Galvanized Handrails

By jwright650 (*****)

Date 12-16-2005 19:40

Yes, the galvanizing can do that to the welds. Happens all the time to our galvanized steel.
John Wright

By Lawrence (*****)

Date 12-16-2005 19:42

Roj,

Off the top of my head I'm thinking you could burn off the galvinized weld joints and than power wire brush off what ever is left.

At this point you will have only the welds as fabricated. The coating process will not make production welds grow :)

Edit: JW Really? Galvanizing can cause metal to raize? Or does the coating just tend to gather more thickly in the less than perfect contour?

By jwright650 (*****)

Date 12-16-2005 19:47

Really, it does!
John Wright

edit: I was told the amount of silicon in the weld metal was a predictor to how much it would raise up. ????

By CHGuilford (****)

Date 12-16-2005 21:14

I second John's comments 200%.

It is thought to be high (relatively speaking) levels of silicon in the weld that causes the iron/zinc compound to become thicker than over the adjacent metal. This makes areas that were ground smooth look like they were not thoroughly ground; as though the welds were flattened but not smoothed.
Some customers have specified low-silicon filler metal in an attempt to avoid the condition. Sometimes it actually works.

If you look on the American Galvanizing Association's website, I think you will find more information on the subject.
You may also want to talk with a reputable galvanizer about it.

Chet Guilford

By UCSB

Date 12-16-2005 23:12

That's a new one on me-- after 20+ years of welding inspection-- several of those years as a third party vender inspection for Alaska State DOT and Public Facilities (almost everything that goes up north is galvanized) I've never seen this phenomena. I have had to follow material to the galvanizer and witness the procedure and the post cleanup.

So, this attracts more tin/zinc to the area that has more silicon then? They should be able to grind the galvanized welds smooth without hurting the galvanize then, eh?

Thanks guys, we learn something new all the time.

Roger

By TimGary (****)

Date 12-16-2005 23:48

I too would affirm John and Chet's position.
I don't know the physics as to why it happens, but it is to be expected.

Tim

By Lawrence (*****)

Date 12-17-2005 02:34

You guys are awsome.

Thats amazin

By swnorris (****)

Date 12-19-2005 12:45

Silicon is the most common reactive alloying element in steel. Most hot rolled structural steel products don't have a significant reactive silicon content, however some welding electrodes do. When filler metal silicon content exceeds around 0.04% this can cause the weld metal to react more vigorously with the zinc than the parent metal, resulting in thicker coating accumulation on the welds. The same thing happens to steels having a high silicon content.