MMA welding (Manual Metal Arc) is a manual arc welding process that uses a coated electrode to fuse two pieces of metal together. It’s one of the oldest and most widely used techniques in the industry, from shipbuilding to heavy machinery maintenance.
In this article, our industrial welding experts in Quebec explain how it works, its advantages and limitations, how it compares to other welding processes, and the safety standards that govern its practice.
Key takeaways
- MMA welding, also known as SMAW or stick welding, uses a consumable coated electrode to create the electric arc.
- It works outdoors and in strong wind, without an external shielding gas, unlike MIG welding.
- It’s not recommended for aluminium or very thin metals: TIG or MIG welding are preferable in those cases.
- In Quebec, the CNESST strictly regulates the personal protective equipment required for this type of work.
MMA welding definition
MMA welding refers to a manual technique that uses an electric arc to fuse metals together with a coated electrode. Among the different welding techniques out there, it’s one of the most versatile and widespread.
MMA stands for Manual Metal Arc. “Manual” refers to the welder’s hand-guided movement of the electrode, “metal” refers to the base material being welded, and “arc” refers to the electrical phenomenon that generates the heat needed for fusion. The process carries the code 111 under the ISO 4063 standard, and it’s also known as SMAW (Shielded Metal Arc Welding) or, more informally, stick welding.
MMA welding is used in pipeline construction, agricultural machinery repair, metal furniture manufacturing, and shipbuilding, all fields where durability matters more than a polished finish.
How does MMA welding work?
MMA welding relies on three mechanisms working together: creating an electric arc, melting the coated electrode, and shielding the weld pool from the surrounding air. Here’s how each one plays its part in the process.
Creating the electric arc
When the electrode is brought close to the workpiece and then pulled back slightly, an electric arc jumps across the gap that forms. This spark generates enough heat to melt the metal on contact, marking the starting point of the weld.
The role of the coated electrode
The coated electrode plays a dual role. It conducts the current that forms the arc, and as it melts, it supplies the filler metal needed for the weld. Its coating also produces shielding gases and a layer of slag that covers the weld bead as it cools.
Protection against oxidation and contamination
Without protection, the molten metal would be exposed to oxygen and nitrogen in the air, which would weaken the weld. The atmosphere created by the electrode’s coating keeps these elements away from the weld pool, ensuring a clean, durable weld.
MMA vs. MIG/MAG vs. TIG welding: what's the difference?
MMA welding stands apart from MIG/MAG and TIG processes through its lack of an external shielding gas and its simple equipment, making it particularly well suited to outdoor job sites. Here are the main differences between the three techniques.
Criterion | MMA | MIG/MAG | TIG |
|---|---|---|---|
Electrode type | Consumable coated electrode | Continuous wire | |
Shielding gas | None (flux coating) | Yes | Yes |
Working environment | Shop and outdoors, even in wind | Mainly shop | Shop (clean, dry) |
Suitable materials | Common steels, cast iron, stainless steel | Ferrous and non-ferrous metals | Stainless steel, aluminum, light alloys |
Typical use case | Job sites, maintenance, thick structures | Industrial production, bodywork | Precision welding, fine finish work |
MMA remains the most robust choice for outdoor work and repairs on thick structures. MIG/MAG welding takes over when execution speed and automation become the priority, while TIG welding is the go-to for precise finishes, particularly on aluminium.
What current and electrode diameter should you use?
Choosing the right electrode diameter and current depends directly on the thickness of the metal being welded. The wrong setting can result in a weak weld or, conversely, burn through the material.
Metal thickness | Electrode diameter | Recommended current |
|---|---|---|
1,5 mm | 1,5 mm | 30 to 40 A |
2 mm | 2 mm | 45 to 65 A |
2 à 3 mm | 2,5 mm | 65 to 80 A |
3 à 5 mm | 3,2 mm | 100 to 115 A |
3 à 10 mm | 4,0 mm | 150 to 170 A |
These values are indicative and should be adjusted according to the electrode manufacturer’s recommendations. For an industrial project, our certified technicians determine the exact parameters based on the material and the required strength.
Advantages of MMA welding
Despite the rise of other techniques, MMA welding remains a preferred choice for many professionals thanks to its versatility, portability, and strong value for money. Here are the main advantages behind its lasting popularity.
Versatility of the process
MMA welding works on a wide range of metals, from mild steel to stainless steel to cast iron. For a project involving several types of materials, this versatility considerably simplifies the work.
Portability and ease of use
MMA welding machines are generally compact and simple to transport, making them ideal for on-site work or tight spaces. The simplicity of the process also makes it accessible to less experienced welders, although professional-grade work always calls for a qualified team.
Cost-effectiveness for a range of projects
MMA requires more affordable equipment than other processes and needs no shielding gas, which lowers operating costs. This cost-effectiveness makes it a solid option for both small one-off jobs and large-scale industrial projects.
Disadvantages of MMA welding
MMA welding also has certain limitations, particularly around execution speed and finish quality, which are important to understand before choosing this process for a given project.
Limits on speed and thin materials
Compared to MIG, MMA is slower, especially on large projects. The intense heat of the arc can also warp or burn through thin metals, making it less suited to precision welding.
Slag removal
After each weld bead, the layer of slag formed by the coating must be removed to reveal a clean weld underneath. This extra step adds time to the process and, if not done properly, can affect the quality of the result.
Equipment needed for MMA welding
Quality MMA welding relies on three elements: the welding machine, the electrode, and the welder’s personal protective equipment. Each of these must be carefully chosen to ensure a safe, durable result.
MMA welding machines run on either alternating current (AC) or direct current (DC), each offering advantages depending on the metal being welded. The choice of electrode, meanwhile, depends on the material, the thickness of the workpieces, and the welding conditions.
On the safety side, welders must wear a welding helmet, heat-resistant gloves, flame-resistant clothing, and safety footwear. According to the Canadian Centre for Occupational Health and Safety (CCOHS), eye and face protection against radiation, sparks, and hot slag is essential, as is a respirator to guard against welding fumes.
MMA welding in Quebec: safety and working conditions
In Quebec, the practice of MMA welding is governed by strict safety standards designed to protect workers from burns and fume exposure. The CNESST requires, among other things, gauntlet gloves, safety footwear, and eyewear or a face shield that meets the CAN/CSA Z94.3 standard, along with flame-resistant cotton clothing free of oil or grease.
Quebec’s climate also works in MMA’s favour on outdoor job sites. Unlike MIG welding, which is sensitive to wind that disperses the shielding gas, MMA performs reliably even in extreme cold or strong wind, a real advantage for industrial work in any season.
FAQ — MMA Welding
No. MMA doesn’t allow for adequate control of aluminium’s oxidation, which compromises weld quality. For this metal, TIG welding or MIG welding with a specific wire is recommended.
MMA stands for Manual Metal Arc, meaning manual arc welding. The process is also known as SMAW (Shielded Metal Arc Welding) or coated electrode welding.
MMA uses a consumable coated electrode and requires no external gas, while MIG uses a continuous wire shielded by gas. MMA is more robust outdoors, while MIG is faster for production work.
Yes. This is one of the process’s main advantages: since it doesn’t rely on an external shielding gas, wind doesn’t affect the stability of the arc or the quality of the weld.
The diameter generally ranges from 1.5 mm for thin sheet metal to 4 mm for workpieces 3 to 10 mm thick. The parameters table above on this page provides the recommended current for each case.
MMA demands real mastery of angle, travel speed, and arc length to guarantee a compliant weld. A specialized company like HARtech ensures a certified, safe result that meets Quebec’s applicable standards.
HARtech, your partner for industrial projects
MMA welding, with its many advantages, remains a cornerstone of industrial welding. But the result’s quality depends on the expertise of those applying it, both technically and safely.
Whether you need a robust process for an outdoor job site or advice on optimizing your industrial mechanics processes, HARtech is here to help. Our certified technicians understand the requirements of every project and are committed to delivering results that meet the highest standards of quality and safety.
Don’t leave your welding projects in just anyone’s hands. Contact HARtech today and discover how our industrial welding experts in Quebec can turn your welding challenges into success
