We had some railing sub'd out to a shop that we have used before. They showed up and the splices had oxidation unlike anything I've seen. This is A53 grade B, welded with E71T1. The base metal is shinny but the weld areas are rusty. Any idea why they look this way?
could it be because they used an elbow and not a bender?
Sorry, couldn't resist. My uneducated guess is more crome or nickel in the pipe, but I am curious to know too!
A53 grade B is plain carbon steel. Neither chrome nor nickel in it, just carbon and manganese. So, it won't look as shiny as it is now for too long. In a couple of weeks it'll start showing a rusty surface, very light at the beginning and then more and more dark as time passes. So, you'll have to paint, or use some other mean, to protect your pipe.
If I were you, I wouldn't bother too much. Just clean the rusty welds with a power wire brush and go ahead.
Giovanni S. Crisi
Sao Paulo - Brazil
hogan,
We do a lot of pipe rails in our shop. Can't tell you "WHY", just that it almost always will. The parent metal of the elbows and pipe don't seem to start rusting, even though they were sanded too, as soon as the weld area. Must just be the differences in physical properties after welding.
Have a Great Day, Brent
The chemistry of the weld is never going to be exactly the same as for the base metal and the microstructure will be different as well. Because the A53 pipe offers so much more surface area, the weld is the the sacrificial (less noble) metal when the corrosion is initiated. As Giovanni notes, the A53 will be just as rusty in a few days.
Best regards - Al
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