Hi everyone, I have a black Diamondback mountain bike. On the tip of the headset, the black paint flakes off, and I think there is rust. I read from other threads that I can use naval jelly or WD40 to remove rust, but I'm afraid it can ruins the paint job. Tip, anyone?

Far too little info about the bike, which model, where is the corrosion, on the frame, or headset etc

Knowing which model from the DB range would help, to ID the frame material, but most useful would be a photo, from your description, could be just the cups of the headset are corroded, and nothing to do with the frame.

If the paint is flaking off, it's no longer adhering to the metal below and is thus already ruined. Acid treatments like Naval Jelly can remove rust, but the acid has to be able to get to the rust and the bare metal that's rusting, which generally means removal of loose, flaking paint. Remove the lifted paint, remove rust, then prime/repaint.

+1

If there is rust under the paint (paint bubbling or flaking) you need to remove the loose paint and the loose rust underneath. Then use a good rust remover like Naval Jelly, or any of quite a few on the market, to remove the remaining rust including rust hiding in the tiny pores of the metal where it hides from sandpaper or steel wool. Rinse very well with warm water with a bit of dish detergent, then rinse with clean water two or three times to make sure to get all of the rust remover off. Lightly sand the area with 400 grit sandpaper to smooth any edges and to take the shine off the paint right around the repair area. Wipe the area with acetone or prep solvent before priming. I like to prime with a rust converting primer (WalMart carries one from Rust Oleum in their automotive section) as a little extra insurance against rust coming back. Let the primer dry overnight then scuff with a fine scuff pad (sometimes called 000 or 0000 synthetic steel wool) then paint with a good quality gloss enamel. Let dry for several days then scuff lightly again and apply a second coat. Dry for a week or two then use a good automotive polish to bring back the luster to the repair and the area around it. Most polishes also wax, unlike buffing compounds. Don't be tempted to rush between coats or to get the area polished. The dry to touch and dry to service times on the paint are just for handling and assembly purposes. Enamel doesn't completely cure (harden) for days or weeks depending on conditions. This won't be as tough as a factory finish, but can hold up well for years.

I know this sounds like a lot of work to fix a small area, but if you just sand the spot and rattle can some paint on it, the result won't look as nice and the rust will likely return in short order.

Thanks guys for the tips. I will post some photos to show. Also, my bike has some rusts on the bolts from the brakes and seat post. I'm planning to buy and replace these bolts and seat post. The bolts I see on the bike store are stainless steel, and seat post is alloy material. Are these rust resistance?

Stainless hardware is extremely corrosion resistant. It also resists galvanic corrosion which can happen when two dissimilar metals are in close contact, such as with regular steel bolts in an aluminum frame. Aluminum alloy seat posts can corrode under the right conditions but don't rust like steel. If you use an aluminum seat post in a steel frame, be sure to use some form of grease or other appropriate anti-seize agent to prevent galvanic corrosion. Remove the seat post a couple times a year and reapply the grease. I've removed severely corroded and seized aluminum posts from steel frames and it's not an easy job.

I'm frustrated. I'm thinking of buying a new bike that is corrosion resistant. My seat post has some rust spots, and I think the cassesette, crank gears, and rear dérailleur are rusty.

Any steel will rust if it's left outside for long enough. You won't find a "rust resistant" bike. It's more about taking care of your bike when it gets wet.

Aluminum, Titanium and Carbon Fiber are pretty rust resistant.

Do they make cassettes, chains, derailleurs and chainrings out of any of those? And I'm pretty sure OP doesn't want to buy a Ti bike. haha (Aluminum DOES rust by the way, it just doesn't change color as much as iron.)

Technically it doesn't, as "rust" specifically refers to Iron Oxide.

Well, my bike looks brand new and has never gotten wet.

That much corrosion indicates the bike is being left outside exposed to rain, sun, salt air, etc. It may have also been ridden in wet conditions and not properly dried after. As corrado33 noted the solution is to store your bike inside and to dry it off after it gets wet.

It will be very difficult and expensive to find a bike made entirely of corrosion resistant materials like carbon fiber or titanium. A good quality bike with steel and aluminum components can be a reasonably priced option that will last for decades if cared for.

Your description above says it does not look brand new. Metals corrode because they are exposed to something that starts the process.

Which one is it?

The paint is peeling off the frame, exposing rust. And many components are decaying. But the bike looks brand new???

The frame looks like in good condition. I dunno, you tell me.



Anyway, how do you take care and prevent from getting rusts?

Looks like it's in pretty good shape. No major problems.

As for preventing rust, well, living in such a dry climate is a good start! Past that, keep paint in good condition so steel surfaces aren't exposed to water and oxygen. If you've got flaking paint, chip it off, remove any rust underneath, and touch up the paint. And don't leave the bike outdoors where it can be exposed to extra rain, dew/frost in "winter" mornings, fog, salt air, or whatever. Bikes are generally meant to be able to get wet, but staying wet isn't good for them.

Rust on small parts like the stem bolt you pictured is pretty easy to deal with. Just take the part off and soak it in something like Evapo-Rust overnight to remove the rust. Rinse, dry, then repaint it, or use wax or something else to make a barrier between the iron and water & oxygen.

your bike does not look to be in as bad a shape as your written description suggests....
it does however show a bit of "lack" of maintenance. Keeping the chain clean and lubed will help preserve it as well as improve the looks of it...most everything else has already been covered by what others have said.

You've got me there. I'm a chemist "rusting" to me is "oxidising because of the elements."

The bike in the pictures above looks in good shape. I agree about the lack of maintenance. Buy a new chain, keep it lubed. Eventually the rust on the cassette will come off if you use it enough and keep the chain lubed. If it really bothers you, take a (brass) wire brush to it.

What about the bolts and screws? These are pretty rusty. I always keep the chain lube. My bike haven't been ridden for a long time.

I have a hard time to take the stem bolt. It is pretty tight. I'm afraid I may strip it if I force it to unscrew.

Oh never mind, I got the stem bolt out. What kind of paint can I use to paint the stem bolt?

I wouldn't paint the bolt. If it's a bit of surface rust, I'd keep it as is. If it's bad, or if it's driving you crazy for whatever reason, your LBS might have a nicer one for a few bucks, or hit up a local industrial fastener place (or mcmaster-carr).

It doesn't me drive nut. I'm worried the rust will spreads to another metal and eats up paint or cause the paint to flake off. Beside, I need to paint the seat post and bolts to prevent future rust.

I noticed the bolts have some blue loctite on. Do I need to apply blue loctite before I screw onto the brakes. Can I use automative grease on the thread of stem bolt and seat post? Do I need specific grease for bicycle?