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Is this a paint issue, or a frame issue?

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Is this a paint issue, or a frame issue?

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Old 06-07-18, 08:18 AM
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Is this a paint issue, or a frame issue?

I already discussed this with @unterhausen on a ride last week, so I thought it best to share photos and ask opinions of other frame builders. Here's what I'm looking at:

It's a fillet brazed steel frame with copper colored powder coat. The powder coat is flaking away from the sharp edge at the top of the seat stay caps.



On the right side, a small flake came off; and I glued it back on with super glue:


I don't see any other cracks:



The seat stay tops are caps brazed into the tube tops, as you can see from this pre-paint photo:


The frame has some damage to the left front dropout and to the derailleur hanger (you can find those photos by looking around in that album on flickr if you want), but has not been crashed.

So my question is, simply, are we looking at a paint issue, or is there some deeper issue?

Thanks in advance!
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Old 06-07-18, 08:30 AM
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The obvious frame "issue" is the less then cleanest brazing and clean up around that seat stay attachment area and what might be some slight undercutting of the seat tube at the top tube's underside (third photo). neither of these likely contributed to the powder paint from flaking off. No surprise that the paint would flake at the corners/edges of the stay eye. Powder doesn't like edges, it can draw back/away from them. Since there's no primer under the powder it's adhesion to the metal is less then nicely done wet paint. Without an etching of the surface (and having that surface truly clean, again look at the third photo) the powder doesn't bite into the metal as well as it might. Since powder is chosen for cost savings and not finished image some degree of "paint performance" loss can be expected.

Very well done powder coating can look and last really well. But I've seen far more poor jobs then best ones. Andy
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Old 06-07-18, 09:33 AM
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Thanks for that reply! So, you don't think it's about to fail on me? That's my main concern.
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Old 06-07-18, 09:56 AM
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Looks like the frame has a poorly done powder coat. I could see left over flux under powder flaking after a while but you have an adhesion issue. Did the frame get any pre powder prep ? like blasting or a wet prep? Or was the frame just powdered after being built?
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Old 06-07-18, 10:14 AM
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Originally Posted by pwyg View Post
Looks like the frame has a poorly done powder coat. I could see left over flux under powder flaking after a while but you have an adhesion issue. Did the frame get any pre powder prep ? like blasting or a wet prep? Or was the frame just powdered after being built?
I don't know. The powder coat was done by a high volume shop that has a good reputation. They mostly do car wheels. I have no doubt they would tell me they thoroughly prep everything; whether it was actually done right in this case, I can't know (well, obviously it wasn't).
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Old 06-07-18, 02:40 PM
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I think the powder coater may have had a little trouble underneath the stays.

I don't understand that first picture at all though. The sharp edge has a discontinuity in it in the pic. Can you take another picture from closer to the downtube looking up at it?

It looks competently done and doesn't look like it's cracking. Could have had a little more filler on the bottom. That is one joint where I don't believe in filing, I just move the filler around with the torch until it looks good. Takes a little effort, but with the right amount of filler it just lays in as a nice fillet. Well, to be honest, my motto is "no file." I like the looks of surface tension at work.
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Old 06-09-18, 11:24 AM
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If there is any flux remaining on the metal, including any inside the seat stays, it can propagate through pin holes in the braze and/or the castings themselves and eat up the paint. Don't ask me how I know this...
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Old 06-12-18, 11:54 AM
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Originally Posted by unterhausen View Post
I think the powder coater may have had a little trouble underneath the stays.

I don't understand that first picture at all though. The sharp edge has a discontinuity in it in the pic. Can you take another picture from closer to the downtube looking up at it?

It looks competently done and doesn't look like it's cracking. Could have had a little more filler on the bottom. That is one joint where I don't believe in filing, I just move the filler around with the torch until it looks good. Takes a little effort, but with the right amount of filler it just lays in as a nice fillet. Well, to be honest, my motto is "no file." I like the looks of surface tension at work.
I'll try for another photo, but it may be a while before I can get to it. I'm on Long Island for the summer.

The discontinuity you see, in the edge, is a fairly large flake of powder coat peeling up. The powder coat has split somewhere in the crevice where you can't see, and along a crescent shaped crack on the outer surface. It's hanging by a narrow bridge at the bottom.
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Old 06-12-18, 12:54 PM
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Originally Posted by rhm View Post


The seat stay tops are caps brazed into the tube tops, as you can see from this pre-paint photo:
What transpired between photos 1 and 5? Time? Do you have some old photos of the powdercoated bike that might show the detail after powdercoating, but before riding?
'
Photo 5 seems to indicate a slender seatstay cap with a smooth transition into the ST/TT braze.

In Photo 1, the seatstay cap appears to be fat and bulbous at the top, with a jagged edge.

What I'd do is first to take calipers and measure the width of the top part of the seatstay cap on the right and left (best you can estimate).

I'd guess that the left side will measure 1 to 2mm wider than the right side, which could be due to a glob of extra powdercoat.

Next, I'd take a knife and see if I could trim off a chunk of that part sticking out, or at least probe it to determine if it is plastic, brass, or steel.

Does your bike have patent vent holes? If so, another option would be to flip the bike upside-down, and squirt some light oil into the vent hole (colored?). I think the seatstay caps are at least partly hollow. If any oil runs out, you could have problems. A negative result would neither confirm or disprove what happened, but would at least support the conclusion that it is OK.

My interpretation is that this could be an extra glob of powder from when it was originally powdercoated, and not a serious issue.

Anything but powder, or signs that it has changed over time would be more worrysome to me.
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Old 06-12-18, 04:10 PM
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his bike fell off the roof of a car. Pennsylvania potholes can be brutal
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Old 06-13-18, 07:54 AM
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Originally Posted by CliffordK View Post
What transpired between photos 1 and 5? Time? Do you have some old photos of the powdercoated bike that might show the detail after powdercoating, but before riding?...
Not really. Here's the best I can do:



Obviously my camera had trouble with the shiny surface and failed to focus well. I have a lot of photos, but most are from the drive side, and though there are a few that show this area, between poor focus and low resolution they don't tell us much.

Originally Posted by unterhausen View Post
his bike fell off the roof of a car. Pennsylvania potholes can be brutal
That's not quite true; the bike came loose and fell about 45 degrees, putting a nasty bend on the front left dropout. I consider that a separate issue-- that is, I don't see how the seat stay issue can be related to the dropout damage (but what do I know).
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Old 06-13-18, 09:56 AM
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Ok, so the paint/powder was good at one time.

If the seatstay is loose, I would think you should be able to feel or see it move, as well as seeing cracks penetrating all the way through. Perhaps put your thumb on the seatstay and seattube, and see if you can feel any movement when you try to move it (within reason).

Also, if the rear-end remains aligned, then that would support the assumption of no damage. from the partial fall.

Any more photos of that stay, pre-powder?

To me that left stay just looks chunkier than the right stay, post powder.

I think you may have had excess powder build-up on that left side that has partly flaked off for some reason.
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Old 06-13-18, 06:05 PM
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ok, sorry for the misinformation.

I don't think there is anything structural wrong with the bike. The powder has some issues from what I see.
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