Welding galvanized steel is difficult and dangerous. Here you will learn exactly why welding galvanized steel is dangerous.
Why is welding galvanized steel dangerous? Welding galvanized steel is dangerous for several reasons, including:
- The resultant fumes which can cause metal fume fever
- The relatively low melting point of zinc
- Traces of lead in the galvanizing coating of steel
- The increased difficulty of welding galvanized steel
Here you will find guidelines on how to safely weld galvanized steel. You will also find guidelines on how to deal with the greater degree of porosity that is often associated with galvanized steel. You will find that this article doesn’t discourage you from welding galvanized steel, rather it informs you of the precautions you should take.
Dangerous Fumes From Welding Galvanized Steel
Welding, cutting, or brazing galvanized steel can lead to Metal Fume Fever, warns the University Of Houston- Clear Lake.
Metal fume fever results from exposure to Zinc Oxide (ZnO) in the workplace. The fever is described by the university as an acute allergic condition.
Metal fine fever is characterized by flu-like symptoms, including headaches, nausea, fevers, and muscle aches, among other common flu symptoms. High levels of exposure can even leave a metallic taste in the mouth.
There is little known about the effects of long-term exposure to zinc oxide; however, it is known that consistent exposure to toxic metals can lead to long term health impacts.
In addition to containing Zinc and Iron, the toxic fumes from welding galvanized steel can also contain lead.
The protective layer in galvanized steel is typically made with Zinc naturally containing ½% lead. Safety is always a top priority when welding, but this is particularly the case when welding galvanized steel. In the following sections, you will see what steps need to be taken in order to weld galvanized steel safely.
Learn More About Welding Galvanized steel – Here, you can find an article from our website: Can You Weld Galvanized Steel? Step by Step Complete Guide
Porosity of Galvanized Steel
Welding galvanized steel can have a significant impact on the degree of porosity in a weld. Porosity is defined as the presence of cavities caused by gas that is trapped within the weld bead.
There are acceptable levels of porosity but welding galvanized steel will lead to higher levels of porosity than you are likely used to seeing. Porosity occurring from welding galvanized steel is the result of the fact that the zinc layer has a lower melting point than both the filler metal or base metal.
The melting point of zinc is 787.2 degrees Fahrenheit, while the melting point of steel is over 2500 degrees Fahrenheit. The melting point of aluminum is 1220 degrees Fahrenheit. As a result of the different melting points, the Zinc actually is melted or vaporized by the welding arc as your weld puddle progresses.
- One way to potentially cut down on porosity is to slightly lower the amperage (or wire feed speed) on your welding machine.
- You should also lower your travel speed while increasing the voltage.
- You will also need to ensure that you hold your welding gun at an angle that is as perpendicular to the welding zone as is possible.
The resin for the perpendicular angle is so you are able to keep the welding arc out in front of the weld puddle by just a hair. Angle the gun towards the side of a weld that has the galvanized metal on it. Preventing a high degree of porosity also involves making sure that your shielding gases flow rates are correct for the welding you are doing.
The broad range 30-50 cubic feet per hour (CFH) is generally considered acceptable, although certain circumstances will require more fidgeting with the settings in order to get the desired results.
If you want to avoid making so many adjustments to get a quality weld bead, then it is recommended that you remove the protective zinc layer from the galvanized steel using methods discussed later in this article.
Related article: How Many Amps Do I Really Need for a MIG Welder?
Wear a Respirator When Welding
Respirators, such as this 3M Paint Project Respirator, are recommended for use during welding. You will certainly need to wear a respirator if you are working in confined spaces such as tanks or closed vessels.
Make sure that the respirator you are using has been approved by either the NIOSH (National Institute For Occupational Safety and Health) or MSHA (Mine Safety and Health Administration).
The 3M Paint Project Mask mentioned above is approved by the NIOSH. If you are welding galvanized steel, you absolutely have to wear a respirator. Even while wearing a respirator, you will still want to work in a well-ventilated area.
Work In A Ventilated Area When Welding
Welding fume particles are usually smaller than 0.1 micrometers, making them invisible to the human eye. This also means that most welding fume particles are respirable.
Particles from welding fumes can penetrate deep into the lungs to the alveolar region of the lungs, where they will remain fixed.
Natural ventilation alone is only acceptable for contaminants less hazardous than metal fumes from welding galvanized steel, according to the University Of Tennessee.
Local Exhaust Ventilation (LEV) is a much more effective way to trap fumes and gases at the source and prevent them from entering the welder’s breathing zone.
What is Local Exhaust Ventilation? >> Check out the video below
Local exhaust ventilation set-ups usually consist of a collection of hoods and ducts. Freely movable hoods are commonly utilized by welders within their workspaces, allowing them at least some degree of mobility in their workspace.
- There are portable fume extractors available such as the Lincoln Electric Miniflex Portable Weld Fume Extractor. This kind of system is ideal for a larger shop, where you will be welding galvanized steel with some degree of regularity.
- For smaller shops, even more, affordable options such as the OrangeA Utility Blower Fume Extractor will help move away potentially dangerous fumes from the welder’s breathing space.
It is critical that local exhaust ventilation systems have enough velocity to draw away contaminants. More details on the recommended velocity can be viewed here.
Grind Off The Zinc Coating
Not only does the zinc coating on galvanized steel present a welding fume hazard, but it also makes it more difficult to perform a clean weld, according to Macro Specialty Steel.
One way to work around this is to grind off the protective zinc coating at the section you plan to be welding.
The American Welding Society (AWS) guidelines suggest that at the zinc coating should be removed at least 1-4 inches from either side of the section; you will be welding and on both sides of the workpiece.
The AWS further states that grinding back the zinc coating is the preferred method to remove this layer, although burning the zinc away or pushing back the molten zinc are other methods that may be utilized for this purpose.
You can grind off the zinc layer on galvanized steel using an angle grinder such as the 11-Amp Dewalt Angle Grinder with a Paddle Switch.
Will Grinding Off The Galvanized Steel Layer Affect The Lifetime Of The Part?
According to the American Galvanizers Association (AGA), removing the galvanizing layer from steel in order to weld will not have a negative effect on the lifetime of the steel part.
However, it is recommended that you restore the zinc coating on the steel via the use of either paint containing zinc dust, zinc-based solders, or sprayed zinc.
Welding galvanized steel can produce dangerous fumes and make the welding process more difficult. You should always make sure that you are working in areas with proper ventilation. You should also wear a respirator.
To make things easier on yourself, it is recommended that you grind off the galvanizing layer prior to welding.