Welding is an essential process across many sectors and is seen as a blend of science and craftsmanship. It’s an indispensable technique that has significantly contributed to shaping our modern world, from sky-high buildings to the vehicles we commute in. Among the plethora of materials used in this domain, galvanized steel takes center stage due to its distinct characteristics and extensive application (automotive, energy, construction, telecommunications, and so forth).
This variant of steel, adorned with a protective zinc layer to guard against rust, is frequently selected for its hardiness and robustness. However, the properties that enhance its attractiveness also introduce unique difficulties, especially during welding.
In this blog article, we aim to probe into the nitty-gritty of galvanized steel, focusing specifically on the risks linked to welding fumes and the essential methods to alleviate these hazards. It is indispensable for welders and individuals who work near the welding operation.
Understanding Galvanized Steel
Galvanized steel, a material extensively adopted in various sectors, is a type of steel that undergoes a process called galvanization. This process entails coating the steel with a layer of zinc. The most typical method employed is hot-dip galvanizing (immersing parts in a bath of molten zinc). The galvanizing technique has been around for over 250 years and has been a pillar of North American industry since the 1890s.
Zinc, a vital, silvery-white metal, is naturally found in the Earth’s crust. But why choose zinc, you might ask? The answer lies in zinc’s property to corrode much slower than steel.
The choice to galvanize steel depends mainly on its intended use. Due to its rust-resistant nature, galvanized steel is ideal for outdoor structures like bridges, fences, and railroads. Additionally, it’s widely utilized in the automobile industry and the manufacturing of domestic appliances.
However, the element that adds to the benefits of galvanized steel – its protective zinc coating – transforms into a potential risk during welding. Herein, the issue of fume hazards becomes a point of focus.
The Art of Welding Galvanized Steel
The process of welding galvanized steel doesn’t differ significantly from welding other kinds of steel, but it does include a few crucial differences due to the zinc layer. This zinc layer interacts with heat differently than raw steel, and potential dangers can surface.
In welding, high heat is directed onto the metal, causing it to liquefy and enabling the welder to reshape and fuse the material. During the welding of galvanized steel, the heat impacts the steel and the zinc layer. As the temperature escalates, the zinc vaporizes and interacts with oxygen in the surroundings to form zinc oxide, producing fumes.
The fumes from galvanized steel pose a significant risk in the welding sector. They contain particles of zinc oxide, a compound that can lead to harmful health impacts if inhaled in large quantities or over an extended duration. They may also have lead oxide, which is equally toxic.
The intensity of fume emission is generally influenced by the welding method deployed, the heat applied, and the thickness of the zinc layer.
To accurately determine the composition of the welding fume in a specific work environment, air sampling is typically required. While zinc oxide and lead oxide are evident and alarming constituents, other substances might also pose threats.
Acknowledging these dangers is vital for welders and individuals accountable for maintaining secure and healthy workspaces.
Health Hazards when Welding Galvanized Steel
Welding galvanized steel presents a number of health dangers, primarily stemming from inhaling the harmful zinc oxide fumes produced during the procedure. Exposure to these fumes can lead to both immediate and prolonged health challenges.
Among the most prevalent immediate health hazards when welding galvanized steel is a condition called ‘metal fume fever,’ arguably the most recognized occupational disease among welders. Hundreds of metal fume fever cases are reported annually in the US alone.
This is particularly problematic as zinc oxide inhalation is one of the most significant contributors to metal fume fever (source: National Library of Medicine).
Metal fume fever presents flu-like symptoms, often including shivers, fever, nausea, and body pains. These symptoms usually appear four to ten hours post-exposure.
According to information provided by pubmed.gov, ‘metal fume fever,’ or ‘galvanize poisoning,’ is generally a benign illness with spontaneous symptom resolution 12 to 48 hours after exposure cessation. However, it carries the potential of severe implications, especially for workers with pre-existing health conditions.
While typically temporary and reversible, the occurrence of metal fume fever is an indicator of excessive fume exposure and warrants immediate attention and action.
Long-term exposure to zinc oxide fumes during the welding of galvanized steel can have grave outcomes. This can include lung damage, leading to conditions such as pneumonitis and pulmonary edema.
Moreover, zinc inhibits the absorption of copper in the body, and overexposure to zinc can result in a copper deficiency, triggering neurological complications.
As stated previously, the fumes produced while welding galvanized steel also comprise lead oxide, which can lead to enduring health complications like lung and brain cancer and even disorders affecting the nervous system.
In general, according to OSHA, the CDC, the IARC, and the CNESST, breathing welding fumes could also cause the following health effects:
- Eye, nose, and throat irritation
- Dizziness and nausea
- Breathing difficulties that could lead to suffocation or asphyxiation
- Lung damage and various types of cancer
- Stomach ulcers
- Kidney damage
- Nervous system damage
- Manganism
- Chest pain
- Asthma
- Bleedings
- Dermatitis or eczema
- Kidney disease
- Bone and joint disorders
- Siderosis (iron oxide in lung tissue after inhalation)
- Stannosis (tin oxide in lung tissue after inhalation)
- Anthracosis (poisoning after inhalation of carbon dust)
- Berylliosis (poisoning after inhalation of beryllium dust)
- Accumulation of fluid in the lungs
Understanding that individual responses to these fumes can differ significantly is vital. Some welders display symptoms after minimal exposure, while others remain symptom-free despite consistent exposure. However, this doesn’t imply that the latter group is invulnerable or at a lesser risk. It underlines employees’ need to follow safety protocols to safeguard their health strictly.
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Regulatory Standards on Welding Fumes
Several regulatory bodies have established guidelines concerning welding fumes to ensure worker safety, including OSHA in the United States and various provincial agencies in Canada. These bodies work to shield workers from potential hazards intrinsic to their jobs.
Abbreviations used in the tables:
- TWA: Time-Weighted Average for 8 hours
- STEL: Short-Term Exposure Limit (maximum for 15 minutes)
- C: Ceiling (must never be exceeded)
- (i): Inhalable particles
- (r): Respirable particles
- ALARA: As Low as Reasonably Achievable
Galvanized steel welding fume regulations in the US
| OSHA PEL | TWA | STEL | C |
| Welding Fumes | 5mg/m3(r) | None | None |
| Zinc Oxide | 5mg/m3(r) | None | None |
To know more about the maximum concentrations allowed for other substances, you can read the following article: Welding Fume Regulations and Exposure Limits in the US.
Galvanized steel welding fume regulations in Canada
| Welding Fumes | TWA | STEL | C |
| Alberta | ALARA | ALARA | ALARA |
| British Columbia | 10mg/m3 (i) 3mg/m3 (r) | 30mg/m3 9mg/m3 | 50mg/m3 15mg/m3 |
| Manitoba | 10mg/m3 (i) 3mg/m3 (r) | None | None |
| New Brunswick | 10mg/m3 (i) 3mg/m3 (r) | None | None |
| Newfoundland and Labrador | 10mg/m3 (i) 3mg/m3 (r) | 30 mg/m3 9 mg/m3 | 50 mg/m3 15 mg/m3 |
| Northwest Territories | 5mg/m3 | 10 mg/m3 | None |
| Nova Scotia | 10mg/m3 (i) 3mg/m3 (r) | None | None |
| Nunavut | 5mg/m3 | 10mg/m3 | None |
| Ontario | 10mg/m3 (i) 3mg/m3 (r) | 30mg/m3 9mg/m3 | 50mg/m3 15mg/m3 |
| Prince Edward Island | 10mg/m3 (i) 3mg/m3 (r) | None | None |
| Quebec | 5mg/m3 | 15mg/m3 | 25mg/m3 |
| Saskatchewan | 5mg/m3 | 10mg/m3 | None |
| Yukon | 5mg/m3 | 5mg/m3 | None |
| Zinc Oxide | TWA | STEL | C |
| Alberta | 2mg/m3 | 10mg/m3 | None |
| Yukon | 5mg/m3(r) | 10mg/m3(r) | None |
| Other Provinces & Territories | 2mg/m3(r) | 10mg/m3(r) | None |
To know more about the maximum concentrations allowed for other substances, you can read the following article: Welding Fume Regulations and Exposure Limits in Canada.
Workplaces are mandated to adhere to these regulations to guarantee employee safety. Failure to comply can result in penalties, encompassing hefty fines and potential litigation. Furthermore, disregarding these regulations can lead to serious health issues for workers, negatively affecting their overall well-being and productivity.
Risk Management: Efficient Fume Extraction and Safety Protocols
Risk management associated with welding galvanized steel primarily revolves around adequate fume control and enforcing efficient safety procedures. The goal is to foster a work environment prioritizing health and safety without sacrificing work process efficiency.
We have developed an 8-step method to address welding fume problems. Here are a few strategies that directly apply to galvanized steel fume. We recommend reading this article for a thorough understanding of the process.
Step 4: Use consumables and materials that produce less toxic fume
Generally, it’s recommended to complete welding before galvanizing the steel.
Otherwise, according to the American Welding Society, galvanized metal must be meticulously cleaned using a grinder or another abrasive method to eliminate the galvanized coating at least 1 to 4 inches from either side of the intended weld and on both sides of the workpiece before welding.
This action diminishes toxic fumes, potentially reducing lead and zinc oxide emissions below the Permissible Exposure Limits (PELs). It also enhances weld quality, as the coating can hinder penetration and induce porosity. The protective layer must be reapplied after welding, whether removed prior or not.
The need for high-performance fume extractors becomes even more pronounced if you weld coated steel. You’ll likely have to choose a filler material designed for zinc-coated materials. The process will require higher heat input to eliminate the zinc from the weld pool and slower welding speeds to burn off as much of the zinc coating ahead of the weld.
Lastly, zinc electroplated steel, featuring a thinner and more uniform zinc coat than hot-dipped or zinc thermal sprayed steel, is more suitable for automatic welding.
Step 5: Use welding fume extractors
The best way to manage fumes is through an efficient extraction system. Welding fume extractors are engineered to capture and filter out the harmful fumes generated during welding, ensuring they do not permeate the workspace and are not inhaled by workers.
A fume extraction gun offers the most efficient extraction of galvanized welding fume for MIG welding. For TIG welding, we recommend using a fume extraction arm.
Dispelling the Milk Myth
It’s important to debunk the misconception that consuming milk can prevent the detrimental effects of zinc oxide fumes, a common myth in the welding industry. This myth likely stems from the belief that the calcium in milk can bind with heavy metals, assisting their elimination from the body. However, no scientific evidence supports this claim, and it’s a dangerous notion that can cultivate a false sense of security.
Closing Remarks
Welding galvanized steel, while indispensable to numerous sectors, introduces a range of health hazards that must not be disregarded. The production of zinc oxide fumes during welding can result in immediate health problems, such as metal fume fever, and pose chronic health risks upon long-term exposure. However, recognizing these hazards is the initial step toward mitigating them. We can considerably minimize these risks through effective safety procedures, such as using efficient fume extraction systems and adhering to best practices in welding. Compliance with regulatory standards guarantees the safety of individual workers and contributes to the overall health of the workplace environment.
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