1989Pre

I am wondering about my top tube lug. There seems to be a substance that will not wipe off. I can get my thumbnail in between the lug and the tube in this area.
The lugs are steel and thermal-bonded to aluminum tubes. What am I looking at, here?

Polaris OBark

A little bit of aluminum oxide. Same thing happens with an aluminum seatpost in a steel frame. It can get stuck. In this case, it also gets stuck. Keep the frame dry. It should be fine.

streetsurfer

I’d Try a soft (tooth) brush and some car polish. It may just be dried wax in the braze joint, where a brush and spritz of water may be all thats needed. The paint looks nice so it is hard for me to imagine it would be corrosion. Try a brush or microfiber towel, and a light polish/wax…not a hard cutting compound…you should know soon enough

Andrew R Stewart 

While I agree with trying to clean off the stuff I disagree with the opinion of nice paint. Note the thin coating at many of the corners, the pump peg is especially poorly done. Any of these thin spots could allow water and/or air to reach the underlying metals. Andy

streetsurfer

I simply meant nice enough to have sealed that joint well enough it may not be corrosion from open exposure.

either way a little cleaning and wax shouldnt hurt it, and may deter progression if it is exposed or growing from beneath.

not a great paint job, I agree. Maybe clean it out and seal with clearcoat or yellow paint if you can make a match.

Canaboo

Aluminum brazed to steel?

unterhausen

Looks like swaged construction to me. The white stuff could possibly be something they put in there to reduce corrosion

1989Pre

Not brazed.., thermal bonded.

Is it possible that moisture infiltrated from the cable housing entry at lug?

1989Pre

I should hope that the edges of the lugs do have a thin coating of paint, rather than a thick layer that obscures the details.
i think the chance of moisture (either as gas or solid), entering through the cable route hole, is far greater than it entering directly through "thin" paint.

Doug Fattic 

Yellow is a weird and difficult color to paint. It runs away from sharp edges no matter how many coats are applied. It is possible that the right amount of paint was applied in this case with the result that the yellow (at least the color I don't know about the paint) did what it almost always does and didn't stick to the sharp edge of these lugs. This used to drive me crazy when Imron was my only chosen brand.

Eventually I found that House of Kolor made a yellow primer. These base coats underneath the yellow color coats prevented me from having to lay the yellow on super thick. What was even more irritating - before I started using H of K primers - was that the yellow would collect in the shoreline making not only a color contrast with the lug edge but look like poor brazing because the shorelines were't clean.

unterhausen

Doug, have you ever had the same problems with white paint? I have seen this with yellow bikes, especially powder coated ones. White powdercoat does the same thing.
OP's bike looks like it might be powder coated. In the case of powder coating, I think it's not really thin, there just isn't pigment at the sharp edges.

base2 

That joint looks to be a Raleigh Technium. Great riding bikes so far as I am to understand. The lug construction however, used an epoxy that was applied between a hot lug & a cold aluminum tube and the 2 were then swaged together in an interference fit. In theory there should be nothing wrong with this arrangement.

But as all bonded things have the potential to become dis-bonded, if water intruded, the aluminum would be the sacrificial anode.

I'm not sure what I'd do in this case. I don't like any of the scenarios.

Is there a way available to test the white residue to establish what it actually is? Wax would be the best possible result. Aluminum-oxide would mean retiring the bike.

EDIT: Is this relevant? https://www.cpsc.gov/Recalls/1996/CP...e-Frame-Recall

1989Pre

Incidentally, the paint is Imron and was applied in 2000 by The Color Factory of Waretown, N.J. It has proven very durable.

Andrew R Stewart 

And i agree. But the question was about the tube joint edges and the pump peg was imaged, so my comments are about them.

I have had two of my own frames painted by The Color Factory and have seen two others done by them too (although many years ago). One was really nice. The others were middling at best. But given their cost not bad.

I am curious as to what the white stuff really is. Andy

unterhausen

When Andy said the paint was thin, he was talking about how you can see metal or primer through the topcoat at the edges. A painter would want to avoid that if at all possible.

Andrew R Stewart 

"I cleaned it with a Q-tip and filled the area with super glue." 1989Pre

As in you found a reason to need coating with the glue? Or just being cautious? Andy

1989Pre

As I have re-itterated, I could get a fingernail in between the lug and the tubing at that point. I sealed that area.

1989Pre

Look at the edges of the lugs. The paint is perfectly done. If you are talking about the pump peg, do you think 22 years of wear could have had an effect at that point?

So, in other words, neither of you know what is taking place at that site I mentioned in my original post. I cleaned the area and filled it with super glue. It is a small amount of galvanic corrosion caused by moisture entering through the cable-routing hole in the lug. I'll take Polaris O Bark's advice.

Andrew R Stewart 

Without our having the bike in front of us we don't really have the ability to better discern what's happening. But we have offered possibilities based on our experiences.

When I look at the image I see the thinning of the pigment along the lower lug's top edge behind the headtube too. Like I said this is not what I call a nice paint job, not terrible but not a good one either. I see no wear of the paint on the peg, no mars or rough areas from miles of a pump being pressed against it and vibrated by road shocks. What type of frame pump are you using?

I think what you did is about right. Resealing the "gaps" in the paint. I am just trying to better understand the "corrosion" you have dealt with and also trying to educate others, in addition to you. Andy

unterhausen

My opinion stands, the paint is very thin at every edge I can see. And it looks thick everywhere else. It's serviceable, but not that great.
I have no idea about the corrosion, if there is any.

Kontact

Galvanic corrosion is common in the bike industry because the bike industry has ignored it. But the Technium joints were developed by Boeing, which is aware of the problem. I have never heard of a Technium aluminum-steel joint failing. Aluminum and steel aren't as bad a mismatch as aluminum and carbon. And that white stuff doesn't look like the powdery aluminum oxide galvanic corrosion produces.

I wouldn't worry about it. Even if there is corrosion, this is not the type of joint that is going to spectacularly fail. There will likely be some looseness or creaking first.