jospl

Dear Bike Forum Members,

I have a Scott Speedster with bubble appearing under the paint towards the front. I purchased this bike probably around 5 years ago and would love to get many more miles on it.

I use my pain cave quite a bit, and cycle on the trainer 3-5 times per week, so sweat is common.

I've taken pictures and posted within my bikeforums album numbered 14005614

I'm not quite sure what the next steps should be. I'm wondering:
1. How can I fix this?
2. What might happen if I don't fix it?

Best regards,
John

carlos danger

get a steel brush to put in your cordless drill. maybe 50-60mm diameter. put it in the drill. turn on the drill, put to frame tubing while spinning, remove rust until unrusted metal is the only thing left. prime, sand, paint, fine-sand, clear coat. done.

questions?

Loose Chain

Prevention is the best cure, clean and wax your bicycle regularly.

You will have to remove the paint, remove the rust, use a rust killer to get any hidden deep in the metal pores and then re-paint as appropriate.

Spraymax 2000K clear is a aerosol can two part clear that is wonderful over many types of paint substrates including rattle can and it dries hard as nails and is impervious to solvents even including MEK etc.

jospl

sounds like a solid plan... i'll do that. plus Loose Chain's recommendation to wax the bike regularly.

jimc101

You will have no bike left in this case, the Scott Speedster is Aluminium, a steel brush will eat that frame nice and easy.

For the OP, how old is the bike and have you tried using the warranty? https://www.scott-sports.com/us/en/support/warranty, (you say its 5 years) exact age and service history will be key here, ad being cosmetic will probably not accepted

As it's Alu, and from how you describe you using it, you will kill anything that can corrode, guess you not using anything to protect the frame from sweat? https://www.amazon.com/Blackburn-Swe.../dp/B00B1UQFQ6 (lots of different brands similar to this are available)

WizardOfBoz

Geez, it's like a thong for a bike...

CliffordK

@jospl's photos:

https://www.bikeforums.net/g/user/496311
https://www.bikeforums.net/g/album/14005614

CliffordK

I think the corrosion is probably a mix of the internal cable routing + sweat.

I don't quite know what I'd do.

It looks like the "bubble" is HUGE. And, you could have some deep corrosion under it. But, the bike should have started with pretty strong aluminum.

As @carlos danger suggested, you can try cleaning and painting. Of course, it would be a lot more work to remove the fork, all the cables, and try to get to the inside to clean and refinish. And, perhaps seal those cables somehow. Caulking?

jospl

Purchased the bike on Dec 26th in 2013 so the 5-year manufactures warranty (thanks for the link) is a no-go. I don't think REI would accept a return this late in the game either but I guess it doesn't hurt to ask.

Here's what I bought in terms of tooling/painting:

• Wire brushes to strip (probably will return one):
  • DEWALT DW4902 1-Inch by 1/4-Inch High Performance Carbon Knot Wire End Brush, 0.020-Inch Wire
  • Century Drill & Tool 76211 Coarse Crimped Cup Wire Brush, 1-3/4"
• Scuff pad to clean: Lot 5 Grey 3M Scuff Pad Scotch Brite 3M Brand
• Paint pen to touch up: Testors, 1, Black
• Clear coat to finish: Spraymax 3680061 2K Clear

I think I'll give it a go this weekend or next. Probably don't want to wait to long.

Thanks for the help.

- John

WizardOfBoz

Do NOT use a ferrous (steel) brush to remove paint. You cannot avoid some minute particles of iron embedding in the aluminum, and after this your frame is toast - it will steadily decay.

Looking at that paint bubble, it almost looks like someone used a steel brush on that section of frame a while back.

You can inspect by getting rid of the paint. Use the stripper. You can then use a plastic scraper and a brass or stainless brush. There are also paint removal pads but if you use these on a drill or on a grinder arbor wear a rubber suit (or at least a Tyvek one) - you'll be shooting gobs of paint and paint thinner everywhere.

02Giant 

A couple of years ago I repainted a friends S-works Tarmac that had spent most of it's life locked in a trainer. The aluminum at the top & head tubes had extensive corrosion both exposed and under bubbling paint. After chemical stripping the aluminum sections of the frame, I abrasive blasted the pitted aluminum, thoroughly cleaned, epoxy primed, skimmed with filler, primed then painted the entire bike.
I should have some pics on the home computer. I'll post a couple of which, when I return home this weekend.

jospl

02Giant--sounds like a job well done. Did you do anything for inside the tubing of the frame? I'll epoxy the entryway for the cable run shut after the repair, but going inside the tube is a bit more commitment than I have at the moment, not to mention not knowing where to start. I'm hoping that won't be the nail in the coffin later on!

Update to my purchases for the job:

• Blue Bear Paint & Urethane Stripping Gel to remove the paint (is that stuff for real? soy beans?)
• Brass brushes (I'll return those steel ones, good call @WizardOfBoz)
• bike thong
• epoxy for priming

Thanks guys.

- John

jospl

Stripped the paint! The thinner is amazing for this task... I'm not sure about using it for paint which wasn't already coming off due to corrosion / nearby chips, but for this purpose I don't think there is a better thinner to use. The stuff is non-toxic (only a slight smell) and sticks like gel. After an hour of sitting there I scrapped the paint off with an aeropress coffee tool. There was not a small amount of corrosion under (no surprise there). I used brass first but moved to the stainless steel brush (bought a combo kit of 10 small bruses) to scrape the thickened white aluminum oxide powder off the metal and the scuff pads were great at finishing touches / polishing / cleaning / etc. After that I sponged the surface down with a small amount of water to remove the dust and such and wiped clean with a towel..

Next step is to mix and spread a thin coat of epoxy over the metal. Once that dries I'll do another coat and epoxy in the grommet used for the wire routing, then I'll sand, paint, and coat with the clear coat, which actually seems a bit overkill to me at $24 a bottle since I'll only be using it to touch up the bike. These shiny parts will offer some good character for the bike. I'll upload some photos...

jospl

Soy-based paint stripping goo at work


Peeled off the corroded area easily


White power puffed up from under the stripped paint pieces (aluminum oxide)







Clear coat for finishing, some paint stripped on the right, epoxy fluids, and an enamel touch-up pen.