Advise for Galvanized Steel

We recently got a local sheet metal company to donate their scrap metal to us. They have 3003 aluminum but not a large amounts. Most of what they can give us would be galvanized steel and I wanted to know what most people would use it for. I was also wondering about any suggestions on machining it and what other types of tooling to use as well as safety. From looking at the scrap I saw everything from angle to strips to sheets as big as 4’x4’.

Don’t weld it.

You can get zinc poisoning from the fumes.

I repeat: Do not weld it.

Machining: My best recommendation is to speak with the sheet metal company, THEY work with this stuff all day, every day: Surely they know how to machine it.

In general, it is steel. Cut it with a hacksaw (or metal-cutting band saw), file it, sand it, drill it. Cut thin sheets with tin snips or aviation shears or a nibbler (manual or electric or pneumatic). Bend it, solder it (silver solder recommended, not brazing), rivet it. All are fine.

It should not come into contact with copper, which will cause electrolysis.

On a robot, some steel can be useful, but often it can be too heavy.

I don’t get why not to put copper with steel. I connect copper to steel, once in a while! :confused:
By you saying “electrolysis,” do you mean that it will break up water when you electrolyze it and place it inside water?

I always cringe when new people are jumped on for spreading misinformation… but I feel that this is a time for learning as well.

You can weld galvanized steel with no issues as long as you use proper equipment. You do not get zinc poisoning from the fumes. However, you should have adequate ventilation (read as borderline too much ventilation) and proper equipment (i.e. respirator) to avoid zinc oxide irritation which is similar to an allergic reaction that results in what is known as “metal fume fever.” It is greatly unpleasant and has symptoms like the common flu. Fever, chills, awful headaches, and other not so fun issues commonly arise. These symptoms will be horribly uncomfortable, but generally clear up in 6-10 hours. If zinc oxide was so bad, we probably wouldn’t rub it all over our bodies every summer. Most cases of major problems from welding galvanized steel are generally related to people who develop pneumonia or already have a weak respiratory or immune system, or where a person was so engulfed in fumes that the building was evacuated for visibility issues due to burning coatings of to prep for welding operations.

If what was said above was true, then stainless steel should really never be welded because it releases chromium. And that stuff is a carcinogen, damages your kidneys, and will kill you if you are exposed to it for too long.

I’m not advocating that every team go out and use galvanized steel on their robot and weld away, but making it sound like the world will end if you do is over the top a bit. In fact, to avoid any issues that could arise, it’s probably smart to try to avoid it. The discomfort you will feel if you aren’t right about your ventilation isn’t worth the end result. Also, in the process of burning off the zinc coating, you will contaminate your weld resulting in a weak bead when using the most common welding alloys and shielding gases.

Steel also is heavy, but you generally can use a lot less of it than aluminum. To get the same strength you need thicker or more aluminum than you would steel. This company has a pretty good explanation of what I’m getting at. To say that you should always use aluminum is like saying you should only ever turn right in a car because it is easier. We have found that in using steel for a frame: it is stiffer, lighter or equal in weight (because we use less material), smaller in volume, and if it gets bent somehow we just bend it back.

I will have to agree with that. It scared me when I read, “you will get zinc poisoning by welding galvanized steel” because this is a type of steel. Many times, you will find steel welded, like in cars. I will have to agree with MrBasse that aluminum is much better on FRC robots. Unless the part is a very important structural part, like a climber hook, make it out of Aluminum. Not only is Aluminum less dense, but it has a greater corrosion resistance, because it is already aluminum oxide, at least on the outside. As long as space isn’t an issue, aluminum will help you work through the metal and strengthen where needed and weaken where needed, because you need three times the amount of steel!

I am just wondering: would machining any of these materials cause any problems? Will there be any fine and dangerous dust in the air that could harm you? This is one of the reason why I am scared of machining (other than zombie machines coming to life and attacking us:D).

Well for one I don’t worry too much about difficulty of machining as anything I get would be sheet metal thicknesses. As for safety, zinc dust, steel dust, aluminum powder, all can be harmful and you take the same precautions for all of them. Ventilate and protect your lungs. I doubt they like aluminum powder.::safety::

Also on weight, personally I’ve not had a problem. Our 2012 bot (photo attached) was 109. Our robot this past season (a 4.5’ tall FCS with a 10pt climb) was 98lbs at inspection. We needed to add weight.





Or… grind off the galvanized coating first before welding. But then it’s not galvanized steel anymore.

The reason I stated here to not weld it is because in the decision tree of pursuing things that have negative consequences, taking actions to avoid the situation should ALWAYS come before taking steps to mitigate the problem. Zinc poisoning / metal fume fever are just semantics for the same result - you can easily get sick if you do this action.

Even worse, is that people who may have a cursory knowledge of welding may not realize that they need to do anything different when welding galvanized steel, and won’t realize until too late. This is the same reason why I will recommend to everyone to never laser cut polycarbonate, since avoiding dangerous fumes in the first place is better than dealing with the consequences.

Since FRC robots aren’t generally subjected to salt bath/sppray tests or acidic or super humid environments, there aren’t really any compelling reasons to use galvanized steel over regular steel or aluminum or polycarbonate etc., especially when a light oil coating can keep your regular steel from rusting.

And yes, while zinc oxide itself is safe in most applications (even noted by the FDA as “generally recognized as safe”), it’s the fumes that are dangerous. Technically water fits this same description.

There is nothing wrong with welding steel, it’s welding galvanized steel that you have to take extra precautions on. Galvanized steel is just any normal steel alloy that is coated in zinc to have better anti-corrosion properties (e.g. not rust).

Except that its free.

Also I assume it would be okay to water jet it?

This discussion is not about steel in general, it is about steel that has been specifically Galvanized. Though I would not recommend inhaling any kind of metal (or wood or plastic for that matter). You are obviously not going to die while being in the same room as a metal being machined, as all of us are still living (though only by satisfying our addiction to robots). Also, steel is heavy (EDIT: dense) it does not form dust very well.

Anybody good enough to weld sheet metal should already know not to breathe any welding fumes. Which means only weld in well ventilated areas. Good practice is to remove all coatings from the weld zone so you don’t contaminate the weld. Zinc fumes have unpleasant short term effects which is a good enough reason to avoid them. Long term effects have not been documented which is different than no long term effects.

To avoid fuming the zinc you only have to remove it from the heat effected zone. Not really an issue here since you are using it for its cost property (free) not corrosion resistance. (Unless this is a devious game hint) Salt water game!!

Don’t forget about the air all around you. There’s water in it too :wink:

When using any new material, find the MSDS. I found a galvanized sheet steel MSDS here that addresses the zinc oxide inhalation hazard.

…like multi-vitamins with minerals for example :slight_smile: … check the label.

…it’s the fumes that are dangerous. Technically water fits this same description.

Yes, do not inhale superheated steam.

Let’s just end this argument about whether zinc fumes are dangerous. Let’s just say, zinc oxide can be dangerous, but isn’t always, so just make sure to have proper ventilation.

It’s never bad to be overcautious, especially when you can be harmed severely, or maybe even killed. That’s why we give safety tests to students before they can use tools!

Just a fan will get you into dealing with all of the symptoms I listed earlier. To avoid a lot of discomfort you need a dedicated welding ventilation system and most likely a respirator for any residual fumes that get past the ventilation system.

(Emphasis mine)

Please, if you don’t actually know what you’re talking about, don’t offer safety advice on the subject.

I’m a professional machinist, so I handle safety concerns regarding our machine shop. I’m not a professional electrician or electrical engineer, so it’s not a very good idea for me to give out safety advice about electricity besides “Don’t touch it”. Misinformation can cause accidents.

For this same reason, people will give out the advice; “Don’t weld galvinized steel”. Even though, as others have pointed out; it can be done. But it can only be done if you really, really know what you’re doing. But “Don’t do it” is a pretty good rule if you don’t know exactly how to do it.

A fan blowing air out of the room to the outside is pretty much the bare minimum for ventilation. It might cut it if you want to get rid of some paint fumes, but when you’re dealing with fumes that are actually dangerous, it’s not going to be good enough.

Please don’t guess when health and safety are involved. You don’t yet have the experience and expertise to give such advice…

…especially when you can be harmed severely, or maybe even killed. That’s why we give safety tests to students before they can use tools!

Have you had any training involving the welding of galvanized steel? If not, I urge you to hold your tongue when you get the urge to answer safety-related questions about it. But please keep asking questions!

[edit]I didn’t see Evan’s note above when I wrote my reply, and I apologize for the redundant message. I didn’t delete it, because I think my final sentence is important.[/edit]

Here is a fact sheet from the the American Welding Society on metal fume fever. Google is you friend.

As a welder I prefer to TIG-braze galvanized steel with silicon-bronze filler material. I find it results in a strong weld joint and greatly reduces the amount of noxious fumes emitted by the joining process due to the low heat input of brazing and the fact that the base steel isn’t actually melted. Several critical parts on our 2013 climbing mechanism were TIG-brazed with silicon-bronze filler.

Others have done a great job of addressing the safety concerns.

Coming back to the original post…

Remember that steel is as strong as aluminum per pound. To accomplish the same task will require the same weight of either metal. With that said, aluminum is usually a better choice because (let’s face it), we’re building relatively low-weight robots compared to industry. Steel is (mostly) harder to machine than aluminum (slower feed rates, smaller cuts, etc).

For machining it, the machine is as important as the tooling. Although a drill press will work, I’d advise a mill for the improved control and precision. For safety, if you’re not cooking it (see previous posts), it’s (mostly) just like machining regular steel.

Personally, I’d advise my team against the galvanized steel in large quantities. We’d never go through enough of it to justify the hassle of storing it and machining it. Plus, we’re always running close to the weight limits and steel would just make that worse.