Stick electrodes are not interchangeable. Two that look identical on the bench can want different polarity, run in different positions and put very different amounts of heat into the joint. The code stamped on the box tells you which is which, and once you can read it the choice stops being guesswork.
This guide covers how electrodes are classified, what the common mild steel types are for, how to match an electrode to the base metal, and how to store and re-dry them so they still work when you come to use them.
In this guide:
Reading the AWS Code
Carbon steel electrodes are classified under AWS A5.1 with a four or five character code. Every part of it means something.
The last digit is the one worth learning, because it sets both the coating type and the current you can run.
| Last digit | Coating | Current |
|---|---|---|
| 0 | Cellulose sodium | DC electrode positive only |
| 1 | Cellulose potassium | AC or DC electrode positive |
| 2 | Titania sodium | AC or DC electrode negative |
| 3 | Titania potassium (rutile) | AC or DC, either polarity |
| 4 | Iron powder titania | AC or DC, either polarity |
| 5 | Low hydrogen sodium | DC electrode positive only |
| 6 | Low hydrogen potassium | AC or DC electrode positive |
| 7 | Iron powder iron oxide | AC or DC, either polarity |
| 8 | Low hydrogen iron powder | AC or DC electrode positive |
The Mild Steel Electrodes You Will Actually Meet
Most stick welding in the UK is done with a handful of classifications. These are the ones worth knowing.
| Code | Current | Positions | Penetration | What it is for |
|---|---|---|---|---|
| E6010 | DC electrode positive only | All | Deep | Pipe root runs and site work. Digs through rust, paint and mill scale where a cleaner electrode would struggle. |
| E6013 | AC or DC, either polarity | All | Light | General fabrication, thin sheet and repair work. Easy to strike and restrike, smooth bead, forgiving. The usual starting point. |
| E7016 | AC or DC electrode positive | All | Medium | Low hydrogen where the job needs higher strength but you want an electrode that runs on AC. |
| E7018 | AC or DC electrode positive | All | Medium | The structural electrode. Thicker sections, restrained joints and anything working to a procedure. Tough, clean, low hydrogen. |
| E7024 | AC or DC, either polarity | Flat and horizontal fillet only | Light to medium | High deposition fill on flat work. The iron powder in the coating puts down a lot of metal quickly. |
Note the third digit on E7024. It is a 2, so it is flat and horizontal fillet only. Trying to run it vertically wastes time and electrodes.
AC, DC Positive or DC Negative
With stick welding, polarity is set by the electrode classification, not by the material. This is the opposite of TIG, where AC is used for aluminium and DC for steel. You do not pick AC because you are welding a particular metal. You pick whatever the electrode on the box requires.
- DC electrode positive puts more heat into the work and gives deeper penetration. Most low hydrogen and cellulosic electrodes want it.
- DC electrode negative puts more heat into the electrode and less into the work. Used on thin material with electrodes that allow it.
- AC suits electrodes designed for it, and has one genuine advantage: it reduces arc blow. If the arc is being pulled off the joint by magnetism, switching to AC with a suitable electrode often cures it.
Check what your machine actually puts out before buying. Some inverters are DC only, which rules out nothing in practice, but an AC only transformer set rules out E6010 entirely. E6011 is the cellulosic classification that will run on AC. Arc blow is covered in more detail in our guide to common MMA welding problems, and the output types are explained in our MMA welder range.
Matching the Electrode to the Base Metal
| Base metal | Electrode | Notes |
|---|---|---|
| Mild and carbon steel | E6013 for general work, E7018 where strength or a procedure demands it | Match or slightly exceed the strength of the parent metal. There is no benefit in going far above it. |
| Low alloy steel for low temperature service | Nickel bearing low alloy types such as E8018-C1 and E8018-C3 | These are chosen for impact toughness at low temperature. Check the datasheet for the temperature the impact values were tested at. |
| 304 and 304L stainless | E308L | The L means low carbon, which reduces the risk of carbide precipitation and the intergranular corrosion that follows it. |
| 316 and 316L stainless | E316L | Molybdenum bearing, for better resistance to pitting and chlorides. |
| Stainless to carbon steel | E309L | The standard choice for dissimilar joints and for buffer layers before cladding. |
| Unknown, difficult or high strength steels | E312 | High ferrite, high strength and very crack resistant. The usual answer when nobody knows what the steel is. |
| Grey cast iron | Nickel types such as ENi-CI | Gives a machinable deposit. Technique matters more than the electrode here, see below. |
| Worn surfaces needing rebuilding | Hardfacing electrodes | Selected by deposit hardness and how many layers it takes to reach it. Check whether the deposit can be machined or only ground. |
Cast iron is about technique, not the electrode
Buying the right nickel electrode is the easy part. Cast iron cracks because of the heat you put in and the rate it cools, so keep the current as low as the arc will tolerate, run short stringer beads of roughly 25 to 50 mm, peen each one while it is still hot, and let the part cool between runs rather than working continuously in one area. Polarity varies between brands on cast iron electrodes, so follow the figure on the box rather than a general rule.
Diameter and Current
| Diameter | Typical current | Usual use |
|---|---|---|
| 2.0 mm | 40 to 70 A | Thin sheet and small repairs |
| 2.5 mm | 60 to 100 A | Light fabrication, root runs |
| 3.2 mm | 90 to 140 A | The general purpose size for most work |
| 4.0 mm | 130 to 190 A | Thicker sections, fill and cap passes |
| 5.0 mm | 180 to 260 A | Heavy plate, flat position |
Treat these as starting points and use the range printed on the box, because it shifts with classification. An E7024 runs noticeably hotter than an E6010 of the same diameter.
- Do not use an electrode thicker than the material on thin sheet. You will blow through before the arc settles.
- Root runs want a smaller electrode than the fill passes, so it fits the gap and you can control the penetration.
- Going up a size to save time is false economy out of position. Gravity wins above about 4.0 mm on vertical work.
Low Hydrogen Electrodes
Hydrogen dissolved in the weld metal causes cracking, and the cracking is usually delayed. A joint can look sound when you put the machine away and be cracked the following morning. Low hydrogen electrodes exist to keep that hydrogen out.
You need them on higher strength steels, on thicker sections, on heavily restrained joints, and any time a welding procedure specification calls for them.
The critical point is that a low hydrogen electrode is only low hydrogen while its coating is dry. The coating absorbs moisture from the air, and moisture is where the hydrogen comes from. A damp E7018 is not a low hydrogen electrode in any useful sense.
You will see an H number on the box, such as H4, H8 or H16. That is the maximum diffusible hydrogen in millilitres per 100 grams of deposited weld metal, so a lower number is better. An R after it indicates a moisture resistant coating. An electrode marked H4R is both the lowest hydrogen grade in common use and the most tolerant of exposure, which is why vacuum packed H4R electrodes are the usual choice for code work.
Storage and Re-drying
This is where most of the confusion sits, because holding and re-drying are two different operations at two very different temperatures, and treating one as the other defeats the point.
| Electrode | Storage | Re-drying |
|---|---|---|
| Cellulosic, E6010 and E6011 | Dry, room temperature, sealed | Do not bake these. They rely on moisture in the coating to produce the arc gas. Drying them ruins them. |
| Rutile, E6013 | Dry, room temperature, sealed | Not normally re-dried. If the coating has taken up damp, replace them. |
| Low hydrogen, E7016 and E7018 | Holding oven or heated quiver, typically 120 to 150 degrees C once opened | Re-bake at roughly 260 to 430 degrees C if moisture is suspected, usually for one to two hours, then transfer straight to a holding oven. |
| Vacuum packed low hydrogen | Usable straight from an unopened pack | Once the pack is open, into a quiver or holding oven. Follow the manufacturer’s exposure limit. |
Those temperatures are typical ranges and the manufacturer’s figures take priority. The point to take away is that 120 to 150 degrees C keeps a dry electrode dry. It does not dry a wet one. For the equipment side, see our guide to welding electrode ovens and quivers or browse the ovens and quivers range.
Checking an Electrode Before You Strike
- Chipped or cracked coating. The flux is doing a job. Where it is missing, the arc is unshielded and you get porosity. Discard them.
- Coating off centre. Hold one up and look down it. If the core wire is not central, the arc will pull to one side and the bead will follow.
- Rust on the core wire. Discard.
- Bent electrodes. Bending cracks the coating even when the damage is hard to see.
- Damp storage. Low hydrogen types can be re-baked. Everything else gets replaced.
It is also worth checking the rest of the circuit. A poor earth or a worn electrode holder causes arc problems that look exactly like a bad electrode, and both are cheap to put right. See electrode holders and earth clamps.
AWS and EN ISO Numbers
Most boxes sold in the UK carry both an American AWS classification and a European EN ISO one. They describe the same electrode using different conventions, and the AWS number is the one most welders quote.
| Material | AWS | EN ISO |
|---|---|---|
| Carbon steel | A5.1 | EN ISO 2560 |
| Low alloy and high strength steel | A5.5 | EN ISO 18275 |
| Stainless steel | A5.4 | EN ISO 3581 |
| Cast iron | A5.15 | EN ISO 1071 |
| Hardfacing | Varies by product | EN 14700 |
If you are welding to a procedure, the consumable has to match what the procedure specifies, and you need the documentation to show it. Buy from a supplier who can provide it.
Frequently Asked Questions
What is the difference between E6013 and E7018?
E6013 is a rutile electrode with light penetration, easy striking and a smooth bead, which suits general fabrication and thin material. E7018 is a low hydrogen iron powder electrode with higher tensile strength, better toughness and medium penetration, used on structural steel and thicker sections. E7018 also has to be kept dry to work properly, while E6013 is far less fussy.
Can I run E7018 on an AC welder?
Yes. The 8 as the last digit means low hydrogen iron powder running on AC or DC electrode positive. E7015, by contrast, is DC electrode positive only. Always check the last digit rather than assuming.
Do I need to bake new electrodes before using them?
Not if they are new, sealed and dry. Vacuum packed low hydrogen electrodes are ready to use from an unopened pack. Re-baking is for low hydrogen electrodes that have been exposed to air or damp storage. Never bake cellulosic electrodes such as E6010, because they need the moisture in their coating.
What electrode joins stainless steel to mild steel?
E309L is the standard choice for that dissimilar joint, and is also used for buffer layers before cladding. E312 is an alternative where the steel is unknown or difficult, because it is high ferrite and very crack resistant.
What size electrode do I need for 3 mm plate?
A 2.5 mm electrode at roughly 60 to 100 A is a sensible starting point, with 3.2 mm if you want to move faster and can control the heat. As a general rule, do not use an electrode thicker than the material you are welding.
Why does my E7018 keep sticking when I strike?
Low hydrogen electrodes are harder to strike than rutile types. Use a scratch start rather than a tap, keep a short arc once it is lit, and make sure the current is at the right end of the range. A machine with hot start makes a noticeable difference. Damp electrodes and a poor earth connection both make it worse.
Can you weld cast iron with a stick welder?
Yes, with a nickel electrode such as ENi-CI. The electrode matters less than the technique. Use low current, run short beads of about 25 to 50 mm, peen each bead while it is hot and let the casting cool between runs so heat does not build up.
What does the L mean in E308L and E316L?
Low carbon. Reducing the carbon content lowers the risk of chromium carbide forming at the grain boundaries when the weld cools, which would otherwise leave the joint vulnerable to intergranular corrosion. For most stainless fabrication the L grade is the safer choice.
Browse the full range of MMA stick electrodes and the rest of our MMA welding supplies. If you are not sure which classification your job calls for, send us the material, thickness and any procedure reference through the technical enquiry form.
