

"Media blasting" (e.g. crushed walnut shells or similar) is what Trek recommended back in the day. It should work fine to remove the original Imron finish; if it's been powder coated since leaving the factory that might be a different story.

interesting answers. thanks.

I have used sandblasters before, all my own art practice, but for cast iron, aluminum, ceramics, and glass. So I am familiar with the mechanics and feel of sandblasters. I chose the acrylic bead media because it seems easier to control and best suited for this project. I've never had to mask any structural object, nor used plastic bead media.

I dont mind taking the time to finish the tight spots myself, What I don't want is to spend hours taking off the base layer getting paint dust everywhere.

Im thinking im just going to mask the hell out of all threaded areas and holes. blast lightly, and finish by hand. Again I really want to avoid chemicals.

its the original paint and i plan on leaving it raw (for now at least)

I don't disagree that it is not wise for an amateur to do the blasting. All my advice is presuming professional services.

I went ahead and blasted the frame

Took it to a DIY place that charges per minute, It took me about 30 minutes to blast the frame and fork, and the tech only charged me 15:). I used their plastic media machine, which uses crushed acrylic/plastic. And was told I could even blast the threads and clean them up, as the media is softer than the metal. I took that with a grain of salt and kept my masking on. Aside from my initial apprehension, it was relatively easy. Never realized how many angles a bike really has. I Had a shop re press the headset cups so i could build it back up. Need it for a race on friday/saturday, then will polish the hell out of it.

http://bikeforums.net/attachment.php...hmentid=394784

I can post more pics if anyone is interested.

More pics when its reassembled :D

And leave it raw after blasted. That would look awesome. I love the look of blasted aluminum. I did various parts of my motorcycle years back to get rid of corroded clearcoat intending on polishing and ended up leaving it all with the blasted dull finish. Loved how it looked.

I want to sandblast mine to bare metal like this then powder coat it. There are some good shops in my area but I'm not sure if any are good with bike frames. All of them say they are but what else would they say. I guess if I did all the masking myself I would feel better About it. Any ideas on what a typical price for the entire process would be?

You are way overthinking this. First the masking and blasting is included in the powder coating price, so it is foolish to do it yourself. Powder coaters know what they are doing, and bike frames are no different than anything else they do. You can't mask the bike yourself anyway since they use special tape that withstands the heat of the oven used to melt to coating. Regular tape that you have access to won't do. $65-100 should do it, but some really big shops have a higher minimum than that. They would do several frames for you for the same price as one. See if you can find a small, specialty shop. The minimum will likely be lower. I had two aluminum rims done with brake track masking done for $25 each.

Good info Rob, thanks.