There are two most basic and easily confused types of welding rods in manual arc welding: acidic welding rods (such as AWS E6013) and alkaline low-hydrogen welding rods (such as AWS E7018). Many welders can’t tell when to use acidic and when to use alkaline. Choosing the wrong welding rod can result in slag inclusion in the pores, or in serious cases, the weld will crack and the pressure-bearing components will be scrapped. Today, they are completely distinguished from five dimensions: coating composition, welding process, mechanical properties, pre-welding management, and applicable working conditions.
I. Basic definition: core standards for distinguishing two types of welding rods
1. Acid welding rod
The coating is mainly made of acidic oxides (silica SiO₂, titanium dioxide TiO₂, iron oxide Fe₂O₃), which forms acidic slag after melting. Representative model: AWS E6013 rutile electrode, the most common ordinary electrode on the market.
2. Alkaline welding rod (low hydrogen type)
The coating is mainly made of alkaline oxides (calcium carbonate marble, CaCO₃, calcium fluoride fluorite, CaF₂). The slag is alkaline and has extremely strong desulfurization, dephosphorization and dehydrogenation capabilities. Representative model: AWS E7018 low hydrogen potassium iron powder type, which is mostly used in important load-bearing structures.
Tips for intuitive appearance identification
- Acid welding rod: The coating color is dark gray and feels delicate;
- Alkaline welding rod: The coating is off-white in color and rough in texture. It is easy to peel and crack when exposed to moisture.
II Detailed comparison of eight core dimensions
| Items | Acidic welding rod | Alkaline low hydrogen welding rod |
|---|---|---|
| Metallurgical properties | Strong oxidizing property, large burning loss of alloy elements; poor deoxidation, desulfurization, and dephosphorization effects; high hydrogen content in welds, prone to cold cracks | Weak oxidizing properties, excellent deoxygenation, desulfurization, and dephosphorization effects; fluorite strongly dehydrogenates, low hydrogen in welds, and extremely strong crack resistance |
| Mechanical properties | Poor weld plasticity and low-temperature impact toughness, average pressure-bearing and fatigue resistance properties | Excellent weld strength, plasticity, and high-low temperature impact toughness, suitable for high-pressure, dynamic load, and low-temperature conditions |
| Welding processability | The arc is soft and stable, with minimal spatter; the slag is glassy and can be easily knocked off after cooling; the shape is beautiful and easy for novices to operate | The arc is hard and the spatter is slightly large; the slag is crystalline and it is difficult to remove slag from the first layer of grooves; the operation technique is demanding and short-arc welding is required. |
| Adaptable power supply | AC and DC, ordinary household AC welding machine can be used for direct welding | Can use both AC and DC; DC forward connection welding is strictly prohibited. |
| Pore Sensitivity | Insensitive to rust, oil, and moisture in the base material, and slightly corroded workpieces are not prone to pores. | Extremely sensitive to water, rust, and oil, trace amounts of impurities will produce dense pores. The base material must be thoroughly polished and cleaned before welding. |
| Drying requirements | Drying requirements are low. When wet, it only needs to be dried at 100~150℃ for 1 hour; if it is dry, it can be used directly. | Forced high temperature drying: 350~400℃ constant temperature for 1~2h; after drying, store it in an insulated cylinder at 80~120℃. Leave it at room temperature for no more than 4 hours. |
| Hazards of smoke | The smoke has low toxicity and low fluoride content. | The coating contains fluorite. Welding produces toxic hydrogen fluoride fumes. Forced ventilation and masks are required. |
| Cost | Low unit price, cheap consumable costs | Higher price, drying and insulation supporting equipment increase construction costs |
III. In-depth dismantling of advantages and disadvantages
(1) Acid welding rod (AWS E6013)
Advantages
- Process-friendly: Stable arc, beautiful shape, simple slag removal.
- Universal equipment: AC welding machines compatible.
- High base material tolerance: No fine polishing for slight rust.
- Simple management: Relaxed storage and drying requirements.
Fatal Shortcomings
- High hydrogen/oxygen content: Poor crack resistance.
- Insufficient impact toughness: Not for key load-bearing components.
- Element burn loss: Cannot weld high-strength alloy steel.
(2) Alkaline low hydrogen welding rod (AWS E7018)
Core Advantages
- Pure welds: Desulfurization, dephosphorization, full cold crack resistance.
- Excellent mechanical properties: Tensile, impact and fatigue resistance.
- High pass rate: Strong impurity removal, few internal defects.
Construction Shortcomings
- High operating threshold: Requires short-arc technique.
- Cumbersome pre-welding: High-temp drying and thorough polishing required.
- Toxic fumes: Strict ventilation requirements.
IV. Scenario selection guide
Choosing Acidic Welding Rods
- Ordinary light steel structures: guardrails, shelves, simple brackets.
- Secondary components with no flaw detection requirements.
- Temporary repairs on site with corroded base materials.
- Novice practice and small AC welding machine operations.
Must Use Alkaline Low-Hydrogen
- Special equipment: pressure pipes, boilers, gas storage tanks (RT/UT).
- Heavy dynamic load structures: bridges, tower cranes, ship hulls.
- Thick plate welding and low temperature environment construction.
- Equipment maintenance of stress-bearing parts to prevent fatigue.
V. Precautions in actual operation
1
Drying management red line
Acidic: low temp only when wet. Alkaline: direct welding without drying = pores and rework costs.
2
Differentiation of welding techniques
Acidic: long and short arcs available. Alkaline: short arc only; stretched arc causes hydrogen penetration.
3
Base material cleaning standards
Acidic: remove thick rust/oil. Alkaline: polish 20mm area to metallic luster; remove all contaminants.
4
Power connection reminder
Alkaline electrodes always use reverse DC connection (Workpiece negative, Clamp positive) for arc stability.
Post time: Jul-16-2026