Let`s talk about rust... // structural issues of rust

Hello everyone,

I built quite a few frames now. Most of them are kept raw. This is because I get really excited on finishing the build and want to get the bike out on the trails. Also, I consider all those bikes as prototypes on which I want to improve the Geometry in the near future anyways…

From time to time I build a Frame that actually rides good! → I ride it a lot and dont want to miss it during the season. Combine that with the humid climate we have in Germany → Rust. Lot`s of rust…

My question is: When do you guys consider a frame being rusted to the point of structural issues.
There`s not a whole lot of information on the effects of rust on thin-walled high-stressed structues. Could be that I just dont find it.

I have one particular Frame that I like a lot, so I would like to have it powdercoated or treated some way. I hit it with a Nylon-wire-wheel on some spots. the rust is deep as you an see on the pictures attached.

What is your opinion? Is the frame rusted beyond the point of structural integrity?
I find it hard to evalute. I feel like this particular frame is corrupted beyond the point of being safe after removing the rust (especially in the highly stressed area on DT-HT-junction.

I`d really appreciate your opinion and hints towards literature / information on the topic.

Thank you!


I have some experience with a rusty bike. I built this in 2011, rode for a couple years then there were a few years where it sat with a cracked down tube. Welded the crack and added a gusset in 2017 and got it rolling. It sat for most of 2020 when I was riding a full suspension, but I put it back together in 2021. To me it’s whatever you’re comfortable with. The choice likely depends on your riding style and a bunch of other factors. Anyway, hopefully these pictures give you an idea of what the surface finish on mine looks like. It still rides fine, no cracks or issues but should probably be retired soon. I considered getting it powder coated but to me it’s not worth putting more money into an old 26” wheel bike. I won’t be leaving a frame raw again unless it’s really a one season test mule type of thing.


From an engineering perspective, I think it’s impossible to say whether it’s safe or not. I think the failure would start as a crack, so you have some buffer.

For the future, there is a good thread on treating raw frames: Clear coat, bluing and other 'see-through' processes

Your current frames would be great test bed to try out those procceses


I also ride raw frames, I don’t have the same climate to contend with as you, but after a winter of commuting(or touring near the ocean), they take on a nice patina. That being said my next frame is getting a clear powder coat, as I have pretty much got the geo where I want it.

I agree with what @Mikesbikester says, its whatever your comfort level is. I would add to that the sort of terrain the bike gets ridden on. If you are jumping 30’ doubles on a heavily rusted frame, you are running a higher risk than cruising flowy trails. I’ve seen and cracked frames (bmx), often from a hard impact (casing a jump). Worst case scenario is ripping a headtube off a bike while at high speeds. I know it has happened and will happen again but blowing a headtube off a bike is rare with steel (in my experience). Steel usually gives some warning signs.

@Amarenaintermezzo I’d keep riding that bike, but I wouldn’t be trying to push the limits with it.


Thanks for the reply. Yeah, i figured it would be hard to judge.

Ive ordered some patina stuff (like cold-blueing) to try some. Im heavilly inspired by John Watsons Retrotec-mod-MTB


@maxwellkeegan @Mikesbikester I`ve decided to retire the frame and get my shit together building a new one (which i will get Powdercoated) It was nice reading your take on it.

Might post some pictures of my trys with cold-blueing