Rust

[Easy-X]

So we've probably all seen some video where some old rusty shit-heap gets stripped down, sand blasted and repainted and if it's several decades old rust is unsurprising. Something less than 10 years old though...

Fair enough if the powder coating or paint layer is damaged but I was watching someone doing a Harley swing arm (yes, yes, harley shite and all that) and the paint was coming off in sheets with surface rust underneath! How do such things happen?! Is the case that the manufacturers have such thin layers of paint that it's barely any protection at all?

The swing arm on my XSR for example. It had a little bit of rust bubbling up in areas where water might collect. So what? Surely the paint layer would fuck that off. (BTW I sanded the affected areas, dabbed on some rust converter and repainted. It's been fine ever since.) Anyhoo, how did it start to rust in the first place?
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[doggone]

Poor quality paint won't help there has been a lot of reformulating to be more 'eco friendly' though they ought to be getting a handle on what does and doesn't work by now.
Even the slightest damage like almost invisible stone chip allows moisture to attack the metal then progress in dampness below the paint if it isn't perfectly adhering.

[trevor saxe-coburg-gotha]

[doggone]

My XSR is one of the early ones (2016) and though it rarely goes out in salt I don't avoid rain. It only gets a wash before MOT day once a year then spray of ACF or similar. Not a spot of rust on it.

[Polarbear]

It's 90% down to application in my view. I've seen ships painted in drydock and the paint has lasted the 5 years till the next dock and in other cases it's been coming off in months. Humidity, temperature and a load of other things are critical.

You would expect all painting in a factory to be critically controlled and I expect it is but if they have issues for whatever reason i doubt if they are going to reblast and put through a load of components if they look ok.
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Triumph Trophy Launch Edition

[Easy-X]

[stinkwheel]

I think a lot of parts have flash-rusted before they ever get painted in the first place.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kawasaki Jimbo]

Labour costs have pushed all but specialist steel manufacturing to the Far East, and cheap (badly made) steel corrodes from the inside. Even some Harley Davidsons are made there now.

[Fat Angry Scotsman]

[A100man]

[Bhud]

I've dealt with quite a few of them now, and I have a great appreciation for old Kwaks. They were painted in thick paint. Very high quality paint. I have more faith in them than in modern bikes. 40+ year old Kawasaki is usuallyt in better condition than 20-year old Kawasaki. They started using much thinner paint about 20 years ago. Thinner steel as well. However, the welds on the old bikes were sufficient but not as good. The welds were iffy to the point of having bits of wire stuck to the frames. Nevertheless, the steel was thicker, stronger, than was needed. And that's why they're still here today.