Clear Powder Coat Over Raw Steel

[Gattonero]

Nice job Emanuel, that FB looks very good!
What lugs are you using on the frame in the 2nd pic?

[emanuel]

Gattonero,
LShen 108 if I remember right, should check my notes.
Grazie, that was the point of the raw finish, to show off the work.
But showing off the work created even more work, there's too much time into getting all the sandpaper marks the same length, direction and intensity.
Besides, colour is fun.

[Clean39T]

Hi folks, I'm necromancing this thread in the hopes that someone can give me a quick opinion on whether this "rust under clear coat" situation is easily remedied by having the frameset blasted in order to be repainted? I believe the bike in question is around 5 years old and you can see that some of the rust is just light spidering, but some is pretty rough. Also, if it's rusted on the outside, is that a good indication the inside looks the same and I should stay away?

Dan Williams

[Andrew R Stewart]

Dan- Most frame rust is what we might call surface or superficial rust and has virtually no impact on strength or long term durability. But some rust can be bad. If the rust has eaten into the frame it can seriously weaken the tubing. Where is the line? Well there is no actual line defining the two conditions, just a continuous range of effect. This is why so many of the questions here are best answered by hands on viewing and not written word or posted photos (although more data is always good).

Surface rust is easily removed with mild blasting or even hand sanding and is a must for good initial prep for painting. Any good painter will take care of this prep step as part of the job.

Inside rust is obviously harder to ascertain but the bottom of the seat tube and the BB end of the chain stays are common areas of internal rust and usually can be seen or felt with fingers. The top tube is likely the next location for rust but much harder to discover. I have used a metal pick to prod and poke at questionable spots. When the pick pushes through the tube wall you have a lot of structural loss due to rust. But before this dramatic point one really doesn't know.

Do know that steel is a wonderful material and gives all kinds of warnings before complete failure, for those who look for the signs. For those who don't look there is the claim "JRA" Andy.

[Clean39T]

Andy, thank you for the detailed reply.

[Mark Kelly]

An easy way to check for tube integrity is with an ultrasonic thickness gauge. Rust has a different acoustic impedance from steel so a good "echo echo" gauge will gve you just the thickness of the intact steel.

I use an old Nova 800 I bought on Ebay for a song. If you were in Oz I could lend it to you.

[halekai]

I have been doing a gun blue process to all of my frames since 2008 or so. I described it in another thread a while back. Essentially I use Van's gun blue, buff it out with steel wool and then take it to my local powder coater. Or as in my personal bikes, I oil them with Marvel Mystery Oil. I need to oil things a few times a year but so far no problems. Ive done about 35 frames, as many forks and stems.

You can see some of my work on my flickr...

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