What is zinc aluminum alloy powder?
Zinc-aluminum alloy powderis a high-performance metal powder material composed of two metal elements, zinc and aluminum. With excellent corrosion resistance, high strength, high hardness, high temperature stability, etc., it is used as a powder galvanized material for steel structures; it is the same as the manufacture of flake zinc-aluminum alloy powder, and can form a zinc-aluminum coating on the surface of steel. Anti-corrosion effect, such as railway systems, steel structure bridges, automobile manufacturing, ships, ports, docks, etc.; zinc-aluminum-based solder, ZnAl5 (melting point 382 ° C) is a zinc-based eutectic solder, suitable for brazing of pure zinc and zinc alloys Welding; ZnAl15 (solid-liquid phase 425-460 ° C) can be used as a general-purpose solder for aluminum-aluminum brazing and aluminum-copper brazing, with good spreadability and mechanical properties.
There are many ways to prepare zinc-aluminum alloy powder, the most commonly used method is mechanical alloying. The method is to mix zinc powder and aluminum powder and carry out high-energy ball milling in a ball mill to make the two metal elements react to form zinc-aluminum alloy powder. The composition distribution of the zinc-aluminum alloy powder prepared by the method is uniform and the particle size is fine, which can improve the mechanical properties and corrosion resistance of the material.
Characteristics and application fields of zinc aluminum alloy powder
The application of zinc aluminum alloy powder is very extensive. 1. In the aerospace field, zinc-aluminum alloy powders can be used to prepare high-strength, high-temperature stable aero-engine parts; 2. In the automotive field, zinc-aluminum alloy powders can be used to prepare lightweight auto parts to improve the performance of automobiles. 3. In the field of electronics, zinc-aluminum alloy powder can be used to prepare high-conductivity electronic components; in the field of construction, zinc-aluminum alloy powder can be used to prepare high-strength, corrosion-resistant building materials.
The application prospect of zinc-aluminum alloy powder is very broad. With the continuous advancement of science and technology and the continuous improvement of people's requirements for material performance, zinc-aluminum alloy powder will be used in more fields. At the same time, the preparation technology of zinc-aluminum alloy powder will also be continuously improved and perfected to make its performance more excellent and its application range wider.
The traditional chromium-free Dacromet coating made of zinc-aluminum mixed powder has good corrosion resistance, no hydrogen embrittlement, and good high temperature resistance. Due to the different densities of zinc powder and aluminum powder, the volume difference is large when the mass is the same. The zinc-aluminum mixed powder is prone to component segregation when preparing the coating solution, especially the zinc-aluminum mixed powder with high aluminum content. The zinc-aluminum mixed powder in the plating solution is difficult to disperse, resulting in a zinc-poor area on the surface of the coating, which cannot provide effective protection.
The development prospect of zinc aluminum alloy powder
In recent years, the research of thermal spraying Al-Zn alloy coating has made some progress. Hot-dip Al-Zn alloy coating has good adhesion, strong wear resistance and corrosion resistance, low cost, and its corrosion resistance is obviously better than that of pure Zn. Al-Zn alloy coating coated with pure Al not only has excellent zinc-rich coating Excellent cathodic protection capability and high corrosion resistance aluminum coating.
At present, there are few research reports on the preparation of Dacromet coatings by using Al-Zn alloy powders, and there are even fewer studies on the influence of Al content on the properties of Al-Zn alloy coatings. In the Zn-Al-Mg-RE-Si alloy coating by arc spraying, Si element can form a dense glass phase in the Zn-Al alloy coating to improve the corrosion resistance of the coating. Based on this, this paper uses several Al-Zn-Si alloy powders with different Al contents to prepare chromium-free Dacromet coatings on the surface of Q235 steel, and discusses the influence of Al contents on the corrosion resistance of the coatings, in order to obtain coating properties . Optimized formula.
Layered Al-Zn-Si alloy powders are used, in which the mass fractions of Al are 20%, 30%, 40% and 55%, hereinafter referred to as Al20, Al30, Al40 and Al55. The mass fraction of Si is constant at 1.6%. The field of view of the electron microscope shows that the structure of the four alloy powders is the same; the diameters of the alloy powders with the same composition are uniform, and the diameters of the four alloy powders are all in the range of 10-15 μm. Alloy powders with the same Al content have the same color, indicating that their composition is uniform; with the increase of Al content in the alloy powder, the color of the alloy powder gradually deepens under the microscope. The layered structure of the four alloy powders is extremely thin (less than 5 μm), mechanically superimposed by smaller irregular layered structures, and the structure of the alloy powder is stable. The XRD patterns of the four alloy powders show that the phase composition of the four alloy powders is consistent, mainly composed of Al and Zn elements, a small amount of Si elements are mainly intergranular phase Al9, and Si, Al, and Zn elements are in the zinc-rich phase and aluminum-rich phase. phase shape.
Paint composition and paint preparation The amount of other components in the paint components except metal powder is determined by basic tests, and thickeners, defoamers and other additives are added according to the viscosity and foaming degree of the paint solution. The coating composition (mass fraction) is 20% to 55% Al-Zn-Si alloy powder, 28.0% binder AC66, 12% dispersant Span, 1.6% corrosion inhibitor sodium phosphomolybdate, 0.5% thickener Hydroxyethylcellulose, 2-3 drops of antifoaming agent isooctyl alcohol, the rest is wetting agent (water + alcohol).
The coating is prepared by the traditional Dacromet "two-baking and two-coating" process, that is, the coating is first coated, then dried and sintered, and then air-cooled to room temperature before coating, drying, and sintering. The coating thickness is 15-20 μm. During the coating preparation process, the adding sequence, process conditions and process flow of each component are strictly controlled.
According to GB/T 6073-1992, use a constant temperature water bath to keep the temperature of 10% NaCl (mass fraction, the same below) solution at (35±2) °C, conduct continuous accelerated soaking test, and adjust the pH value to 6. 5. Replace the brine every 6 days to ensure that the test parameters are constant and controllable, and the time is 74 days. The microscopic morphology and composition of the alloy powder and coating before and after corrosion were analyzed by SEOLJSM-6360 scanning electron microscope and genesis2000xm60 energy spectrometer (EDS); the corrosion products of the coating were analyzed by Bruker D8 ADVANCE X-ray diffraction (XRD) Phase analysis. The macroscopic morphology of Cu(Ka) target coating shows that with the increase of Al content in Al-Zn-Si alloy powder, the surface gloss of the coating increases obviously, and gradually transitions from dark gray to dull. Metallic luster to bright silvery white, in which the surface of Al55 coating is flat, smooth and dense, with good metallic luster.
The surface SEM morphology of the coating can be seen from Figure 2: the structure of the Al-Zn alloy coating is mainly affected by the structure of the alloy powder, so there is no significant difference in the microscopic morphology of Al-Zn alloy coatings with different compositions. The microscopic appearance is uniform and dense, without defects such as micropores, and the coating is complete. The flake-shaped alloy powders are closely overlapped with each other and evenly distributed on the surface of the sample to form a thin film alloy layer.
(1) The surface gloss of Al-Zn-Si alloy chromium-free Dacromet coating increases with the increase of Al content; the surface roughness is mainly affected by the powder structure, and the coating surface prepared by flake alloy powder is smooth and dense, and the Al55 The comprehensive surface morphology of zinc-aluminum alloy coating is the best.
(2) Al makes the coating have better salt water immersion corrosion resistance. Within a certain range, with the increase of Al content, the corrosion resistance of the coating is enhanced. When the Al content is 55%, the salt water corrosion resistance of the Al-Zn coating is better.
(3) The Al55 coating has good chemical corrosion resistance. During the corrosion process, the in-situ growth produces a dense coating of corrosion products, which enhances the barrier effect of the coating to a certain extent and delays corrosion.
TIJO introduces high-quality zinc-aluminum alloy powder to improve and optimize on the original basis. It is mainly used for the manufacture of environmentally friendly high-corrosion-resistant coatings - zinc-aluminum coatings (also known as chromium-free Dacromet coatings) required for flake zinc-aluminum alloys Powder, flaky zinc-aluminum alloy powder is an important functional new powder material. The powder is light gray, uniform in color, dry without agglomeration, and without impurities. Using nitrogen atomization, the alloy has high purity, high sphericity, controllable particle size distribution, powder thickness can be sieved, and products with different components and different particle sizes can be customized according to customer requirements.
We provide; -100, -200, -300, -400 mesh (equivalent to -150, -75, -48, -38μm) (d50) 15-20, 11-15, 6-10, 4-6, 2 -4μm and other specifications.