JP2001335960A - Method for improving weather resistance of galvanized plating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the weather resistance of a galvanized plating on zinc and to prevent deterioration in its corrosion resistance even in case of prolonged exposure to strong ultraviolet rays. SOLUTION: In the case of chemical conversion treatment and coating performed after galvanizing, a Co and/or Mn compound is added to either or both of a chemically treating solution and a coating solution to form a film containing the same metals on the surface of the plating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a treatment solution for improving the weather resistance of a zinc-based plated material coated with zinc or a zinc alloy, and to a zinc-based plated material having improved weather resistance. The present invention is particularly effective in preventing the corrosion resistance of zinc-based plated products that are stored outdoors or are being used without painting.

[0002]

2. Description of the Related Art Zinc or zinc alloy plating is excellent in rust prevention of steel products and is inexpensive. Therefore, large-to-small parts can be obtained from primary processed products such as steel plates and wire rods by various forming methods such as press forming. It is most widely used as a plating method for iron and steel up to secondary processed products.

[0003] In recent years, in particular, zinc-based plating is often applied to a base material for painting, for example, the use of plated steel sheets for automobile bodies has become common, and the application area of zinc-based plating has been widened. Particularly in the case of automobiles, it has become common to apply zinc-based plating to small parts such as bolts and nuts to prevent deterioration of corrosion resistance from the parts.

[0004] As a post-treatment of zinc-based plating, a chemical treatment called a chemical conversion treatment is often performed in order to improve one or more characteristics such as corrosion resistance, coating adhesion, and post-paint corrosion resistance. Typical chemical conversion treatments are a chromate treatment and a phosphate treatment. Chromate treatment is a treatment having a large effect of improving corrosion resistance, and phosphate treatment is a treatment mainly for the purpose of improving paint adhesion.

[0005] In order to eliminate the deterioration of the working environment and the complexity of wastewater treatment in chromate treatment using a treatment solution containing hexavalent chromium, a chemical conversion treatment solution containing only trivalent chromium and further containing no chromium at all. A chemical conversion solution called non-chrome or chromium-free has been developed. Recently, the performance of non-chromium chemical conversion treatment liquids has been improved, and an effect of improving corrosion resistance that is not inferior to that of chromate treatment has been obtained. Therefore, it has been applied to zinc-based plating materials.

[0006] In addition, particularly for zinc-based plating materials used without painting or painted after molding, the plating surface subjected to chemical conversion treatment is mainly used to prevent the plating surface from being damaged during use or processing. It is also practiced to coat with a hard thin transparent inorganic or organic film by coating.

[0007]

As described above, zinc-based plated materials have excellent rust-preventive properties. In particular, if a coating is applied after chemical conversion treatment, the coating has a protective effect, and the corrosion resistance is extremely high. It will be good. However, recently, with the relocation of factories to regions with strong ultraviolet rays such as Southeast Asia, the corrosion resistance of zinc-based plating materials stored or used in outdoor environments in such regions may deteriorate over time. Has become a problem. For example, as described above, only the chemical conversion treatment, or a zinc-based plated material that has been subjected to chemical conversion treatment and post-treatment by coating, after long-term storage in an environment exposed to sunlight in such an area, coating, corrosion resistance Phenomena such as deterioration and peeling of the coating occur.

[0008] In other words, the weather resistance of the zinc-based plating material is not high enough to withstand outdoor exposure in an unpainted state in a region near the equator where ultraviolet rays are strong, such as Southeast Asia. The weather resistance of the zinc-based plated material has not received much attention so far. However, exports of galvanized parts, such as automobile parts, to Southeast Asia are increasing, and some parts are often stored outdoors or in an environment close to the outdoors. Has become an issue.

[0009] Improving the weatherability of zinc-based plated materials is not only important in Southeast Asia. Also in Japan, for example, as a building and civil engineering material, a relatively thick zinc-based plating material may be used outdoors without painting. Also in this case, by improving the weather resistance of the zinc-based plated material, a reduction in the corrosion resistance during long-term outdoor exposure is prevented, and the advantage that the service life of the product is extended is obtained.

[0010]

Means for Solving the Problems The present inventors have attempted to improve the weather resistance by a simple method so that the corrosion resistance does not decrease when a zinc-based plated material is exposed outdoors for a long time without painting. As a result of the investigation, a source of Co ions and / or Mn ions was added as a part of the film forming component to the chemical conversion treatment solution or coating solution used in the post-treatment of the zinc-based plating,
It has been found that forming a film containing Co and / or Mn on zinc-based plating improves weather resistance.

Although the reason why a film containing Co and / or Mn improves the weather resistance of zinc-based plating has not been elucidated, Co and Mn have a base and a rust preventive film (chemical conversion film or coating film). It has the function of improving adhesion,
It is presumed that this contributes to the improvement of weather resistance.

Here, the present invention is characterized in that at least one layer containing cobalt and / or manganese is formed on the surface of a zinc-based plating material on which zinc or zinc alloy plating has been applied. This is a method for improving the weather resistance of a zinc-based plated material.

According to another aspect, the present invention is characterized in that at least one layer containing cobalt and / or manganese is provided on a plating surface of a zinc-based plating material plated with zinc or a zinc alloy. It is a zinc-based plated material with excellent weather resistance that is unpainted and suitable for placing in an outdoor environment. The outdoor environment means not only the outdoor environment but also any environment where sunlight enters.

The coating may be one or both of a chemical conversion coating and a coating coating. That is, when forming both the chemical conversion treatment film and the coating film, one or both of them may contain Co and / or Mn.

According to the present invention, Co ions and / or Mn
There is also provided a processing solution for improving the weather resistance of a zinc-based plated material, characterized by containing ions as a film-forming component. The film formation of the treatment liquid can be performed by chemical conversion treatment or coating.

In the present invention, "chemical conversion treatment" refers to the
(Zinc-based plating) means a treatment for forming a film by a reaction between the treatment solution components, particularly an oxidation-reduction reaction, and "coating" means a treatment for forming a protective film performed after the chemical conversion treatment. The coating may or may not react with the base (chemical conversion coating) and the component of the processing solution. Since the object of the present invention is to improve the weather resistance of an unpainted zinc-based plated material, the coating contains substantially no coloring pigment.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The zinc-based plating material for improving the weather resistance in the present invention is not particularly limited. The form may be any of a primary processed product such as a steel plate, a wire rod, and a pipe material, and a secondary processed product formed by various forming processes such as press forming, casting, forging, cutting, and drilling. The secondary processed product includes both a final product and an unfinished product, and may be a part.

The base material of the zinc-based plating material is usually steel, but is not limited thereto. The plating type may be either pure zinc or a zinc alloy, and the plating method may be either electroplating or hot-dip plating. Representative examples of zinc alloys suitable for plating include, but are not limited to, Zn-Ni, Zn-Fe, and Zn-Al. Zinc alloy plating also includes zinc alloy plating in which Zn is a small element, such as hot-dip Zn-55% Al alloy plating, which has high corrosion resistance and is increasingly applied to building materials and the like. Also, a zinc-based plated material that has been subjected to a heat treatment after plating, such as galvannealed alloy, may be used. The adhesion amount of the zinc-based plating may be the same as the conventional one, but is not particularly limited. The zinc-based plating material may be a multi-layer plating material obtained by performing plating twice or more, and in that case, at least one plating layer may be a zinc-based plating material.

According to the present invention, Co ions and / or
A film containing Co and / or Mn is formed on the surface of a zinc-based plating material using a treatment solution containing Mn ions. This coating need not be provided in direct contact with the plating. For example, when two layers of film are formed on the plating,
Co and / or Mn may be contained in either the upper or lower coating.

The treatment liquid containing Co ions and / or Mn ions is not particularly limited as long as it has a film-forming function capable of forming a film containing Co and / or Mn. However, if Co ions and / or Mn ions are included in the treatment solution used as a post-treatment for zinc-based plating, the conventional method can be used without any additional steps to improve weather resistance. Improvement can be achieved, which is advantageous. In that sense, it is preferable that the treatment liquid used for one or both of the chemical conversion treatment and the coating performed after plating contains Co ions and / or Mn ions, and also serves as the treatment for improving the weather resistance of the present invention. . Hereinafter, this aspect will be described.

When performing both the chemical conversion treatment and the coating, the chemical conversion treatment that requires a reaction with the plating metal (particularly Zn) is performed first, and the coating is performed later. When a chemical conversion treatment and / or a coating is used to form a Co and / or Mn-containing film for improving weather resistance according to the present invention, a compound serving as a source of Co ions and / or Mn ions is added to the treatment solution. Except for the above, processing may be generally performed in the same manner as in the related art. Therefore, for example, a commercially available chemical conversion treatment solution or coating solution is used, and an appropriate Co
By adding and dissolving a source of ions and / or Mn ions, and then proceeding with the treatment in the same manner as before, the improvement of the weather resistance of the present invention can be achieved. That is, the process is exactly the same as the conventional process except for the operation of adding the source compound to the processing solution, and it is not necessary to perform a special process for improving the weather resistance.

In the chemical conversion treatment, a reaction occurs between the zinc-based plating material and the components of the chemical conversion treatment solution. Therefore, if necessary,
Before the chemical conversion treatment, a treatment for activating the surface by removing the oxide film from the surface of the zinc-based plated material is performed. If the chemical conversion treatment is performed immediately after hot-dip plating, or even in the case of electroplating, if the chemical conversion treatment is performed immediately after electroplating in a continuous electroplating line such as a steel plate, the surface is active. Not required. When dried after electroplating, when the secondary processed product is electroplated even if it is not dried (the plating surface often adsorbs organic brightener), and when a long time has passed after hot-dip plating, the active It is preferable to carry out a chemical treatment. This activation can be performed by dipping, spraying, or the like using an aqueous acid solution. Before that, if the surface of the zinc-based plating material is contaminated with oil or the like, it is preferable to perform degreasing such as alkali degreasing.

The type of chemical conversion treatment is not particularly limited. Any of chromate treatment, phosphate treatment, trivalent chromium treatment, and non-chromium conversion treatment may be used. Further, there is no limitation on the amount of adhesion, the forming method, and the forming conditions. Generally, the chemical conversion treatment solution is adjusted to an acidic pH so that Zn on the plating surface is dissolved and taken into the film.

For the chromate treatment, a reaction type (immersion type),
There are treatment methods such as a coating type and an electrolytic type, and any of them may be used. Zinc phosphate treatment is most often used as a phosphating treatment, but other phosphating treatments may be used.

For the non-chromium chemical conversion treatment, there is a method of using treatment solutions having various compositions, and any of them may be used. The most common non-chromium chemical conversion solution is silica sol
(Also called colloidal silica, wet silica, etc.) or silicate (eg, alkali metal salt of silicic acid) as the main film-forming component, and coexisted with various metal ions or metal compounds, and adjusted to acidic pH It is. As a main film-forming component, instead of the silica sol, a treatment liquid using another metal oxide sol such as titania sol or zirconia sol, or a metal salt such as tungstate or molybdate can be used.

After the chemical conversion treatment, the film is washed with water, heated to an appropriate temperature and dried to form a chemical conversion treatment film. However, when coating is performed after the chemical conversion treatment, it is preferable to perform coating immediately after washing with water without drying. As a result, a drying step that requires energy costs can be omitted once, and a surface cleaning treatment after drying is not required.

The coating, as described above, is not a normal coating, is a colorless pigment-containing, generally transparent, very thin protective coating. However, the coating may contain fine particles of submicron such as silica, titanium oxide, and alumina which do not hinder transparency. The thickness of the coating is usually about 0.5 to 5 μm. The coating may be inorganic, organic, or a combination of both, and the film forming components are not particularly limited as long as the protective film can be formed.

As the film forming component of the inorganic coating,
Various metal salts (eg, silicates, tungstates, molybdates, etc.), metal oxide sols (eg, silica, alumina, titania, zirconia, etc.) or hydrolyzable organic metals that are precursors thereof A solution of a compound (eg, a silicate ester, a silane coupling agent, an alkoxytitanium, an alkoxyzirconium, etc.) can be used.

The film-forming components of the organic coating include:
Various thermoplastic or thermosetting synthetic resins can be used. For example, polyolefins such as polyethylene,
Acrylic, epoxy, polyester, polyurethane, polyimide, polyamide and the like can be used. When the film forming component is only a synthetic resin, a bake-curable resin used as a primer, for example, epoxy, polyester, polyurethane or the like is preferable. Organic film-forming components other than synthetic resins can also be used, and examples thereof include high-molecular-weight organic substances derived from natural products such as tannic acid, phytic acid, and alginic acid.

In the coating liquid, in addition to the film forming components,
Additives such as coloring agents such as dyes and thickeners such as methylcellulose can be contained, but it is preferable that pigments are not contained except for the fine particles described above.

The application of the coating solution may be performed by any of conventional coating methods such as spraying, dipping, roll coating, and brushing, and an appropriate method may be selected according to the form of the zinc-based plating material. After the application of the coating liquid, the coating liquid is usually dried without washing with water to form a coating film. However, when the coating liquid is reactive with the base, the film is formed even if washed with water. The drying temperature is set according to the film forming components of the coating liquid.

The chemical conversion solution is generally an aqueous system. Although a solvent-based coating liquid can be used, an aqueous-based coating liquid is easier to handle. According to the present invention, in order to improve the weather resistance of a zinc-based plated material, a compound serving as a supply source of Co ions and / or Mn ions is added to at least one of the chemical conversion treatment solution and the coating solution to obtain Co and A chemical conversion coating and / or coating containing Mn is formed.

Examples of the additive compound include hydroxides of Co or Mn, inorganic acid salts (eg, nitrates, sulfates, chlorides, carbonates, etc.), organic acid salts (eg, acetates, etc.), and complexes ( Although carbonyl complexes and acetylacetonate complexes are possible, inorganic acid salts are preferred from the viewpoint of cost and ease of handling.

In order to sufficiently obtain the effect of improving the weather resistance of the zinc-based plating material, the amount of the metal of Co and / or Mn in the formed chemical conversion treatment film and / or coating is 0.2 mg / m 2.
It is preferably ² or more, more preferably 0.5 mg / m
² or more. The upper limit is not particularly limited, and may be increased to 10,000 mg / m ² . Co compounds are expensive, so Co
It is preferable that the concentration be 500 mg / m ² or less. The amount of the Co and / or Mn compound to be added to the chemical conversion treatment solution or the coating solution is set so that such an amount of Co and / or Mn is obtained. For this purpose, it is generally preferable that the content of Co and / or Mn in the liquid as a metal is 0.2 g / L or more. The metal content in the liquid is Co
Is preferably 5 g / L or less, and Mn is preferably 100 g / L or less.

The zinc-based plated material according to the present invention, which has at least one layer containing Co and / or Mn on the plating surface, has excellent weather resistance and is suitable for long-term outdoor use in a region with strong ultraviolet rays such as Southeast Asia. Even if stored in the environment,
Very little decrease in corrosion resistance. Therefore, even after coating, the problems such as a decrease in corrosion resistance and peeling of the coating, which are seen in the conventional product, do not occur.

[0036]

EXAMPLE Zinc plating and subsequent post-treatment were carried out by the following three treatment methods A, B and C. The zinc-based plating materials used, the drying conditions after plating, the plating method, the composition of the treatment solution, the treatment methods and the conditions, etc. are summarized in Tables 1 to 5. Both the chemical conversion treatment solution and the coating solution used are aqueous, and the balance of the indicated composition is water. In the examples, one or both of the chemical conversion treatment solution and the coating solution contained a manganese and / or cobalt compound.
For comparison, a treatment of a comparative example in which neither the chemical conversion treatment liquid nor the coating liquid contained a manganese or cobalt compound was performed. % In the examples is% by mass unless otherwise specified.

Process diagram Method A: Electroplating → water washing → acid activation → water washing → chemical conversion treatment → water washing → drying, method B: electroplating → water washing → acid activation → water washing → chemical conversion treatment → water washing → coating → drying, method C: Hot dip plating → Chemical conversion treatment → Washing → Coating →
Drying.

Method A Electrogalvanizing a cold-rolled steel sheet or bolt with a commercially available zinc or zinc alloy plating solution (adhesion thickness 8 μm).
m), washed with water, and then immersed in an acid aqueous solution containing 2 mL / L of 67.5% nitric acid at room temperature for 5 seconds to perform an activation treatment.
Thereafter, after washing with water, a chemical conversion treatment was performed by immersion or electrolysis using a chemical conversion treatment solution (all aqueous) having a predetermined composition, followed by washing with water and drying.

Method B In the same manner as in Method A, electrolytic zinc plating (adhesion thickness: 8 μm),
After performing water washing, activation treatment with an acid, water washing, chemical conversion treatment, and water washing, a coating liquid of a predetermined composition was applied by dipping or spraying before drying, and dried without washing with water.

Method C : A steel material (angle) coated with hot-dip zinc or a zinc alloy is subjected to a chemical conversion treatment using a chemical conversion treatment solution having a predetermined composition, washed with water, and then immersed in a coating solution having a predetermined composition before drying. And dried as it was without washing with water.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

[0045]

[Table 5] In order to evaluate the weather resistance of the post-treated zinc-based plated materials obtained in the above Examples and Comparative Examples, a part of the test materials were subjected to an accelerated weather resistance test (Sunshine Carbon Arc) in accordance with JIS D0205. Light type weather resistance test) [WAN-1S] to 300
Time went. In this test, the specimen is exposed to strong ultraviolet light under hot and humid conditions.

A salt water spray test (JIS Z2371) was performed for 24 hours on both the test material which had been subjected to the accelerated weathering test for 300 hours and the test material which had not been subjected to the accelerated weathering test, and the white rust generation area ratio was measured. If the corrosion resistance of the test material after performing the weather resistance test is lower than the corrosion resistance of the test material subjected to the salt spray test without performing the test, the weather resistance is poor. The results of the corrosion resistance are shown together with the film forming components in the treatment liquid in Table 6 below.

[0047]

[Table 6] As shown in Table 6, the zinc-based plated materials of Comparative Examples 1 to 5 were the same as any of the examples except that Co or Mn was not added to any of the chemical conversion treatment and the coating. . Before performing the weather resistance test, all of the zinc-based plated materials of these comparative examples had a white rust generation area ratio of 0% in the salt spray test and were excellent in corrosion resistance. However, after the accelerated weathering test was performed for 300 hours, the corrosion resistance was remarkably low, with the area ratio of white rust occurrence in the salt spray test being 40 to 90%.
The results were the same in Comparative Example 6 in which a chemical conversion treatment was performed with a hexavalent chromate treatment solution known to have high corrosion resistance.

As can be seen from the results of this comparative example, although there has not been much of a problem in the past, the zinc-based plated material is not sufficiently weather-resistant, and its corrosion resistance is reduced by temperature, humidity, and sunlight. In the chemical conversion treatment or the chemical conversion treatment + coating, the zinc-based plating material cannot be sufficiently protected against ultraviolet rays, and the weather resistance still remains low.

On the other hand, even when the same chemical conversion treatment or chemical conversion treatment + coating is carried out, according to the present invention, one or both of the chemical conversion treatment solution and the coating solution contain Co ions and / or Mn ions, and these are used. In the example in which the metal-containing film was formed on the plating surface, the area ratio of white rust in the salt spray test remained 0% even after the accelerated weathering test was performed for 300 hours, and good corrosion resistance was maintained. Was. In other words, chemical conversion coating or coating film
Only by adding Co and / or Mn, the weather resistance of the zinc-based plated material was significantly improved.

[0050]

According to the present invention, it becomes a supply source of Mn ions and / or Co ions to a chemical conversion treatment solution or a coating solution used in a chemical conversion treatment or coating performed as a post-treatment of a zinc-based plating material. Addition of a small amount of a compound can significantly improve the weather resistance of zinc-based plating materials, and eliminates the deterioration of corrosion resistance even when unpainted zinc-based plating materials are exposed to strong ultraviolet light in a high-temperature, high-humidity environment. Or be suppressed. That is, it is possible to improve the weather resistance of the zinc-based plated material without performing any special treatment for improving the weather resistance.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C23C 22/83 C23C 22/83 (72) Inventor Yasuhiro Nagatani 50 Nodamachibawari, Kariya City, Aichi Prefecture Yuken Kogyo Co., Ltd. (72) Inventor Nariya Kamiya 50 Nobacho, Noda-cho, Kariya-shi, Aichi Prefecture F-term (reference) 4K026 AA02 AA07 AA12 AA13 BA01 BA05 BA12 BB08 CA13 CA18 CA26 CA27 CA29 CA31 CA32 CA33 CA37 CA39 CA41 EA07 EA12 EB06 EB08 4K044 AA02 BA10 BA12 BA13 BA14 BA17 BA21 BB03 BB04 BC02 CA04 CA11 CA16 CA18 CA53

Claims (7)

[Claims] 1. A zinc-based plating material characterized by forming at least one layer containing cobalt and / or manganese on a surface of a zinc-based plating material on which zinc or zinc alloy plating has been applied. How to improve weather resistance. 2. The method according to claim 1, wherein the film is formed by a chemical conversion treatment and / or coating. 3. An unpainted outdoor environment characterized by having at least one layer containing cobalt and / or manganese on a plating surface of a zinc-based plating material on which zinc or zinc alloy plating has been applied. Suitable to put on,
A zinc-based plated material with excellent weather resistance. 4. The zinc-based plating material according to claim 3, wherein said film is a chemical conversion film and / or a coating film. 5. A film forming treatment for improving the weather resistance of a zinc-based plated material coated with zinc or a zinc alloy, characterized by containing Co ions and / or Mn ions as a film forming component. liquid. 6. The treatment solution according to claim 5, wherein the film is formed by a chemical conversion treatment. 7. The processing solution according to claim 5, wherein the film is formed by coating.