JP5886114B2 - Zn-Al alloy plating method - Google Patents

Description

  The present invention relates to a Zn—Al-based alloy plating method capable of obtaining a sufficient plating adhesion amount at a relatively low bath temperature.

For example, hot-dip Zn plating is widely used as a plating for steel materials used in civil engineering structures and building structures. The durability of hot-dip Zn plating is demonstrated according to the amount of adhesion. For example, the melting applied to steel used in severe corrosive environments such as coasts where the concentration of sea salt particles is high and areas where anti-freezing agents are sprayed. For Zn plating, an adhesion amount of 550 g / m ² or more is required according to HDZ55 of JIS H8641.

  A Zn-Al alloy is known as a plating material having higher corrosion resistance than Zn. However, since Al suppresses an alloy reaction between Fe and Zn in a steel material, the adhesion amount of Zn-Al alloy plating is higher than that of hot-dip Zn plating. Few. Therefore, in the Zn-Al alloy plating, the time required for the steel material to be exposed after the surface deterioration starts is not significantly different from the molten Zn plating. Therefore, the corrosion resistance of the entire coating of the Zn-Al alloy plating is the molten Zn plating. It is not necessarily high compared with.

  In order to obtain a sufficient amount of deposition of Zn—Al alloy plating, it is known that a two-bath method of treating with a Zn—Al alloy plating bath after treatment with a hot Zn plating bath mainly composed of Zn is effective. Yes. However, the two-bath method using a molten Zn plating bath and a Zn—Al alloy plating bath has a problem that so-called burn, which is an abnormal growth of the Fe—Zn alloy layer, and peeling of the Zn—Al alloy layer due to burn.

  In order to solve such problems, Japanese Patent Application Laid-Open No. 4-160143 (Patent Document 1) describes a treatment using a hot-dip Zn plating bath containing 0.03% by weight of Ni as a Zn-Al alloy plating method by a two-bath method. After the treatment, a method of treating with a hot dip Zn plating bath containing 3 to 10% by weight of Al is disclosed.

However, since the Zn—Al alloy plating by the method of Patent Document 1 can only obtain an adhesion amount of about 350 to 430 g / m ² , the corrosion resistance in an environment with a high chloride ion concentration is insufficient.

Here, it can be said that the Zn—Al alloy plating surely has higher corrosion resistance than the hot-dip Zn plating if it can realize an adhesion amount of 550 g / m ² or more required for hot-dip Zn plating with the HDZ55 of JIS H8641.

In JP-A-4-280952 (Patent Document 2), as a Zn-Al alloy plating method by a one-bath method, Al is contained in 3 to 10% by weight, Ni is contained in 0.01 to 0.10% by weight, and the balance A method of treating at a bath temperature of 490 to 600 ° C. using a Zn—Al alloy plating bath composed of Zn and inevitable impurities is disclosed. In this plating method, Ni is added to the plating bath in order to increase the bath temperature in order to increase the adhesion amount as compared with the conventional one-bath method and to suppress excessive adhesion of plating. Accordingly, when the conventional one-bath method was only attached amount of about 200 g / ^{m 2,} in an attempt to obtain the deposition amount of 350~440g / ^{m 2} greater than 300 g / ^{m 2} obtained by 2-bath method Yes.

However, the adhesion amount of the Zn—Al alloy plating by the method of Patent Document 2 is less than 550 g / m ^{2 of the} adhesion amount required for hot-dip Zn plating in a severe corrosion environment, so that the corrosion resistance in a severe corrosion environment is sufficient. It cannot be said. In addition, since this plating method has a relatively high bath temperature, the steel material may be affected by thermal distortion. Furthermore, there are problems of deterioration of the plating work environment due to the high bath temperature, an increase in fuel cost, and a shortening of the life of the plating tank.

  In JP-A-7-233458 (Patent Document 3), as a Zn-Al alloy plating method by a one-bath method, Al is selected from one or two selected from 2 to 20% by weight, Ni and Co. A method is disclosed in which a treatment is performed at a bath temperature of 430 to 500 ° C. using a Zn—Al alloy plating bath containing a total of 0.005 to 2.0% by weight of the components, the balance being Zn and inevitable impurities. . This plating method attempts to obtain a relatively large amount of adhesion while suppressing the influence of thermal distortion on the steel material by a relatively low bath temperature of 500 ° C. or less.

  However, since the Zn-Al alloy plating method of Patent Document 3 is a one-bath method, the alloy reaction of Fe and Zn is suppressed by Al present in a relatively high concentration in the plating bath, and the surface of the steel material is Fe-Al. -There is a problem that the Zn alloy layer is not sufficiently formed and an unplated portion is likely to occur. In addition, the cooling rate of plating is set to 5 ° C./sec or more, and this cooling rate can be realized in the continuous plating process, but is difficult to realize in the batch type plating process.

  In Japanese Patent Application Laid-Open No. 2004-83950 (Patent Document 4), a steel material was subjected to Zn plating and solidified, and then heated to a temperature at which this Zn plating layer could be in a molten state, and then subjected to Zn plating. A method is described in which Zn—Al alloy plating is performed by pouring a molten Zn—Al alloy at 420 to 650 ° C. onto the surface of a steel material. This plating method is advantageous in that the size of the steel material to be plated is not limited depending on the size of the plating tank, and a tank for the Zn-Al alloy bath is not required.

JP-A-4-160143 JP-A-4-280952 JP 7-233458 A JP 2004-83950 A

  However, the Zn-Al alloy plating method of Patent Document 4 has a problem that the thickness of the Zn-Al alloy plating layer tends to be uneven because the molten Zn-Al alloy is poured onto the surface of the molten Zn plating layer. is there.

  Moreover, when a Zn-Al alloy molten metal exceeds 490 degreeC, there exists a possibility of giving the influence of a thermal distortion to steel materials, the environmental deterioration of the metal-plating operation resulting from the height of hot water temperature, and the problem of increase in fuel cost.

  Accordingly, the problem of the present invention is that a sufficient amount of plating can be obtained, the influence of thermal strain on the material to be plated is small, non-plating can be prevented, and a plating film having a good surface state can be obtained. It is providing the Zn-Al type alloy plating method.

In order to solve the above problems, the present invention is summarized as follows.
(1) The material to be plated is composed of 0.001 to 0.01% by weight of Al, 0.01 to 0.1% by weight of Ni, the balance of Zn and inevitable impurities, and a bath temperature of 420 to 490 ° C. After being immersed in 1 plating bath, Al is 4 to 20% by weight, Ni is 0.01 to 0.1% by weight, Mg is 1 to 5% by weight, and Pb is 0.5 to 1.4% by weight. Is at least one selected from the group consisting of 0.05 to 0.5 wt%, In is 0.05 to 0.5 wt%, and Sn is 0.1 to 1.0 wt%, with the balance being Zn and inevitable A Zn—Al-based alloy plating method comprising an impurity and dipping in a second plating bath having a bath temperature of 420 to 490 ° C.
(2) The Zn—Al-based alloy plating method according to the above (1), wherein the plating adhesion amount is 550 g / m ² or more.

  ADVANTAGE OF THE INVENTION According to this invention, the influence of the thermal distortion to a to-be-plated material is little, and it can obtain the Zn-Al type alloy plating film which has a sufficient surface state and sufficient adhesion amount, preventing non-plating. Moreover, since the adhesion amount equivalent to hot-dip Zn plating is obtained, the Zn-Al type alloy plating film whose corrosion resistance is higher than hot-dip Zn plating reliably is obtained.

  Hereinafter, the present invention will be described in detail.

  In the Zn—Al-based alloy plating method of the present invention, first, a steel material as a material to be plated is composed of 0.001 to 0.01% by weight of Al, 0.01 to 0.1% by weight of Ni, and the balance of Zn and It is immersed in a first plating bath made of inevitable impurities and having a bath temperature of 420 to 490 ° C. After dipping in the first plating bath, Al is 4 to 20% by weight, Ni is 0.01 to 0.1% by weight, Mg is 1 to 5% by weight, and Pb is 0.5 to 1.4% by weight. At least one selected from the group consisting of 0.05 to 0.5% by weight of Bi, 0.05 to 0.5% by weight of In and 0.1 to 1.0% by weight of Sn, with the balance being Zn And immersed in a second plating bath composed of inevitable impurities and having a bath temperature of 420 to 490 ° C.

By the first plating bath, an Fe—Zn alloy layer and a single Zn layer having a uniform thickness are formed on the surface of the material to be plated, and a molten Zn plating film having a uniform thickness is formed. By this first plating bath, an adhesion amount of 550 g / m ² similar to that of a normal hot-dip Zn plating film can be obtained. Next, a Fe—Al—Zn alloy layer and a Zn—Al layer are formed in this order from the substrate side to the surface of the material to be plated by the second plating bath, and the Zn—Al alloy plating film having a uniform thickness is formed. Is formed. Thus, the Fe—Zn alloy layer in which the alloy reaction is not suppressed by Al is formed by the first plating bath that has almost no Al content and is mainly Zn. Thereafter, the second plating bath having a large Al content promotes the alloy reaction of Fe—Zn or Zn and Al, in which the alloy reaction proceeds more easily than Fe alone, thereby providing a large amount of Fe—Al—. A Zn alloy layer can be formed. The Zn—Al-based alloy plating film formed by the first plating bath and the second plating bath has an adhesion amount of 550 g / m ² similar to a general hot-dip Zn plating film. Therefore, a plating film having higher corrosion resistance than the hot-dip Zn plating film can be obtained. As the material to be plated, steel materials can be widely applied.

  The first plating bath can suppress so-called burns, which are abnormal growth of the Fe—Zn alloy layer, by 0.01 to 0.1 wt% of Ni, and make the thickness of the Fe—Zn alloy layer uniform. be able to. As a result, plating growth failure in the second plating bath due to burn can be prevented, and peeling of the plating film and dullness of the plating surface can be prevented. Here, when the Ni content in the first plating bath is less than 0.01% by weight, the effect of suppressing abnormal growth of the Fe—Zn alloy layer becomes insufficient. On the other hand, when the content of Ni in the first plating bath is larger than 0.1% by weight, the effect of suppressing the abnormal growth of the Fe—Zn alloy layer reaches its peak, and Ni reacts with Fe or the like in the plating bath. As a result, an intermetallic compound is formed, and the aggregate of the intermetallic compound adheres when the material to be plated is pulled out of the plating bath, causing a surface state defect.

  Further, 0.001 to 0.01 wt% Al in the first plating bath can suppress abnormal growth of the Fe—Zn alloy layer, so-called burn, and make the thickness of the Fe—Zn alloy layer uniform. be able to. As a result, plating growth failure in the second plating bath due to burn can be prevented, and peeling of the plating film and dullness of the plating surface can be prevented. Here, when the Al content in the first plating bath is less than 0.001% by weight, the effect of suppressing abnormal growth of the Fe—Zn alloy layer becomes insufficient. On the other hand, if the Al content in the first plating bath is larger than 0.01% by weight, the alloy reaction of Fe and Zn is hindered, and an unplated portion may occur.

  Moreover, since the bath temperature of the first plating bath is 420 to 490 ° C., it is possible to prevent inconvenience that thermal distortion occurs in the material to be plated, and it is possible to prevent the plating film from cracking due to the thermal distortion of the material to be plated. Furthermore, the environment of the plating operation can be improved, the fuel cost of the plating bath can be reduced, and the plating tank can be prevented from being damaged due to the high temperature. Here, when the bath temperature of the first plating bath is higher than 490 ° C., the influence of thermal strain becomes large, and there is a possibility that the material to be plated is distorted and the plating film is cracked. Furthermore, there may be problems such as deterioration of the plating work environment, increase in the fuel cost of the plating bath, and shortening of the life of the plating tank. On the other hand, if the bath temperature of the first plating bath is lower than 420 ° C., the viscosity of the plating solution is increased, causing problems such as uneven thickness of the plating film and poor surface condition. is there.

  The second plating bath forms a Zn—Al plating layer having higher corrosion resistance than Zn with 4 to 20% by weight of Al. Here, when the Al content of the second plating bath is less than 4% by weight, the corrosion resistance is not sufficiently improved. On the other hand, if the Al content of the second plating bath is greater than 20% by weight, the effect of improving the corrosion resistance will reach its peak, making it difficult to further improve the corrosion resistance. Further, if the Al content is larger than 20% by weight, the melting point of the plating bath becomes high, so that it is necessary to raise the bath temperature, which causes inconvenience of thermal distortion of the material to be plated and inconvenience of cracking of the plating film. It can happen. Furthermore, there may be problems such as deterioration of the plating work environment, increase in the fuel cost of the plating bath, and shortening of the life of the plating tank. Furthermore, the material to be plated is annealed by the heat of the plating bath, and the mechanical properties of the material to be plated may be deteriorated.

  The second plating bath promotes the diffusion of Al into the Fe—Zn alloy layer formed on the surface of the base material of the material to be plated in the first plating bath with 0.01 to 0.1% by weight of Ni. The formation of the Fe—Al—Zn alloy layer can be promoted, and as a result, the plating adhesion amount can be effectively increased. Here, when the Ni content in the second plating bath is less than 0.01% by weight, the effect of diffusing Al into the Fe—Zn alloy layer becomes insufficient. On the other hand, if the Ni content in the second plating bath is greater than 0.1% by weight, the effect of Al diffusion into the Fe—Zn alloy layer reaches its peak, and Ni reacts with Fe and the like in the plating bath. As a result, an intermetallic compound is formed, and the aggregate of the intermetallic compound adheres when the material to be plated is pulled out of the plating bath, causing a surface state defect.

  Further, since the second plating bath contains Ni, the viscosity of the plating solution can be effectively lowered, so that it is possible to prevent excessive adhesion of plating and to prevent dripping and to remove dripping. Thus, it is possible to reduce the time and effort of finishing, and to obtain a good surface state of plating.

  The second plating bath can improve the corrosion resistance of the plating film due to a synergistic effect with Al by 1 to 5% by weight of Mg. Here, if the content of Mg is less than 1% by weight, the effect of improving the corrosion resistance of the plating film becomes insufficient. On the other hand, when the content of Mg is larger than 5% by weight, the effect of improving the corrosion resistance of the plating film reaches its peak, and the plating film becomes hard and brittle. Cracks can occur.

  In the second plating bath, Pb is 0.5 to 1.4% by weight, Bi is 0.05 to 0.5% by weight, In is 0.05 to 0.5% by weight, and Sn is 0.1 to 1%. The viscosity of the plating solution can be effectively lowered by at least one selected from the group consisting of 0.0 wt%. Accordingly, it is possible to prevent inconveniences that occur when the material to be plated is pulled up from the plating bath. Moreover, while being able to make the thickness of a plating film uniform, the plating surface can be smoothed and the plating film of a favorable surface state is obtained. Here, when Pb is less than 0.5% by weight, the effect of reducing the viscosity of the plating solution becomes insufficient. On the other hand, when Pb is larger than 1.4% by weight, the effect of reducing the viscosity of the plating solution reaches its peak. It becomes. On the other hand, when Bi is less than 0.05% by weight, the effect of reducing the viscosity of the plating solution is insufficient. On the other hand, when Bi is greater than 0.5% by weight, the effect of reducing the viscosity of the plating solution is peaked. Become. Moreover, when In is less than 0.05% by weight, the effect of reducing the viscosity of the plating solution becomes insufficient. On the other hand, when In is greater than 0.5% by weight, the effect of reducing the viscosity of the plating solution is peaked. Become. On the other hand, when Sn is less than 0.1% by weight, the effect of reducing the viscosity of the plating solution becomes insufficient. On the other hand, when Sn is larger than 1.0% by weight, the effect of reducing the viscosity of the plating solution is peaked. Become.

  Moreover, since the bath temperature of the second plating bath is 420 to 490 ° C., it is possible to prevent inconvenience that thermal distortion occurs in the material to be plated, and it is possible to prevent the plating film from being cracked due to the thermal distortion of the material to be plated. Furthermore, the environment of the plating operation can be improved, the fuel cost of the plating bath can be reduced, and the plating tank can be prevented from being damaged due to the high temperature. Here, when the bath temperature of the second plating bath is higher than 490 ° C., the influence of thermal strain becomes large, and there is a possibility that the material to be plated is distorted and the plating film is cracked. Furthermore, there may be problems such as deterioration of the plating work environment, increase in the fuel cost of the plating bath, and shortening of the life of the plating tank. In particular, when the bath temperature of the second plating bath exceeds 490 ° C., the oxidation of Mg in the plating bath proceeds rapidly, and there is a problem that the plating operation becomes difficult. On the other hand, if the bath temperature of the second plating bath is lower than 420 ° C., the viscosity of the plating solution may increase and cause problems such as uneven thickness of the plating film and poor surface condition. is there.

In the Zn—Al-based alloy plating method of the present invention, the plating adhesion amount is 550 g / m ² or more.

The Zn—Al-based alloy plating method of the present invention can obtain a plating adhesion amount of 550 g / m ² or more required for hot-dip Zn plating by HDZ55 of JIS H8641. Therefore, the plating film produced by this Zn—Al-based alloy plating method surely has higher corrosion resistance than the hot-dip Zn plating film in a severe corrosion environment. As a result, the life of the steel structure can be extended by using a member plated by the Zn—Al-based alloy plating method of the present invention, for example, on a steel structure installed on a beach or the like. The plating adhesion amount is preferably 800 g / m ² or less.

Hereinafter, the present invention will be described in more detail with reference to examples.
As a specimen to be plated, a SS400 steel plate, which is a general structural rolled steel, was used. The dimension of the steel plate is 150 mm × 75 mm × 6.0 mm. As a pretreatment, this steel plate was degreased by immersing it in a 12% NaOH aqueous solution at 60 ° C. for 10 minutes, followed by washing with water. Thereafter, the substrate was dipped in a 15% HCl solution for 30 minutes for pickling and washing with water. Subsequently, it was immersed in a flux solution (Nagaflux FC, manufactured by Nagai Pharmaceutical Co., Ltd.) for 1 minute, lifted from the flux solution, and then naturally dried to prepare a material to be plated.

Example 1
The material to be plated is designated as No. 1 in Table 1. 5 types of test specimens were produced by sequentially immersing in the first and second plating baths having the compositions and bath temperatures shown in 1 to 5 for 90 seconds each. No. In any of 1 to 5, the first plating bath is composed of 0.005% by weight of Al, 0.05% by weight of Ni, the balance is Zn and inevitable impurities, and the bath temperature is 440 ° C. No. 1 is that the second plating bath is composed of 10% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 1% by weight of Pb, the balance being Zn and inevitable impurities, and the bath temperature is 460 ° C. It is. No. 2 shows that the second plating bath is No. 2. Instead of 1 Pb, 0.1% by weight of Bi is contained. No. 3 shows that the second plating bath is No. 3. 2 to which 0.5% by weight of Sn is added. No. No. 4 shows that the second plating bath is No. 4. 2 with 0.8 wt% Sn and 0.1 wt% In added. No. No. 5 shows that the second plating bath is No. 5; 1, to which 0.1% by weight of Bi, 0.8% by weight of Sn, and 0.1% by weight of In are added.

No. above. About the test body of 1-5, the measurement of the plating adhesion amount, the evaluation of the surface state of plating, and the salt spray test were done. The measurement of the plating adhesion amount was based on the indirect method in JIS H 0401 (hot dip galvanizing test method). That is, after measuring the weight of the specimen subjected to the plating treatment, the plating film was dissolved and removed with hydrochloric acid, the weight was measured again, and the difference in the measured weights was defined as the amount of plating adhesion. The surface condition was evaluated by visual observation and evaluated according to the following criteria.
Good: The surface is smooth and there is no plating defect.
Good: There are irregularities, and some burns are observed.
Inferior: Non-plating, pinholes, dross adhesion, and peeling are observed.
The salt spray test is performed in accordance with JIS Z 2371 (salt water spray test method), and at 100 hours, 300 hours, 600 hours, 1000 hours and 2000 hours from the start of spraying salt water, The amount of mass loss was measured.

(Comparative Example 1)
The material to be plated is designated as No. 1 in Table 1. 6-No. In the first plating bath and the second plating bath having the composition and bath temperature shown in FIG. 13, each was sequentially immersed for 90 seconds to prepare eight types of test specimens. No. In any of 6 to 13, the first plating bath is composed of 0.005% by weight of Al, 0.05% by weight of Ni, the balance is Zn and inevitable impurities, and the bath temperature is 440 ° C. No. Reference numeral 6 denotes only the first plating bath, which is a conventional hot dip Zn plating. No. No. 7, the second plating bath is composed of 3% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 1% by weight of Pb, the balance being Zn and inevitable impurities, and the bath temperature is 460 ° C. It is. No. 7 is outside the scope of the present invention because Al in the second plating bath is too small. No. In No. 8, the second plating bath is composed of 21% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 1% by weight of Pb, the balance being Zn and inevitable impurities, and the bath temperature is 470 ° C. It is. No. No. 8 is outside the scope of the present invention because Al in the second plating bath is excessive. No. 9, the second plating bath is composed of 10% by weight of Al, 0.05% by weight of Ni, 0.5% by weight of Mg, 1% by weight of Pb, the balance being Zn and inevitable impurities, and the bath temperature is 460 ° C. No. No. 9 is outside the scope of the present invention because Mg in the second plating bath is too small. No. No. 10, the second plating bath is composed of 10% by weight of Al, 0.05% by weight of Ni, 6% by weight of Mg, 1% by weight of Pb, the balance being Zn and inevitable impurities, and the bath temperature is 460 ° C. It is. No. No. 10 is out of the scope of the present invention because Mg in the second plating bath is excessive. No. No. 11 is a second plating bath in which Al is 10% by weight, the balance is Zn and inevitable impurities, and the bath temperature is 460 ° C. No. No. 11 is out of the scope of the present invention because the second plating bath is composed only of Al, Zn and inevitable impurities. No. In No. 12, the second plating bath is 0.05% by weight of Ni, the balance is Zn and inevitable impurities, and the bath temperature is 460 ° C. No. No. 12 is out of the scope of the present invention because the second plating bath is composed only of Ni, Zn, and inevitable impurities. No. In No. 13, the second plating bath is composed of 3% by weight of Mg, the balance is Zn and inevitable impurities, and the bath temperature is 460 ° C. No. No. 13 is outside the scope of the present invention because the second plating bath is composed only of Mg, Zn and inevitable impurities. About the test body produced using these plating baths, the amount of plating adhesion, the evaluation of the surface condition of plating, and the salt spray test were performed.

The evaluation of the adhesion amount and surface state of Example 1 and Comparative Example 1 are as shown in Table 1, and the salt spray test results of Example 1 and Comparative Example 1 are as shown in Table 2. In Table 2, the unit of mass loss is g / m ² .

  As can be seen from Table 1, the plating film by the plating method of Example 1 is No. 1. Any one of 1 to 5 has a sufficient adhesion amount and a good surface condition. Further, as can be seen from Table 2, No. 1 in Example 1 was obtained. The plating films formed by the plating methods 1 to 5 are No. 1 in Comparative Example 1. Compared with the hot-dip Zn plating film produced only by the first plating bath 6, all of them have significantly higher corrosion resistance. On the other hand, the plating film of No. 7 of Comparative Example 1 has a low surface condition and low corrosion resistance because there is little Al in the second plating bath. The plating film of No. 8 in Comparative Example 1 has high corrosion resistance because the Al content of the second plating bath is excessive, but the surface condition is poor. The plating film of No. 9 in Comparative Example 1 has a good surface state but low corrosion resistance because Mg in the second plating bath is too small. The plating film of No. 10 of Comparative Example 1 has high corrosion resistance because the Mg of the second plating bath is excessive, but the surface state is poor. In the plating film of No. 11 of Comparative Example 1, since only Al is added to Zn in the second plating bath, the surface state is poor and the corrosion resistance is also low. The plating film of No. 12 of Comparative Example 1 has a good surface condition but very low corrosion resistance because only Ni is added to Zn in the second plating bath. The plating film of No. 13 in Comparative Example 1 has a good surface state but is very low in corrosion resistance because only Mg is added to Zn in the second plating bath.

(Example 2)
The material to be plated is designated as No. 3 in Table 3. 14-No. Each sample was immersed for 90 seconds in the first and second plating baths having the composition and bath temperature shown in FIG. 37 to prepare 24 types of test specimens. No. In any of 14 to 31, the first plating bath is composed of 0.005% by weight of Al, 0.05% by weight of Ni, the balance being Zn and inevitable impurities, and the bath temperature is 440 ° C. No. 14 and 15, the second plating bath is composed of 5 or 19% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 1% by weight of Pb, the balance being Zn and inevitable impurities. The temperature is 460 ° C. No. In Nos. 16 and 17, the second plating bath is composed of 10% by weight of Al, 0.02 or 0.09% by weight of Ni, 3% by weight of Mg, 1% by weight of Pb, and the balance of Zn and inevitable impurities. The bath temperature is 460 ° C. No. 18 and 19, the second plating bath is composed of 10% by weight of Al, 0.05% by weight of Ni, 2 or 4% by weight of Mg, 1% by weight of Pb, the balance being Zn and inevitable impurities. The temperature is 460 ° C. No. 20 and 21, the second plating bath is 10% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 0.5 or 1.4% by weight of Pb, the balance being Zn and inevitable impurities The bath temperature is 460 ° C. No. 22 and 23, the second plating bath is 10 wt% Al, 0.05 wt% Ni, 3 wt% Mg, 0.05 or 0.5 wt% Bi, the balance is Zn and inevitable impurities The bath temperature is 460 ° C. No. 24 and 25, the second plating bath is 10% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 1% by weight of Pb, 0.1 or 1% by weight of Sn, and the balance It consists of Zn and inevitable impurities, and the bath temperature is 460 ° C. No. 26 and 27, the second plating bath is 10 wt% Al, 0.05 wt% Ni, 3 wt% Mg, 1 wt% Pb, 0.05 or 0.5 wt% In, The balance consists of Zn and inevitable impurities, and the bath temperature is 460 ° C. No. 28 and 29, the second plating bath is composed of 10% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 1% by weight of Pb, the balance being Zn and inevitable impurities, and the bath temperature is It is 430 degreeC or 480 degreeC. No. No. 30, the second plating bath is composed of 10% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 0.5% by weight of Sn, the balance being Zn and inevitable impurities, and the bath temperature is 460 ° C. No. No. 31, the second plating bath is composed of 10% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 0.3% by weight of In, the balance being Zn and inevitable impurities, and the bath temperature is 460 ° C. No. 32-No. 37, the second plating bath is composed of 10% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 1% by weight of Pb, the balance being Zn and inevitable impurities, Is 460 ° C. No. In Nos. 32 and 33, the first plating bath is 0.002 or 0.009% by weight of Al, 0.05% by weight of Ni, the balance is Zn and inevitable impurities, and the bath temperature is 440 ° C. No. In Nos. 34 and 35, the first plating bath is 0.005 wt% Al, 0.02 or 0.09 wt% Ni, the balance is Zn and inevitable impurities, and the bath temperature is 440 ° C. No. In Nos. 36 and 37, the first plating bath is 0.005 wt% Al, 0.05 wt% Ni, the balance is Zn and inevitable impurities, and the bath temperature is 430 or 480 ° C. About the test body produced using these plating baths, the amount of plating adhesion and the evaluation of the surface state of plating were performed by the same method as in Example 1. Evaluation of the adhesion amount and surface state of Example 2 is as shown in Table 3.

(Comparative Example 2)
The material to be plated is designated as No. 4 in Table 4. 38-No. In the first plating bath and the second plating bath having the composition and bath temperature shown in 55, each was sequentially immersed for 90 seconds to prepare 18 types of test bodies. No. In any of 38 to 49, the first plating bath is composed of 0.005% by weight of Al, 0.05% by weight of Ni, the balance being Zn and inevitable impurities, and the bath temperature is 440 ° C. No. 38 and 39, the second plating bath is composed of 10% by weight of Al, 0.005 or 0.11% by weight of Ni, 3% by weight of Mg, 1% by weight of Pb, the balance being Zn and inevitable impurities. The bath temperature is 460 ° C. No. 38 and 39 are outside the scope of the present invention in that Ni in the second plating bath is too small or too large. No. 40 and 41, the second plating bath is 10% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 0.4 or 1.5% by weight of Pb, the balance being Zn and inevitable impurities The bath temperature is 460 ° C. No. 40 and 41 are outside the scope of the present invention in that Pb of the second plating bath is too small or too large. No. 42 and 43, the second plating bath is 10 wt% Al, 0.05 wt% Ni, 3 wt% Mg, 0.04 or 0.6 wt% Bi, the balance is Zn and inevitable impurities The bath temperature is 460 ° C. No. 42 and 43 are outside the scope of the present invention in that Bi of the second plating bath is too small or too large. No. 44 and 45, the second plating bath is 10 wt% Al, 0.05 wt% Ni, 3 wt% Mg, 0.05 or 1.1 wt% Sn, the balance is Zn and inevitable impurities The bath temperature is 460 ° C. No. 44 and 45 are outside the scope of the present invention in that the Sn of the second plating bath is too small or too large. No. 46 and 47, the second plating bath is 10 wt% Al, 0.05 wt% Ni, 3 wt% Mg, 0.01 or 0.6 wt% In, the balance is Zn and inevitable impurities The bath temperature is 460 ° C. No. 46 and 47 are outside the scope of the present invention in that the In of the second plating bath is too small or too large. No. 48 and 49, the second plating bath is composed of 10 wt% Al, 0.05 wt% Ni, 3 wt% Mg, the balance is Zn and inevitable impurities, and the bath temperature is 418 ° C. or 500 ° C. is there. No. 48 and 49 are outside the scope of the present invention in that the bath temperature of the second plating bath is too low or too high. No. 50-No. In No. 55, the second plating bath is composed of 10% by weight of Al, 0.05% by weight of Ni, 3% by weight of Mg, 1% by weight of Pb, and the balance of Zn and inevitable impurities. Is 460 ° C. No. In Nos. 50 and 51, the first plating bath is 0.0005 or 0.011 wt% Al, 0.05 wt% Ni, the balance is Zn and inevitable impurities, and the bath temperature is 440 ° C. No. 50 and 51 are outside the scope of the present invention in that Al in the first plating bath is too small or too large. No. In 52 and 53, the first plating bath is 0.005% by weight of Al, 0.005 or 0.11% by weight of Ni, the balance is Zn and inevitable impurities, and the bath temperature is 440 ° C. No. 52 and 53 are outside the scope of the present invention in that Ni in the first plating bath is too small or too large. No. In Nos. 54 and 55, the first plating bath is 0.005 wt% Al, 0.05 wt% Ni, the balance is Zn and inevitable impurities, and the bath temperature is 418 or 500 ° C. No. 54 and 55 are outside the scope of the present invention in that the bath temperature of the first plating bath is too low or too high. The test specimen thus obtained was subjected to measurement of the plating adhesion amount and evaluation of the plating surface condition. Evaluation of the adhesion amount and surface state of Comparative Example 2 is as shown in Table 4.

  As can be seen from Table 3, No. 2 in Example 2 was obtained. 14 to 21, 24 to 29, and 32 to 37 are cases where Pb is included in the second plating bath, and all have good performance. In particular, no. No. 32 has the maximum plating adhesion amount and a good surface state. No. 2 in Example 2. Nos. 22 and 23 are cases where Bi is contained in the second plating bath, and both the plating adhesion amount and the surface state are good. No. 2 in Example 2. Nos. 24 and 25 are cases where Sn is contained together with Pb in the second plating bath, the plating adhesion amount is good, and there is no problem in the surface state. No. 2 in Example 2. Nos. 26 and 27 are cases where In is contained together with Pb in the second plating bath, the plating adhesion amount is good, and there is no problem in the surface state. No. 2 in Example 2. 28 and 29 are cases where the bath temperature of the second plating bath is set to a low temperature or a high temperature within the scope of the present invention, and the amount of plating adhesion is good and the surface condition is better at a high temperature. There is no problem with the surface condition even at low temperatures. No. 2 in Example 2. No. 30 is a case where Sn is contained in the second plating bath, the amount of plating adhesion is relatively good, and there is no problem in the surface state. No. 2 in Example 2. 31 is a case where In is contained in the second plating bath, the amount of plating adhesion is relatively good, and there is no problem in the surface state. No. 2 in Example 2. 32 and 33 are cases where Al in the first plating bath is set in a small amount or a large amount within the scope of the present invention, and both the adhesion amount and the surface state are good. In particular, No. 1 in which the amount of Al was 0.002% by weight. No. 32, the adhesion amount reached the highest value in the example. No. 2 in Example 2. Nos. 34 and 35 are cases where Ni in the first plating bath is set to a small amount or a large amount within the scope of the present invention, and both the adhesion amount and the surface state are good. No. 2 in Example 2. 36 and 37 are cases where the bath temperature of the first plating bath is set to a low temperature or a high temperature within the scope of the present invention, and both the adhesion amount and the surface state are good.

On the other hand, as can be seen from Table 4, the comparative example 2 No. Nos. 38, 43 and 45 have good surface conditions, but the coating adhesion amount does not reach 550 g / m ² required for hot-dip Zn plating with HDZ55 of JIS H 8641, and the corrosion resistance under severe corrosive environment Is not enough. Moreover, No. 2 of Comparative Example 2 was used. In Nos. 39 to 42, 44, and 46 to 49, the plating adhesion amount is good, but the surface condition is inferior. As described above, when the composition or bath temperature of the second plating bath is outside the range of the present invention, a defect occurs in at least one of the corrosion resistance and the surface state of the plating film. Moreover, No. 2 of Comparative Example 2 was used. 50 to 55 have a good plating adhesion amount but a poor surface condition. Specifically, no. In No. 51, when the material to be plated was pulled up from the first plating bath, an unplated portion was generated on a part of the surface. In 52 and 55, when the material to be plated was pulled up from the second plating bath, an unplated portion was generated on a part of the surface. Thus, when the composition or bath temperature of the first plating bath is out of the range of the present invention, the surface state of the plating film is defective.

Claims (2)

  The material to be plated is a first plating in which Al is 0.001 to 0.01 wt%, Ni is 0.01 to 0.1 wt%, the balance is Zn and inevitable impurities, and the bath temperature is 420 to 490 ° C. After being immersed in the bath, Al is 4 to 20% by weight, Ni is 0.01 to 0.1% by weight, Mg is 1 to 5% by weight, Pb is 0.5 to 1.4% by weight, and Bi is 0.00. At least one selected from the group consisting of 05-0.5 wt%, In 0.05-0.5 wt% and Sn 0.1-1.0 wt%, with the balance consisting of Zn and inevitable impurities A Zn—Al-based alloy plating method characterized by immersing in a second plating bath having a bath temperature of 420 to 490 ° C. In the Zn-Al system alloy plating method of Claim 1,
A Zn—Al-based alloy plating method, wherein the plating adhesion amount is 550 g / m ² or more.