American Welding Society Forum
Safety related question here. I've read to only weld galvanized steel outdoors or with proper ventilation (which I'd assume means a face-worn air supply and a means to exhaust the fumes). I've never seen any more details than this. So, here's a few questions:
1) I know that galvanized looks like a rough grey finish where zinc-plated is a smooth shiny silver finish. What is actually the difference between galvanized and zinc-plated though? Don't both involve adding zinc to the exterior?
2) I'd assume it's the zinc that is the safety concern. Are the safety rules the same for galvanized and zinc-plated? I don't recall ever seeing any safety concerns about zinc-plated material, but perhaps I just haven't looked deep enough. Or is galvanized and zinc-plated pretty much interchangeable terms?
3) Assuming the zinc is the safety concern, what gas is actually produced? What are it's ill effects? In what concentration is it harmful vs. not harmful to a person?
4) What are substitutes for galvanized or zinc-plated material? (I'm thinking nuts, bolts, clamps, perhaps even some tools like locking pliers, etc.). Stainless steel plated or chrome plated? How can you tell if something is chrome-plated or zinc-plated? They look pretty much the same, don't they? Is there any simple test that a hobby welder could do?
I know these are pretty basic questions, but hopefully the answers will be useful for a lot of folks who read these posts! I've done a few web searches and the answers don't seem to be readily available, so I'm hoping the highly experienced folks here can provide the details...
Here is a link to this board concerning the very topic you have questioned. Also type in "galvanize" in the search option and you'll see alot of discussion has already taken place about welding over hot dipped material. The plating you described as shiny, that's because of the process used to get the zinc to adhere. The hot-dipped is dull and not as shiny. Read over some of these posts and let me know if it helps with your question. I don't like to see that yellow-green smoke. It will make me sick after awhile. We use a disposable respirator mask from 3M #8514 that works pretty good.
When you use that link, you will have to scroll to the top of the page to read it all.
Hope this helps,
Just to clarify here, hot dipped galvanized products can be dull or shiny. It depends largely on how the galvanizer controlled his process; alloy percentages in the tank, time in the tank, quenching, and other concerns.
You are correct, I was speaking generaly about the finish. I have used galvanizers that use more nickle in the soup and use a different pickeling process that makes for a nice shiny surface. I like the look of the shiny finish on our steel, it dresses it up.
Thanks John! I read the post you referred me to...very informative! (For some reason, it doesn't show up on a search, so I really appreciate the post.)
So, more questions here: what other metals produce toxic gases when welded? I've heard copper does...how dangerous? Does the chromium in chrome moly steel or stainless steel pose any hazards?
Welding plumes period, have lots of "bad for ya stuff" in them, read the can your electrodes come in. MSDS sheets are available for download or printing from the mfg's web sites.
Some nuts and bolts may be cadmium plated. This also creates a toxic gas when welded.
1- Usually galvanized means dipped into molten zinc. Plated generally means electroplated. I've seen terms like electro galvanized used (generally to confuse the uninitiated). Galvanized has a much thicker layer of zinc.
2- Since the plated layer is much thinner less fume would be produced.
3- Zinc oxide, not a gas but very fine particles. A mask labled for particulates should provide quite good protection. Good ventilation is always nice. The advice "keep your head out of the fumes" always applies.
4- Mechanical connection (bolts rivits glue) avoid zinc fumes and do not destroy the zinc as welding does in the area of the connection. Lower temperature (solder, careful low temp brazing) can also save the zinc coating. Galvanizing after welding is probably the best solution. Zinc is soft (easily scraped away with a pocket knife). Chrome and nickel, similar colored metals you might find as plating are much harder.
When this subject was discussed once before I found exposure limits posted somewhere (OSHA I think but not sure). Zinc was listed at exposure levels hundreds of times higher than other materials (like cadmium) which might easily be encountered when welding.
Be careful but don't worry yourself to death.
Beware of painted surfaces also. The fumes from some paints are terrible for you.
Answear to question number 3 is Zinc Oxide, it just floats in the air, I have welded lots of it, and it will make you sick to your stomach, I've found drinking milk takes care of it. It spatters alot too, so protect yourself. Do some over head work with it and you'll find that out quick. The toxicity level's, or exposure limits I'm not sure of.
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