CN115261842A - Organic composite passivation treating fluid for hot-dip galvanized sheet and use method thereof - Google Patents

Abstract

The invention belongs to the technical field of surface treatment of hot galvanized plates, and provides an organic composite passivation treating fluid for hot galvanized plates and a using method thereof, wherein the treating fluid comprises the following raw materials in percentage by mass: 10-15% of waterborne epoxy resin, 1-10% of organic corrosion inhibitor, 1-3% of nano-particles, 1-5% of waterborne organic cosolvent and the balance of water. According to the invention, the water-based epoxy resin, the conductive organic corrosion inhibitor and the nano particles are combined, and the mixture is coated on the surface of the hot-dip galvanized plate by adopting a roller coating or dip coating mode, and then is baked and dried to obtain the uniform and compact high-performance organic composite coating. The water-based epoxy resin forms a compact effective barrier layer after being cured, the organic corrosion inhibitor and the nano particles are used as physical barriers to intercept corrosive ions from entering the surface of the galvanized plate, so that a double protection effect is achieved, the corrosion resistance of a surface coating is improved, and the corrosion resistance of the galvanized plate is improved.

Description

A kind of organic composite passivation treatment solution for hot-dip galvanized sheet and using method thereof

technical field

The invention belongs to the technical field of surface treatment of hot-dip galvanized sheets, and relates to a hot-dip galvanized surface treatment method with excellent corrosion resistance, in particular to an organic composite passivation treatment solution for hot-dip galvanized sheets and a use method thereof.

Background technique

As a common surface protection method, hot-dip galvanizing provides cost-effective protection for the use of steel materials. The zinc layer can not only serve as a barrier layer to prevent the corrosive medium from contacting the steel base, but also act as a sacrificial anode to slow down the corrosion of the steel base. However, with the increasing requirements for anti-corrosion in increasingly harsh service environments, traditional hot-dip galvanized steel sheets no longer meet the needs of contemporary anti-corrosion. In order to further improve the corrosion resistance of the hot-dip galvanized steel sheet, the surface of the hot-dip galvanized sheet is usually passivated. Among them, the most economical and effective surface treatment is chromate passivation technology, which has simple process, low cost, good film adhesion, and self-healing effect. It is a classic process to improve the corrosion resistance of hot-dip galvanized sheets. However, chromate coatings containing hexavalent chromium are carcinogenic. For safety and environmental considerations, there has been an increasing demand for environmentally friendly chromium-free passivation treatment processes in recent years.

At present, the most concerned chromium-free treatment technologies for hot-dip galvanized surfaces include the passivation of inorganic substances such as molybdate, phosphate, silicate, and rare earth metal salts, and the passivation of organic substances such as phytic acid and silane, as well as some organic/inorganic composites. Synergistic passivation technology. Among them, after the environment-friendly inorganic passivation treatment (including conversion treatment such as molybdate, phosphate, silicate, rare earth metal salt, etc.), the corrosion resistance of the film layer is far lower than that of the chromate passivation film. There is a problem of insufficient corrosion resistance; after organic passivation treatment (including phytic acid, silane, etc.), although the corrosion resistance of the film layer has improved, the conductivity of the film layer will decrease. There may be a problem of poor grounding; organic/inorganic composite passivation technology (including silane/rare earth composite film, etc.) combines the advantages of both, but the metal surface treatment composed of general water-based resin and inorganic components still has acid resistance. , Alkaline and salt spray resistance.

At the same time, with the increasing demand for galvanized sheets with good coating properties in the domestic automobile, household appliances, construction and other industries, the adhesion of hot-dip galvanized passivated sheets after coating has become a problem that restricts subsequent processing and industrial applications. difficulty. At the same time, in the coating process, electrostatic spraying has gradually become the most commonly used spraying process in production because it can greatly improve the utilization rate of paint, and has the characteristics of high spraying efficiency, uniform coating, and less pollution. The principle of electrostatic coating is to generate an electric field by applying DC high voltage between the workpiece and the coating tool, and use electrostatic attraction to make the paint evenly adsorbed on the workpiece. At this time, in order to make the hot-dip galvanized sheet after surface treatment meet the requirements of electrostatic coating, it is necessary to give the hot-dip galvanized passivation sheet good surface conductivity. Therefore, in order to meet the various application requirements of the coating process, the surface treatment technology of hot-dip galvanized sheet gradually develops into multifunctional composite coatings, such as high-performance coatings integrating corrosion resistance, electrical conductivity, and coating properties.

For example, the patent number is: CN107400883A, the invention patent named: silane/zirconium composite treatment agent before coating of galvanized sheet and its preparation method discloses a silane/zirconium composite treatment agent and its preparation method before coating of galvanized sheet, The composite treatment agent is mainly composed of silane, zirconium fluoride complex, zirconate, rare earth cerium salt, alcohol and deionized water, etc. The composite treatment agent is prepared by chemical compounding, and the composite treatment agent can be Applied to the chemical conversion surface treatment of galvanized sheet before painting. The silane composite film layer obtained by the composite treatment agent has excellent combination performance with organic coatings, and has good coating performance.

For example, the patent number is: CN102251239B, and the name is: A kind of invention patent of color-coated chromium-free passivation solution for galvanized steel sheets based on water-based epoxy resin composites. Passivation solution, the components of the chromium-free passivation solution and their content per liter are: organic resin: 100-300g/L; organic acid: 20-75g/L; inorganic salt: 2-6g/L; oxidant: 3 ~12g/L, pH adjuster: appropriate amount; deionized water: remaining amount. Phosphoric acid is used as a pH regulator to adjust the pH of the chromium-free passivation solution to 2-3. The invention organically combines water-based epoxy resin, organic acid, inorganic salt and oxidizing agent to form a dense organic-inorganic composite passivation film after acting on the galvanized sheet. Coating process, reduce cost.

For example, the patent number is: CN102070927B, and the name is: the invention patent of water-based surface treatment agent for color coating pretreatment of galvanized steel sheet discloses a water-based surface treatment agent for color coating pretreatment of galvanized steel sheet, and the galvanized steel sheet provided by the invention The components and mass percentages of the water-based surface treatment agent for color coating pretreatment are as follows: water-based resin, 20-60%; organosilane, 1-5%; inorganic corrosion inhibitor, 0.5-2.5%; sealant, 0.5-3%; agent, 1~3; deionized water, the balance. The invention organically combines inorganic corrosion inhibitors, nanoparticles, organic silanes and water-based resins to form a composite passivation film, improves the coating performance of the galvanized sheet after surface treatment, and can meet the requirements of the color coating process.

The above organic/inorganic passivation treatment methods can all achieve the effect of enhancing the bonding force between organic coatings and hot-dip galvanized sheets. However, compared with traditional chromate passivation, they all have the disadvantage of insufficient corrosion resistance. At the same time, in order to meet According to the requirements of electrostatic coating, the film layer after passivation treatment also needs to meet certain conductivity requirements. Therefore, it is very necessary to develop a paintable passivation treatment process with excellent corrosion resistance and conductivity.

Contents of the invention

The invention provides an organic composite passivation treatment solution for hot-dip galvanized sheets and a using method thereof. The purpose is to solve the problem of insufficient corrosion resistance of the hot-dip galvanized passivation treatment composed of general water-based resin and inorganic components and the problem of poor conductivity of the organic coating.

The present invention is to form a layer of water-based epoxy resin with excellent corrosion resistance, good electrical conductivity and coating performance on the hot-dip galvanized surface under certain process conditions by adding organic corrosion inhibitors and nanoparticles with conductive properties to the water-based epoxy resin. Epoxy resin/organic corrosion inhibitor/nanoparticle composite coating.

The specific plan is as follows:

An organic composite passivation treatment solution for hot-dip galvanized sheets, the raw materials include:

The preparation method of the treatment solution is as follows: adding the water-based organic co-solvent, the organic corrosion inhibitor, the nano-particles and the water-based epoxy resin into water in sequence, and stirring evenly at room temperature to obtain a surface passivation solution.

Preferably, the water-based epoxy resin is one of polyurethane resin, polyvinyl alcohol resin, acrylic resin and butyral resin.

Preferably, the organic corrosion inhibitor is one of polyaniline, polypyrrole and polythiophene.

Preferably, the nanoparticles are one of nano-carbon black particles, nano-graphene and nano-silicon oxide.

Preferably, the aqueous organic co-solvent is one of n-heptane, tetrachloroethane, dimethylformamide, cyclohexane and tetrahydrofuran.

Preferably, the organic corrosion inhibitor and the water-based organic co-solvent are dissolved in water, stirred at room temperature for 10-30 minutes, then the nanoparticles are added, stirred for 8-10 minutes, and finally the water-based epoxy resin is added and stirred evenly.

Another object of the present invention is to provide a method for using an organic composite passivation treatment solution for hot-dip galvanized sheets, after the surface passivation treatment solution described in claim 1 is coated on the surface of a galvanized sheet, and then baked dry.

Preferably, the coating is carried out by roll coating or dip coating.

Preferably, the baking and drying temperature is 80-150° C., and the baking and drying time is 40-60 minutes.

Further, the thickness of the composite coating obtained after the baking and drying is 5-7 μm.

The beneficial effects of the present invention are:

① Various components in the surface passivation solution of hot-dip galvanized sheet provided by the present invention have synergistic effects: the organic corrosion inhibitor in the passivation solution is a conductive polymer doped with anions, which can accept free electrons by releasing anions To achieve electrical conductivity, it and water-based epoxy resin can ensure the electrical conductivity of the surface passivation layer through molecular entanglement and electrostatic interaction, while the organic corrosion inhibitor can also act as a physical barrier with nanoparticles to intercept electrons in the metal The transmission between the surface and the electrolyte improves the corrosion resistance of the film layer.

②The galvanized sheet prepared by the surface passivation solution of hot-dip galvanized sheet provided by the present invention not only has good coating performance, but also has certain electrical conductivity, which can meet the coating requirements, especially the use requirements of electrostatic coating.

③ The surface passivation solution for hot-dip galvanized sheet provided by the present invention is a green and environment-friendly surface treatment solution.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the following technical solutions in the present invention are clearly and completely described. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Unless otherwise specified, all terms used in the specification have the meanings commonly understood by those skilled in the art. Well-known functions or constructions are not described in detail for brevity and/or clarity.

First prepare the surface passivation treatment solution for hot-dip galvanized sheet, the raw materials are calculated by mass percentage, water-based epoxy resin 10-15%, organic corrosion inhibitor 1-10%, nanoparticles 1-3%, water-based organic co-solvent 1-5% %, the balance is water. Dissolve the organic corrosion inhibitor and water-based organic co-solvent in water, stir at room temperature for 10-30 minutes, then add nanoparticles and stir for 8-10 minutes, and finally add water-based epoxy resin and stir evenly. Among them, the water-based epoxy resin is one of polyurethane resin, polyvinyl alcohol resin, acrylic resin, and butyral resin; the organic corrosion inhibitor is one of polyaniline, polypyrrole and polythiophene; the nanoparticles are nano-carbon black particles , nano-graphene and nano-silicon oxide; the water-based organic co-solvent is one of n-heptane, tetrachloroethane, dimethylformamide, cyclohexane and tetrahydrofuran.

Then, the above-mentioned hot-dip galvanized sheet surface passivation treatment solution is coated on the surface of the galvanized sheet by roll coating or dip coating, and baked and dried at 80-150° C. for 40-60 minutes.

The following will be further elaborated in conjunction with the following examples and comparative examples. The test methods described in the examples, unless otherwise specified, are conventional methods; the reagents and materials, unless otherwise specified, can be obtained from commercial sources.

Example 1

The preparation of the surface passivation treatment solution for the hot-dip galvanized sheet in this example: raw materials are calculated by mass percentage, 2% polyaniline is dissolved in 5% n-heptane, 80% water is added, stirred at room temperature for 10 minutes, and then 3% nanometer Carbon black particles, stirred for 8 minutes, and finally added 10% polyurethane resin, stirred evenly. The prepared passivation treatment solution was coated on the surface of the galvanized sheet by roller coating, and baked and dried at 120° C. for 40 minutes.

Example 2

The preparation of the surface passivation treatment liquid of this embodiment hot-dip galvanized sheet: the raw materials are calculated by mass percentage, 4% polypyrrole is dissolved in 1% tetrachloroethane, add 80% water, stir at room temperature for 10min, then add 2% polypyrrole Nano-graphene, stirring for 8 minutes, and finally adding 13% polyvinyl alcohol resin, stirring evenly. The prepared passivation treatment solution was coated on the surface of the galvanized sheet by roller coating, and baked and dried at 100° C. for 50 minutes.

Example 3

The preparation of the surface passivation treatment liquid for the hot-dip galvanized sheet of this embodiment: raw materials are calculated by mass percent, 6% polythiophene is dissolved in 2% dimethylformamide, add 77% water, stir at room temperature for 10 minutes, then add 3 % nano-silica, stirred for 8 minutes, and finally added 12% acrylic resin, and stirred evenly. The prepared passivation treatment solution was coated on the surface of the galvanized sheet by roller coating, and baked and dried at 80° C. for 60 minutes.

Example 4

The preparation of the surface passivation treatment solution for the hot-dip galvanized sheet in this embodiment: the raw materials are calculated by mass percentage, 8% polyaniline is dissolved in 3% cyclohexane, 76% water is added, stirred at room temperature for 10 minutes, and then 2% nanometer Graphene, stirred for 8 minutes, finally added 11% butyral resin, and stirred evenly. The prepared passivation treatment solution was coated on the surface of the galvanized sheet by roller coating, and baked and dried at 110° C. for 50 minutes.

Example 5

The preparation of the surface passivation treatment liquid of the hot-dip galvanized sheet in this embodiment: raw materials are calculated by mass percentage, 10% polypyrrole is dissolved in 4% tetrahydrofuran, add 70% water, stir at room temperature for 10min, then add 1% nano-silicon oxide , stirred for 8 minutes, and finally added 15% polyurethane resin, and stirred evenly. The prepared passivation treatment solution was coated on the surface of the galvanized sheet by roller coating, and baked and dried at 150° C. for 40 minutes.

Comparative example 1

The preparation of the surface passivation treatment solution for hot-dip galvanized sheet in this embodiment: the raw materials are calculated by mass percentage, 10% polyurethane resin and 90% water are mixed and stirred for 20 minutes. The prepared passivation treatment solution was coated on the surface of the galvanized sheet by roller coating, and baked and dried at 120° C. for 40 minutes.

Comparative example 2

The preparation of the surface passivation treatment liquid of the hot-dip galvanized sheet in this embodiment: the raw materials are calculated by mass percentage, 3% nano-graphene, 10% polyurethane resin and 87% water are mixed and stirred for 20 minutes. The prepared passivation treatment solution was coated on the surface of the galvanized sheet by roller coating, and baked and dried at 120° C. for 40 minutes.

Comparative example 3

The preparation of the surface passivation treatment liquid for hot-dip galvanized sheet in this embodiment: the raw materials are calculated by mass percentage, 2% polypyrrole, 10% polyurethane resin and 88% water are mixed and stirred for 20 minutes. The prepared passivation treatment solution was coated on the surface of the galvanized sheet by roller coating, and baked and dried at 120° C. for 40 minutes.

test result

Evaluate the corrosion resistance of the galvanized sheet after the present invention's treatment is to carry out the corrosion test by the method and the condition stipulated in GB/T10125, then evaluate the corrosion result according to the regulations of GB12335-90 (accounting for the total area with the corrosion area after 72h expressed as a percentage). Among them, the smaller the corrosion area, the better (currently, the corrosion resistance of the hot-dip galvalume coating generally requires NSST/72h corrosion area ≤ 5%). The test results are shown in Table 1.

Evaluate the paintability of the galvanized sheet after the present invention's treatment is to carry out according to the adhesion (cross-cut test) of the double coating after the sample is coated with varnish: the cross-cut test is with reference to the national standard GB/T9286, utilizes QFH cross-cut test After the knife is scratched on the surface, lightly brush the surface of the sample with a soft brush, seal the scratched part with Scotch600 transparent tape for 5 minutes, pull out the tape within 1 to 2 seconds, and observe the shedding area of the smooth edge of the cut . If the varnish coating has no peeling off or warping, it is grade 0; if there is slight warping, it is grade 1; if there is a small amount of peeling off, it is grade 2; if there is a lot of peeling off, it is grade 3. The test results are shown in Table 1.

Through the comparison of Examples 1-5 and Comparative Examples 1-3, it can be seen that the galvanized sheet treated with the surface passivation solution provided by the present invention has both excellent corrosion resistance and coating performance.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Table 1 The results of corrosion resistance and coating properties in Examples 1 to 5 and Comparative Examples 1 to 3

Corrosion resistance (corrosion area)/% Paintability Example 1 3 0 Example 2 1 0 Example 3 2 0 Example 4 3 1 Example 5 3 0 Comparative example 1 7 1 Comparative example 2 6 1 Comparative example 3 4 1

Claims (10)

1. An organic composite passivation treating fluid for hot-dip galvanized sheets is characterized in that: the treatment fluid comprises the following raw materials in percentage by mass:

the preparation method of the treatment liquid comprises the following steps: and sequentially adding the water-based organic cosolvent, the organic corrosion inhibitor, the nano particles and the water-based epoxy resin into water, and uniformly stirring at normal temperature to obtain the surface passivation solution.

2. The treatment liquid according to claim 1, characterized in that: the waterborne epoxy resin is one of polyurethane resin, polyvinyl alcohol resin, acrylic resin and butyraldehyde resin.

3. The treatment liquid according to claim 1, characterized in that: the organic corrosion inhibitor is one of polyaniline, polypyrrole and polythiophene.

4. The treatment liquid according to claim 1, characterized in that: the nano-particles are one of nano-carbon black particles, nano-graphene and nano-silicon oxide.

5. The treatment liquid according to claim 1, characterized in that: the aqueous organic cosolvent is one of n-heptane, tetrachloroethane, dimethylformamide, cyclohexane and tetrahydrofuran.

6. The treatment liquid according to claim 1, characterized in that: dissolving the organic corrosion inhibitor and the water-based organic cosolvent in water, stirring for 10-30 min at normal temperature, then adding the nanoparticles, stirring for 8-10 min, and finally adding the water-based epoxy resin and stirring uniformly.

7. A use method of an organic composite passivation treatment fluid for a hot-dip galvanized sheet is characterized by comprising the following steps: the surface passivation treatment solution of claim 1 is applied to the surface of a galvanized plate and then baked and dried.

8. Use according to claim 7, characterized in that: the coating is carried out by adopting a roll coating or dip coating mode.

9. Use according to claim 7, characterized in that: the baking and drying temperature is 80-150 ℃, and the baking and drying time is 40-60 min.

10. Use according to claim 7, characterized in that: the thickness of the composite coating obtained after baking and drying is 5-7 mu m.