Preparation method of zinc alloy surface corrosion-resistant organic composite coating

Abstract

The invention provides a preparation method of a zinc alloy surface corrosion-resistant organic composite coating, and aims to prepare a high-corrosion-resistant coating on the zinc surface through in-situ growth, so that the binding force between the zinc alloy coating and a matrix is improved, and meanwhile, the corrosion resistance of the zinc alloy coating is greatly improved. The preparation method comprises the following steps: carrying out electrolytic oxidation on the surface of the zinc alloy by regulating and controlling the oxidation current density in a sodium hydroxide and sodium carbonate solution with a specific ratio, carrying out sealing treatment in combination with PFDTMS, and preparing the organic composite coating on the surface through in-situ growth. Therefore, the corrosion of the zinc alloy is optimized, and the zinc alloy is suitable for being used in a highly corrosive environment.

Description

Technical Field

[0001] The invention relates to a method for preparing a zinc alloy surface coating, in particular to a method for preparing a zinc alloy surface corrosion-resistant organic composite coating. Background Art

[0002] my country is in the leading position in global zinc resource reserves and consumption, ranking first in the world. Zinc alloys are widely used in cathodic protection facilities such as ships, offshore oil production platforms, port terminal buildings, and submarine oil pipelines, and play a vital role in the anti-corrosion of marine equipment. Due to its own corrosion resistance, zinc alloys are mainly used as building decoration materials, mostly used in fields such as roofs or exterior walls. However, in order to expand the scope of use of zinc alloys and increase their service life, it is necessary to construct a corrosion-resistant coating on the surface of the zinc alloy. Therefore, the research on the surface treatment process of zinc alloys is of great practical value. The present invention adopts an in-situ coating construction process to accurately modify the surface of the zinc alloy, enriching the surface treatment process of non-ferrous metals and improving the production added value of zinc alloys, which has great significance and social value.

[0003] Therefore, in response to the above problems, the present invention designs a method for preparing a corrosion-resistant organic composite coating on the surface of a zinc alloy, which can develop and improve the corrosion resistance of the zinc alloy through in-situ growth, improve the bonding strength between the zinc alloy coating and the substrate, and at the same time greatly improve the corrosion resistance of the zinc alloy, which is beneficial to greatly improve the service life of the zinc alloy in a strong corrosive environment, while reducing the energy consumption and other costs in the production process, thereby expanding the application field of the zinc alloy. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a corrosion-resistant organic composite coating on a zinc alloy surface. The present invention aims to grow a corrosion-resistant coating on the zinc surface, thereby improving the bonding force between the zinc alloy coating and the substrate, and greatly improving the corrosion resistance. Zinc alloy is mainly used as a building material in practical applications, so its corrosion resistance is very important. The corrosion resistance mechanism of zinc alloy is that when the alloy plate is in the atmospheric environment, it will be exposed to various corrosive components in the air, mainly oxygen, water vapor and carbon dioxide. Corrosion products will be generated on the alloy surface in the early stage. As the exposure time in the atmosphere passes, the early corrosion products generated on the surface will gradually develop into more stable corrosion products. A part of zinc hydroxide will form basic zinc carbonate with zinc carbonate, and the other part will gradually decompose into zinc oxide. If the area where the zinc alloy is used is a marine atmospheric environment, it will also react, and the corrosion effect will be more intense, and basic zinc chloride will be further generated to destroy the alloy structure.

[0005] The present invention adopts the method of electrolytic oxidation on the surface of zinc alloy in a sodium hydroxide and sodium carbonate solution with a specific ratio, electrolytic oxidation is carried out by adjusting the oxidation current density, and sealing treatment is carried out in combination with perfluorodecyltrimethoxysilane (PFDTMS), and an organic composite coating is prepared on the surface by in-situ growth, which is suitable for manufacturing and use in a highly corrosive environment.

[0006] The present invention achieves the purpose of the invention through the following technical solutions: A method for preparing a corrosion-resistant organic composite coating on a zinc alloy surface, the method is carried out according to the following steps: 1) The raw materials used in the present invention are 0.5-2% by weight of Mn and the rest is zinc. The zinc alloy is heated and smelted in a resistance furnace, then turned into a cylindrical shape and then extruded into a rod; 2) The above-mentioned rod-shaped alloy raw material is cut into alloy discs with a thickness of 2 mm by a wire cutting machine, and then the discs are punched and polished step by step with sandpaper of specifications of 600#, 1000#, 1500# and 2000#, and then ultrasonically cleaned with deionized water, air-dried, coated with glue and dried, and placed in a drying container for use; 3) Take a mixture of 5~15g / L sodium hydroxide and 5~15g / L sodium carbonate as the electrolyte. Under 30℃ water bath heating conditions, the oxidation current density is 3~14A / dm 2 , the reaction time is 30min, and a coating is formed on the alloy surface after the reaction is completed; 4) Perfluorodecyltrimethoxysilane (PFDTMS) was mixed with water and methanol in a certain ratio, and stirred in a water bath at 30°C for 4 hours to obtain a silane impregnation solution. The above sample was immersed in the silane impregnation solution, reacted at 40°C for 2 hours, and dried.

[0007] The corrosion-resistant organic composite coating according to claim 1, characterized in that the self-corrosion current density I corr For 10 -10 ~10 -4 A / cm 2 , the corrosion potential is -0.2~-2V.

[0008] The advantages and effects of the present invention are: 1. The present invention aims to solve the key technical problem that the existing zinc alloy has poor corrosion resistance and short service life in a strong corrosive environment, and develops a new type of zinc alloy surface coating preparation method. By combining an appropriate electrolyte ratio with an electrolytic oxidation method, an organic composite coating is constructed on the alloy surface. The impedance generated by the coating greatly improves the corrosion resistance of the alloy. The invention is suitable for manufacturing equipment used in a strong corrosive environment, improves the service life of the zinc alloy, and expands the application range of the zinc alloy. The method is simple to prepare and has a lower cost than the existing preparation process. 2. The present invention prepares a corrosion-resistant organic composite coating by in-situ growth; compared with the zinc alloy coating method prepared by conventional processes, this preparation method has stronger bonding force, which is beneficial to optimizing the corrosion defects of the zinc alloy; and the process is simple, which is beneficial to reducing costs and saving energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a microstructure photograph of the zinc alloy organic composite coating prepared in Example 1 of the present invention; Figure 2 This is a comparison diagram of the polarization curves of the zinc alloy with the coating formed in Example 1 of the present invention and the original sheet. DETAILED DESCRIPTION

[0010] The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings. Example 1

[0011] The weight percentage of the rod-shaped zinc alloy used as the raw material of the present invention is wt.%: Mn 0.5, and the rest is zinc. The alloy raw material is cut into alloy discs with a thickness of 2 mm by a wire cutting machine, and the discs are punched and polished step by step with sandpapers of 600#, 1000#, 1500# and 2000# specifications, and then ultrasonically cleaned with deionized water, air-dried, glued and dried, and placed in a drying container for use.

[0012] The electrolyte was a mixture of 9 g / L sodium hydroxide and 11 g / L sodium carbonate. Under 30°C water bath heating conditions, the oxidation current density was 10 A / dm 2 The reaction time is 30 minutes, and a film layer is formed on the alloy surface after the reaction is completed.

[0013] Perfluorodecyltrimethoxysilane (PFDTMS) was mixed with water and methanol in a certain ratio, and stirred for 4 hours in a water bath at 30°C to obtain a silane impregnation solution. The sample after the reaction was soaked in the silane impregnation solution, reacted at 40°C for 2 hours, and dried.

[0014] The above reaction sample was used as the working electrode, the counter electrode was a graphite electrode, and the reference electrode was a saturated calomel electrode. At room temperature, a 3.5wt.% NaCl solution was used, the pH value was neutral, the scan rate was 1mv / s, and the scan range was -1~1V. The oxidation current density was 10A / dm 2 The self-corrosion current density I corr is 1.548×10 -9 A / cm 2 , the corrosion potential is -0.26V. Example 2

[0015] The weight percentage of the rod-shaped zinc alloy used as the raw material is wt.%: Mn 2, and the rest is zinc. The alloy raw material is cut into alloy discs with a thickness of 2 mm by a wire cutting machine, and the discs are punched and polished step by step with sandpaper of specifications of 600#, 1000#, 1500# and 2000#, and then ultrasonically cleaned with deionized water, air-dried, glued and dried, and placed in a drying container for use.

[0016] The electrolyte was a mixture of 9 g / L sodium hydroxide and 11 g / L sodium carbonate. Under 30°C water bath heating conditions, the oxidation current density was 8 A / dm 2 The reaction time is 30 minutes, and a film layer is formed on the alloy surface after the reaction is completed.

[0017] Perfluorodecyltrimethoxysilane (PFDTMS) was mixed with water and methanol in a certain ratio, and stirred for 4 hours in a water bath at 30°C to obtain a silane impregnation solution. The sample after the reaction was soaked in the silane impregnation solution, reacted at 40°C for 2 hours, and dried.

[0018] The above reaction sample was used as the working electrode, the counter electrode was a graphite electrode, and the reference electrode was a saturated calomel electrode. At room temperature, a 3.5wt.% NaCl solution was used, the pH value was neutral, the scan rate was 1mv / s, and the scan range was -1.8~0V. The oxidation current density was 8A / dm 2 The self-corrosion current density I corr is 9.962×10 -9 A / cm 2 , the corrosion potential is -1.04V. Example 3

[0019] The weight percentage of the rod-shaped zinc alloy used as the raw material is wt.%: Mn 1, and the rest is zinc. The alloy raw material is cut into alloy discs with a thickness of 2 mm by a wire cutting machine, and the discs are punched and polished step by step with sandpapers of specifications of 600#, 1000#, 1500# and 2000#, and then ultrasonically cleaned with deionized water, air-dried, glued and dried, and placed in a drying container for use.

[0020] The electrolyte was a mixture of 9 g / L sodium hydroxide and 11 g / L sodium carbonate. Under 30 °C water bath heating conditions, the oxidation current density was 12 A / dm 2 The reaction time is 30 minutes, and a film layer is formed on the alloy surface after the reaction is completed.

[0021] Perfluorodecyltrimethoxysilane (PFDTMS) was mixed with water and methanol in a certain ratio, and stirred for 4 hours in a water bath at 30°C to obtain a silane impregnation solution. The sample after the reaction was soaked in the silane impregnation solution, reacted at 40°C for 2 hours, and dried.

[0022] The above reaction sample was used as the working electrode, the counter electrode was a graphite electrode, and the reference electrode was a saturated calomel electrode. At room temperature, a 3.5wt.% NaCl solution was used, the pH value was neutral, the scan rate was 1mv / s, and the scan range was -1.8~0V. The oxidation current density was 12A / dm 2 The self-corrosion current density I corr is 7.181×10 -9 A / cm 2 , the corrosion potential is -0.84V. Example 4

[0023] The weight percentage of the rod-shaped zinc alloy used as the raw material of the present invention is wt.%: Mn 1.2, and the rest is zinc. The alloy raw material is cut into alloy discs with a thickness of 2 mm by a wire cutting machine, and the discs are punched and polished step by step with sandpapers of specifications of 600#, 1000#, 1500# and 2000#, and then ultrasonically cleaned with deionized water, air-dried, glued and dried, and placed in a drying container for use.

[0024] Perfluorodecyltrimethoxysilane (PFDTMS) was mixed with water and methanol in a certain ratio, and stirred in a water bath at 30°C for 4 hours to obtain a silane impregnation solution. The above sample was immersed in the silane impregnation solution, reacted at 40°C for 2 hours, and dried.

[0025] The above samples were used as working electrodes, graphite electrodes were selected as counter electrodes, and saturated calomel electrodes were selected as reference electrodes. At room temperature, 3.5wt.% NaCl solution was used, the pH value was neutral, the scanning rate was 1mv / s, and the scanning range was -1.8~0V. The self-corrosion current density of the blank sample I was obtained. corr is 4.573×10 -5 A / cm 2 , the corrosion potential is -1.27V.

Claims

1. A method for preparing a corrosion-resistant organic composite coating on a zinc alloy surface, the method being carried out according to the following steps: 1) The raw materials used in the present invention are 0.5-2% by weight of Mn and the rest is zinc. The zinc alloy is heated and melted in a resistance furnace, then turned into a cylinder and then extruded into a rod; 2) The above-mentioned rod-shaped alloy raw material is cut into alloy discs with a thickness of 2 mm by a wire cutting machine, and then the discs are punched and polished step by step with sandpaper of specifications of 600#, 1000#, 1500# and 2000#, and then ultrasonically cleaned with deionized water, air-dried, coated with glue and dried, and placed in a drying container for use; 3) Take a mixture of 5~15g / L sodium hydroxide and 5~15g / L sodium carbonate as the electrolyte. Under 30℃ water bath heating conditions, the oxidation current density is 3~14A / dm 2 , the reaction time is 30min, and a coating is formed on the alloy surface after the reaction is completed; 4) Perfluorodecyltrimethoxysilane (PFDTMS) was mixed with water and methanol in a certain ratio, and stirred in a water bath at 30°C for 4 hours to obtain a silane impregnation solution. The above sample was immersed in the silane impregnation solution, reacted at 40°C for 2 hours, and dried.

2. The corrosion-resistant organic composite coating according to claim 1, characterized in that: The self-corrosion current density I corr For 10 -10 ~10 -4 A / cm 2 , the corrosion potential is -0.2~-2V.

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