Why Clear Coat Over Raw Steel is Bad Jan 15, 2013


Photo by Nao Tomii

“Ooooh. Wowwww. So pretty! Can’t we just put a clear coat on it?”

This is what came out of Lauren’s mouth when I showed her photos of her Icarus Porteur. What came next was a very simple conversation that many frame builders have with their clients on why this isn’t a good idea. We’ll use this photo from Tomii Cycles as an example, only because it’s the most recent, clean fillet photo I’ve seen on my Flickr feed.

I’ve heard just about every frame builder complain about the double edged sword that is fine fillet brazing. With social media becoming a powerful tool for builders, they expose a precious part of their process: bare fillets. If you’re a master at finishing, you take pride in your pinhole-free, smooth fillets. They’re evidence of a lot of precise work and while they look great raw, they need to be painted.

Why? Oxidation. Rust destroys steel and the only thing that keeps it from forming is a primer. If you simply clear-coated or clear powdered a frame, it would rust. Even in a matter of weeks it would be present. For the longevity of a steel frame’s lifespan, it needs to be properly primed and painted. Don’t forget to Frame Saver, either!

“But what about those fillets? You can’t cover them up!” Well, good fillets and good paint go hand in hand. You can cover bad fillets with good paint but they’ll look like shit. If your fillets aren’t smooth, or show the profile of mis-mitered tubes, paint will not cover that up. You don’t see the bad fillets being macro photographed now, do you?

A good builder doesn’t need to use filler and painters love them for it. It makes their job easier and the paintwork shows. Simply rub your finger over a fine fillet braze to feel the difference. Or watch the light reflect off the paint as it coats the shorelines. The best thing for an immaculately-finished fillet frame is a great coat of paint.

While Lauren was initially a bit bummed that her pretty, raw frame would be covered with paint, after explaining this, she understood. Especially after I showed her examples of exceptional paint covering exceptional fillets. So as a public service announcement for your builder, don’t even bother bringing this up! I’m sure they’d rather save their energy to discuss paint options with you.

  • Gregory Ralich

    “You don’t see the bad fillets being macro photographed now, do you?” They are… sometimes.

  • in case people argue “but ti is raw!”, that’s because ti’s version of oxidation actually makes the metal stronger through the microscopic structure that forms on the surface, whereas steel becomes more brittle with its rust. 

  • if I’m not mistaken, there are clear primers out there, you could feasibly clear prime then clear coat.

    • You have to sand a primer, even a clear primer.

      • Jimmy.

        If the internet says you can’t you usually can, POR15 will do it without a worry.

        It’ll stick to a bare frame and as it is moisture cured you should have less issues with rust forming under the clear. As with any paint, you have to do a good job with your prep.

  • Someone needs to create a clear primer! I can dream at least….

    • Einar Andersen

      I’m pretty sure i have heard of that somewhere

  • ElCapitaineDuderino

    What about plates? Chrome, nickel, zinc (probably kinda ugly), gold (at the fillets only?)…

  • Jonathan Buck

    Clear powder coat. $$$, but worth it. It is baked at a lower temp so it is ideal for frames.
    Not sure why you never see it in cycling. It is everywhere in the automotive/ moto world. 

    • To powder coat a frame, you have to sandblast it. This preps the steel, removes oils, etc but in the process, it removes the texture and color people want
      To see, making it pointless. People do clear powder steel, without blasting it but it always rusts underneath, like my Geekhouse touring bike did.

      • Kevin Sparrow

        you can dip the frame in chemicals to clean/removing all oils and then powder the frame. Its been done before. It’s all about the prep. ask any pro motorcycle powder coating facility. I am sure they do it all the time on tanks and pipes….

        • An they all eventually oxidize. At least that’s what the shops around here in Austin told me.

  • Kevin Sparrow

    clear powder bro…

    • You usually sandblast a frame before you powder coat a frame. But that’s not the texture or color people want. So many people don’t sandblast the powder and it never sticks to the frame, causing it to rust.

      • Kevin Sparrow

        it sticks better than you think… Ive got a test frame i practiced on and still no rust.

  • I don’t think it’s common but Rivendell have sold bikes with a clear powdercoat and I couldn’t imagine Grant Petersen allowing an unpragmatic frame be sold. 

    http://www.flickriver.com/photos/[email protected]/2480107305/

    • Yeah, as do BMX, MTB and a lot of fixed frames but they still rust and usually, at the welds / fillets. My Geekhouse rusted a lot and the clear powder job was pristine.

  • Frame Saver is a VERB. I love it!

  • Majaco

    Blasting fillets can also cause problems. Gotta hand sand those bad boys.

  • The issue with powder coat is without prepping the surface properly, any scratch that occurs is an open door for moisture and other contaminants to creep into the finish. Why jeopardize your investment?
    There are several varieties of primer, either self-etching (typically requiring PrepSolv or equivalent), epoxy or other 2k primers used as the first step to making a protective finish to a steel frame. It’s mechanical adhesion that’s required (hence blasting or scuffing a frame) for the primer to really bite into your substrate. The subsequent steps (sanding, sealing, top coat, clear coat) contribute to a protected and preserved frame. It’s all in the prep work, baby! You can’t work backwards.

  • Dupont Starblast at the right pressure is not hard on fillets at all if you know how to blast. Silver is can be hit or miss but is more often than not a problem. It depends on how well the builder brazed with the silver (and what kind- system48, filletpro, etc).

  • Dan

    What does Ezra over at Fast Boy Cycles use? I’ve seen a few of his raw frames and it seems like some sort of oil/wax finish. 

    • Yeah, you can do that but you have to reapply often and it’ll still rust. That’s the thing, most frames are documented before they’re out, being ridden. In a year, that bike will look a lot different.

  • We don’t all rock smoothed fillets some older companies keep them built up looking like an Aluminium TIG weld looks.

    Curtis Bikes here in the UK have done that since 1972 when BMX started to grow in the UK.
    This seems abit unique in todays bespoke frame building community but does show what a decent fillet joint can look like.

    Brian Curtis now teaches a new generation of builders at the Bicycle academy.


    • holy shit those fillets are gorgeous. well-laid unfinished fillets are a thing of beauty. the old jack taylors weren’t finished at the bottom bracket because it gets gunky down there anyway. said so by the man himself. also finishing bb fillets is a pain.

      •  Yeh I’m quite proud to own a Curtis frame but then again i suppose there is something nice about owning a frame thats been built in your own country for you by a guy in a small workshop.

        I think it looks quite nice and different,i find smoothing fillets can sometimes pose as a good way for poor brazes to be well hidden.

  • corrosion cant be that bad…. i mean you road your icarus’ fork raw without any problems, didn’t you?

    • If I were to continue to ride it like that, it would have eventually become a problem, yes. Which is why I’m getting it painted. Rust was already forming around the shorelines of the fillets. With some steel, it isn’t as much of a problem as with others. Modern steel has a lot more to lose than your typical 4130.

      Bottom line for me was, why pay good money for a custom frame, only to risk it becoming structurally compromised by rust?

  • James Valiensi

    You could make the frame from stainless steel then clear coat. KVA and Columbus make excellent SS tube sets, and use FilletPro low temp filler.

    • Matthew Joly

      I have a raw KVA SS fillet braze frame.  Primary motivation is to have a frame I can take on the train, etc. without worrying about paint scratching.  The fillets looked amazing at first.  Still do but are definitely starting to tarnish. 

      Fillets as in the picture above are like sunsets – beautiful but ephemeral.

  • James Valiensi

    Here is a SS frame with clear

  • I hope Sizemore sees this shit…
    Homie has never painted a bike and it drives me nuts!

    • Didn’t he have to rebuild one of his bikes because rust corroded the steel so heavily?

      • The mention of Sizemore piqued my memory to a beautiful gun-blued frame he made.  After a quick search, it turned out I was thinking of someone else, but have a read on this flickr set description.  It’s someone’s rust experience with stripping a steel VO frame and partially copper plating / gun bluing with a clearcoat over everything.

        I still remember hearing about someone’s raw/blued frame locked up in a marine environment in Seattle though.  I want to say rust took it over in a month’s time.

  • frankly i don’t give a flying deed about being pretty, for me it’s about the soul. but how come my BMW frame is clearcoat om bare metal, i ride the shit out of it, and i see no rust anywhere. i live in holland and this is the third bit of snow its seeing, and snow means salt. no cracks it the coat, got some scratches from crashing and parking. i think you guys should start riding before listening to whats being said on internet and ask some real riders, brands and builders whats important, good and working.
    when a clearcoat is cracking, its a bad one, and that will make a frame rust on concentrated places, which is bad. so ask yourself if you paintjobs are worth it. you can leave steeel bare, it rusts and nothing more will happen, rust and corrosion are a natural way of protection agains more wear. ofcourse if its standing still outside for a long time, or even some weeks it will rust more and more. but if its used, there is no problem. believe me i even rode a beachrace with a bare marinoni a long time ago.
    it also depends on the quality of steel you use.
    im getting a bit annoyed with people who just came into the bike business,(which is good) and telling everyone on internet untrue or half true things about bikes. or believe they are the saviours of biking and craft, while most of it is based on a vitral story and not on experience. you would’nt even know how to tune a bike. IMO.

    • Your BMW is ok because Joe makes sure the frames are sandblasted (or chemical dipped) before they’re coated. And they are tig welded, not brazed. A BMW, like most BMX bikes and MTBs are made with utilitarianism in mind. They’re not brazed, or lugged. There are no shorelines, just a bead at the joints.

      There’s a big difference between what I’m talking about and what you’re confused about. Remember, I had a Gangsta track years before you did. So don’t get annoyed with me, I tune my own bikes (and I ride road bikes, not just track bikes). This is based on me talking to frame builders over time. You should do the same before you come here with your smugness.


  • richniques

    I clear coated a raw steel frame and road it for months rust free in rain. It wasn’t till they started salting the roads in the winter when some rust spots appeared. 

  • Cole Larsen

    Rust makes rust. There are likely moisture and oils under the clear if that happens… I would think that maybe it can’t be done due to current technology and processing but if it could be cleared without these I’m sure it wouldn’t. Saying its not deteriorating at all under the paint is a bit of a Schrodinger cat type of situation is it not?

  • Good god man, there has got to be a way!

  • Zoli

    I’m planning to buy a On One frame made of Chromo steel and you have the option of choosing raw clearcoated or painted. I’m not sure whic one I will choose but I really like the unpainted look. As far as I know Chromo rusts on the surface just like aluminium but it doesn’t cause structural damage in the tubes. I was unable to find out if the frames are welded or brazed and if they rust at the joints but who in their right mind would build frames in the UK that can’t handle mud and moisture? Can anyone enlighten my about this?

    • Aluminum doesn’t rust, FWIW. Steel will rust inside and out if you don’t care for a clear coated frame. Frame saver everything and just watch the surface rust.

  • Ron Garvin

    John Watson will prob comment here saying Im wrong and that my frame will rust through in a week but Ive been riding a raw steel frame for over 2 years without any signs of rust or corrosion. Early on the bike got a through wipedown (with a silicone based oil) and has been through rain, sleet,snow and a few washes with no issues. Let lauren have a raw (or cleared raw) frame if she wants it. If its good chromo its not gonna rust fast at all anyway, but even if it did start it could easily be remedied temporarily until she could have it painted… Its all about how you maintain your stuff and if she has a gorgeous frame with awesome brazing, then let her show off that beautiful work! Not all frames are built up with that much craftsmanship, so if shes paying for it let her have what she wants. She will also enjoy keeping it clean, and protecting it more knowing that its what she wanted. And if a few days, weeks,months goes by and she wants the added protection of paint or would rather have a new color then she can have it painted. And youd be surprised at the filler and shitty craftsmanship I’ve found under beautiful paintwork…

    • Matthew Moore

      Any idea what oil you used exactly? I just built my first frame and I plan on keeping it raw for the first year of riding so I can keep an eye on it out of curiosity. I was suggested marine clearcoat, but I’m interested in this silicone oil.

  • Emanuel Ferretti

    We do some, it’s a lot of work.

    sanding is key, you have to make the frame shine, the sanding marks have to be the same direction intensity and size. it takes a long time. We use clear powdercoat, after a chemical bath. I do the last sanding operations with gloves on to avoid any chance of finger marks, and the painter gets it about 30mins max after I’ve finished.

    As I said, it’s a lot of work, but I think the results speak for themselves:
    http://www.flickr.com/photos/[email protected]/11479478715/in/set-72157637981137916



    http://www.flickr.com/photos/[email protected]/sets/72157638373528876/

    Great paint looks great as well.There’s no reason not to mix the two. My rohloff,dropbar,hydro disc touring frame will be done this way.

  • nunya

    hey what method of clear did they use on this?


  • Alabaster Jones

    Soo many opinions….
    And lil old me just over here sanding this steel beach cruiser dreaming of the results. ..

  • Jason Smith

    Not sure my other post made it. Anyway I have a tange prestige mountain bike factory clear coated 20 year ago (Epoxy). It has no rust even where the paint wore through 15+ years ago. Theres no plating on the frame its just good steel.

  • Will S

    If the electrolyte has been sealed off from the anode and cathode and the surface has been prep with a moisture killing solvent then a clear coat is fine.