Introduction
Explanation of what alloy steel is
Alloy steel is a type of iron-carbon alloy that contains alloying elements other than iron and carbon.
By adding one or more appropriate alloying elements to common carbon steel and adopting appropriate processing techniques, it is possible to obtain special properties such as high strength, toughness, wear resistance, corrosion resistance, low temperature resistance, high temperature resistance and non- -magnetism, depending on the added elements and processing methods.
Explanation of how alloy steel is made
Alloy steel is formed by adding alloying elements to steel materials. During this process, the basic elements of steel, namely iron and carbon, will interact with the newly added alloying elements.
Under such interactions, the structure and substance of the steel will undergo certain changes, and the overall performance and quality of the steel will also be improved.
Therefore, the production of alloy steels is increasing and their range of applications is becoming more and more extensive.
Overview of different types of steel alloys and their corrosion resistance
Corrosion-resistant alloys have the ability to resist corrosion from the environment, but cannot be used in environments containing fluorine.
Among them, corrosion-resistant metal materials mainly include three types: iron-based alloys (i.e. stainless steel), nickel-based corrosion-resistant alloys and reactive metals:
1. Corrosion-resistant stainless steel mainly refers to the 300 series of stainless steel, such as 304, which is resistant to atmospheric or seawater corrosion, and the most commonly used corrosion-resistant alloy – Hastelloy C-276, 316L, 317L, etc. ; austenitic stainless steel with higher corrosion resistance, such as 904L, 254SMO; duplex steel 2205, 2507, etc.; Corrosion resistant alloy 20 containing Cu, etc.
2. Nickel-based corrosion-resistant alloys mainly include Hastelloy alloys and Ni-Cu alloys.
Due to the face-centered cubic structure of nickel itself, its crystallographic stability allows it to accommodate more alloying elements, such as Cr and Mo, than Fe, thus achieving the ability to withstand various environments.
At the same time, nickel itself has a certain corrosion resistance, especially resistance to stress corrosion cracking caused by chloride ions.
By strongly reducing corrosive environments, complex mixed acidic environments and solutions containing halide ions, the nickel-based corrosion-resistant alloys represented by Hastelloy have absolute advantages over iron-based stainless steels.
3. Reactive metals, which have excellent corrosion resistance, are normally represented by Ti, Zr and Ta. Titanium is the most typical representative, and titanium materials have wide applications, especially in corrosive environments that stainless steel cannot adapt to.
The corrosion resistance principle of titanium material is to form a dense oxide film in an oxidizing atmosphere to provide protection.
Therefore, it generally cannot be used in highly reducing or highly sealing corrosive environments.
At the same time, the application temperature of titanium material is generally below 300 degrees Celsius. It is important to note that reactive metals cannot be used in environments containing fluorine.
Advantages of Using Alloy Steel for Corrosion Resistance
The advantages of using corrosion-resistant alloys are as follows:
1. Alloys are not as sensitive to temperature as rubber and resin coatings and are less likely to be damaged under abnormal operating conditions.
2. All-alloy devices generally do not require emergency cooling systems.
3. Cleaning and descaling alloy components is much easier than coating, without worrying about damaging the coating.
4. Inspection and repair of alloy surfaces are also much easier and only qualified welders are required for repair work.
5. Although there are certain requirements for the construction method and environment of alloy components, they are much less stringent than those for rubber and resin coatings.
6. The performance changes of alloy products are generally smaller than those of rubber and resin, which have a shelf life. Furthermore, the inspection of alloy materials is relatively simple.
Factors Affecting Corrosion Resistance
Comparison with other materials used for corrosion resistance
Corrosion Resistance : The ability of a metallic material to resist the corrosive destruction of the surrounding medium is called corrosion resistance. It is determined by the composition, chemical properties and structural morphology of the material. Chromium, nickel, aluminum and titanium can be added to steel to form a protective film, while copper can change the electrode potential, and titanium and niobium can improve intergranular corrosion, which can improve corrosion resistance.
Introduction
Metallic materials are widely used in many areas due to their versatility and accessibility, but their susceptibility to corrosion also affects their performance, limiting the use of metallic materials.
To solve this, the use of metal can be reduced or direct contact with reactive media can be avoided as much as possible when using metallic materials.
Furthermore, electrochemical corrosion protection can be carried out using the polarizing effect of yin and yang to improve the protection of metallic materials. This is of great practical importance to extend the service life of metal materials, reduce application costs and improve application efficiency.
1. Corrosion of metallic materials and their dangers
1.1 Corrosion of Metallic Materials
Corrosion of metallic materials refers to a phenomenon in which metallic materials are damaged by chemical or electrochemical reactions when they come into contact with the surrounding environment.
In nature, most metals exist in various compound forms, and the chemical activity of metallic elements is generally higher than that of their compounds.
Therefore, these metals spontaneously evolve into their natural states of existence, making metallic corrosion a spontaneous and universal phenomenon that is inevitable.
According to the corrosion mechanism of metal material, corrosion can usually be divided into chemical corrosion and electrochemical corrosion.
Chemical corrosion refers to the corrosion phenomenon that occurs when metallic materials come into contact with non-electrolytes in the surrounding medium and undergo chemical oxidation-reduction reactions.
It is the corrosion that occurs when metallic materials are in organic solutions (aromatic hydrocarbons, crude oil, etc.).
Electrochemical corrosion mainly refers to the corrosion phenomenon that occurs when metal materials come into contact with electrolytes, and the metal surface chemically reacts with the electrolyte solution to form hydrogen absorption corrosion or hydrogen evolution corrosion. For example, carbon steel reacts with oxygen, carbon dioxide, and water in the air to form rust.
1.2 Corrosion risks
Corrosion weakens the strength and mechanical properties of metallic materials, shortening their useful life and even making metallic materials ineffective, causing economic losses. According to reports, China's economic losses caused by corrosion in 2014 have already exceeded RMB 200 billion.
On a global scale, the economic losses caused by corrosion are beyond imagination. Losses caused by corrosion also include the energy consumed during metal smelting and recycling.
At the same time, corrosion can also cause pollution of land and water resources. Corrosion can also cause damage to industrial equipment, bridge constructions and ships, resulting in economic losses or even posing a threat to personal safety. Many accidents are caused directly or indirectly by corrosion.
Therefore, research on anticorrosion of metallic materials is of great importance.
2. Factors affecting corrosion
2.1 Intrinsic reasons for the metal
Metal corrosion has a close relationship with the metal itself, such as the forces generated on the surface of metallic materials and internal characteristics, all of which have a direct relationship with metal corrosion. Metals with regular, structurally intact external shapes generally exhibit better corrosion resistance than metals with surface defects.
When internal forces are concentrated, the accelerated rate of metal corrosion can threaten the quality of the metal and cause greater damage to the metal surface.
2.2 External metal conditions
The main external causes of accelerated metal corrosion include:
(1) Operational media. The most significant factor affecting steel materials in operating media is the pH value, which is an important index for distinguishing electrolyte solutions. Therefore, the impact of pH value on the degree of corrosion is complex.
(2) Temperature changes. In general, the higher the temperature, the faster the rate of metal corrosion.
(3) Pressure differences. In general, increasing pressure increases the solubility of the gas in the solution, causing the area of corrosion on the metal to expand until it gradually spreads over the entire surface of the metal.
3. Preventing metal corrosion
3.1 Protecting the Metal Surface
There are two treatment methods, namely phosphating and chlorination.
Metal phosphating:
After removing oil and rust from steel products, they are immersed in a solution consisting of metal and carbonate ion. After treatment with a solution containing phosphates of Zn, Mn, Cr, Fe, etc., an insoluble film of phosphate salt forms on the surface of the metal, which forms a water-insoluble component.
This process is called phosphate treatment. The color of the phosphate film changes from dark gray to black gray and is five to twenty microns thick with strong resistance to anti-corrosion erosion.
The structure of phosphate film has many pores, easily adsorbs paint, and if used at the bottom of the paint layer, it can increase its anti-corrosion resistance.
Metal chlorination: Steel products are treated with a mixture of sodium chloride and sodium nitrite solution after hot treatment, and a blue iron oxide film is formed on the surface, called “blue”. This hydrogen film is flexible and lubricating and does not affect the precision of the parts.
Precision equipment such as spring steel and fine iron wire, as well as optical equipment components, can be used for blue treatment.
Another anti-corrosion method is non-metallic coating: the plastic-coated metal surface is better than that of paint, the plastic covering layer is delicate and smooth, the color is very bright, and has the function of corroding erosion and decoration. Ceramics containing SiO2 such as glass ceramics with high SiO2 content, have good anti-corrosion erosion effects.
3.2 Heavy-duty anti-corrosion coating technology
The coating process of heavy-duty anti-corrosion coatings is very elegant and simple and is still used in many places. According to the development of coating technology, the anti-corrosion coating of the steel bridge surface is the key to the anti-corrosion of steel bridges.
In this regard, both foreign brand coatings and domestic old brand coatings have similar anti-corrosion coating processes and types, which are composed of many coating systems including primer, intermediate coating and topcoat.
The types of coatings are epoxy rich zinc primer, epoxy mica iron oxide intermediate coating, epoxy polyurethane topcoat and epoxy color and chlorinated rubber topcoat, etc.
In the passive corrosion resistance effect of the coating system, the factory first primer has a passive corrosion resistance effect, but the sterilization effect is not ideal.
Under the cathodic protection of anti-corrosion primer, if zinc powder and zinc-rich primer are added, it will help in the cathodic protection of steel.
3.3 Hot spray anti-corrosion technology
There are two types of spray coatings, flame spray and arc spray. Flame spray: its heat source is combustible gas, its method is to melt metal wire and powder, then atomize and spray on the surface of the object.
O2 and C2H2 flame spray was the initial anti-corrosion spray of European and American steel bridges and achieved significant anti-corrosion effects.
Arc spray: using an arc spray device, heating, melting, atomizing and spraying two charged metal wires to produce anti-corrosion coatings, as well as long-lasting anti-corrosion composite coatings with organic sealing, is the anti-corrosion principle of arc spray.
3.4 Ionic Implantation Technology
Ion implantation technology was developed in the 1970s and is a surface modification technology, different from common coating technologies such as electroplating, lithium electrodeposition and chemical vapor deposition.
It is a new technique that uses high-speed and high-energy impacts to change the surface characteristics, and high-energy ions are quickly implanted on the surface of the substrate in a vacuum state, which can dense the surface structure, implant the surface of the substrate with high saturated solid solutions, metastable phases and non-crystalline and balanced alloys, thus improving the anti-corrosion and erosion resistance of the substrate surface.
For example, ion implantation of metals is used to improve the surface chemical properties and increase the anti-corrosion erosion function of the metal surface. Surface modification of aluminum and zinc alloys was already a hot spot of research when ion implantation technology was developed.
In recent years, ion implantation technology has been gradually applied to magnesium alloys to improve their anticorrosiveness.
3.5 Hot-dip galvanizing anti-corrosion technology
Hot-dip galvanizing is an anti-corrosion technology used to coat metals such as zinc, tin, lead and other low-melting point metals.
Metallic coatings are produced by immersing metal in a bath of molten metal. This technology is widely used for the production of thin steel sheets and food storage containers, as well as for chemical corrosion resistance and coating of electrical cables.
Hot-dip galvanizing of aluminum is mainly used for high-temperature oxidation protection of steel components.
As the demand for anti-corrosion coatings and cost control in the manufacturing process increases, hot-dip galvanizing technology is gradually evolving towards the development of metal alloy coating technology.
3.6 Electrochemical corrosion protection technology
Based on the related theory in electrochemistry, the “electrochemical protection method” is used in metal devices and becomes the cathode of the corrosion cell, thereby preventing or reducing metal corrosion and erosion.
The first method is the “sacrificial anode protection method”, which uses a metal or alloy with a lower electrode potential than the protected metal as the anode, fixed to the protected metal to form a “corrosion electrode”, thus protecting the metal as the anode. cathode. Zinc, aluminum and alloys are commonly used as sacrificial anodes.
This method is mainly used to protect various metallic devices located at sea, such as ship hulls, and to increase the corrosion resistance of devices such as oil tanks and pipelines.
The second method is to apply external current, using the protected metal and another additional electrode as the two poles of the battery, so that the metal is protected as the cathode under the action of the external direct current.
This method is mainly used to prevent corrosion and erosion of metal devices by soil, sea water and river water.
Conclusion
In conclusion, metal materials have important application value, and the corrosion protection of metal materials is also an important research topic for technology workers.
Recently, with the in-depth research of metal materials corrosion work, metal materials anti-corrosion technology and process have achieved certain results.
However, some new materials with strong corrosion resistance are restricted in their promotion and use due to cost reasons, and some anti-corrosion process methods also face problems such as environmental damage, high process cost and complicated operating conditions.
Therefore, further research on corrosion protection measures for metallic materials still has important research value and practical significance.
Comparing Alloy Steel to Other Materials
Comparison with other materials used for corrosion resistance
Corrosion resistance of non-ferrous metals and their alloys
| Metal material usage selection table | ||||||||||||||
| Fluid | material | |||||||||||||
| Carbon steel | cast iron | 302/304 | 316 | bronze | Monel | Hastelloy B | Hastelloy C. | stainless steel | titanium | Cobalt-chrome | 416 | 440°C | 17-4PH | |
| stainless steel | stainless steel | 20# | Liga6# | stainless steel | stainless steel | |||||||||
| acetaldehyde | A | A | A | A | A | A | Me me | A | A | Me me | Me me | A | A | A |
| Acetic acid, gas | W | W | B | B | B | B | A | A | A | A | A | W | W | B |
| Acetic acid, vaporization | W | W | A | A | A | A | A | A | A | A | A | W | W | B |
| Acetic acid, steam | W | W | A | A | B | B | Me me | A | B | A | A | W | W | B |
| acetone | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| acetylene | A | A | A | A | Me me | A | A | A | A | Me me | A | A | A | A |
| alcohol | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| lead sulfate | W | W | A | A | B | B | A | A | A | A | Me me | W | W | Me me |
| ammonia | A | A | A | A | W | A | A | A | A | A | A | A | A | Me me |
| ammonium chloride | W | W | B | B | B | B | A | A | A | A | B | W | W | Me me |
| Ammonium nitrate | A | W | A | A | W | W | A | A | A | A | A | W | B | Me me |
| Ammonium phosphate (monobasic) | W | W | A | A | B | B | A | A | B | A | A | B | B | Me me |
| ammonium sulfate | W | W | B | A | B | A | A | A | A | A | A | W | W | Me me |
| ammonium sulfite | W | W | A | A | W | W | Me me | A | A | A | A | B | B | Me me |
| aniline | W | W | A | A | W | B | A | A | A | A | A | W | W | Me me |
| benzene | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Benzoic acid | W | W | A | A | A | A | Me me | A | A | A | Me me | A | A | A |
| Boric acid | W | W | A | A | A | A | A | A | A | A | A | B | B | Me me |
| butane | A | A | A | A | A | A | A | A | A | Me me | A | A | A | A |
| calcium chloride | B | B | W | B | W | A | A | A | A | A | Me me | W | W | Me me |
| calcium hypochlorite | W | W | B | B | B | B | W | A | A | A | Me me | W | W | Me me |
| carbolic acid | B | B | A | A | A | A | A | A | A | A | A | Me me | Me me | Me me |
| carbolic acid | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Carbon dioxide (dry) | W | W | A | A | B | A | A | A | A | A | A | A | A | A |
| Carbon dioxide (wet) | A | A | A | A | W | B | A | A | A | A | A | B | B | Me me |
| carbon dioxide | B | B | B | B | A | A | B | A | A | A | Me me | W | A | Me me |
| carbon tetrachloride | W | W | B | B | B | A | A | A | A | Me me | Me me | A | A | A |
| Carbonic acid H2C03 | A | A | B | B | B | A | A | A | A | W | B | W | W | W |
| Chlorine, dry | W | W | W | W | W | W | W | B | W | A | B | W | W | W |
| Chlorine, damp | W | W | W | W | B | W | W | A | B | W | B | W | W | W |
| Chlorine, liquid | W | W | W | B | W | A | W | A | W | A | B | W | W | W |
| Chromic acid H2Cr04 | A | A | A | A | B | B | A | A | A | A | A | A | A | A |
| Coke oven gas | W | W | B | B | B | W | Me me | A | A | A | Me me | A | A | A |
| copper sulfate | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| ethane | B | B | A | A | A | A | A | A | A | A | A | A | A | A |
| ether | W | W | A | A | A | A | A | A | A | A | A | B | B | Me me |
| Chloroethane | A | A | A | A | A | A | Me me | A | A | A | A | A | A | A |
| ethylene | A | A | A | A | A | A | Me me | Me me | A | Me me | A | A | A | A |
| glycol | W | W | W | W | W | W | W | B | W | A | B | W | W | Me me |
| ferric chloride | B | B | A | A | A | A | A | A | A | A | A | A | A | A |
| HCHO Methyl Ketone | Me me | W | B | B | A | A | A | A | A | W | B | W | W | B |
| Formaldehyde HCO2H | B | B | B | A | A | A | A | A | A | A | A | Me me | Me me | Me me |
| Freon, wet | B | B | A | A | A | A | A | A | A | A | A | Me me | Me me | Me me |
| Freon, dry | A | A | A | A | A | A | A | A | A | A | A | B | B | Me me |
| Refined gasoline | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Hydrochloric acid, vaporization | W | W | W | W | W | W | A | B | W | W | B | W | W | W |
| Hydrochloric Acid, Free | W | W | W | W | W | W | A | B | W | W | B | W | W | W |
| Hydrofluoric acid, vaporization | B | W | W | B | W | W | A | A | B | W | B | W | W | W |
| Hydrofluoric Acid, Free | A | W | W | B | W | A | A | A | B | W | Me me | B | B | Me me |
| hydrogen | A | A | A | A | A | A | B | A | A | A | A | A | A | A |
| hydrogen peroxide | Me me | A | A | A | W | B | A | B | A | A | Me me | B | B | Me me |
| Hydrogen sulfide, liquid | W | W | A | A | W | W | A | A | B | A | A | W | W | Me me |
| magnesium hydroxide | A | A | A | A | B | A | A | A | A | A | A | A | A | Me me |
| Methyl ethyl ketone | A | A | A | A | A | A | A | A | A | Me me | A | A | A | A |
| natural gas | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| nitric acid | W | W | A | B | W | W | W | B | A | A | W | W | W | B |
| oxalate | W | W | B | B | B | B | A | A | A | B | B | B | B | Me me |
| oxygen | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| methanol | A | A | A | A | A | A | A | A | A | A | A | A | B | A |
| Lubricating oil, refined | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Phosphoric Acid, Vaporization | W | W | A | A | W | W | A | A | A | B | A | W | W | Me me |
| Phosphoric Acid, Free | W | W | A | A | W | B | A | A | A | B | A | W | W | Me me |
| Phosphoric acid vapor | W | W | B | B | W | W | A | Me me | A | B | W | W | Me me | |
| Picric Acid | W | W | A | A | W | W | A | A | A | Me me | Me me | B | B | Me me |
| calcium chlorite | B | B | A | A | B | B | A | A | A | A | Me me | W | W | Me me |
| Potassium hydroxide | B | B | A | A | B | B | A | A | A | A | Me me | B | B | Me me |
| propane | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Rosine, rosin | B | B | A | A | A | A | A | A | A | Me me | A | A | A | A |
| Sodium acetate, sodium carbonate, sodium chloride | A | A | B | A | A | A | A | A | A | A | A | A | A | A |
| Sodium Chromate | A | A | A | A | A | A | A | A | A | A | A | B | B | A |
| sodium hydroxide | W | W | B | B | A | A | A | A | A | A | A | B | B | B |
| Sodium hypochlorite | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Sodium thiosulfate | A | A | A | A | W | A | A | A | A | A | A | B | B | A |
| tin dichloride | W | W | W | W | B.C | B.C | W | A | B | A | Me me | W | W | Me me |
| hard acid | W | W | A | A | W | W | A | A | A | A | Me me | B | B | Me me |
| Sulfate solution | B | B | W | A | W | B | A | A | A | A | Me me | W | W | Me me |
| sulfur | A | W | A | A | B | B | A | A | A | A | B | B | B | Me me |
| dry oxygen disulfide | A | A | A | A | W | A | A | A | A | A | A | Me me | Me me | Me me |
| Dry sulfur dioxide | A | A | A | A | W | A | A | A | A | A | A | A | A | A |
| Sulfuric acid, vaporization | A | A | A | A | A | A | B | A | A | A | A | B | B | Me me |
| Sulfuric acid, free | A | A | A | A | A | A | B | A | A | A | A | B | B | Me me |
| Sulfite | W | W | W | W | W | W | A | A | A | B | B | W | W | W |
| Tar | W | W | W | W | B | B | A | A | A | B | B | W | W | W |
| Sulfite | W | W | B | B | B | W | A | A | A | A | B | W | W | Me me |
| Tar | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Trifluoroethylene | B | B | B | A | A | A | A | A | A | A | A | B | B | Me me |
| turpentine | B | B | A | A | A | B | A | A | A | A | A | A | A | A |
| Vinegar | W | W | A | A | B | A | A | A | A | Me me | A | W | W | A |
| Water, boiler water supply | B | W | A | A | W | A | A | A | A | A | A | B | A | A |
| Water, distilled water | A | A | A | A | A | A | A | A | A | A | A | B | B | Me me |
| sea water | B | B | B | B | A | A | A | A | A | A | A | W | W | A |
| zinc chloride | W | W | W | W | W | W | A | A | A | A | B | W | W | Me me |
| zinc sulfate | W | W | A | A | B | A | A | A | A | A | A | B | B | Me me |
| Symbol: | A – Capable of or currently being successfully applied | |||||||||||||
| B – Pay attention to the registration process | ||||||||||||||
| C – Cannot be applied | ||||||||||||||
| IL – Lack of information | ||||||||||||||
| This table is used to describe how to select the appropriate material when reacting with a fluid. The recommendations in the table are not absolute, as the corrosivity of materials is related to factors such as fluid concentration, temperature, pressure and impurities. Therefore, it should be noted that this table serves as a guide only. | ||||||||||||||
| Monel | ||||||||||||||
| Hastelloy “B”、（“C”） | ||||||||||||||
| Stainless Steel #20-Durimet20 | ||||||||||||||
| Cobalt Chrome Alloy #6-Alloy6 (Co Cr) | ||||||||||||||
Corrosion resistance of non-ferrous metals and alloys
In industry, steel is known as black metal, while all other metals are called non-ferrous metals. Non-ferrous metals and their alloys are often used in the manufacture of water treatment equipment, chemical containers and related equipment components because of their good corrosion resistance and low temperature performance.
Copper and its alloys
Copper and its alloys have high conductivity, thermal conductivity, plasticity and cold workability, as well as good corrosion resistance in many media.
1. Pure Copper
Also known as red copper. Copper is relatively stable in general atmospheric conditions, industrial atmospheric conditions, marine atmospheric conditions, and is also stable in weak to medium strength non-oxidizing alkalis and acids.
If the solution contains oxygen or oxidants, corrosion will be more severe. Copper is not resistant to corrosion by sulfides (such as H2S).
Copper has high conductivity, thermal conductivity, plasticity and good processing properties, as well as good cold workability. However, copper has low strength, low moldability, and low corrosion resistance in some media and is rarely used as a structural material.
2. Copper alloys
Common copper alloys are brass and bronze.
1) Brass
An alloy of copper and zinc is called brass. To improve its performance, tin, aluminum, silicon, nickel, manganese, lead, iron and other elements are often added, forming a special brass alloy.
Characteristics: Mechanical properties are closely related to zinc content; moldability is good; corrosion resistance is good; Brass with zinc content greater than 20% can cause stress corrosion cracking in humid atmospheres, sea water, high temperature and high pressure water, steam and all environments containing ammonia after cold working.
Brass is susceptible to dezincification corrosion in neutral solutions, seawater and acid pickling solutions after annealing, which can be prevented by adding 0.02% arsenic to the brass.
2) Bronze
All copper alloys in which the main added element is not zinc, but tin, aluminum, silicon and other elements, are commonly called bronze. Common bronzes include tin bronze, aluminum bronze, and silicon bronze.
Characteristics: Tin bronze has worse castability than brass and better corrosion resistance than pure copper and brass, but poor resistance to acid corrosion.
Aluminum bronze has better mechanical properties than brass and tin bronze and greater resistance to corrosion in atmospheres, sea water, carbonic acid and most organic acids than brass and tin bronze.
Silicon bronze has higher mechanical properties than tin bronze and a lower price, and has good moldability and cold and hot pressure processing properties.
Aluminum and its alloys
1. Aluminum
Characteristics: Aluminum has a low density, with a specific gravity of 2.7, about a third of that of copper; It has good conductivity, thermal conductivity, plasticity and cold workability, but low strength, which can be improved by cold deformation; can withstand various pressure processing.
Aluminum is an element with a highly negative electrode potential and is also stable in strong oxidizing media and oxidizing acids (such as nitric acid).
Halogen ions have a destructive effect on aluminum oxide film, so aluminum is not resistant to corrosion in hydrofluoric acid, hydrochloric acid, seawater and other solutions containing halogen ions.
Applications: Widely used in manufacturing reactors, heat exchangers, chillers, pumps, valves, tank cars, pipe fittings, etc.
2. Aluminum alloys
Pure aluminum has low resistance, but some elements such as copper, magnesium, zinc, manganese, silicon, etc. are added to aluminum
Titanium and its alloys:
1. Pure Titanium:
Characteristics: Pure titanium is a reactive element. It has good passivation properties, with a stable passivating film that demonstrates good corrosion resistance in many environments. It is known as the “king of seawater corrosion resistance”.
At high temperatures, titanium is highly chemically active and reacts violently with elements such as halogens, oxygen, nitrogen, carbon and sulfur.
Titanium generally does not undergo pitting corrosion and, with the exception of a few individual media (such as fuming nitric acid and methanol solution), does not undergo intergranular corrosion; Titanium has low sensitivity to stress corrosion cracking and has good anti-corrosion fatigue properties and good resistance to crevice corrosion.
2. Titanium alloys:
Features: The mechanical and corrosion resistance properties of titanium alloys are significantly improved compared to pure titanium.
In industry, titanium alloys are used instead of pure titanium. The main forms of corrosion in titanium alloys are hydrogen cracking and stress corrosion cracking.
Nickel and its alloys:
1. Nickel:
Characteristics: Nickel has very high corrosion resistance in all temperature and concentration ranges of alkaline solutions and all types of molten alkalis.
However, nickel is not very resistant to corrosion in environments containing sulfur gases, concentrated ammonia water and strongly aerated ammonia solutions, as well as oxygenated acids and hydrochloric acid.
Nickel has high strength, high plasticity and cold resistance, and can be cold rolled into very thin sheets and made into fine wires.
Nickel is rare and expensive and is mainly used in water treatment engineering and chemical engineering to manufacture equipment for alkaline media and in processes where iron ions would cause catalytic interference and stainless steel cannot be used.
2. Nickel alloys:
Monel alloy in Ni-Cu alloys has good mechanical properties and machinability, is easy to process under pressure and cut, and has good corrosion resistance. It is mainly used for corrosion-resistant parts and equipment working under high temperature loads.
Hastelloy alloy (0Cr16Ni57Mo16Fe6W4) in Ni-Mo alloys is resistant to all concentrations of hydrochloric and hydrofluoric acid at room temperature.
The Inconel alloy (0Cr15Ni57Fe) in Ni-Cr alloys has good mechanical properties at high temperatures and high resistance to oxidation, being one of the few materials that resist the corrosion of concentrated MgCl2.
Conclusion
In this article, we introduce what an alloy is, explain the difference between corrosion and rust, and take a detailed look at the advantages of corrosion-resistant alloys and the use of corrosion-resistant alloys. Furthermore, we also discuss in detail the factors that affect the corrosion resistance of metal materials. Finally, we provide a corrosion resistance performance table of main metallic materials and analyze the corrosion resistance of non-ferrous metals and their alloys.
After reading this, I believe you now have a clear answer to the question “Does the alloy rust?”.
