Explain this!

[Barry Wolk]

While working on my limousine I noticed that the roof assembly is made of 4 pieces. The pieces are butt-welded using a bronze welding rod. The steel pieces are isolated from each other by the bronze filler.

Before grinding, you can see a faint orange line.

http://i244.photobucket.com/albums/gg18/barry2952/Limo/IMG_3928.jpg

After grinding there's an accumulation of metal filings evenly spaced along the weld line as though the iron filings are being held magnetically. How can that be?

http://i244.photobucket.com/albums/gg18/barry2952/Limo/IMG_3926.jpg

[Shelly Harris]

Could "electrolysis" have something to do with it?

[Barry Wolk]

Could "electrolysis" have something to do with it?

You may have something. I immediately thought of the Bearded Lady, but then the thought passed as I thought about the slight current that happens when dissimilar metals make contact. I wonder if I have anything sensitive enough to check for current. Would an oscilloscope tell me anything? First I'd have to learn how to use it.

[Chuck Lutz]

I wouldn't be surprised if it wasn't electomagnetic in some way. Opposing pieces of sheet metal with neg and pos charges (perhaps from grinding or static elec) grouping on a non-magnetic material (brazed area). The brass filler used our shop processes is called Everdur (Silicone Bronze).