Guide to Welding Electrodes
An electrode is a metal wire that is coated. It is made out of materials with a similar composition to the metal being welded. There are a variety of factors that go into choosing the right electrode for each project.
SMAW or stick electrodes are consumable, meaning they become part of the weld, while TIG electrodes are non-consumable as they do not melt and become part of the weld, requiring the use of a welding rod.The MIG welding electrode is a continuously fed wire referred to as wire.
Electrode selection is critical to ease of cleanup, weld strength, bead quality and for minimizing any spatter. Electrodes need to be stored in a moisture free environment and carefully removed from any package (follow the directions to avoid damage).
Covered Welding Electrodes
When molten metal is exposed to air, it absorbs oxygen and nitrogen, and becomes brittle or is otherwise adversely affected.
slag cover is needed to protect molten or solidifying weld metal from
the atmosphere. This cover can be obtained from the electrode coating.
composition of the welding electrode coating determines its usability,
as well as the composition of the deposited weld metal and the electrode
The formulation of Welding electrode
coatings is based on well-established principles of metallurgy,
chemistry, and physics. The coating protects the metal from damage,
stabilizes the arc, and improves the weld in other ways, which include:
- Smooth weld metal surface with even edges.
- Minimum spatter adjacent to the weld.
- A stable welding arc.
- Penetration control.
- A strong, tough coating.
- Easier slag removal.
- Improved deposition rate.
metal-arc electrodes may be grouped and classified as bare or thinly
coated electrodes, and shielded arc or heavy coated electrodes. The
covered electrode is the most popular type of filler metal used in arc
welding. The composition of the electrode covering determines the
usability of the electrode, the composition of the deposited weld metal,
and the specification of the electrode. The type of electrode used
depends on the specific properties required in the weld deposited. These
include corrosion resistance, ductility, high tensile strength, the
type of base metal to be welded, the position of the weld (flat,
horizontal, vertical, or overhead); and the type of current and polarity
Popular Welding Electrode (E6010) used for general purpose fabrication, construction, pipe welding, and shipbuilding
The American Welding Society’s classification number series for welding electrodes has been
adopted by the welding industry. The electrode identification system for
steel arc welding is set up as follows:
- E indicates electrode for arc welding.
- The first two (or three) digits indicate tensile strength (the
resistance of the material to forces trying to pull it apart) in
thousands of pounds per square inch of the deposited metal.
- The third (or fourth) digit indicates the position of the weld. 0
indicates the classification is not used; 1 is for all positions; 2 is
for flat and horizontal positions only; 3 is for flat position only.
- The fourth (or fifth) digit indicates the type of electrode
coating and the type of power supply used; alternating or direct
current, straight or reverse polarity.
- The types of coating, welding current, and polarity position
designated by the fourth (or fifth) identifying digit of the electrode
classification are as listed in table 5-4.
- 6) The number E6010 indicates an arc welding electrode
with a minimum stress relieved tensile strength of 60,000 psi; is used
in all positions; and reverse polarity direct current is required.
Coating, Current and Polarity Types Designated By the Fourth Digit in the Electrode Classification Number
|ac, dcrp, dcsp
|ac, dcsp, dcrp
|Iron Powder Titania
|ac, dcsp, dcrp
|Low hydrogen sodium
|Low hydrogen potassium
|Iron powder iron oxide
|Iron powder low hydrogen
|ac, dcrp, dcsp
When the fourth (or last) digit is 0, the type of coating and current to be used are determined by the third digit.
The welding electrode identification system for stainless steel arc welding is set up as follows:
- E indicates electrode for arc welding.
- The first three digits indicated the American Iron and Steel type of stainless steel.
- The last two digits indicate the current and position used.
- The number E-308-16 by this system indicates stainless steel
Institute type 308; used in all positions; with alternating or reverse
polarity direct current.
Classification System for Submerged Arc Electrodes
The system for identifying solid bare carbon steel for submerged arc is as follows:
- The prefix letter E is used to indicate an electrode. This is
followed by a letter which indicates the level of manganese, i.e., L for
low, M for medium, and H for high manganese. This is followed by a
number which is the average amount of carbon in points or hundredths of a
percent. The composition of some of these wires is almost identical
with some of the wires in the gas metal arc welding specification.
- The electrode wires used for submerged arc welding are given in
American Welding Society specification, "Bare Mild Steel Electrodes and
Fluxes for Submerged Arc Welding." This specification provides both the
wire composition and the weld deposit chemistry based on the flux used.
The specification does give composition of the electrode wires. This
information is given in table 8-1.
When these electrodes are used with specific submerged arc fluxes and
welded with proper procedures, the deposited weld metal will meet
mechanical properties required by the specification.
- In the case of the filler reds used for oxyfuel gas welding, the
prefix letter is R, followed by a G indicating that the rod is used
expressly for gas welding. These letters are followed by two digits
which will be 45, 60, or 65. These designate the approximate tensile
strength in 1000 psi (6895 kPa).
- In the case of nonferrous filler metals, the prefix E, R, or RB
is used, followed by the chemical symbol of the principal metals in the
wire. The initials for one or two elements will follow. If there is more
than one alloy containing the same elements, a suffix letter or number
may be added.
- The American Welding Society's specifications are most widely
used for specifying bare welding rod and electrode wires. There are also
military specifications such as the MIL-E or -R types and federal
specifications, normally the QQ-R type and AMS specifications. The
particular specification involved should be used for specifying filler
The most important aspect of solid welding electrode wires and rods in
their composition, which is given by the specification. The
specifications provide the limits of composition for the different wires
and mechanical property requirements.
Occasionally, on copper-plated solid wires, the copper may flake
off in the feed roll mechanism and create problems. It may plug liners,
or contact tips. A light copper coating is desirable. The electrode wire
surface should be reasonably free of dirt and drawing compounds. This
can be checked by using a white cleaning tissue and pulling a length of
wire through it. Too much dirt will clog the liners, reduce current
pickup in the tip, and may create erratic welding operation.
Temper or strength of the wire can be checked in a testing
machine. Wire of a higher strength will feed through guns and cables
better. The minimum tensile strength recommended by the specification is
140,000 psi (965,300 kPa).
The continuous electrode wire is available in many different
packages. They range from extremely small spools that are used on spool
guns, through medium-size spools for fine-wire gas metal arc welding.
Coils of electrode wire are available which can be placed on reels that
are a part of the welding equipment. There are also extremely large
reels weighing many hundreds of pounds. The electrode wire is also
available in drums or payoff packs where the wire is laid in the round
container and pulled from the container by an automatic wire feeder.
The coatings of welding electrodes
for welding mild and low alloy steels may have from 6 to 12 ingredients,
- cellulose to provide a gaseous shield with a reducing
agent in which the gas shield surrounding the arc is produced by the
disintegration of cellulose
- metal carbonates to adjust the basicity of
the slag and to provide a reducing atmosphere
- titanium dioxide to help
form a highly fluid, but quick-freezing slag and to provide ionization
for the arc
- ferromanganese and ferrosilicon to help deoxidize the
molten weld metal and to supplement the manganese content and silicon
content of the deposited weld metal
- clays and gums to provide
elasticity for extruding the plastic coating material and to help
provide strength to the coating
- calcium fluoride to provide shielding
gas to protect the arc, adjust the basicity of the slag, and provide
fluidity and solubility of the metal oxides
- mineral silicates to
provide slag and give strength to the electrode covering
metals including nickel, molybdenum, and chromium to provide alloy
content to the deposited weld metal
- iron or manganese oxide to adjust
the fluidity and properties of the slag and to help stabilize the arc
- iron powder to increase the productivity by providing extra metal to
be deposited in the weld.
The principal types of welding electrode coatings for mild steel and are described below.
- Cellulose-sodium (EXX10): Electrodes of this type cellulosic material
in the form of wood flour or reprocessed low alloy electrodes have up to
30 percent paper. The gas shield contains carbon dioxide and hydrogen,
which are reducing agents. These gases tend to produce a digging arc
that provides deep penetration. The weld deposit is somewhat rough, and
the spatter is at a higher level than other electrodes. It does provide
extremely good mechanical properties, particularly after aging. This is
one of the earliest types of electrodes developed, and is widely used
for cross country pipe lines using the downhill welding technique. It is
normally used with direct current with the electrode positive (reverse
- Cellulose-potassium (EXX11): This electrode is
very similar to the cellulose-sodium electrode, except more potassium is
used than sodium. This provides ionization of the arc and makes the
electrode suitable for welding with alternating current. The arc action,
the penetration, and the weld results are very similar. In both E6010
and E6011 electrodes, small amounts of iron powder may be added. This
assists in arc stabilization and will slightly increase the deposition
- Rutile-sodium (EXX12): When rutile or titanium dioxide
content is relatively high with respect to the other components, the
electrode will be especially appealing to the welder. Electrodes with
this coating have a quiet arc, an easily controlled slag, and a low
level of spatter. The weld deposit will have a smooth surface and the
penetration will be less than with the cellulose electrode. The weld
metal properties will be slightly lower than the cellulosic types. This
type of electrode provides a fairly high rate of deposition. It has a
relatively low arc voltage, and can be used with alternating current or
with direct current with electrode negative (straight polarity).
- Rutile-potassium (EXX13): This electrode coating is very similar to the
rutile-sodium type, except that potassium is used to provide for arc
ionization. This makes it more suitable for welding with alternating
current. It can also be used with direct current with either polarity.
It produces a very quiet, smooth running arc.
powder (EXXX4): This coating is very similar to the rutile coatings
mentioned above, except that iron powder is added. If iron content is 25
to 40 percent, the electrode is EXX14. If iron content is 50 percent or
more, the electrode is EXX24. With the lower percentage of iron powder,
the electrode can be used in all positions. With the higher percentage
of iron paler, it can only be used in the flat position or for making
horizontal fillet welds. In both cases, the deposition rate is
increased, based on the amount of iron powder in the coating.
- Low hydrogen-sodium (EXXX5): Coatings that contain a high proportion of
calcium carbonate or calcium fluoride are called low hydrogen, lime
ferritic, or basic type electrodes. In this class of coating, cellulose,
clays, asbestos, and other minerals that contain combined water are not
used. This is to ensure the lowest possible hydrogen content in the arc
atmosphere. These electrode coatings are baked at a higher temperature.
The low hydrogen electrode family has superior weld metal properties.
They provide the highest ductility of any of the deposits. These
electrodes have a medium arc with medium or moderate penetration. They
have a medium speed of deposition, but require special welding
techniques for best results. Low hydrogen electrodes must be stored
under controlled conditions. This type is normally used with direct
current with electrode positive (reverse polarity).
hydrogen-potassium (EXXX6): This type of coating is similar to the low
hydrogen-sodium, except for the substitution of potassium for sodium to
provide arc ionization. This electrode is used with alternating current
and can be used with direct current, electrode positive (reverse
polarity). The arc action is smother, but the penetration of the two
electrodes is similar.
- Low hydrogen-potassium (EXXX6): The
coatings in this class of electrodes are similar to the low-hydrogen
type mentioned above. However, iron powder is added to the electrode,
and if the content is higher than 35 to 40 percent, the electrode is
classified as an EXX18.
- Low hydrogen-iron powder (EXX28):
This electrode is similar to the EXX18, but has 50 percent or more iron
powder in the coating. It is usable only when welding in the flat
position or for making horizontal fillet welds. The deposition rate is
higher than EXX18. Low hydrogen coatings are used for all of the
higher-alloy electrodes. By additions of specific metals in the
coatings, these electrodes become the alloy types where suffix letters
are used to indicate weld metal compositions. Electrodes for welding
stainless steel are also the low-hydrogen type.
oxide-sodium (EXX20): Coatings with high iron oxide content produce a
weld deposit with a large amount of slag. This can be difficult to
control. This coating type produces high-speed deposition, and provides
medium penetration with low spatter level. The resulting weld has a very
smooth finish. The electrode is usable only with flat position welding
and for making horizontal fillet welds. The electrode can be used with
alternating current or direct current with either polarity.
- Iron-oxide-iron power (EXX27): This type of electrode is very similar
to the iron oxide-sodium type, except it contains 50 percent or more
iron power. The increased amount of iron power greatly increases the
deposition rate. It may be used with alternating direct current of
There are many types of coatings other than
those mentioned here, most of which are usually combinations of these
types but for special applications such as hard surfacing, cast iron
welding, and for nonferrous metals.
Figure 5-32: Electrode Drying Oven
Electrodes must be kept dry. Moisture destroys the desirable
characteristics of the coating and may cause excessive spattering and
lead to porosity and cracks in the the formation of the welded area. Electrodes exposed
to damp air for more than two or three hours should be dried by heating
in a suitable oven (fig 5-32)
for two hours at 500°F (260°C).
After they have dried, they should be
stored in a moisture proof container. Bending the electrode can cause
the coating to break loose from the core wire. Electrodes should not be
used if the core wire is exposed.
Electrodes that have an "R" suffix in the AWS classification have a higher resistance to moisture.
The Types of Electrodes
Bare welding electrodes are made of wire compositions required
for specific applications. These electrodes have no coatings other than
those required in wire drawing. These wire drawing coatings have some
slight stabilizing effect on the arc but are otherwise of no
consequence. Bare electrodes are used for welding manganese steel and
other purposes where a coated electrode is not required or is
undesirable. A diagram of the transfer of metal across the arc of a bare
electrode is shown in figure 5-29.
Molten metal transfer with a bare electrode.
Light Coated Electrodes
Light coated welding electrodes have a definite composition. A light coating
has been applied on the surface by washing, dipping, brushing, spraying,
tumbling, or wiping. The coatings improve the characteristics of the
arc stream. They are listed under the E45 series in the electrode
The coating generally serves the functions described below:
- It dissolves or reduces impurities such as oxides, sulfur, and phosphorus.
- It changes the surface tension of the molten metal so that the globules
of metal leaving the end of the electrode are smaller and more
frequent. This helps make flow of molten metal more uniform.
- It increases the arc stability by introducing materials readily ionized
(i.e., changed into small particles with an electric charge) into the
- Some of the light coatings may produce a slag.
The slag is quite thin and does not act in the same manner as the
shielded arc electrode type slag.
Light Coated Electrode
Figure 5-30: Arc Action Obtained With a Light Coated Electrode
Shielded Arc or Heavy Coated Electrodes
Shielded arc or heavy coated welding electrodes have a
definite composition on which a coating has been applied by dipping or
extrusion. The electrodes are manufactured in three general types: those
with cellulose coatings; those with mineral coatings; and those whose
coatings are combinations of mineral and cellulose. The cellulose
coatings are composed of soluble cotton or other forms of cellulose with
small amounts of potassium, sodium, or titanium, and in some cases
added minerals. The mineral coatings consist of sodium silicate,
metallic oxides clay, and other inorganic substances or combinations
thereof. Cellulose coated electrodes protect the molten metal with a
gaseous zone around the arc as well as the weld zone. The mineral coated
electrode forms a slag deposit. The shielded arc or heavy coated
electrodes are used for welding steels, cast iron, and hard surfacing. See figure 5-31 below.
Shielded Arc Electrode
Figure 5-31: Arc Action Obtained With A Shielded Arc Electrode
Functions of Shielded Arc or Heavy Coated Electrodes
These welding electrodes produce a reducing gas shield around the arc. This
prevents atmospheric oxygen or nitrogen from contaminating the weld
metal. The oxygen readily combines with the molten metal, removing
alloying elements and causing porosity. Nitrogen causes brittleness, low
ductility, and in Some cases low strength and poor resistance to
They reduce impurities such as oxides, sulfur, and phosphorus so that these impurities will not impair the weld deposit.
They provide substances to the arc which increase its stability. This
eliminates wide fluctuations in the voltage so that the arc can be
maintained without excessive spattering.
By reducing the
attractive force between the molten metal and the end of the electrodes,
or by reducing the surface tension of the molten metal, the vaporized
and melted coating causes the molten metal at the end of the electrode
to break up into fine, small particles.
The coatings contain
silicates which will form a slag over the molten weld and base metal.
Since the slag solidifies at a relatively slow rate, it holds the heat
and allows the underlying metal to cool and solidify slowly. This slow
solidification of the metal eliminates the entrapment of gases within
the weld and permits solid impurities to float to the surface. Slow
cooling also has an annealing effect on the weld deposit.
The physical characteristics of the weld deposit are modified by
incorporating alloying materials in the electrode coating. The fluxing
action of the slag will also produce weld metal of better quality and
permit welding at higher speeds.
Nonconsumable welding electrodes for gas tungsten-arc (TIG)
welding are of three types: pure tungsten, tungsten containing 1 or 2
percent thorium, and tungsten containing 0.3 to 0.5 percent zirconium.
Tungsten electrodes can be identified as to type by painted end marks as follows.
- Green -- pure tungsten.
- Yellow -- 1 percent thorium.
- Red -- 2 percent thorium.
- Brown -- 0.3 to 0.5 percent zirconium.
Pure tungsten (99. 5 percent tungsten) electrodes are generally
used on less critical welding operations than the tungstens which are
alloyed. This type of electrode has a relatively low current-carrying
capacity and a low resistance to contamination.
Thoriated tungsten electrodes (1 or 2 percent thorium) are
superior to pure tungsten electrodes because of their higher electron
output, better arc-starting and arc stability, high current-carrying
capacity, longer life, and greater resistance to contamination.
Tungsten welding electrodes containing 0.3 to 0.5 percent zirconium
generally fall between pure tungsten electrodes and thoriated tungsten
electrodes in terms of performance. There is, however, some indication
of better performance in certain types of welding using ac power.
Finer arc control can be obtained if the tungsten alloyed electrode is ground to a point (see figure 5-33).
When electrodes are not grounded, they must be operated at maximum
current density to obtain reasonable arc stability. Tungsten electrode
points are difficult to maintain if standard direct current equipment is
used as a power source and touch-starting of the arc is standard
practice. Maintenance of electrode shape and the reduction of tungsten
inclusions in the weld can best be accomplished by superimposing a
high-frequency current on the regular welding current. Tungsten
electrodes alloyed with thorium and zirconium retain their shape longer
when touch-starting is used.
Tungsten Electrode Taper
Figure 5-33: Correct Electrode Taper in Tungsten Electrode
The welding electrode extension beyond the gas cup is
determined by the type of joint being welded. For example, an extension
beyond the gas cup of 1/8 in. (3.2 mm) might be used for butt joints in
light gage material, while an extension of approximately 1/4 to 1/2 in.
(6.4 to 12.7 mm) might be necessary on some fillet welds. The tungsten
electrode of torch should be inclined slightly and the filler metal
added carefully to avoid contact with the tungsten. This will prevent
contamination of the electrode. If contamination does occur, the
electrode must be removed, reground, and replaced in the torch.
Direct Current Arc Welding Electrodes
The manufacturer’s recommendations should be
followed when a specific type of welding electrode is being used. In general,
direct current shielded arc electrodes are designed either for reverse
polarity (electrode positive) or for straight polarity (electrode
negative), or both. Many, but not all, of the direct current electrodes
can be used with alternating current. Direct current is preferred for
many types of covered, nonferrous, bare and alloy steel electrodes.
Recommendations from the manufacturer also include the type of base
metal for which given electrodes are suited, corrections for poor
fit-ups, and other specific conditions.
In most cases, straight polarity electrodes will provide less
penetration than reverse polarity electrodes, and for this reason will
permit greater welding speed. Good penetration can be obtained from
either type with proper welding conditions and arc manipulation.
Alternating Current Arc Welding Electrodes
Coated electrodes which can be used with either direct or
alternating current are available. Alternating current is more desirable
while welding in restricted areas or when using the high currents
required for thick sections because it reduces arc blow. Arc blow causes
blowholes, slag inclusions, and lack of fusion in the weld.
Alternating current is used in atomic hydrogen welding and in
those carbon arc processes that require the use of two carbon
electrodes. It permits a uniform rate of welding and electrode
consumption. In carbon-arc processes where one carbon electrode is used,
direct current straight polarity is recommended, because the electrode
will be consumed at a lower rate.
Electrode Defects and Their Effects
If certain elements or oxides are present in
electrode coatings, the arc stability will be affected. In bare
electrodes, the composition and uniformity of the wire is an important
factor in the control of arc stability. Thin or heavy coatings on the
electrodes will riot completely remove the effects of defective wire.
Aluminum or aluminum oxide (even when present in 0.01 percent),
silicon, silicon dioxide, and iron sulphate unstable. Iron oxide,
manganese oxide, calcium oxide, and stabilize the arc.
When phosphorus or sulfur are present in the electrode in excess
of 0.04 percent, they will impair the weld metal because they are
transferred from the electrode to the molten metal with very little
loss. Phosphorus causes grain growth, brittleness, and "cold shortness"
(i. e., brittle when below red heat) in the weld. These defects increase
in magnitude as the carbon content of the steel increases. Sulfur acts
as a slag, breaks up the soundness of the weld metal, and causes "hot
shortness" (i. e., brittle when above red heat). Sulfur is particularly
harmful to bare, low-carbon steel electrodes with a low manganese
content. Manganese promotes the formation of sound welds.
If the heat treatment, given the wire core of an electrode, is
not uniform, the electrode will produce welds inferior to those produced
with an electrode of the same composition that has been properly heat
The different types of electrodes have different deposition rates due to
the composition of the coating. The electrodes containing iron power in
the coating have the highest deposition rates. In the United States,
the percentage of iron power in a coating is in the 10 to 50 percent
range. This is based on the amount of iron power in the coating versus
the coating weight. This is shown in the formula:
These percentages are related to the requirements of the American
Welding Society (AWS) specifications. The European method of specifying
iron power is based on the weight of deposited weld metal versus the
weight of the bare core wire consumed. This is shown as follows:
Thus, if the weight of the deposit were double the weight of the core
wire, it would indicate a 200 percent deposition efficiency, even though
the amount of the iron power in the coating represented only half of
the total deposit. The 30 percent iron power formula used in the United
States would produce a 100 to 110 percent deposition efficiency using
the European formula. The 50 percent iron power electrode figured on
United States standards would produce an efficiency of approximately 150
percent using the European formula.
There are two types of nonconsumable
- The carbon electrode is a non-filler metal electrode used
in arc welding or cutting, consisting of a carbon graphite rod which may
or may not be coated with copper or other coatings.
- The tungsten electrode is defined as a
non-filler metal electrode used in arc welding or cutting, made
principally of tungsten.
Welding Society does not provide specification for carbon welding electrodes but
there is a military specification, no. MIL-E-17777C, entitled,
"Electrodes Cutting and Welding Carbon-Graphite Uncoated and Copper
This specification provides a classification system based on
three grades: plain, uncoated, and copper coated. It provides diameter
information, length information, and requirements for size tolerances,
quality assurance, sampling, and various tests. Applications include
carbon arc welding, twin carbon arc welding, carbon cutting, and air
carbon arc cutting and gouging.
Stick welding electrodes vary by:
- size: common
sizes are 1⁄16, 5⁄64, 3⁄32 (most common), 1⁄8, 3⁄16, 7⁄32, 1⁄4, and 5⁄16
inch. Core wire used with electrodes needs to be narrower than the
materials that are welded.
- material: stick welding electrodes come in cast iron, high carbon steel, mild steel, iron-free (nonferrous) and special alloys.)
referred to as tensile strength. Each weld needs to be stronger than
the metal being welded. This means that the materials in the electrode
need to be stronger as well.
- welding position (horizontal, flat etc): different electrodes are used for each welding position.
- iron powder mix
(up to 60% in flux): iron powder in the flux increases the amount of
molten metal available for the weld (heat turns powder into steel).
- soft arc designation: for thinner metals or for metals that don't have a perfect fit or gap.
SMAW Welding Electrode Diagram
As described above there are many kinds of electrodes. Heretare the most popular stick welding (SMAW) electrodes:
- E6013 and E6012: For thin metals and joints that do not easily fit together.
- E6011: Good for working on surfaces that are oily, rusted or has dirt. Versatile in that it works with DC or AC polarity. Creates little slag, another big plus. Note that this electrode should not be placed into an electrode oven.
- E6010: Similar to the E6011 but only works with direct current (DC). Note that this electrode should not be placed into an electrode oven.
- E76018 and E7016: Manufactured with iron powder in the flux. Creates strong welds, but has a puddle that might present some control issues for beginners.
For Additional Reading
Storing and Redrying Electrodes
Page Author: Jeff Grill