Coating on embed plate 1

I'm very used to exterior exposure conditions so my brain automatically defaults to wanting to protect steel so take my answer with a grain of salt.

If you really aren't worried about corrosion, then I would think that an uncoated plate for interior exposure (especially if this is climate controlled) would be acceptable. You could always have them field paint the surface of the embed plate after they weld their attachments to it for a bit added protection and not much more cost.

If this is not a big ticket item in the grand scheme of the project, I would be inclined to not mess around and require them to HDG the embed plates with headed studs. When they go to weld their attachments to it, they will have to grind off the zinc. At that point, I usually require them to field repair it with a zinc based solder per ASTM A780. Contractors always complain about this and instead try and substitute a cold-galvanizing spray.

Design guides for service life are minimal and many times are based on Engineering judgement based on your familiarity with the local environment. If in your experience, you do not see a lot of corroded embed plates on the inside of buildings, I would think that it would not be a concern. For example, in my environment, we found that pouring non-shrink grout beneath highway sign structures exacerbated the corrosion issue with anchor bolts so we stopped doing so based on experience.

My approach has practically always been to just HDG since we don't usually weld to the plate. And I would otherwise agree to leave it alone in this case, but we are talking 100s of embedded plates. We would approve the cold galv spray. Is grinding the zinc off something you ever gets complaints about?

If the contractor plans ahead they can "mask" the weld area off so they dont need to grind prior to welding. Also I typically allow cold galv paint but it does not have a great appearance so top coat if aesthetics is a concern.

Grinding the zinc off is no problem. They usually need to clean it anyway prior to welding to remove residue and taking a minute to run a grinding wheel over the surface is not an issue.

I don't know that I've ever seen embed plates inside the building envelope that were galvanized. Is it common to HDG these in other climates?

I would say coating/painting is more common for interior than galvanized. However no one blinks when galvanized or zinc coated bolts, all thread, strut, and cfs is used so there is that.

I didn't think there was any problem welding galvanized steel?

The fumes can cause galvanize poisoning illness. That’s an interesting tidbit about the masking - I never knew you could do that with hot dipped galvanizing.

retrograde, even with stick welding, you need a clean welding environment. The presence of the zinc would most likely produce an unsound weld more susceptible to inclusions and poor penetration.

GC-Hopi, masking paint is a common technique but I had no idea that they could "mask" galvanizing. I'm curious on what they use to mask it that wouldn't burn up in the kettle.

azcats, probably not, but then again, in the desert you could probably build an entire bridge out of uncoated steel and it would last 75 years

From my notes...

-IF WELDING OF HDG STEEL IS REQUIRED, REMOVE ALL GALVANIZING FROM AREAS TO BE WELDED TO PROVIDE 1" MIN BASE METAL AROUND ALL WELDS. WORK SHALL BE DONE IN ACCORD WITH AWS RECOMMENDATION WZC. PROVIDE VENTILATION AS REQUIRED. CLEAN FINISHED WELD AND TOUCH UP WITH TWO COATS OF ZINC RICH PRIMER. PRIMER SHALL OVERLAP EXIST GALVANISING BY 1/2" MIN.


Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

It causes spatter and porosity of the weld. The fumes are also unhealthy... I think the term is 'zinc headache'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Here is some info on masking for Hot dip galvanizing (keep in mind, it doesn't only have to survive the heat from the kettle, it also has to survive the acid bath before that):



D1.1 does not specifically address the requirement to remove galvanizing before welding (that I am aware of).
Section 7.14.1 (2020 edition) states, "Base metal shall be sufficiently clean to permit welds to be made that will meet the quality requirements of this code."
7.14.4.2 states, "Welds are permitted to be made on surfaces with surface protective coatings or anti-spatter compounds, except those that are prohibited in 7.14.4.1, provided the quality requirements of this code can be met." 7.14.4.1 lists Water, Oil, Grease, and Other Hydrocarbon Based Materials as the prohibited items.

To me, D1.1 is intentionally not disallowing the welding of galvanized steel, but it may be very difficult to still meet the quality requirements of the code if you do so.

AWS does have another publication, D19.0 "Welding Zinc-Coated Steel" that does require the removal of zinc before welding (for the reasons mentioned above).

I've actually experienced the galvanize poisoning myself and it was rough. I was doing a walkdown inspection of a nuclear plant under construction and walked into a room with 5 guys welding HDG beams to HDG embed plates, 3 stories underground with minimal ventilation. It was the first and only time I stopped work on a project in my career. Extreme example for sure, but I suppose because of that experience I'm now a bit of a hardo when it comes to taking precautions with welding and galvanized steel. Those welders could have easily died from the fumes they were exposed to. We should try to engineer safety into our designs where we can. I like the idea of masking off the weld zones.

It's also worth noting that it's not just the zinc. Zinc and lead coexist naturally and are typically mined together. So the chances of having lead in the HDG is relatively high and the lead can enter the lungs just as easily with more long term effects than the zinc (as far as 'metal fume fever' - another name for it - is currently understood).

For 2 or 3 summers, I worked in a galvanising shop... and with the exception of a little aluminum... it was zinc... like 99.9% stuff.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

My nephew welds out in the oil patch and now they must wear air assist masks. He was telling me recently that he didn't like it at first, but now when he comes home at night he can tell it makes a big difference.