Framebuilders - Frame Corrosion Question

Hi, I purchased a nice, new frame in January. It's polished steel, supposedly with a clear coat over it. It looks great.

Except that little brown splotches, maybe a quarter inch to an inch in size, have begun appearing on random surfaces of the frame over the past few weeks. Most of the discoloration is down at the bottom bracket area. Other splotches (some of which seem to have little tentacles that radiate out from a larger center) are on a rear seat stay and on the front fork. So far I've seen about a half a dozen of these splotches, and the worst one is on the rear seat stay.

Most of the splotches are smooth to the touch, however a few of the splotches have texture on them, as if they've come through the clear coat, assuming it's there.

I've got several hundred miles on the bike, and I sweat a lot. The splotches, except maybe around the bottom bracket, don't seem to be in places where I'd drip sweat.

What happened? Bad or non/existent clear coat?

And what remedy, short of suing the person who sold me the bike, might I have?

- Might I be able to re-polish by hand these splotchy areas (I have no experience with that)?

- Is there a way to stop the spread of these splotches? Maybe a new clear coat, or just somehow strip off whatever clear coat might be on the frame, and then paint it?

As you probably know, clear coated frames are prone to this, and some companies seem to have greater or lessor success, more variability than others. There does not seem to be one foolproof product that one can just use with confidence. Part of this may related to different degrees of corrosion resistance in metals, and permeability in clear coats. Some of the tubing I store in my shop stays rust free indefinitely, and some of it looks like solid rust as the first breeze from out of doors comes through the shop.

I suppose you can pursue the usual remedies. Paint is the best bet. Paint itself may or not be so wonderful, but epoxy primer is good stuff, and the paint does a pretty good job protecting that from the uv.

my understanding is that this is very common. In fact, I have heard that this often happens under powdercoat, but we don't see it because most powdercoat is opaque.

This just reminded me I have never done anything about the FAQ, going to make a link to this thread in there

MassiveD wrote: "As you probably know, clear coated frames are prone to this,"

If I'd known, I wouldn't have purchased the bike! The "polished steel" was a selling point. Why buy it if it's going to end up covered in rust?

The idea of painting my lovely, polished steel frame, for which I paid a lot extra over the regularly painted version, seems unfair, but then, life isn't always fair. I think the the seller owes me new paint job or another bike that's already painted.

Icyclist- Your builder made you happy. They did what you asked for. Now with new knowlege you want some other quality. Seems to me like you bought too soon. Andy.

it's really too bad, but I blame the builder too. It's not too hard to find discussions of this on the internet, and the people who follow through on it usually report failure. I'd really be interested to hear about the Speedvagens that were made with clearcoat, although they weren't polished

I'm at odds with this ethic we are talking about. Builder is in the know (or so we hope). Customer wants what he sees on line, thinks is cool. Who is right/wrong here? Is this clear over raw steel a safety issue? Will it distruct catastriphicly? I don't think so. Will it have a limited life span? Will it need future "maintainance" to survive? Yes. Like other choices that a rider makes about his equipment some choose short term gain, some the long term.

The big loss as I see it is the builder's rep if his name gets out. Andy.

We don't have any statement from the OP that he requested the clearcoat. If we don't know if it was requested by him or the builder sold him on it, we don't know whose character to assassinate.
To the OP, take a look at a product called ProtectaClear. The company claims it will protect metal even in a marine environment. I have no idea if it really works but would love to find out. If you try it, let us know.

The big loss as I see it is the builder's rep if his name gets out. Andy.
the OP is riding the builder's bike around with visible rust under the clear -- it's a walking bad advertisement. The builder's best interest is to get it fixed and chalk it up as an expensive lesson. This is one of many reasons that builders shouldn't give them away, some frames are going to require expensive rework.

I am curious if the OP was the motivation for this finish or if the builder presented it as an option that the OP decided he liked.

I would only clear over stainless, and even then I'm not sure about it. There is someone that posts over on the MTBR forums that does this and reports no problems, I didn't think he was selling frames though.

Brompton has a clear also, and my friend has had one for a couple of years, so far so good.

I think custom builders shouldn`t build stuff they know to be crap, for a variety of reasons. Of course another possibility is that there is a painter somewhere in the background also.

Did a search on Bromptons and people report problems with the clear coat also. Sound like the same problem you are having.

from what I can tell, a lot of times there is real reluctance for the painter/powdercoater to do the clear.

We don't have any statement from the OP that he requested the clearcoat. If we don't know if it was requested by him or the builder sold him on it, we don't know whose character to assassinate.
To the OP, take a look at a product called ProtectaClear. The company claims it will protect metal even in a marine environment. I have no idea if it really works but would love to find out. If you try it, let us know.

As a professional working in keeping fatigue lifed parts alive under coatings for expected service periods of 35 years, I would like to say: balls.

Clearcoats contain no anticorrosive pigments, have a very short diffusion path to substrate and piss-awful surface adhesion energies to metals. It's hard enough keeping reactive metals intact under leaching, semisoluble anticorrosive pigment loaded three-layer paint systems, let alone under none of the above.


the OP is riding the builder's bike around with visible rust under the clear -- it's a walking bad advertisement. The builder's best interest is to get it fixed and chalk it up as an expensive lesson. This is one of many reasons that builders shouldn't give them away, some frames are going to require expensive rework.

I am curious if the OP was the motivation for this finish or if the builder presented it as an option that the OP decided he liked.

I would only clear over stainless, and even then I'm not sure about it. There is someone that posts over on the MTBR forums that does this and reports no problems, I didn't think he was selling frames though.

As the only reason stainless steels remain stainless is ready access to atmospheric oxygen, I'd be inclined not to clearcoat them. It tends to defeat that behaviour :(


from what I can tell, a lot of times there is real reluctance for the painter/powdercoater to do the clear.

You do surprise me ;-)

If you like the look of polished steel finished, get a stainless steel (953, XCr, or KVA) frame and don't clear coat it. It'll look new for a lifetime.

http://i32.photobucket.com/albums/d7/k4drd/Bicycles/Waterford%20B07014/B07014TopHeadLugmed.jpg

As the only reason stainless steels remain stainless is ready access to atmospheric oxygen, I'd be inclined not to clearcoat them. It tends to defeat that behaviour :(
The only reason I mentioned this is that I know some stainless bicycles are clear coated. This always surprised me a little.

Clearcoats contain no anticorrosive pigments, have a very short diffusion path to substrate and piss-awful surface adhesion energies to metals. It's hard enough keeping reactive metals intact under leaching, semisoluble anticorrosive pigment loaded three-layer paint systems, let alone under none of the above.



As the only reason stainless steels remain stainless is ready access to atmospheric oxygen, I'd be inclined not to clearcoat them. It tends to defeat that behaviour :(


As is so frequently the case, you include more information than we can easily absorb so some clarification will be needed.

I understand that a coherent oxide layer is important for the function of "stainless" steel and that access to oxygen is important for the establishment of this layer, yet KVA recommend the use of Boeshield T9 on any frame constructed from their MS2 steel. I'm not sure why.

I understand that a coherent oxide layer is important for the function of "stainless" steel and that access to oxygen is important for the establishment of this layer, yet KVA recommend the use of Boeshield T9 on any frame constructed from their MS2 steel. I'm not sure why.

Perhaps I'm looking in the wrong place, but the KVA website section on MS2 Bicycle Tubing Care & Maintenance (http://www.kvastainless.com/care-maintenance.html) doesn't mention this.

Perhaps I'm looking in the wrong place, but the KVA website section on MS2 Bicycle Tubing Care & Maintenance (http://www.kvastainless.com/care-maintenance.html) doesn't mention this.

It's in their FAQ (http://www.kvastainless.com/bicycles-frequently-asked-questions.html)s: "A complete frame made with MS2™ tubing can be media blasted, brushed or mirror finished, and/or left raw, without clear coat. We suggest a liquid or paste car wax or you can use WD-40 to clean and follow with a specialty metal protectant coating such as Boeshield T-9® to help protect the finish.

OK; thanks.

It seems unecessary to me. I use Boeshield T-9 on the interior surfaces of my aluminum airframe, and it leaves a waxy coating on the surface that I'm not sure I'd like on my stainless bicycle frame.

http://boeshield.com/: "The [Boeshield T-9] formulation, based on a unique combination of solvents and waxes, is designed to penetrate metal pores and dissolve minor corrosion, then leave a resilient waxy coating that lasts for many months." and "Dries to a clean Paraffin Wax film so it will not pick up dirt."

OK; thanks.

It seems unecessary to me. I use Boeshield T-9 on the interior surfaces of my aluminum airframe, and it leaves a waxy coating on the surface that I'm not sure I'd like on my stainless bicycle frame.

I]

OT..... does this mean you are building a plane now also?

OT..... does this mean you are building a plane now also?

Yep; a two place Zenith CH601XL Zodiac. The airframe is aluminum alloy.

http://i32.photobucket.com/albums/d7/k4drd/N415SC/ZodiacXLinFlight.jpg

This direction of thread that SS needing a layer of oxide has me thinking. How soon does this layer establish itself? If it does this in minutes of time after cleaning and/or brazing (and flux removal) then by the time that any inhibitor is applied it might be a moot point. Andy.

According to several sources on the interwebz, the chromium oxide passivation layer, which is only a few molecules thick, reforms over a few hours.

"After the bath and a rinsing phase, the passive layer will begin to form. It may take a couple of hours (and as much as 24 hours) for the passive layer to completely regenerate. After this 24-hour rest time, testing the passivity of the stainless steel is imperative and can be performed simply with a passivation tester meter. Proper testing of finished parts will not only satisfy quality control engineers and end users, but will also serve as validation of the entire passivation bath procedure."

http://www.productionmachining.com/articles/determine-passivation-of-stainless

To the OP;
If the frame is already polished and you like that look (who doesn't) consider having it electroless nickel plated. EN is a catalytic deposition so no current is used, meaning no hydrogen embrittlement and very even deposition.
A medium phosphorous NE can be matte or bright and is an excellent corrosion inhibitor.

If the frame is already polished and you like that look (who doesn't) consider having it electroless nickel plated. EN is a catalytic deposition so no current is used, meaning no hydrogen embrittlement and very even deposition.

That's interesting. I googled "electroless nickel plating" and THIS (http://www.caswellplating.com/electroplating-anodizing/nickel-plating-kits/electroless-nickel-plating-kits.html) popped up. Do you think a DIY kit like the "Jumbo" (600 square inches) would work on a polished bare 4130 bicycle frame? At $349 it would be a pricey experiment.

I did a quick calculation, and it looks like my 61cm (24") frame has an exterior surface of about 530 square inches.

Sorry for my slow replies, been away, holidays, all that jazz, so I'll try to go around the new stuff ASAP...

Why do KVA recommend Boeshield? Essentially, and in the kindest way possible to the fine gentlemen and women there, because they don't know what they're talking about. The buzz around KVA is that they found a cost-effective way of making high strength stainless steel tubing for bike frames. Their patents are all based around clever tubing manufacturing routes, not an intimate understanding of discrete metallurgy. And I salute them for their clever use of design. But stainless steels much prefer being wet to being oily, if you catch my drift. Anything that stops oxygen getting at a high chromium steel stops the very mechanism by which it survives. I can understand why they suggest it - because it prevents waterborne reducing agents, like chloride ions getting at the surface in the first place and doing terrible, terrible damage. But a far better way of stopping it is to WASH THE DAMNED STUFF OFF. If waxes really stopped salty water getting at steel, then you'd only need to underseal a car once.

Second, you can drive a horse and cart through the different degree of stainlessness of 'stainless' steels. Aerospace makes a point of not using the word at all if it can be helped and refers instead (usually) to high chromium martensitic, dual-phase or precipitation hardening steels as 'corrosion-resisting' and conventional 'stainless', high chromium, austenitic steels as corrosion-resistant. That's because, for example, Greek Ascoloy or Carpenter 455 has ****ty corrosion resistance compared to, oh 21-6-9 or 318LN. So the passivity and the degree of passivation of a given corrosion resisting or resistant steel can vary by as much as two orders of magnitude, and is well rated by the empirical PREN number. Most ASTM, MIL and equivalent passivation procedures take minutes and the product is most passive immediately after completion. Exposure to corrodants in the air is demonstrably accumulative, not subtractive.

Third, the surface 'film' isn't just plain chromium oxide, but that's a digression for later if any of you are particularly interested :-)

Fourth, autocatalytic metallic deposition reactions that are galvanic in nature may still have free hydoxonium* ions kicking about, so don't think that EN is blameless. It can achieve some quite remarkable hardnesses, too, which is interesting. Until you realise it has the ductile elongation of a carrot, and once cracked, it's excellent barrier properties start becoming a galvanic corrosion accelerator...



*There's no such thing as a naked hydrogen ion. In real life it binds up with a water molecule to form H3O+, the hydroxonium ion.

Third, the surface 'film' isn't just plain chromium oxide, but that's a digression for later if any of you are particularly interested :-)



Yes, please.

And another question regarding the combination of corrosion resistant steel and brazing alloys. I built my wife a rack out of 304L tubing using Cycle Design's "Fillet Pro" silver alloy. The areas of steel which were heated seem to have much less corrosion resistance than the other areas, so I'm thinking some form of passivation is needed. Per your previous advice, I was going to use citric acid (which I've got) or orthophosphoric (which I can get easily).

My question is: the fillets are also showing surface corrosion, is there any treatment which will prevent this re-forming? It's easy enough to clean up with citric acid and scrubbing, but I'd like to slow the rate at which it re-forms.

An aside you may find interesting: I used to be a brewer, we had an old copper brewhouse we'd brought in from Belgium: 100 Hl capacity so quite large physically. We cleaned the outside of the kettle weekly with a mixture of wort and sulphuric acid while it was hot: this quickly "set" to a glaze which kept its shine for about a week if the wort was all malt. If the wort had sucrose added (as some of the commercial beers did) it was much less effective.

Yes, please.

And another question regarding the combination of corrosion resistant steel and brazing alloys. I built my wife a rack out of 304L tubing using Cycle Design's "Fillet Pro" silver alloy. The areas of steel which were heated seem to have much less corrosion resistance than the other areas, so I'm thinking some form of passivation is needed. Per your previous advice, I was going to use citric acid (which I've got) or orthophosphoric (which I can get easily).

My question is: the fillets are also showing surface corrosion, is there any treatment which will prevent this re-forming? It's easy enough to clean up with citric acid and scrubbing, but I'd like to slow the rate at which it re-forms.

An aside you may find interesting: I used to be a brewer, we had an old copper brewhouse we'd brought in from Belgium: 100 Hl capacity so quite large physically. We cleaned the outside of the kettle weekly with a mixture of wort and sulphuric acid while it was hot: this quickly "set" to a glaze which kept its shine for about a week if the wort was all malt. If the wort had sucrose added (as some of the commercial beers did) it was much less effective.


FIRST! All the following temperatures are in celcius, not farenheit!


What you've experienced is weld sensitisation in unstabilised stainless steels. 304 is a nominal 18-10 steel, but that 18% chromium is locally depleted at grain boundaries in regions of the alloy that are allowed to sit too long in the temperature range 600-800 degrees, which in a fillet brazing operation you are likely to experience. 304 steel contains approximately 0.06% carbon, which doesn't sound much, but allowed to combine completely with chromium to form carbides, which it does at that temperature range, will drag the grain boundary chromium content to sometimes lower than 10%. Chromium atoms are about the same size as iron ones, so they diffuse very slowly at all temperatures in the solid, but carbon, being tiny has a massive diffusion rate, measuring in the millimetres a minute near the solidus and microns a minute even at low hot working temperatures. Chromium forms a carbide about two orders of magnitude more stable than iron, so preferentially, any free carbon will combine with all the chromium it can get it's little carbon hands on.

Because chromium diffuses so slowly, it can't get to the grain boundaries to 'even out' the decrease in free chromium in any realistic time. Your grain boundaries lose their free chromium, which is what gives you corrosion resistance, and hey presto, intergranular corrosion begins.

The only solution for a weldment is to cheat, heat the whole lot to over 1100 degrees and then quench into water. You've brazed though, so you can't really do that :(

If you can get hold of 304L or 321/347 stainless tube for the next project, that won't suffer the same issues. the latter has carbon below the threshold for easy carbide formation, the other two have it all tied up by either titanium or niobium, whose own carbides are both three time more stable than chromium carbide.


As for the sulphuric wash and wort, that's understandable. Sulphuric acid is used in a laboratory setting to clean glassware because it's both a powerful acid and a powerful oxidising agent. You'd have been removing handling contamination and organics from the surface and generating a varnish on the freshly cleaned surface. However, strong acids cleave disaccharide bonds, and the sucrose in your wort would have been using up some of your sulphuric acid....

Thanks for that. I thought the tube I had was 304L but I'll have to check.

Any suggestions on reducing the rate of corrosion on the fillet material?

That's the strange bit. I wouldn't have expected to find corrosion on the fillet, with it being a high nickel, high silver material and therefore cathodic to the tubing. Hmmmm

I've used Nickel-Silver (i.e. RBCuZn-D, no silver content) on 304 stainless and the fillet doesn't tarnish at all. I did a sample joint years ago and I left it outside for a long time. The stainless doesn't seem to be affected either...

Since there is a metalurgical expert around (thanks Falanx btw, fantastic info all around). KVA says silver brazing or TIG welding (with heat treatment) is fine, but that higher-temp brazing with Ni-Silver is not okay. Sorta goes against intuition since it still is lower temp than welding so I'm wondering why...

Silver brazing tends to be performed at tempratures below both sensitizing to proper stainless steels, like the AISI 3xx series, and deleterious ot the heat-treatment of high strength transformable corrosion-resisting steels like the alloys used by KVA and Carpenter/Reynolds (they are heat treated in different ways, but both have a final treatment temperature quite close to each other). Nickel-silver alloys melt at much higher temperatures, well into that range and often above it.

Welding, on the other hand doesn't leave such a large heat-affected zone as repeated fillet-building heating passes when brazing. It's waaaay above the danger zone and therefore the whole weldment must pass through that temperature range, but it tends not to sit in that range long enough for much sensitisation in 3xx type steels unless the section is massive. KVA (And Carpenter/Reynolds, for that matter) know that welding undoes the quench and temper/ quench and precipitation hardening stages, and so recommend heat-treatment to restore the strength after, but the effect on corrosion resistance even without re-cycling the whole frame is lower. And not only because it's initial corrosion resistance is poor compared to 3xx steels.

OK, thanks, I've cleaned up the fillet and stainless corrosion with a citric scrub and we'll see what recurs. We live on the coast and it's a rack so it gets crap splashed on it from the roads, so there might be something causing this (no snow here so no road de-icing with salt).

On heat treating KVA - my first design idea called for welding small tube sections together to make faux lugs and using these to join the large tubes by brazing..

I asked KVA about post weld heat treating the faux lugs and they said not necessary but a temper cycle would benefit the final result. I've gone away from this idea so it's a moot point.

Silver brazing tends to be performed at tempratures below both sensitizing to proper stainless steels, like the AISI 3xx series, and deleterious ot the heat-treatment of high strength transformable corrosion-resisting steels like the alloys used by KVA and Carpenter/Reynolds (they are heat treated in different ways, but both have a final treatment temperature quite close to each other). Nickel-silver alloys melt at much higher temperatures, well into that range and often above it.

Welding, on the other hand doesn't leave such a large heat-affected zone as repeated fillet-building heating passes when brazing. It's waaaay above the danger zone and therefore the whole weldment must pass through that temperature range, but it tends not to sit in that range long enough for much sensitisation in 3xx type steels unless the section is massive. KVA (And Carpenter/Reynolds, for that matter) know that welding undoes the quench and temper/ quench and precipitation hardening stages, and so recommend heat-treatment to restore the strength after, but the effect on corrosion resistance even without re-cycling the whole frame is lower. And not only because it's initial corrosion resistance is poor compared to 3xx steels.

Thanks. So if I understand correcly, there is loss of strength and corrosion resistance from high-temp brazing. For the former I guess the thicker butted end alleviates the issue (like brass brazing on regular steel), and for the latter well I guess testing would tell whether it's a serious issue for the desired application. Just curious because it's an inexpensive way to join the material (kinda moot point since the high-strenght stainless bicycle tubes are quite pricey) and the fillet doesn't tarnish.

Yes, simply, for high strength, corrosion resisting steels, the usual brass brazing temperatures are a no-no, for reasons that are dependant on the specific alloy family.

A nice thick butt certainly reduces the stress overhead, by both putting more material in the way and ensuring the finite heat input has more metal to get through before it makes its way to the sensitive thinner tubing.

Rather than get all deep into galvanics and cathodic-anodic behaviour, a fat fillet would be better than a thin one, for corrosion resistance, all other things being equal.

Icyclist- Your builder made you happy. They did what you asked for. Now with new knowlege you want some other quality. Seems to me like you bought too soon. Andy.

I'm long in replying. However, I think it's more along the lines of I made the person who sold me the bike happy. It was the seller who advertised a clear coated frame.

With my new knowledge, I feel that I bought something I did, in fact, not bargain for. Currently, the seller has offered me a new frame, while asking me to wait a while as he searches for a fix for my current frame (i.e., refinishing the bike and clear coating it in such a way that it won't corrode).

Customer wants what he sees on line, thinks is cool....Will it have a limited life span? Will it need future "maintainance" to survive? Yes. Like other choices that a rider makes about his equipment some choose short term gain, some the long term.

The big loss as I see it is the builder's rep if his name gets out. Andy.

Choosing a bike touting the quality of a clear-coated, polished steel frame should not be considered a short-term gain. The typical consumer - me, for example - is not going to go online and google "clear-coated polished steel bicycle frame problems issues concerns." The selling point that the steel frame is clear coated is in fact a claim that the bike's polished state is protected.

Icyclist- I don't deny your claim of being unimformed. In my earlier posts i assumed that you had been the first owner, not an after the fact buyer. But this does open the discussion to whether a seller has to educate the buyer. In a realestate transaction the boundries are pretty well established by previous lawsuits. In privet bicycle transactions, not so much. Andy.