What is the positive electrode called?

What are electrodes and where are they used: types by materials

When creating metal structures or performing other types of repair or construction work, you cannot do without the use of welding. Connecting in this way is considered a rather complex process, requiring the use of special equipment and consumables - electrodes.

What is an electrode? A welding electrode is a rod with or without a coating, with the help of which a weld is formed and the edges of the elements are connected. For each welding method, it is necessary to select a separate type of consumable that corresponds to the required technological and quality parameters.

What's happened?

The design of the electrodes, despite the different areas of application, is the same. What are the electrodes made of? The main elements are as follows:

• rod - made of metallic or non-metallic materials;
• coating (some varieties may not have);
• contact tip.

The main part of the product is a rod that melts when heated at high temperatures by current and fills the weld pool with metal . The closer the composition of the rod is to the material of the elements being connected, the higher the quality of the created seam.

The coating is intended to create an inert gas environment around the electrode during the welding process, preventing foreign impurities from entering the bath. The correct selection of the type of electrode based on its coating is largely determined by the conditions of the welding process and the type of metal being joined.

The uncovered tip of the electrode is used to ignite an arc that melts the rod and the product space around it.

To create a seam and connect parts, the welder moves the electrode in a spiral - this is how a strong bond of substances is ensured . Thanks to this technology, the peak temperature effect is constantly shifting, elements that are not yet connected melt, the bath filled in other places gradually cools down, and a strong permanent connection is formed.

Manufacturing materials

To produce the core base of welding and surfacing electrodes, a special wire is used, the requirements for which are set out in GOST 2246-70 . The standard describes the chemical composition and grades of metal, main dimensions, special markings, storage and transportation.

Surfacing electrodes, as well as those used for welding, are made from cold-drawn steel wire with a cross-section of 0.3-12 mm.

Wire is available in three categories:

• carbon , used for welded joints of parts made of low-alloy and carbon steels;
• alloyed , used for elements made of structural, heat-resistant, low-alloy steel grades;
• high-alloy , designed for workpieces made of stainless steel, chromium-nickel and chromium alloys.

The classification of electrodes used for surfacing and welding processes is based on the following principles:

• appointment;
• technological specifics;
• thickness and type of coating;
• chemical composition of the coating and rod;
• mechanical characteristics of the seam;
• coating formation method.

The following requirements apply to the properties of consumables:

• guarantee of arc stability and a well-formed seam;
• formation of a weld with the required chemical composition;
• uniform joint melting of wire and coating;
• minimizing electrode metal spattering;
• maximum process efficiency;
• ease of slag removal;
• ensuring the required coating strength;
• possibility of long-term storage;
• minimal release of toxic substances during welding.

Less common but popular conductors include carbon electrodes for welding copper wires, for example, in an electric drill or in engines.

Coating materials

The classification of welding electrodes is based on the type of coatings, which differ in chemistry and properties. There are several types of coating:

1. Acidic , from oxides of silicon, iron or manganese. The use of products with such a coating provokes the appearance of cracks on heated parts. At the same time, the seam is reliably protected from the appearance of pores.
2. Rutile . Consists of titanium dioxide or concentrated rutile. During welding, virtually no spatter is generated; the metal completely goes into the seam being created.
3. Ilmenite . The properties of such coatings are in the middle between acidic and rutile.
4. Basic , formed from fluorine compounds or carbonates. Types of electrodes with such a coating add plasticity to the weld metal and increase its toughness during machining. They make it possible to create a crack-resistant seam, while the presence of oxidizing elements in the bath, which provoke a high susceptibility to corrosion of the connection line, is not allowed.
5. Cellulose , which contains about 50% organic substances. Hydrogen electrodes are made with such coating ; work with them is based on the phenomenon of electrolysis, the occurrence of redox reactions with changes in the pH level. A seam with increased density is formed, which allows the use of products for vertical welding.

Thickness

According to GOST 9466-75, electrodes are divided into types in accordance with the standard coating thickness . The classification is based on the calculation of the ratio of the total diameter of the product D to the cross-section of the rod d. In accordance with this parameter, electrodes are manufactured:

• thin , D/d >1.2 – designation M;
• medium size - from 1.2 to 1.45, marked with the letter C;
• thick – 1.45-1.8, designated by the letter D;
• especially thick , parameter ratio more than 1.8 (G).

Areas of application

The selection of electrodes for performing a particular job is made according to the following criteria:

• for inexperienced welders, rutile conductors should be chosen; for experienced workers, the type of coating does not matter much;
• type of electrode – consumable or non-consumable;
• type of structure, equipment or elements to be welded (for electric motors one type is needed, for surfacing excavator buckets another type is needed);
• steel grade;
• thickness of elements;
• type of current and its polarity;
• characteristics of the purchased electrodes.

For inexperienced users

For beginners in welding, it is preferable to use electrodes with a rutile layer. These products are easy to use compared to other types. The most popular brands include:

• ANO-4;
• MP-3 (also called “blue electrodes” due to the corresponding color);
• OK 46.00;
• UTP 65D.

Household use

Welding work carried out in everyday life is characterized by a low level of complexity. They require a normal or low quality seam, since the main goal is to connect the required elements that do not experience serious loads and are not subject to significant wear .

The most often performed in domestic conditions include assembly work to create small metal structures (greenhouses, fence posts), restoration welding of a car in garages or on construction sites.

For household manual arc welding, electrode brands:

• ANO . Suitable for all types of inverters used as welding power sources.
• SSSI . They allow you to create a high-strength seam, can be used for products of any complexity, but are distinguished by their “obstinate” character. To perform welding with electrodes of this brand, some experience is required.
• MP-3 . Products for universal use. Can be used to connect even damp, corroded surfaces that have not been subjected to pre-abrasive treatment.

Stainless steel

For joining stainless steel, it is preferable to use non-consumable tungsten electrodes. When using conductors for ferrous metals, the connection will not be characterized by the required strength and aesthetics of the seam.

The most commonly used brands are:

1. NZh-13;
2. OZL-8;
3. TsL-11;
4. TsT-15.

Cast iron

Cast iron is one of the most popular materials that has found its application in various branches of construction and industry.

To connect cast iron products the following are used:

• MNC-2.
• OZZHN-1.
• OZCH-2.
• TsCh-4.
• OK 92.18.

Pipes

When choosing electrodes for connecting pipes, the thickness of the elements is taken as the main parameter. The thicker the walls of the pipe, the greater the thickness of the conductor should be chosen.

The pipes are connected in one of four ways, on which the required brand of electrode also largely depends:

• overlap;
• in the corner;
• end-to-end;
• vtavr.

Welding of critical pipelines must be done with electrodes for connections of increased complexity. For domestic mains (plumbing, heating systems), there are no special requirements for the strength of seams.

The most popular types of consumables include:

• ZIO-20.
• TML-1U.
• UONI-13/55.
• TsU-5.

For inverters

Inverter welding is one of the common joining methods. The devices allow you to obtain welding current of direct or reverse polarity. In the latter case, heat is concentrated at the end of the conductor, while the product being welded acts as a positive anode, and a negative electrode as a cathode . Welding efficiency depends on the uniformity of potential distribution .

Almost all types of coated rods are suitable for work; beginners should use rutile electrodes.

Classification by purpose

The most important point in using an electrode of one brand or another is its compatibility with the material of the products to be welded or fused.

For each processing method, a specific type of conductor should be selected, used only for its intended purpose.

For example, if an electrode is produced for welding, it will definitely not be able to make surfacing. Just as a conductor produced for non-ferrous metals will not be able to connect ferrous metals.

According to their purpose, electrodes are divided into types, each of them has its own letter designation:

• U - conductors for working with parts made of carbon and low-alloy steel grades. They are distinguished by high tensile strength, the value of which reaches 600 MPa.
• M - for welding products made of alloy steels with a resistance of up to 600 MPa. This group also includes rods for fusing worn surfaces of rails, as well as stalinite electrodes.
• T - for connecting parts made of heat-resistant steel grades, often used in electrodynamics.
• B – for working with elements made of high-alloy steels with special characteristics.
• N – for welding surface layers of metal elements

The separation of electrodes is carried out in accordance with GOST standards, which provide their detailed descriptions and scope of application.

Source: https://svarka.guru/oborudovanie/rashodniki-i-kompletuyushie/chto-takoe-elektrody.html

Types of electrodes for manual arc welding

Manual arc welding is used to solve domestic and professional problems. Moreover, the result of its use depends not only on the skill of the welder, but also on the consumables. Currently, there are dozens of manufacturers that produce various brands of electrodes. Based on a number of characteristics, they can be divided into several types.

How the electrode works

The electrode is a metal core coated with a special compound called “coating”. During operation, the core melts and, together with the metal of the product, forms a seam. At the same time, the coating burns to form gas, which is necessary to protect the welding zone from the harmful effects of air (we are talking primarily about the negative impact of oxygen and nitrogen on the molten metal).

Manual arc welding

What problems does the electrode solve?

In general, electrodes solve several problems at once:

1. The substances that make up the coating are characterized by a low ionization potential. As a result, the electric arc, after ignition, is easily saturated with free ions, which support and stabilize the combustion process.
2. Coating the electrodes not only creates a gas cloud during combustion, but also contributes to the formation of a layer of slag on top of the weld. It performs a protective function and at the same time reduces the cooling rate of the molten metal. This creates favorable conditions for removing unwanted impurities or non-metallic inclusions from the seam.
3. An important condition for obtaining high-quality seams is the absence of oxygen in them. Therefore, the electrode coating contains special substances – deoxidizers. During the welding process, they enter into a chemical reaction with oxygen and “bind” it.
4. Another important function is alloying the weld metal with a number of elements in order to improve its properties. For this purpose, the electrode contains chromium, silicon, manganese, titanium, etc.

Purpose of electrodes The name “electrode” itself comes from two Greek words: elektra and hodos. They are translated as "electricity" and "road".

Types of electrode coatings

Electrode coatings can have different compositions. The stability of the arc, the viscosity of the slag and molten metal, the behavior of the metal during the transition to the weld pool and other parameters depend on them. There are several types of coatings.

Rutile

The main element of rutile coating is titanium dioxide. When using such electrodes, metal spattering is reduced, its fluidity increases and an abundant layer of slag is formed, which is then easily separated.

The seams are smooth, and re-ignition of the arc is noticeably easier. At the same time, electrodes are difficult to dry and there is a high risk of pore formation when using them. They are suitable for operation on direct and alternating current.

Using rutile electrodes, it is convenient to weld low-carbon steels of small thickness.

Pulp

The coating composition includes cellulose, as well as silicon and magnesium ferroalloys. The coating provides increased gas formation during arc combustion and reliable protection of the weld pool.

During operation, a small amount of quickly hardening slag is formed, which is convenient when welding vertical seams. At the same time, they have an unaesthetic appearance and low ductility.

In addition, the use of cellulose electrodes is accompanied by increased metal spattering. Their use is optimal for DC welding.

Basics

The main elements of electrode coatings of this type are calcium and magnesium carbonates: magnesite, dolomite or marble. They provide mechanical strength, high ductility and chemical purity of the weld metal. Welding work can be performed in any spatial position.

Electrodes with this type of coating can be used in the manufacture of critical structures. In this case, the seams are quite rough, the slag is difficult to remove, and the electric arc is unstable. Basic coated electrodes are more suitable for experienced welders.

In addition, they are highly hygroscopic and easily absorb moisture, so they need special attention during storage. Their use is optimal on direct current of reverse polarity.

Sour

The composition of the acid coating includes oxides of manganese and iron. These elements provide arc stability and easy slag separation, but the metal in the weld pool becomes too liquid. For this reason, acid-coated electrodes are only suitable for horizontal welds.

When using them, it is possible to maintain high operating speeds, but there is a risk of undercuts or cracks. In addition, electrodes cannot be dried at high temperatures, so they may contain moisture, which deteriorates the quality of the seams. Additionally, it should be noted that acid coating is considered the most hazardous to health.

Such electrodes can be used on direct and alternating current.

Electrodes with different coatings

Electrodes for different types of steels

To obtain high-quality welds, the chemical composition of the electrode core must be similar to the chemical composition of the metal being welded. On this basis, consumables intended for welding carbon, alloy, high-alloy, stainless and heat-resistant steels, as well as aluminum and cast iron are distinguished. For domestic needs, electrodes made of carbon and low-alloy steels are most often used.

Spatial position

There are five main spatial positions of the electrodes in which welding work can be carried out:

1. The lower horizontal one is considered the most convenient and productive. A special case of this is the boat position.
2. The T-type is similar to the lower horizontal, but requires more welding skill. In this case, the formation of undercuts on the vertical surface and sagging on the horizontal surface is possible.
3. The horizontal position of the electrode on a vertical surface is considered quite difficult. To use it in practice, a bevel is most often made on the upper edge of the elements being connected.
4. Vertical seams can be welded in two ways: up or down. In the first case, better quality of seams is ensured, and in the second - higher speed.
5. The ceiling spatial position is considered the most difficult. It is not suitable for connecting thin elements and is used only when it is impossible to carry out welding work in any other way.

Manufacturers must indicate in what spatial positions welding work can be carried out using electrodes.

Spatial positions of the electrode

Importance of slag

The slag formed during manual arc welding is divided into two types: “long” and “short”. In the first, the viscosity increases slowly with decreasing temperature.

For this reason, electrodes with coatings that form “long” slags are not suitable for welding in vertical and overhead spatial positions.

For “short” slags, the viscosity increases much faster, so they effectively prevent liquid metal from flowing out of the weld pool. This result is obtained by electrodes with basic or rutile coating.

Type and polarity of current

Welding work can be performed using alternating or direct current. The first option is less desirable. It leads to increased spattering of molten metal, and the seam itself is less accurate and of less quality. When using direct current, direct and reverse polarity can be used.

Straight polarity

The part is connected to the positive pole, and the electrode holder is connected to the negative pole. In this case, it is the part that is exposed to more heat. For this reason, straight polarity is used when welding metals that have a high melting point or significant thickness.

Reverse polarity

When using reverse polarity, the part is connected to the negative pole and the electrode to the positive pole. In this case, the electrode heats up more, and the work as a whole is performed in a gentle mode. Reverse polarity is optimal for welding thin sheet parts or stainless steel.

Electrode properties

The properties of electrodes mean their three components:

1. Physical properties of the coating. These include coefficients of volumetric and linear expansion, gas permeability, density, viscosity, heat capacity, solidification and melting temperatures.
2. Chemical properties of the coating. They mean the ability of the coating to alloy and deoxidize the molten metal.
3. Mechanical properties of weld metal. These include hardness, toughness, elongation, ductility, corrosion resistance and hardness.

In the catalog or passport for each brand of electrodes, manufacturers indicate their most important characteristics.

Calcination of electrodes

The coating of welding electrodes is capable of absorbing moisture from the air. In this case, the wet coating burns unevenly and does not melt well. As a result, welding work becomes difficult, and the resulting seams may have defects in the form of cracks or pores. To remove excess moisture from the electrodes, they are calcined at a certain temperature (this is indicated in the documents for the electrodes or on the packaging) in special ovens or in a regular household oven.

We talked about the main types of electrodes. This information will help you more accurately select the required brand for a specific type of work and obtain high-quality seams.

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Source: https://vistek-weld.ru/reviews-articles/vidy-elektrodov-dlya-ruchnoy-dugovoy-svarki/

How to determine the polarity of the electrodes?

Welding is a manual labor, but welders must have a sufficient amount of technical knowledge, even if physics was something supernatural for them at school.

One of the mandatory concepts that you need to know is “welding current” . The welder must have a good understanding of polarity and the impact it has on the welding process.

On welding machines and electrodes you can see the designations AC or DC, which describe the polarity of the current. Why do electric currents and polarities occur during welding? Let's look at these concepts carefully.

What is alternating (AC) and direct (DC) current?

AC from English “alternating current” means alternating current , and DC “direct current” means direct current .

AC alternates the direction of current, but DC flows in only one direction.

Welding machines and electrodes marked DC have a constant polarity, while those marked AC change polarity 120 times per second with a current frequency of 60 hertz.

How do alternating and direct current differ in welding?

Direct current (DC) welding creates smoother, more stable arcs and produces less spatter. It is easier to weld in the vertical and upper positions.

However, alternating current (AC) may be the preferred choice of new welders as it is often used in low-cost, entry-level welders. AC is also common in shipbuilding welding or any environment where the arc may float from side to side.

What is polarity?

The electrical circuit that occurs when the welding machine is turned on has a negative and a positive pole - this property is called polarity . Polarity is important in welding because choosing the correct polarity affects the strength and quality of the weld. Using the wrong polarity can result in a lot of spatter, poor fusion and loss of control of the welding arc.

When welding with alternating current, polarity is not required!

In turn, welding using direct current is of two types:

— welding with direct polarity

— welding with reverse polarity

Polarity
straight	reverse
negative	positive
(–)	(+)

The welding process will vary depending on the direction, polarity of the current: positive (+) or negative (–) .

Positive DC polarity (DC+) will provide high penetration rates, while negative DC polarity (DC–) will give less penetration but higher deposition rates (eg on thin sheet metal). Various shielding gases can further influence the welding process.

Welding with straight polarity current

Direct polarity welding is usually understood as welding, during which a positive charge the part (product) being from the welding machine, i.e. The welding cable connects the workpiece being welded to the (+) terminal of the welding machine. A negative charge is supplied to the electrode through an electrode holder connected by a cable to the (–) terminal.

When welding with direct polarity current, the main temperature load falls on the metal part being welded . That is, it heats up more, which allows the root of the weld to be deepened.

Direct polarity current is recommended to be used when it is necessary to cut metal structures and weld thick-walled parts, as well as in other cases when it is necessary to achieve a large heat release, which is precisely a characteristic feature of this type of connection.

Reverse polarity current welding

Reverse polarity welding is usually understood as welding, during which a negative charge is the part (product) being welded from the welding machine, i.e. The welding cable connects the workpiece being welded to the (–) terminal of the welding machine. A positive charge is supplied to the electrode through an electrode holder connected by a cable to the (+) terminal.

When welding with reverse polarity current, more heat is released at the electrode , and heating of the part comparatively reduced . This allows for more “delicate” welding and reduces the likelihood of burning through the part.

Welding with reverse polarity current is recommended for use when it is necessary to weld thin sheets of metal, stainless steel, alloy steel, and other steels and alloys that are sensitive to overheating.

Since alternating current (AC) is half positive and half negative, its welding properties are right in the middle of the positive and negative polarity of direct current (DC). Some welders choose alternating current (AC) if they want to avoid deep penetration. For example, during repair work on rusty metals.

Although alternating current itself has no polarity, if alternating current welding electrodes are used with direct current, they will show poorer results. Therefore, electrode manufacturers usually indicate the most appropriate polarity on the electrode coating and packaging.

Understanding the direction and polarity of welding current is important for proper welding. Knowing how these factors affect your weld will make your job easier.

Source: https://rem-serv.com/kak-opredelit-polyarnost-elektrodov/

The main types of welding electrode coatings that you definitely need to know

The coating of welding electrodes is a homogenized mass of mixed chemical compounds applied to a special metal rod.

the task of such substances is to ensure the required properties of the weld and promote correct, uninterrupted combustion of the arc during welding. Depending on the final goals, certain types of electrodes with certain properties are produced.

Their diversity and assortment are constantly updated on the market. Let's take a closer look at the most important varieties.

Cellulose electrodes

Such coatings are made from cellulose (up to 50%), which consists of organic materials, where wood flour is mainly used. The composition may also include ferroalloys, resins of organic origin, and talc. Cellulose electrodes are thin, form a small amount of easily removable slag and are most suitable for positional welding (when working with vertical seams, the slag does not slide down).

Good results are obtained with one-sided welding in any position, when welding the root of a seam on pipelines. In this case, the reverse seam bead is smooth and relatively neat. When heated, the electrodes dissociate into hydrogen and carbon dioxide, which in turn serve as shielding gases. Typically a constant current source is used. With the help of stabilizers for cellulose electrodes, alternating current can be used.

According to GOST, they correspond to the following types of electrodes: E 42, E 46 and E 50.

Flaws

The weld metal contains a relatively high amount of hydrogen, which reduces the ductility of the weld, and therefore cold cracks are likely. Characteristic splashes.

Rutile coated electrodes

As you know, rutile is a titanium mineral. For this type of electrode, the coating uses a titanium dioxide (TiO2) concentrate applied to steel rods. It produces an acidic slag and provides gas protection from hydrogen, nitrogen oxides and carbon. These electrodes are used for low-carbon steels in any spatial position.

In the GOST classification, mechanical properties are comparable to types E 42 and E 46. The addition of a small amount of cellulose to rutile electrodes provides an additional reserve for gas protection. Sometimes a small addition of cellulose to rutile will further improve performance, a combination called rutile-cellulose coating (RC).

In addition, there can be combinations with basic and acidic coatings (RB and RA respectively).

Peculiarities. Compared to acid-based electrodes, rutile “brothers” when welding produce metal that is more resistant to cracks, they produce less spatter and a stable, strong burning of the welding arc at alternating current. Relatively not susceptible to rust, oxidation, and moisture.

Rutile electrodes produce easily separated slag and perform well when welding vertical seams. Porosity is possible in rare cases when welding technology is violated, for example, if too thick electrodes are used for thin metal or there are gaps in T-joints.

They perform remarkably well in areas with short seams, where frequent breaks and repeated ignitions of the arc are necessary.

Weak sides

Rutile electrodes exposed to moisture can be used only after 24 hours (preliminary calcination will be required for about an hour at temperatures above two hundred degrees Celsius). It is undesirable to use them for welding structures exposed to high temperatures and creep.

Acid coated electrodes

This type of electrode coating contains metal oxides, including iron oxide, silicates and manganese oxides, which produce acidic slag. According to GOST, they correspond to types E 38 and E 42. Direct and alternating current can be used.

 Due to the high oxygen content, acidic electrodes increase the temperature, making the metal highly fluid. On the one hand, the listed features contribute to quick welding, but on the other hand, they can lead to the appearance of pores, low strength of the weld, and undercuts.

 To level this out, some deoxidizing agents are added to improve the mechanical properties and the ability of the slag to be easily removed.

Flaws

An extended arc, the presence of rust and oxides significantly increase the likelihood of hot cracks and pores in the weld. Acidic electrodes increase the hydrogen content in the weld pool. They are toxic and have increased splash formation.

Basic electrodes or low hydrogen electrodes

The base electrode variety contains calcium carbonate, magnesium carbonate, calcium fluoride and other minerals (such as fluorspar). These electrodes must be kept dry and properly warmed before use. Gas protection includes carbon dioxide with low levels of hydrogen and oxygen.

 Hydrogen control provides protection from atmospheric exposure, making the electrodes suitable for high- and low-alloy steels, for steels with low carbon content. When welding under the influence of high arc temperatures, dissociation of carbonates occurs, which ultimately contributes to an increased basicity of slags and the appearance of a protective gas environment with virtually no hydrogen evolution.

Additionally, calcium fluoride binds the hydrogen component. Because of these features, the variety received its second name - calcium fluoride electrodes. They are indispensable for structures with a rigid base, for hardening steels prone to cold cracks, and also form seams that are not prone to rapid aging.

Low-hydrogen electrodes are used in manual arc welding regardless of spatial position.
The seams can be of considerable thickness. Type in accordance with GOST 9467-75 on mechanics of deposition: compared with E42A - E50A.

Weak sides

Pores may appear if the metal being welded has rust or oxidation. The arc when burning is less stable than that of other types of electrodes. Mainly used with direct current. For alternating, you will need potash or special potassium-sodium compounds combined with heating of the electrodes (up to 400 °C).

Electrodes containing iron powder

Iron powder is added to all types of coatings to improve the efficiency of electrodes. Additional iron powder increases the deposition rate. This reduces the voltage, allowing the cellulose electrodes to handle alternating current. In addition, the additive controls the viscosity of the slag. This property is very useful in positional welding.

conclusions

Let us summarize briefly in tabular form.

The coating of welding electrodes differs in its parameters, properties, and scope of application. We examined the main types of coatings, identified the main advantages and disadvantages. We hope that the material will be as useful as possible for you, our dear readers.

Source: https://blog.svarcom.net/news/osnovnye-vidy-pokrytij-svarochnyh-elektrodov-kotorye-obyazatelno-nuzhno-znat.html

Cathode and anode in theory and practice

> Theory > Cathode and anode in theory and practice

The cathode is the electrode of the device that is connected to the negative pole of the current source. Anode is the opposite. This is the electrode of the device connected to the positive pole of the current source.

Redox process at electrodes

Note! To make it easier to remember the difference between them, use a cheat sheet. The words “cathode” - “minus”, “anode” - “plus” have the same number of letters.

Application in electrochemistry

In this branch of chemistry, a cathode is a negatively charged electrical conductor (electrode) that attracts positively charged ions (cations) during oxidation and reduction processes.

Electrolytic refining is the electrolysis of alloys and aqueous solutions. Most non-ferrous metals undergo this type of cleaning. Electrolytic refining produces metal with high purity. Thus, the purity of copper after refining reaches 99.99%.

An electrolytic process takes place on the positive electrical conductor during refining or purification. During this process, metal with impurities is placed in an electrolyzer and made into an anode.

Such processes are carried out using an external source of electrical energy and are called electrolysis reactions. They are carried out in electrolyzers.

It functions as an electric pump, pumping negatively charged particles (electrons) into the negative conductor and removing it from the anode. It doesn't matter where the current comes from.

At the cathode, the metal is cleaned of foreign impurities. A simple cathode is made of tungsten, sometimes tantalum. The advantage of a tungsten negative electrode is the durability of its manufacture. Disadvantages include low efficiency and cost-effectiveness.

Complex cathodes have different structures. Many of these types of conductors have a special layer applied to the bare metal on top, which enables greater performance at relatively low temperatures. They are very economical.

Their disadvantage is that their performance is not very stable.

The finished pure metal is also called a cathode. For example, a zinc or platinum cathode. In production, the negative conductor is separated from the cathode base using cathode stripping machines.

When negatively charged particles are removed from an electrical conductor, an anode is created on it, and when negatively charged particles are pumped onto an electrical conductor, a cathode is created. During electrolysis of the metal being purified, its positive ions attract negatively charged particles on the negative conductor, and a reduction process occurs. The most commonly used anodes are:

• zinc;
• cadmium;
• copper;
• nickel;
• tin;
• gold;
• silver;
• platinum.

Zinc anodes are most often used in production. They are:

• rolled;
• cast;
• spherical.

Rolled zinc anodes are most commonly used. Nickel and copper are also used. But cadmium is almost never used because of its toxicity to the environment. Bronze and tin anodes are used in the manufacture of electronic printed circuit boards.

Galvanization (galvanostegy) is the process of applying a thin layer of metal to another object in order to prevent corrosion of the product, oxidation of contacts in electronics, wear resistance, and decoration. The essence of the process is the same as during refining.

Zinc and tin are used to increase the corrosion resistance of the product. Galvanizing can be cold, hot, galvanic, gas-thermal and thermal diffusion. Gold is used mainly for protective and decorative purposes. Silver increases the resistance of electrical appliance contacts to oxidation.

Chrome – to increase wear resistance and protect against corrosion. Chrome plating gives products a beautiful and expensive look. Used for applying to handles, taps, rims, etc. The chrome plating process is toxic, therefore it is strictly regulated by the legislation of different countries.

The picture below shows the galvanization method using nickel.

Nickel plating of a kettle using galvanization

Application in vacuum electronic devices

Here the cathode acts as a source of free electrodes. They are formed during their knocking out of metal at high temperatures. The positively charged electrode attracts electrons released by the negative conductor. In different devices, it collects them to varying degrees. In electron tubes it completely attracts negatively charged particles, and in cathode ray devices - partially, forming an electron beam at the end of the process.

Marking

As a standard, the cathode is marked as “-”. The anode sign is “+”. But in galvanics, due to the fact that the negative charge on the conductor is supplied not by an external current source, but by the oxidation reaction of the metal, the cathode will receive a positive charge of the electrical conductor. Therefore, in batteries, when the current changes direction, the signs “+” and “-” change.

These properties of cathodes and anodes have found wide application in industry for metal cleaning and electroplating.

1n5819 diode: characteristics

Source: https://jelectro.ru/teoriya/katod-i-anod.html

Electrodes with basic coating: brands, designations, features of calcium fluoride coating

The main purpose of the electrode coating is to protect the welding arc and ensure the required quality of the seam. The coating does not allow the arc to come into contact with atmospheric gases (nitrogen, hydrogen and oxygen). It also protects the weld seam from the formation of pores or cracks.

Basic electrode coating - characteristics

Any electrode coating is a mixture of crushed components and a binder. The powder mixture is applied to a metal rod and serves to protect against various external factors.

The main coating is designated by the letter "B" . This mixture is produced from calcium and magnesium carbonates. These include elements such as marble, magnesite, dolomite. Fluorspar (CaF2) is also added to the listed minerals as a slag diluent. calcium fluoride coated electrodes .

Characteristics:

• The gas-protective environment that is formed during the welding process consists almost entirely of CO and CO2.
• The low hydrogen content allows the formation of strong seams without the risk of cracks .
• Low content of oxygen and various impurities (for example, sulfur and phosphorus) in the weld metal.
• In most cases, work should be carried out on direct current . The presence of plastic spar in the coating composition impairs the performance of alternating current electrodes. Therefore, most often a direct current of reverse polarity is needed.

Application

Basic coated electrodes are excellent for use in the following applications:

• welding of mild steels with high sulfur content;
• steels with a high content of sulfur, carbon, phosphorus;
• welding of hardening steels, in which cold cracks can form;
• when welding low-alloy and high-alloy steels, which are used under heavy loads and high temperatures;
• if you need to weld parts of large thickness;
• when welding rigid structures.

Advantages and disadvantages

When comparing the basic coating of electrodes with other types, both advantages and disadvantages of this type can be identified.

The benefits include:

1. High ductility and toughness.
2. Low content of gases and various impurities in the weld metal.
3. Resistant to hot cracking.
4. High resistance to hydrogen sulfide cracking.

   Ideal for welding pipelines carrying hydrogen sulfide compounds.

5. Reliably weld critical structures.
6. It is convenient to make seams of any spatial position .
7. Low oxidizing capacity.

   The process of deoxidation and alloying of metal is improved.

The disadvantages include:

1. Increased sensitivity to moisture. Electrodes with such a coating should be stored in a dry place.
2. The welding arc may burn unstable if alternating current is used.
3. Lengthening the arc during welding often leads to the appearance of pores in the weld.

4. If the coating is moistened, the hydrogen content in the deposited metal increases. This can also lead to the formation of pores.
5. It is necessary to calcinate the electrodes immediately before welding , since the optimal level of coating humidity should be 0.3%.
6. If there is rust on the surface of the structures being welded, this also often causes pores to appear in the seam.

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Kobelco LB-52U

They are produced at a subsidiary of the largest Japanese metallurgical concern Kobe Steel. Designed for welding critical structures made of steels with low carbon content. Widely used in cases where it is impossible to implement double-sided welding. Excellent for welding pipelines.

After welding with these electrodes, a minimal amount of residual slag remains. The seam is uniform, has high ductility, there are no cracks or gaps. Learn more about LB-52U.

IMPORTANT! The electrodes are highly sensitive to moisture. Before use, they must be calcined at temperatures up to 300°C. Otherwise, the electrode may burn poorly, and, accordingly, the quality of the seam will noticeably decrease.

OZL-8

Used when working with types of steel containing chromium and nickel. Provides a strong seam that is resistant to corrosion. Ideal for welding highly loaded components. When cooled, the seam retains its strength and does not crack. However, sudden cooling of the weld should not be allowed, as this promotes rapid crystallization and the formation of cracks.

Among the advantages of this brand:

• affordable price (compared to other electrodes of this class);
• ease of stitching.

SSSI 13/55

One of the best for welding critical structures. Best suited for working with carbon steel. Advantages:

• A special coating material, which when molten resembles resin, eliminates the possibility of the formation of slag ulcers . All slag is effectively removed from the seam.
• High strength seam , resistant to alternating loads.

FEATURES : The use of UUSI electrodes requires the welder to have some experience. Due to the nature of the coating, they are difficult to light. With a short break in work, the molten coating instantly “seizes” at the tip, so the electrode will have to be cleaned.

ESAB OK 61.30

Manufactured in Sweden (learn more about the manufacturer and its electrodes). Ideal for welding the following grades of stainless steel:

• 304L;
• 308L;
• 03X18H9;
• 06X18H11.

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Welding with electrodes with basic coating

When using electrodes with a basic coating for welding, several nuances need to be taken into account:

1. Do not extend the welding arc. In this case, the metal is saturated with nitrogen, which significantly reduces the strength of the weld. May cause cracks.
2. The working surface must be completely dry. Otherwise, pores may form in the seam.
3. Mandatory requirements for storing electrodes must be observed. Store only in a dry place at a temperature not lower than 15°C. Some manufacturers pack electrodes in vacuum packaging. This significantly extends their shelf life without the need for re-calcination.

Calcination of electrodes with basic coating

Calcination is carried out to achieve a minimum level of humidity of the electrodes. For products with a base coating, the critical moisture level is 0.3%. Depending on the specific brand of electrodes, the calcination mode may differ. As a rule, manufacturers indicate these requirements.

On average, the calcination requirements are as follows:

• temperature 300-350oC;
• exposure for 2 hours (but no more).

The products of South Korean enterprises are of high quality, which ensures their popularity among welders of various levels

Further "

Scope of applicationCharacteristicsTechnological features of weldingSpecial propertiesChemical composition (%) of deposited material

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DescriptionField of applicationCharacteristicsTechnological features of weldingChemical composition (%) of deposited metalSpecial

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DescriptionField of applicationCharacteristicsSpecial propertiesChemical composition (%) of deposited metalAnalogsDescriptionP48S –

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DescriptionField of applicationCharacteristicsSpecial propertiesChemical composition (%) of deposited metalAnaloguesDescriptionP48M –

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Field of applicationCharacteristicsSpecial propertiesChemical composition (%) of the deposited metalAnalogueField of applicationElectrodes P62MR

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DescriptionField of applicationCharacteristicsSpecial propertiesTechnological features of weldingChemical composition (%) of deposited material

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DescriptionField of applicationCharacteristicsTechnological features of weldingSpecial propertiesDescriptionGeKa LASER B47 electrodes with low

Next » Choose manufacturers and sellers of welding electrodes by clicking on the link below to the page of our catalog of companies.

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Source: https://WeldElec.com/pokrytie-elektrodov/osnovnoe/

Cathode and anode

Sometimes it is necessary to connect the electrodes of a device or element to a DC power source. They are connected, observing polarity. Cathode and anode are the names of the conductors (electrodes) of the device with which this connection is made. There is no clear definition of these two terms. They are distinguished depending on the chemical and physical processes in which these designations are used.

Concept of cathode and anode

In electrical engineering, the terminal connected to the positive terminal of the power supply (PS) is called the anode (A). The electrode connected to the minus terminal of the IP is the cathode (K). Translated from Greek, anode means “ascending, upward movement,” and cathode means “descending, downward movement.” These names can be found in such sections of physics and chemistry as:

• galvanic power supplies;
• electrolysis and electroplating;
• semiconductors and vacuum electronics.

In addition, these terms denote the terminals of elements on the circuits and the signs of their charge.

Designation in electrochemistry and non-ferrous metallurgy

What is a diode - operating principle and device

The concept of anodes in electrolytic processes applies to positively charged electrodes. Electrolysis, by which various chemical elements are isolated or purified, is the effect of electric current on an electrolyte. Electrolytes are solutions of salts or acids. The other electrode involved in this reaction is the cathode.

Attention! A reduction reaction occurs at the negatively charged cathode (K), and an oxidation process occurs at the anode (A). In this case, “A” can be partially destroyed, participating in the purification of metals from unwanted additives.

In the metallurgical industry, anodes are used when applying protective layers to a product using the electrochemical method (plating) or electro-refining. Electrical cleaning allows you to dissolve rough metal (with impurities) on “A” and deposit it on “K” in a purified form.

A number of commonly used anodes are made of metals:

• zinc;
• copper;
• nickel;
• cadmium;
• lead (an alloy of lead and antimony);
• silver;
• gold;
• platinum.

Nickel plating, galvanizing and other application of protective or aesthetically sought-after coatings on products are carried out mainly from base metals.

With the help of “A” from precious metals, the electrical conductivity of components of electrical products is increased and layers of precious metals are applied to jewelry.

For your information. The pure metal deposited on the cathode is also called the "cathode". For example, pure copper obtained in this way is called “copper cathode”. Then it is used to make copper foil, wire and other things.

Anode and cathode in vacuum electronic devices

Cathode - definition and practical application

An electron tube is the simplest vacuum device. It consists of the following parts:

These three elements make up a vacuum diode. It has a cylindrical “K”, inside of which there is a filament. It heats up “K” to increase thermionic emission.

In such devices, electrons leave “K” and travel to “A” in a vacuum, thereby creating an electric current. The anode is the electrode of the lamp with a positive potential. It is made in the form of a box surrounding the mesh and “K”.

It can be made of molybdenum, tantalum, graphite, nickel. Its design is different, sometimes it has fins for heat removal.

The grid is an element located in the middle that controls the flow of particles. Most often it is made in the form of a spiral wrapping around the cathode.

Important! The larger the surface area of ​​the cathode, and the hotter it is, the more current flows through the lamp.

“A” and “K” for a vacuum diode

Anode and cathode in semiconductor devices

How to test a zener diode with a multimeter

Semiconductor elements conduct electricity in a specific direction. If we consider a semiconductor diode, then its electrodes are also called “cathode” and “anode”.

When a direct voltage is applied to it: a positive charge to the anode, the diode is open. If a positive potential comes to the cathode, the diode is closed. Such a diode has a pn junction between these two regions and is picky about the applied polarity.

The output of an element from the p-region is called “A”, from the n-region - “K”.

Anode and cathode sign

Which sign is indicated by “K”, which “A”, depends on what procedure and in what area is being considered. In electrochemistry, there are two devices that have different symbols: an electrolyzer and a galvanic cell.

During electrolysis (redox chemical interaction under the influence of an external IP), the minus “-” denotes the cathode. It is on it that metals are reduced due to an excess of electrons. The plus “+”, in turn, marks the anode (positive electrode), where metals are oxidized due to a lack of negatively charged particles.

Signs of charges during electrolysis

In a galvanic cell, oxidation occurs without external influence of electricity. If we take a copper-zinc battery as an example, a large number of electrons (minus) accumulate at the anode. When moving along the external chain, they participate in the reduction of copper. This means that in this case the positive electrode will be the cathode.

Attention! In galvanic cells, the plus is the cathode, the minus is the anode. In electrolyzers, it’s the other way around—the anode is considered a plus, and the cathode is considered a minus.

Charge signs for a galvanic battery

For semiconductor devices, both the sign and the term are clearly assigned to the pins of the part. The anode is the “plus”, the cathode is the “minus” of the diode.

Why is there confusion?

Everything happens because there is no clear connection between minus and plus to the components called “K” and “A”. Michael Faraday also came up with a simple polarity marking rule for this pair of electrodes.

What is an anode, according to his explanation? When memorizing the definition, the scientist suggested drawing an analogy with the Sun. Where the current enters (rising) is the anode, where the current leaves (sunset) is the cathode.

For batteries, the polarity at the anode and cathode changes depending on whether it operates as a galvanic cell (when discharging) or as an electrolyser (when charging).

DC welding also ambiguously determines “A” and “K” when igniting the arc with direct or reverse polarity.

Signs “A” and “K” for DC welding

How to determine anode and cathode

What a cathode and anode are is clarified in particular moments: when determining the terminals of semiconductor elements or when identifying electrodes in electrochemical processes.

A semiconductor diode requires positional placement in electrical circuits. For correct connection it is necessary to identify the pins. This can be done according to the following criteria:

• markings applied to the element body;
• length of part leads;
• tester readings when taking measurements in ohmmeter mode or checking diodes;
• using a current source with known polarity.

Marking of semiconductors of this type can be done by applying a graphic designation of a diode to the housing. Then minus (K) is the output from the side of the vertical line into which the arrow outline rests. The diode leg from which the arrow comes out is the plus (A). This is how the forward direction of the current is graphically indicated - from “A” to “K”.

Another way to designate the anode of a diode element can be one or two colored dots or a pair of narrow rings applied to the body. There are structurally designed diodes in which the negative (cathode) terminal is marked with a wide silver ring. The 2A546A-5 (DM) diode serves as such an example.

Examples of marking diodes

The length of the LED legs, which have never been soldered into boards, can also indicate the polarity of the leads. For LED diodes, the long leg is the positive electrode, and the short leg is the negative terminal. In addition, the shape of the body (the edge of the circle) can serve as a guide.

Polarity of LED diode terminals

When using a multimeter to determine the polarity of the contact terminals of a semiconductor, connect it in diode testing mode. If numbers appear on the display, it means the diode is connected in the forward direction. In this case, the red probe is connected to the anode “+”, the black one is connected to the cathode “-”.

If you don’t have a tester at hand, you can determine the names of the diode terminals by assembling a series circuit from a battery, a light bulb and a diode. When switched on directly, the light bulb will light up, which means that the batteries are plus on the anode and similarly minus on the other electrode.

Information. The LED electrodes can be identified using a constant voltage supply with a known polarity and a current-limiting resistor connected in series. The glow of the element will indicate direct switching. For this purpose, you can take a 3 volt RG2032 battery and a 1 kOhm resistor.

Turning on an LED via a limiting resistor

As for semiconductors, there is always a strict correspondence of names. In other cases, correct determination of the ongoing electrochemical reactions will help to clearly navigate the identification of electrodes.

Source: https://amperof.ru/teoriya/katod-i-anod.html

What are anode and cathode?

Often the problem arises of determining which electrode is the cathode and which is the anode. First you need to understand the terms.

The concept of cathode and anode - a simple explanation

In complex substances, electrons are distributed unequally between atoms in compounds. As a result of interaction, particles move from an atom of one substance to an atom of another. The reaction is called redox. The loss of electrons is called oxidation, the element that loses electrons is called a reducing agent.

The addition of electrons is called reduction; the receiving element in this process is the oxidizing agent. The transfer of electrons from a reducing agent to an oxidizing agent can occur through an external circuit, and then it can be used as a source of electrical energy. Devices in which the energy of a chemical reaction is converted into electrical energy are called galvanic cells.

The simplest classical example of a galvanic cell is two plates made of different metals and immersed in an electrolyte solution. In such a system, oxidation occurs on one metal and reduction occurs on another.

IMPORTANT! The electrode at which oxidation occurs is called the anode. The electrode on which reduction occurs is the cathode.

From school chemistry textbooks there is an example of a copper-zinc galvanic cell that operates using the energy of the reaction between zinc and copper sulfate.

In the Jacobi-Daniel device, a copper plate is placed in a copper sulfate solution (copper electrode), and a zinc plate is immersed in a zinc sulfate solution (zinc electrode).

The zinc electrode releases cations into the solution, creating an excess positive charge in it, while at the copper electrode the solution is depleted in cations, here the solution is negatively charged.

Closing the external circuit causes electrons to flow from the zinc electrode to the copper electrode. Equilibrium relations at the phase boundaries are interrupted. An oxidation-reduction reaction is taking place.

The energy of a spontaneously occurring chemical reaction is converted into electrical energy.

If a chemical reaction is provoked by the external energy of an electric current, a process called electrolysis occurs. The processes occurring during electrolysis are the opposite of the processes occurring during the operation of a galvanic cell.

ATTENTION! The electrode where reduction occurs is also called the cathode, but in electrolysis it is negatively charged, while the anode is positively charged.

Application in electronics

Today, semiconductor types of diodes are used.

In electronics, the property of diodes to pass current in the forward direction and not in the reverse direction is widely used.

The operation of the LED is based on the property of semiconductor crystals to glow when current is passed through the pn junction in the forward direction.

Galvanic DC sources - batteries

Chemical sources of electric current in which reversible reactions occur are called batteries: they are recharged and used repeatedly.

When a lead-acid battery operates, an oxidation-reduction reaction occurs. Lead metal oxidizes and gives up its electrons, reducing the lead dioxide that accepts the electrons. The lead metal in a battery is the anode and is negatively charged. Lead dioxide is the cathode and is positively charged.

As the battery discharges, the substances of the cathode and anode and their electrolyte, sulfuric acid, are consumed. To charge the battery, it is connected to a current source (plus to plus, minus to minus). The direction of the current is now the opposite of what it was when the battery was discharged.

Electrochemical processes on the electrodes are “reversed”. Now the lead electrode becomes the cathode, undergoing a reduction process, and lead dioxide becomes the anode, with the oxidation procedure taking place. The battery recreates the substances necessary for its operation.

Why is there confusion?

The problem arises because a certain charge sign cannot be firmly attached to the anode or cathode. Often the cathode is a positively charged electrode and the anode is a negatively charged one. Often, but not always. It all depends on the process occurring at the electrode.

ATTENTION! A part that is placed in an electrolyte can be both an anode and a cathode. It all depends on the purpose of the process: you need to apply another layer of metal to it or remove it.

ACϟDC. Understanding Welding Current and Polarity

Welding is a manual labor, but welders must have a sufficient amount of technical knowledge, even if physics was something supernatural for them at school.

One of the mandatory concepts that you need to know is “welding current” . The welder must have a good understanding of polarity and the impact it has on the welding process.

On welding machines and electrodes you can see the designations AC or DC, which describe the polarity of the current. Why do electric currents and polarities occur during welding? Let's look at these concepts carefully.