With the development of economy, the demand for chemical products is increasing, and more and more production equipments are running beyond design capabilities. Therefore, for chemical companies worldwide, it is urgent to prevent process equipment from being damaged due to corrosion failures. The problem. Many experts believe that material protection and anti-corrosion measures are important guarantees to reduce maintenance costs and ensure the safe and stable operation of the plant.
In recent years, the competition in engineering construction in the chemical industry has become increasingly fierce. In order to reduce the bidding price, the successful bidder has not paid enough attention to anti-corrosion measures such as the use of high-quality alloys, surface treatment technology, corrosion inhibitors, cathodic protection, and on-line corrosion monitoring systems. Developing countries are particularly prominent.
At present, the chemical industry requires more and more protection and protection for new and existing industrial components. The demand for coatings and anti-corrosion technology has grown rapidly. However, the division of labor in the anti-corrosion industry is very small. There are many companies engaged in this industry, and the sales of products vary widely. At present, the main companies producing protective coatings worldwide include DuPont, BASF, Akzo Nobel, and ICI.
Organic polymers are one of the main products in the family of anti-corrosion coatings. In order to meet increasingly stringent requirements, the performance of such coatings has been continuously improved. For example, Shell Group's Carilon series of ester polyketone polymers can be used as anti-corrosion primers for metal pipes and containers; U.S. Ausimont Company has developed a new type of perfluorinated material that can be used as a large-scale storage tank and high pressure in the pharmaceutical industry. The primer of the container can not only prevent the internal corrosion of the tank and the container, but also does not react chemically with mineral acids, alkalis, oxidants and containers, and does not react with the key pharmaceutical ingredients.
In addition, a new type of thermoplastic coating developed by the British Aocit Group can be used to protect steel equipment against corrosion in corrosive environments. Its coating can protect the equipment in operation, and it can also protect the production of sealed equipment. It is especially suitable for Protect the inside of the flange and other special shapes. According to the manufacturer, this type of paint can remove rust spots more easily than other paints. It is more versatile than plastic flange protection covers and can significantly reduce the cost of anti-corrosion for offshore oil platforms.
At the same time, Eurotech USA plans to commercialize a new type of polyurethane that can be used in crack-resistant composites, chemical preservatives, and sealants. The new material is said to have better chemical resistance than conventional polyurethanes and is safer to produce because it is not manufactured from toxic isocyanate precursors. Instead, it is made of a cyclic carbonate or the like, and the cost of this new type of polyurethane can completely compete with conventional polyurethanes.
High-temperature resistant plastics are playing a more and more important role in various anti-corrosion applications under the “low temperature†state according to industrial standards for chemical processes. Various fluoropolymers, especially polytetrafluoroethylene (PTFE), can actually resist the corrosion of any chemical. When reinforced with glass fiber and graphite fiber, PTFE can even withstand high temperatures above 500 degrees. However, when used as pressure seals, valve seals, and valve seats, PTFE and other fluoropolymers have fatal weaknesses, ie, low temperature flow problems. A thermoplastic that prevents cold flow is PEEK, which, although not as chemically resistant as fluoropolymers, is the closest material to its properties. In addition, epoxy resins can also provide a wide range of corrosion resistance, especially in marine and chlorine environments.
New materials with better corrosion resistance and strength continue to flow into the market in recent years. Such as stainless steel for pipes and heat exchangers, materials for making reactors reinforced with vanadium, high-strength steels used at high temperatures, and the like. There may be special requirements for the production of these materials to ensure their corrosion resistance in different applications, and these special requirements are often not found in industry standards and specifications.
In the past few decades, high-chromium alloys have proven to perform well in both reduced and oxidizing environments, adding elements that are resistant to corrosion, making them more suitable for use in harsh atmospheres and solutions. The heat-resistant iron alloy with high chromium content can be used to manufacture large-caliber thick-walled boiler tubes for power stations. At the same time, researchers are focusing on developing new materials and applications in the chemical process industry. The Japan Research and Development Center is cooperating with a number of Japanese companies to develop a super metal whose performance surpasses existing materials. The available grain size of the ferroalloy is between 10-100 microns. Researchers are working hard to reduce the grain size to less than 1 micron, and to increase their strength and toughness to give them better corrosion resistance.
Chemical equipment used in highly corrosive media, such as concentrated **, **, **, hydrobromic acid, chlorinated organic compounds and acidic metal chloride aqueous solutions, only a few materials can be manufactured, and in metal materials, due to manufacturing costs After eliminating the precious metals, only high-melting-point titanium can do the job.
Since the surface energy can form an extremely stable titanium oxide layer, titanium has excellent corrosion resistance to many oxidizing substances and reducing substances, and only hydrofluoric acid and fluoride ions can erode the titanium material. Therefore, almost all types of chemical equipment and components, such as containers, pipes, valves, mixers, etc., can be made of titanium. However, due to the difference in heat transfer in the same environment, the heat exchanger is more susceptible to corrosion. Therefore, using a titanium material as a heat exchanger can better reflect its superior performance. Generally, due to the weight and cost reasons, the thickness of the parts made of titanium material is very thin, which also makes the heat transfer performance of the titanium material equipment good, the heat exchange surface area is greatly reduced, and the device structure can be more compact. In addition, the titanium material has good ductility and is easily cooled and molded into various parts. At the same time, the titanium material has high strength and can withstand higher operating pressure than the plastic parts. Titanium has a melting point of 3,000 degrees, and under this condition, it will form brittle compounds with other metals. Therefore, the quality of titanium equipment also has a lot to do with design experience and manufacturing technology.
In addition, surface treatment is another effective way for metal materials to improve corrosion resistance. Applying a silver-based solder alloy to the surface of stainless steel can increase its strength and give it good corrosion and oxidation resistance. This type of technology has been used in the production of heat exchangers, etc. It is now being evaluated for applications in aluminum and ceramics. U.S. Microplasma has developed a so-called Micro Plasma Process (MPP) electrochemical micro-arc oxidation process that can be applied to aluminum alloys to form a thick coating that is resistant to corrosion, wear, and heat. Insulation performance. The MPP process can also be used for the surface protection of steel. Research is currently underway and further applied to titanium and magnesium.
In general, making full use of existing anti-corrosion technology and selecting suitable anti-corrosion materials not only can make the production process more safe and reliable, but also can effectively reduce management costs and maintenance costs. How to produce more economical and practical anti-corrosion materials and improve the anti-corrosion effect of the device will still be the direction that this century's engineering and scientific research personnel will work hard for.
In recent years, the competition in engineering construction in the chemical industry has become increasingly fierce. In order to reduce the bidding price, the successful bidder has not paid enough attention to anti-corrosion measures such as the use of high-quality alloys, surface treatment technology, corrosion inhibitors, cathodic protection, and on-line corrosion monitoring systems. Developing countries are particularly prominent.
At present, the chemical industry requires more and more protection and protection for new and existing industrial components. The demand for coatings and anti-corrosion technology has grown rapidly. However, the division of labor in the anti-corrosion industry is very small. There are many companies engaged in this industry, and the sales of products vary widely. At present, the main companies producing protective coatings worldwide include DuPont, BASF, Akzo Nobel, and ICI.
Organic polymers are one of the main products in the family of anti-corrosion coatings. In order to meet increasingly stringent requirements, the performance of such coatings has been continuously improved. For example, Shell Group's Carilon series of ester polyketone polymers can be used as anti-corrosion primers for metal pipes and containers; U.S. Ausimont Company has developed a new type of perfluorinated material that can be used as a large-scale storage tank and high pressure in the pharmaceutical industry. The primer of the container can not only prevent the internal corrosion of the tank and the container, but also does not react chemically with mineral acids, alkalis, oxidants and containers, and does not react with the key pharmaceutical ingredients.
In addition, a new type of thermoplastic coating developed by the British Aocit Group can be used to protect steel equipment against corrosion in corrosive environments. Its coating can protect the equipment in operation, and it can also protect the production of sealed equipment. It is especially suitable for Protect the inside of the flange and other special shapes. According to the manufacturer, this type of paint can remove rust spots more easily than other paints. It is more versatile than plastic flange protection covers and can significantly reduce the cost of anti-corrosion for offshore oil platforms.
At the same time, Eurotech USA plans to commercialize a new type of polyurethane that can be used in crack-resistant composites, chemical preservatives, and sealants. The new material is said to have better chemical resistance than conventional polyurethanes and is safer to produce because it is not manufactured from toxic isocyanate precursors. Instead, it is made of a cyclic carbonate or the like, and the cost of this new type of polyurethane can completely compete with conventional polyurethanes.
High-temperature resistant plastics are playing a more and more important role in various anti-corrosion applications under the “low temperature†state according to industrial standards for chemical processes. Various fluoropolymers, especially polytetrafluoroethylene (PTFE), can actually resist the corrosion of any chemical. When reinforced with glass fiber and graphite fiber, PTFE can even withstand high temperatures above 500 degrees. However, when used as pressure seals, valve seals, and valve seats, PTFE and other fluoropolymers have fatal weaknesses, ie, low temperature flow problems. A thermoplastic that prevents cold flow is PEEK, which, although not as chemically resistant as fluoropolymers, is the closest material to its properties. In addition, epoxy resins can also provide a wide range of corrosion resistance, especially in marine and chlorine environments.
New materials with better corrosion resistance and strength continue to flow into the market in recent years. Such as stainless steel for pipes and heat exchangers, materials for making reactors reinforced with vanadium, high-strength steels used at high temperatures, and the like. There may be special requirements for the production of these materials to ensure their corrosion resistance in different applications, and these special requirements are often not found in industry standards and specifications.
In the past few decades, high-chromium alloys have proven to perform well in both reduced and oxidizing environments, adding elements that are resistant to corrosion, making them more suitable for use in harsh atmospheres and solutions. The heat-resistant iron alloy with high chromium content can be used to manufacture large-caliber thick-walled boiler tubes for power stations. At the same time, researchers are focusing on developing new materials and applications in the chemical process industry. The Japan Research and Development Center is cooperating with a number of Japanese companies to develop a super metal whose performance surpasses existing materials. The available grain size of the ferroalloy is between 10-100 microns. Researchers are working hard to reduce the grain size to less than 1 micron, and to increase their strength and toughness to give them better corrosion resistance.
Chemical equipment used in highly corrosive media, such as concentrated **, **, **, hydrobromic acid, chlorinated organic compounds and acidic metal chloride aqueous solutions, only a few materials can be manufactured, and in metal materials, due to manufacturing costs After eliminating the precious metals, only high-melting-point titanium can do the job.
Since the surface energy can form an extremely stable titanium oxide layer, titanium has excellent corrosion resistance to many oxidizing substances and reducing substances, and only hydrofluoric acid and fluoride ions can erode the titanium material. Therefore, almost all types of chemical equipment and components, such as containers, pipes, valves, mixers, etc., can be made of titanium. However, due to the difference in heat transfer in the same environment, the heat exchanger is more susceptible to corrosion. Therefore, using a titanium material as a heat exchanger can better reflect its superior performance. Generally, due to the weight and cost reasons, the thickness of the parts made of titanium material is very thin, which also makes the heat transfer performance of the titanium material equipment good, the heat exchange surface area is greatly reduced, and the device structure can be more compact. In addition, the titanium material has good ductility and is easily cooled and molded into various parts. At the same time, the titanium material has high strength and can withstand higher operating pressure than the plastic parts. Titanium has a melting point of 3,000 degrees, and under this condition, it will form brittle compounds with other metals. Therefore, the quality of titanium equipment also has a lot to do with design experience and manufacturing technology.
In addition, surface treatment is another effective way for metal materials to improve corrosion resistance. Applying a silver-based solder alloy to the surface of stainless steel can increase its strength and give it good corrosion and oxidation resistance. This type of technology has been used in the production of heat exchangers, etc. It is now being evaluated for applications in aluminum and ceramics. U.S. Microplasma has developed a so-called Micro Plasma Process (MPP) electrochemical micro-arc oxidation process that can be applied to aluminum alloys to form a thick coating that is resistant to corrosion, wear, and heat. Insulation performance. The MPP process can also be used for the surface protection of steel. Research is currently underway and further applied to titanium and magnesium.
In general, making full use of existing anti-corrosion technology and selecting suitable anti-corrosion materials not only can make the production process more safe and reliable, but also can effectively reduce management costs and maintenance costs. How to produce more economical and practical anti-corrosion materials and improve the anti-corrosion effect of the device will still be the direction that this century's engineering and scientific research personnel will work hard for.