Welding electrodes are coated for many reasons. The most common reason is to protect the metal from oxidation. Oxidation can cause the weld to break down over time.
Another reason electrode is coated is to prevent the weld puddle from sticking to the electrode. This can cause problems with the weld quality.
Finally, a coating can help provide a good surface for arc welding. It can be challenging to start and maintain an arc on the electrode without a good coating.
What is Electrode Coating?
An electrode coating is a thin layer (1-3 MM) of material applied to the surface of an electrode. The purpose of the coating is to improve arc stability and increase the life of the electrode.
Coated electrodes are typically used for manual welding operations due to their brittleness. If the coating is placed inside a long tube, the electrode can be in the form of a bare wire in the form of a coil allowing continuous and automatic welding.
What are the Benefits of Using Coated Welding Electrodes?
More Control Over the Current
One significant benefit of using an electrode coating is it offers you greater control over current during the welding process. Coatings help to concentrate the welding current, resulting in less spatter and smoother, neater welds.
In addition, the increased current can penetrate deeper into the material, creating stronger welds. While bare electrodes exist, they are less commonly used due to the increased risk of spatter and uncontrolled arcs. As a result, electrode coatings provide a significant advantage in terms of quality and precision.
Avoid Impurities & Slag
The coating on electrodes helps to prevent the weld pool from reacting with oxygen in the atmosphere, which reduces the chance of oxidation. Secondly, the coating helps to prevent slag from being present on the surface of the weld bead after it has been removed from the arc.
Slag is formed when flux becomes molten during a welding process and can act as an insulator, protecting the molten metal from oxidizing. By preventing slag from being present on the weld bead, it helps to ensure that the weld is of high quality and will not be susceptible to cracking or other defects.
Classification of Welding Electrodes
A number ranging from 1-8 signifies the unique properties of each electrode. For instance, 1 tells you about the nature of the coating material. The coating is generally classified into three varieties: cellulose, mineral, or a combination of both.
Besides, the number lets you know each electrode’s most suited current type. The following numbers also determine factors such as tensile strength and electrode position.
Each welding electrode serves a different purpose. Make sure to use the one that best suits your welding needs.
Cellulose & Organic Materials
These coatings comprise one-third of cellulose and two third of other organic materials. The decomposition of cellulose into gas form by welding with an arc creates three separate layers reinforcing the joint and increasing its durability.
Additionally, they also protect the weld pool from impurities. Using cellulose coatings also ensures higher-quality weld joints by protecting against porosity.
This coating leaves slag on the weld piece. You might think of slag as an annoying side effect, but it serves a beneficial purpose. The slag leftover from these electrodes lets it cools down quite slowly compared to cellulose coating, which allows the settling down of impurities without compromising the structure.
Many fabricators use electrode coatings with a combination of cellulose and minerals to provide the best of both worlds. Since these coatings can have anywhere from just one or two components upwards to ten different ingredients, their chemical diversity provides significant benefits when welding certain types of metals.
In welding, it is crucial that fabricators not only have shielding gas protection but also slag corrosion resistance so they can work with temperamental base metals without worrying about their equipment being damaged by acid exposure during production.
The Five Most Common Types of Electrode Coatings
Each electrode has different characteristics and serves a different purpose. The following are the most commonly used electrodes in the welding industry.
1:Cellulose Coated Electrode
It is the most suitable electrode for welding vertically. But the drawback is it leaves a thin slag, but you don’t have to worry about it as it is easily removable.
When these coatings are exposed to heat, they produce gases such as CO2 and hydrogen, which aids in preventing weld pool contamination. The downside is hydrogen embrittlement risk due to its breakdown into carbon dioxide and water when heated. Cellulose best work with DC when it’s in its purest form.
However, in some cases where elements have been added onto these coatings during production processes, then yes, AC power may be used.
2:Rutile Coated Electrode
Like cellulose coating, these electrode uses contain a higher titanium dioxide percentage and cost you a bit higher than cellulose. These electrodes emit certain gases when exposed to heat, making them best suited for welding low-carbon steel.
The drawback is it leaves traces of titanium on your weld piece. You can also mix rutile with cellulose to ensure maximum protection of the weld pool from contamination. Also, these coating produces less spatter and smoke and are suitable for all welding positions.
But as the electrodes are costly, I recommend using them for metals that require deeper penetration, such as aluminum.
3:Iron Oxide Electrode
Iron oxide electrodes provide excellent arc control and allow clean, precise placement of beads. They produce a little easy-to-remove slag on the weldment and best work with both AC/DC currents.
However, this coating contains a higher oxygen percentage, resulting in weaker welds. Besides, the risk of hydrogen embrittlement also exists but is relatively low compared to cellulose.
You can use these electrodes for welding various ferrous metals, but I suggest you not use them with aluminum as they contain a higher oxygen percentage.
These electrodes are composed by mixing inorganic materials such as clay, silica, and iron oxide. They possess excellent welding characteristics, and the elements present in them don’t contaminate the weld pool.
They are compatible with both AC/DC, and I suggest you do not use them for stainless steel because these components cause a reduction in corrosion resistance.
5:Basic or Low Hydrogen
The primary electrode coating is formed by mixing fluorite and calcium carbonate and works excellently with steel. These are also known as hydrogen-controlled electrodes.
But they require extra care before you use them for welding. If you don’t do so then, then the chemical composition of the coating is compromised, which leads to weaker welds. To prevent it, you need to store electrodes in a dry place, and don’t forget to bake them before use.
Additionally, the weld formed using these electrodes is less prone to porosity and cracks because they deposit low-control hydrogen.
Moreover, these electrodes are difficult to control, so you should be an experienced welder to use them properly.
Care Tips For Coated Welding Electrodes
Anyone who has ever used a welding machine knows that electrodes are essential for the process to work correctly. But many people don’t realize that electrodes must be adequately maintained to work effectively. Here are a few tips on how to properly care for your electrodes:
1. Keep them clean – Electrode tips can become clogged with dirt and debris over time, affecting the quality of your welds, so it’s important to keep them clean. The best way to do this is to use a wire brush to remove any build-up on the tips.
2. Store them properly – When not used, electrodes should be stored in a dry place because if they become wet, they can rust and become unusable.
3. Inspect them regularly – It’s important to inspect your electrodes regularly for signs of wear and tear. If you notice any damage, it’s best to replace them before using them again.
By following these simple tips, you can ensure that your electrodes will last longer and work better.