car led headlight Surface treatment types
Surface treatment is the process of forming a coating on the surface of a workpiece by a certain method. The purpose of the surface treatment is to impart a beautiful and anticorrosive effect to the surface of the product. The surface treatment methods are all due to the following several commonly used methods:
Electroplating: The parts to be plated are immersed in an aqueous solution containing the metal compound to be deposited, passed through the bath with an electric current, and the plated metal is deposited and deposited on the parts. General plating with zinc, copper, nickel, chromium, copper nickel alloy, sometimes boiled black (blue), phosphating, etc. are also included.
2, hot-dip galvanized: through the carbon steel parts immersed temperature is about 510 ℃ dissolved zinc plating tank to complete. As a result, the iron-zinc alloy on the surface of the steel gradually becomes the passivated zinc on the outer surface of the product. Hot dip aluminizing is a similar process.
3, mechanical plating: through the coating of metal particles to impact the product surface, and the coating cold welding to the surface of the product.
The general use of more electroplating screws, but used in electric power, highways and other outdoor hexagonal wood screws with hot-dip zinc; electroplating costs generally 0.6-0.8 yuan per kilogram, hot-dip zinc is generally 1.5-2 yuan / Kg, higher cost.
The quality of electroplating with its corrosion resistance as the main measure, followed by the appearance. Corrosion resistance is to imitate the product working environment, set the test conditions, to be corrosion test. The quality of electroplated products is controlled in the following ways:
Product surface does not allow partial uncoated, scorched, rough, dark, peeling, crusting conditions and obvious stripes, does not allow pinhole pitting, black plating slag, passivation film loose, cracked, fall off and serious Passivation marks.
2, coating thickness:
The working life of a fastener in a corrosive atmosphere is proportional to its coating thickness. Generally recommended economic plating thickness of 0.00015in ~ 0.0005in (4 ~ 12um).
Hot dip galvanized: The standard average thickness of 54 um (call diameter ≤ 3/8 to 43 um), the minimum thickness of 43 um (call diameter ≤ 3/8 to 37 um).
3, coating distribution:
Using different deposition methods, the coating on the surface of the fastener aggregation is also different. Plating metal plating is not evenly deposited on the outer peripheral edge of the corner get thicker coating. In the threaded portion of the fastener, the thickest coating is located on the top of the thread crest, tapering along the flanks of the thread, depositing the thinnest at the base of the tooth, whereas the hot dip galvanizing is the opposite and the thicker coating settling at the inside corner and At the bottom of the thread, a mechanically plated coating has the same metal deposition tendency as hot dip, but is smoother and more uniform in thickness over the entire surface.
4, hydrogen embrittlement:
During processing and handling of fasteners, especially during pickling and caustic washing prior to plating and subsequent electroplating, hydrogen atoms are adsorbed on the surface, the deposited metal coating then captures hydrogen. When the fastener is tightened, the hydrogen is turned toward the portion where the stress is most concentrated, causing the pressure to increase beyond the strength of the base metal and causing minor surface cracking. Hydrogen is particularly active and quickly penetrates newly formed fractures. This pressure-burst-infiltration cycle continues until the fastener breaks. Usually occurs within a few hours after the first stress application.
In order to eliminate the threat of hydrogen embrittlement, fasteners are heated and baked as quickly as possible after plating to allow hydrogen to bleed out of the coating. The baking is usually performed at 375-4000F (176-190C) for 3-24 hours.
As mechanical zinc plating is non-electrolyte, this virtually eliminates the threat of hydrogen embrittlement
5. Auto-catalytic Plating, commonly known as "Chemical Plating", "Electroless Plating" and other self-catalytic nickel-phosphorus plating and industrial applications
Electroless nickel plating is currently the fastest growing surface treatment technology in the world. It is pollution-free, easy to operate and can be coated with a wide range of substrate and coating good wear and corrosion resistance by the industry's widespread attention and favor.
Self-catalytic nickel-phosphorus plating (hereinafter referred to as electroless nickel) technology, is currently the world's fastest growing low-temperature surface enhanced high-tech. It was originally developed for industrial applications as a substitute for electroplated nickel and electrochromized chromium and has since been developed for versatile uses such as corrosion resistance, abrasion resistance and electromagnetic shielding properties. Especially in the world as a pollution-free surface treatment technology, access to green technology reputation, by the industry's widespread attention and favor. Its application covers almost all industrial areas. The Application of Electroless Nickel Plating in the Oil and Gas Industry Oil and gas have been the test field for electroless nickel plating for many years and electroless nickel plating has performed well in a wide range of applications.About 15% of all electroless nickel plating in North America is for Oil and Gas Industry The most valuable properties that have proven to be of value to the oil and gas industry are the thickness uniformity of coatings, excellent corrosion resistance, and wear / erosion resistance.Many of the traditional matrix materials used in this area are characterized by the use of electroless plating Nickel and greatly reduce manufacturing costs and extend service life.It is of particular importance to extend the life expectancy because of the high cost of downtime replacement parts in the oil and gas industry.The role of the oil and gas industry is divided into three main components, Ground operations, underground / downhole operations, and offshore operations.The equipment is typically exposed to harsh environmental conditions such as hydride, hydrogen sulfide, carbon dioxide, salt water, seawater and reefs containing high levels of sulfide and is also combined with inhalation of sediment and Mud-induced wear problems, and in some cases temperatures up to 250º C. Typical parts that improve performance with electroless nickel plating Include: ground operations ---- blowout preventer, brake system, throttle, compressor, gas turbine, pump body, pump, connecting pipelines and valves; underground / downhole operation --- coupler, logging tool , Plugs, dividers, pumps, safety valve fittings and tubing. Thickness uniformity at sea operations - BOPs, gas turbines / compressors, heat exchangers, pumps, riser connectors and valves Electroless nickel plating - Corrosion resistance and wear resistance make it widely used in valves and flow control devices.Obviously, these devices are the key equipment for well operations, the main economic factor is the well operation of the equipment has good performance and long life expectancy. Acceptable properties to electroless nickel plating are their corrosion resistance, finish and thickness uniformity, which provide the ball valve plug with the required surface conditions and improved sealing of the seat portion. Initially only electroless plating Nickel is seen as a possible alternative to hard chrome, and electroless nickel plating is now dominant in this market. The most typical example in this area is low carbon steel ball valves, often 75 micron thick electroless nickel Layers can be seen electroless nickel plating in the oil and gas industry For example, a plant in the Middle East produces crude oil containing 55% hydrogen sulphide in its gas at a temperature of 80ºC and a pressure of 20 MN / m2 (3000 psi). Under these conditions, due to corrosion, Surface cracking and erosion of the failure of low-carbon steel ball valve to make the longest life of only 3 months. And 75-micron ball valve with electroless nickel plating greatly extended the service life of the equipment, after two years of continuous operation has not seen Equipment damage to the surface. The same benefits are achieved with ball valves using a seawater injection system that operates by pumping seawater under high pressure to force the crude oil to the surface. In Ghawar, Saudi Arabia, the valve uses a 75 micron thick chemical Nickel plating has successfully undergone operating conditions and found no damage to the coating over four years of operation Electroless nickel addition to the ball valves that have been successfully used in the oil and gas industry has also succeeded in the application of valve components in other fields of engineering For example, the valves for large ball valves manufactured for the Aswan dam project in Egypt have been electroless nickel plated, and valve components must be able to open and close as often as required Reliable operation. This reliability is provided by the 75-micron electroless nickel coating protecting the stem from corrosion and wear. The 106-ton giant valve has a 260cm hole diameter and exceeds the 6-ton weight on the stem alone. In the Khuff gas well, the performance of valves, restrictors and other components subjected to electroless nickel plating also gave the impression that Khuff gas wells are less temperate and originate from marble and limestone formations, which typically contain 6% (mol) ) Of carbon dioxide and 0.1 mol% of hydrogen sulfide, which also contains about 28 L / Mm3 of hexane-based condensate and 7 L / Mm3 of water at a wellhead pressure of typically 35 MN / m2 (5000 psi) at a temperature of 90 ° C, Gas flow rates are typically greater than 6 m / s. Under these conditions, damage to the steel components due to corrosion / erosion is very serious. Pitting and erosion cause a metal loss of 3-5 mm per year on the carbon steel restrictor , And 25 microns thick electroless nickel plating on all wetted surfaces successfully solved the problem by applying electroless nickel plating to overcome ball valve problems in these environments, typically using 75-micron thick electroless plating The nickel layer protects the ball from corrosion for at least six years Corrosion resistance, hardness, surface finish, lubricity are very beneficial for the production and performance of fire-rated flow valves, requiring these valves to operate without air bubbles during normal operation and act as a throttle valve after accidental exposure to temperatures of 650ºC, Electroless nickel plating is also used in some key safety valves. For example: blowout preventer is a safety valve for shutting down oil and gas wells in emergencies, consisting of a hydraulically driven piston that cuts in Oil and gas pipelines, plug the flow of oil and gas. After testing, only one set of devices required to run once in an emergency, but must ensure that good performance, therefore, in the piston or seal surface corrosion and physical damage is not allowed to commonly used about 100 microns Thick electroless nickel has been to achieve the desired hardness and corrosion resistance.
6. Immersion Plating (Immersion Plating) Using copper sulfate, stannous sulfate as the main salt displacement reaction immersion plating on the surface of the steel parts made of copper-tin alloy layer. By adding a fluorine-containing anion and carboxyl anion complexing agent, the control of copper, tin ions replacement reaction rate of 15% to 39% of the copper content of the alloy coating, the appearance of 18 ~ 22K gold, the film combination Good force, good corrosion resistance There are two types of chemical plating imitation gold, one is the use of reductant chemical reduction type, the formation of the coating is generally brown or poor color of gold, the coating adhesion is poor. Immersion plating that is replacement plating or contact plating, is a no external current or reductant, the use of potential difference between the two kinds of electromotive force-driven displacement reaction. Immersion plating equipment, high efficiency, low cost
7. Anodizing Close to surface coating, electrochemical oxidation of metals or alloys. The metal or alloy parts as the anode, the electrolytic method to form an oxide film on the surface. Metal oxide film changes the surface state and performance, such as surface coloring, improve corrosion resistance, wear resistance and hardness, to protect the metal surface. For example, aluminum anodization, the aluminum and its alloys placed in the corresponding electrolyte (such as sulfuric acid, chromic acid, oxalic acid, etc.) as an anode, under the specific conditions and an applied current electrolysis. The anodic aluminum or its alloy is oxidized to form a thin layer of aluminum oxide on the surface with a thickness of 5-20 microns and a hard anodized film of 60-200 microns. Anodized aluminum or its alloy, to improve its hardness and wear resistance, up to 250 ~ 500 kg / mm 2, good heat resistance, hard anodized film melting point up to 2320K, excellent insulation, resistance Wear voltage up to 2000V, enhanced corrosion resistance, in the ω = 0.03NaCl salt fog by thousands of hours without corrosion. The thin oxide film has a large number of micropores, can absorb a variety of lubricants, suitable for the manufacture of engine cylinders or other wear parts; membrane microporous adsorption ability can be colored into a variety of beautiful and beautiful colors. Non-ferrous metals or their alloys (such as aluminum, magnesium and their alloys) can be anodized, this method is widely used in mechanical parts, aircraft parts, precision instruments and radio equipment, daily necessities and architectural decoration and so on.
Added: In addition to metals, other substances in the anode caused by the oxidation, also known as "anodizing"
Added: In the actual process, for the anodized aluminum, more can be used in everyday life, that the characteristics of this process, the surface of aluminum parts to produce a hard protective layer, can be used for the production of kitchen utensils and other daily necessities. But the cast aluminum anodizing effect is not good, the surface is not only good, but also only black. Aluminum profiles will be better.
8. Chemical Conversion Coating; Chemical Conversion Coating Steel Blackening, commonly known as "black" steel Phosphating ... Composite plating (dispersion plating) composite plating Electricity Chemical or chemical use of the right to use metal ions and suspended uniformly in the solution ... Steel Black, commonly known as "black pot" Phosphating (Phosphating)
10 Metal Dyeing (Metal Coloring)
11 Paint (Finishing), including a variety of coatings such as hand-painted, electrostatic coating, electrophoretic coating, etc.
12 hot dip (Hot dip) ,. Hot-dip coating referred to as hot-dip plating, is to be plated metal material immersed in the lower melting point of other liquid metal or alloy coating method. The basic feature of this method is the formation of an alloy layer between the base metal and the coating metal
13 Galvanizing, commonly known as "lead water"
14 Tinning, Hot dip tinning It is mainly to use the semi-automatic coating to be coated by half automatic continuous washing, pickling to remove dirt and rust stains to be plated on the surface of the substrate, After dipping the flux to facilitate the subsequent tin plating process after dipping the tin solution, and then after a series of sabotage, knocking hammer, turning and other steps, in order to remove the plating on the body of excess liquid tin and tin liquid uniform Arranged on it, and then applied to the cooling and drying, you can get a pair of work in accordance with the above steps produce hot dip tin
15 cathode sputtering, charged particles with sufficient energy or neutral particles collide with the surface of the object, the energy can be passed to the surface atoms. As long as the surface atomic energy greater than their own ionization energy, you can get rid of the surrounding atoms bound to leave the surface, this phenomenon is called sputtering.
16 vacuum plating (Vacuum Plating), vacuum plating, including vacuum deposition, sputtering and ion plating several types, they are used in the vacuum conditions, by means of distillation or sputtering deposited on the surface of various metals And non-metallic film, in this way can be very thin surface coating, but also has the advantages of good speed and good adhesion outstanding, but the price is higher, the type of metal can be operated less commonly used for higher-grade
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