Ok, I have a question, quarry.

I want to know if anybody has seen any data, testing done on galvanized metal. Here is what I am looking at. I know some "welders" think and do the old "use a 6010 and burn it out" trick then run a 7018 over the 6010. Maybe they wire wheel the 6010 or maybe they just use the chipping hammer and a wire brush if we are lucky. I prefer the grind the galvanizing off of the weld, especially when the engineer and owner of the structure specifically mentions doing so. For two reasons, (A) Galvanized coating looks an awful lot like contamination to me and (B) I absolutely hate getting the skin seared off my legs and arms when these molten blobs drip onto me.

The data I am looking for, most likely not anything out there tested like this because the lab guy I deal with all the time said, "all of the tests we have done have been ground properly and galvanized removed".

So, in a non perfect world I am wondering if there is any test data where somebody said, "I wonder what the micro structure looks like? I wonder what the tensile tests and x-rays would reveal?". I am surely not the first guy to ponder this question and I am almost positive that somebody somewhere has done tests to prove that welding directly over galvanized steel is....bad mojo.

If I have a few thousand dollars laying around or my own personal lab I would like to run some tests. Three sets of test plates, all galvanized and beveled as per AWS D1.1. First test plate would be run properly, 7018, uphill, galvanized coating removed, backing strip. Second set, galvanized coating in place and run a 7018 uphill over the galvanized, backing strip. Third test plate, 6010 downhill(or 6011 as it seems some prefer, can you say Farm Code? Has our Farm Code been published yet???), remove the slag with a wire wheel, ideally or with a wire brush the fill the remaining with 7018 uphill. For the last two tests to be accurate the backing strips would also have to be galvanized to accurately portray real world situations.

I guess my question to the American Welding Society would be, do you have some free time to run some tests? I would like to see results of something like this so show "weldors" that they are in fact weakening the weld? Am I correct in presuming this? I see galvanizing as contamination, molten metal from two members with the filler rod and now add in molten zinc? Will the molten zinc boil off? It appears to me that when I have done it on one particular job several years ago that it mixes with the filler metal and base metal causing a silvery weld bead. Is there porosity in the weld? Underneath the very code worthy visual? Other than the fact that you can definitely see the silver from where it was obviously welded over galvanized? X-rays, tensile tests, images of the micro structure compared to a properly welded plate with galvanizing removed?

Maybe its not hypercritical as some would be lead to believe or in their infinite metallurgical experience(being a smart azz) they know better because "Daddy did it all the time on the farm".

Now, I guess I am looking for well educated replies, information to back up said replies not some "it'll be alright" type of dribble.

Thanks to all and if there is no data, AWS? Would you mind doing an article on this in the journal?

Shawn

A quick review of the literature Henry provided via his links provided some interesting contradictions.

One article seemed to say there was no "real" problems with welding galvanized materials and mentioned metal fume fever had no long lasting affects on the welder. Speaking with 40 plus years experience I would tend to disagree with both points. I agree that electroplated galvanized materials is thin enough that most of the zinc is volatized. HDG is a different story. Metal fume fever; I experienced it more than once and the last time happened when welding metal decking inside a closed are (renovation project). Now I only need a small exposure to zinc to bring on the aches and pains associated with MFF.

The second article states the zinc is rejected to the centerline of the weld bead during welding. I believe that is solute rejection and it is associated with centerline cracking. One article says the zinc is volatized, the second says it is rejected to the centerline of the weld.

The Galvanizer's Association recommends removing the zinc for up to four inches from the weld joint.

The controversy continues.

My position is considered to be conservative; I remove the galvanize from the joint, but then those that say I'm overly cautious are not the people behind the welding helmet.

Best regards - Al

In the end, someone has to make a decision with regards to whether it is necessary to remove the zinc before welding or to leave it in place and "burn" through it. Reading through the links provided by Henry provides the reader with the thoughts of other people that have expressed their opinions on the subject. As pointed out be Brent, there are contradictions in the literature, but isn't that true with many things in life?

Generally, the more we read on a subject, the better understanding we have for the subject being studied. Hopefully the literature we study is based on first hand knowledge and research rather than simple conjecture and opinion. That appears to be a deficiency in this instance. The welding processes we use in structural fabrication are generally SMAW, FCAW, SAW, and for limited applications; GTAW.  Maybe we can get Henry to use his magic fingers and unmatched skills to search for more links that address HDG and the processes we most frequently encounter.

"There is galvanizing and then there is galvanizing." I like that. It is so understated.

As for my position when engineers ask for an opinion when some contractor stakes a position that removing the zinc before welding is a waste of time, I defer to the code and say, "Let them qualify their WPS with the zinc intact." It is amazing how quickly the contractor agrees to remove the HDG.

Best regards - Al