JP2002275611A - Columnar material plated with zinc alloy, method for producing the same and flux used in the production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a columnar material plated with a zinc alloy, which exhibits excellent corrosion resistance under a wide corrosive environment ranging from a high chlorine concentration environment to a low chlorine concentration environment, a steel columnar product having a structure, which is obtained by using the columnar material plated with the zinc alloy, and a method for producing the columnar material plated with the zinc alloy by a one-step dry dipping method. SOLUTION: The columnar material plated with the zinc alloy is characterized in that its surface is coated with a plated layer containing, as main components, Zn, Mg and Al, the phases of Zn-Mg-based intermetallic compounds (MgZn2 , Mg2 Zn11 ) are present in the plated layer, and the volume ratio of the Zn-Mg-based intermetallic compounds to the whole plated layer is <=50 vol.%. The phases of the Zn-Mg-based intermetallic compounds form each a continuous phase along Zn grain boundary or island shaped phases having the distance between adjacent phases of >=0.05 μm. Further, the phase of a Al-Zn alloy forms a dendritic phase or island shaped phases, and the volume ratio of the Al-Zn alloy phase to the plated layer is <=80 vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a column made of zinc alloy plating having excellent corrosion resistance. More specifically, Zn-Mg containing Zn, Mg and Al as main components
The present invention relates to a zinc alloy-plated column material obtained by hot-dip coating an Al alloy, a plating method thereof, and a pretreatment agent composition for pretreating a steel material surface to be plated in the method.

[0002]

2. Description of the Related Art Generally, wood and surface-treated materials have been used for pillars used for holding lighting poles for street lighting, railway overhead lines, electric wires, telephone wires, and the like. Used, and then reinforced concrete. However, due to its excellent landscape, long-lasting durability over several decades, and ease of handling during construction, corrosion-resistant surface treatment by zinc plating or painting has been used on steel. Was. However, regular repairs are applied in normal zinc plating and painting, but the improved corrosion resistance of the plating makes it possible to omit or simplify the painting and reduce the frequency of repairs. It also leads to reduction of running costs required for shortening and maintenance and management.

[0003] A condition required for the column material is that when a flaw is generated due to mechanical wear or collision of a small object, rust is not easily generated at the flaw portion. On the other hand, Al plating, which has been known for a long time as plating excellent in corrosion resistance, tends to generate red rust from scratched portions in an environment having a low chloride ion concentration, and is not always suitable for steel tower applications used on land. On the other hand, there is provided a Zn-Al alloy plating in which corrosion resistance is enhanced by adding Al to Zn. A typical example is Zn-55% A.
There is 1 plating. Since this plating is mainly made of Al, the corrosion resistance of the plating layer itself is almost equal to that of Al plating, and since it contains Zn, it is difficult for red rust to be generated from a flawed portion.

Other than Zn-55% Al plating, there is Zn-Al alloy plating in which the Al content is suppressed to about 5 to 10%. This Zn-Al alloy plating is Zn-55% A
Even though it is not as good as 1 plating, it has overwhelmingly good corrosion resistance as compared with Zn plating, and is therefore widely used today for structures and the like. However, the above Zn-Al alloy plating tends to elute rapidly when exposed to a high pH environment such as in concrete, and its alkali resistance is
Even inferior to traditional Zn plating is often scattered. Thus, Zn-Al-based plating is not necessarily suitable for use as a so-called composite structure such as a reinforcing member of a concrete structure or a concrete foundation member of a steel structure.

Next, from the viewpoint of plating properties, the above Z
In the case of n-Al alloy plating, if the addition amount of Al is about 10% by mass or less, one-step contact plating can be performed by pretreating a steel material with a water-soluble flux. However, when the amount of Al added is large, the Al in the bath tends to cause a chemical reaction with the flux component, and the quality deterioration such as non-plating and adhesion of foreign matter becomes remarkable.

For this reason, a wet method of floating a molten salt flux on a plating bath surface or a two-stage plating method of plating a Zn—Al alloy after applying Zn plating is often used. In the former method, the flux component is easily mixed into the plating bath, and the composition control of the plating bath is complicated. In the latter method, since at least two plating baths need to be prepared, the cost required for plating tends to increase.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention is directed to an environment having a high chloride ion concentration, such as a coastal region, an environment having a low chloride ion concentration, such as an inland region, a mountainous region, and the like. In a wide corrosive environment up to the environment,
An object of the present invention is to provide a zinc alloy-plated column material having excellent corrosion resistance.

Further, the present invention provides a method for producing the zinc alloy-plated column material by a one-stage dry brazing method, which is relatively easy in quality control and economically advantageous.

[0009]

Means for Solving the Problems The present inventors have proposed Zn-M
g-Al-based alloy plating has high corrosion resistance equal to or higher than Zn-Al-based plating, and, in addition to the above composition,
When the Zn-Mg based intermetallic compound phase is present in the plating layer, it has been found that the corrosion resistance is particularly improved.
An Mg-Al based alloy plated steel wire was provided.

As a result of intensive studies aimed at further increasing the corrosion resistance and application to uses other than wires, the following was newly found. That is, if (1) the proportion of the Zn—Mg based intermetallic compound phase in the entire plating layer exceeds 50%, the corrosion resistance is reduced. (2) The Zn—Mg based intermetallic compound phase depends on the content of Mg. It becomes a continuous phase or an island phase. In the latter case, if the distance between adjacent Zn—Mg-based intermetallic compound phases is less than 0.05 μ, the corrosion resistance decreases, and (3) the Al content increases. Al-Z
Although an n-alloy phase is generated, if the proportion of the Al-Zn alloy phase in the entire plating layer exceeds 80%, the corrosion resistance decreases. (4) Zn-Mg-Al alloy plating usually has two layers. Although it exhibits a structure, the corrosion resistance can be improved by controlling the ratio of the thickness of each layer and the metal composition to an appropriate range, and (5)
It has been found that by controlling the quantitative relationship between Al and Al within a certain range, Zn-Mg-Al-based alloy plating can be applied to steel materials other than wires.

The present invention has been made based on the above series of findings.
It was completed by limiting the plating composition and the solidification structure and layer structure of the plating layer, and further defining the flux composition suitable for blow plating, and the gist thereof is listed below. That is, (1) Z column is formed on the surface of the steel column or a member constituting the column.
It has a plating layer containing n, Mg and Al as main components, and a Zn-Mg based intermetallic compound phase is present in the plating layer,
A zinc alloy plated column material characterized in that the proportion of the Zn-Mg based intermetallic compound phase in the entire plating layer is 50% or less by volume.

(2) In the plating layer containing Zn, Mg and Al as main components, the Zn—Mg based intermetallic compound is θ
The zinc alloy-plated column material according to the above (1), which is a (Mg ₂ Zn ₁₁ ) phase and forms a continuous phase along a Zn grain boundary. (3) In the plating layer containing Zn, Mg and Al as main components, the Zn—Mg based intermetallic compound is η (MgZn
₂ ) The zinc alloy-plated column material according to (1), wherein the column material is an island-shaped phase, and a distance between adjacent η phases is 0.05 μ or more.

(4) In the plating layer containing Zn, Mg and Al as main components, the Al-Zn alloy phase forms a dendritic or island-like phase, and the proportion of the Al-Zn alloy phase in the entire plating layer is The zinc alloy-plated column material according to the above (3), which is 80% or less by volume%. (5) In the plating layer containing Zn, Mg and Al as main components, a lower layer containing at least Fe and Al immediately above the surface of the steel material and having a ratio of Al to the total amount of Fe and Al of 49% by mass or more. And at least Zn and Mg
A two-layer structure constituted by an upper layer containing
The thickness of the lower layer is 90% or less with respect to the total plating thickness, and the total thickness of the lower layer and the upper layer is 100 to 8 in terms of Zn equivalent.
Above, wherein it is a 00g / m ² (1) ~
The zinc alloy-plated column material according to any one of (4) and (4).

(6) The steel columns are equilateral angle steel, unequal angle iron, unequal thickness angle steel, flat steel, H-shaped steel, I-shaped steel, steel pipe, tapered pipe, different diameter pipe, The above-mentioned (1) to (1) to (1) to (4), characterized in that the steel plate is a steel column material produced by deforming and further joining these and further combining some of them.
(5) The column material made of zinc alloy plating according to any one of (5). (7) The members forming the column are equilateral angle iron, unequal angle iron, unequal thickness angle iron, flat steel, H-shaped steel, I-shaped steel, steel pipe, tapered pipe, different diameter pipe, steel plate, A bolt, a nut, a washer, a rivet, or a steel member produced by deforming or joining these, and combining some of them, according to any one of the above (1) to (5). Zinc alloy plated column material.

(8) The above-mentioned (6) or (7), wherein the steel column and the steel member are all or partially coated with an organic coating. The zinc alloy-plated column material according to any one of the above. (9) The above (6) to (8), wherein part or all of the plating surface has a portion in contact with concrete.
The zinc alloy-plated column material according to any one of the above.

(10) ZnCl ₂ is 60 to 9% by mass.
5%, at least one kind of alkali metal or alkaline earth metal hydride or silicic fluoride in total of 0.1 to 10%, alkali metal or alkaline earth metal fluoride or chloride 1-30% in total of any one or more of the substances, and Sn, P
any one of chlorides of b, In, Tl, Sb or Bi
A flux containing 0.1 to 10% in total of more than one kind and a total concentration of 10 to 60 (mass / volume%).

(11) ZnCl ₂ is 60 to 9% by mass.
5%, at least one of fluorides of an alkali metal element or an alkaline earth metal element in a total amount of 0.1 to 10
%, At least one kind of chloride of an alkali metal element or an alkaline earth metal element in a total content of 1 to 30%, and a total concentration of 10 to 60 (mass / volume%). Flux.

(12) After the surface of the steel material is degreased and pickled, the steel material is immersed in the flux described in the above (10) or (11), and then the flux attached to the surface of the steel material is dried to obtain a mass. %: Mg: 0.05 to 7%, Al:
0.01 to 20%, and the balance consists of Zn and inevitable impurities. The content of Mg ([Mg]) and the content of Al ([Al]) are expressed in mass%, [Mg] <(7 [Al] +28) /9.8 and [Mg] <(25 [Al] +0.4) /1.8 are immersed in a hot-dip bath simultaneously satisfying the following relationship. Is cooled at a rate of 0.1 to 50 ° C./sec until at least reaches the melting point of the plating layer. (13) The method for producing a zinc alloy-plated column material according to the above (12), wherein the hot-dip bath is a hot-dip bath to which 10% by mass or less of Si is added based on the Al content. .

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The zinc alloy-plated column material according to the present invention includes an equilateral angle iron, an unequal angle iron, an unequal thickness angle iron, a flat steel, an H-shaped steel, an I-shaped steel, a steel pipe, and a taper. Pipes, pipes of different diameters, steel plates, bolts, nuts, washers, rivets, and
It is a steel member produced by combining and deforming some of them, and is a steel column and a product for a column constituted by using part or all of these steel members. The zinc alloy plated column material of the present invention is Zn-Mg-A
It is characterized in that an l-based alloy is hot-dip plated.

The cross section of the Zn—Al—Mg based alloy plating was measured for 500 to 500 μm using a scanning electron microscope or an optical microscope.
When observed at a magnification of about 1000, it can be confirmed that the plating layer has a two-layer structure. In addition, these layers are
When analyzed by an instrumental analytical method such as A, the lower layer immediately above the ground iron is an Fe-Al alloy layer, and the upper layer above it is Zn and Mg.
It is recognized that the layer contains.

First, the solidification structure of the upper layer will be described. When Mg is mixed in the Zn plating bath, a Zn—Mg based intermetallic compound is generated inside and on the surface of the plating layer.
This intermetallic compound is found to be an η (MgZn ₂ ) phase and a θ (Mg ₂ Zn ₁₁ ) phase by analysis such as EPMA (linear analysis). These intermetallic compounds tend to elute preferentially to the Zn-based parent phase. At that time, since they have a sacrificial anticorrosion effect on the parent phase, the effect of delaying the corrosion of Zn, which is the main constituent of the plating layer, is reduced. is there.

Where the Zn-Mg based intermetallic compound phase elutes is a small hole or a continuous minute crack,
Since the elution part is densely filled with corrosion products,
Corrosion hardly progresses. In addition, the corrosion product is a dense and chemically stable basic compound, which forms a film and covers the plating surface, thereby improving the corrosion resistance. When the Mg concentration in the plating bath is low, Zn-Mg
The intermetallic compound phase is a θ phase, and is likely to be formed almost continuously at the grain boundary of the Zn crystal. On the other hand, when the Mg concentration increases, the Zn-Mg based intermetallic compound phase becomes an η phase, and exhibits a sea-island structure precipitated in an island shape in the Zn matrix.
In any case, there is no change in the contribution of the plating to high corrosion resistance, but when the volume ratio of the Zn—Mg based intermetallic compound phase to the entire plating exceeds 50%, the plating layer becomes brittle. The volume ratio is preferably 50% or less because cracking and peeling are likely to occur.

When the η phase is precipitated in the form of islands, the elution portions of the η phase are connected to each other when the adjacent η phase comes close to each other and grow into large pores. Therefore, also in this case, the filling with the corrosion product becomes incomplete, and local corrosion easily occurs. Such a tendency becomes conspicuous when the distance between the adjacent η phases is less than 0.05 μ. Therefore, the distance is preferably 0.05 μ or more.

If Al is mixed in the Zn plating bath, Al
Is mainly consumed to form the lower layer of the Fe-Al alloy, but when the Al concentration in the bath increases, Al precipitates in the upper layer as an island-like or dendritic Al-Zn alloy phase. This phase is
Since it is harder to elute than Zn, there is no sacrificial anticorrosion effect on Zn as in the η phase. When the Al-Zn alloy phase occupies a large volume in the plating layer, the volume of the Zn matrix phase decreases, and red rust easily occurs. This trend is
Since the Al-Zn alloy phase becomes remarkable when it exceeds 80% of the entire plating layer, the ratio of the Al-Zn alloy phase is preferably 80% or less.

The corrosion of the Al—Zn alloy phase proceeds by two kinds of chemical changes, namely, elution of Zn and oxidation of Al.
Since the Al oxide generated thereby is chemically stable, if the Al-Zn alloy phase uniformly covers the steel surface,
High corrosion resistance can be expected. However, in order to make this possible, it is necessary to use a plating bath in which Al is added at a high concentration, which undesirably increases the plating temperature.

Next, the metal composition of the upper and lower layers will be described. The metal composition of the upper layer depends on the plating bath composition, plating conditions,
Although it fluctuates depending on cooling conditions and the like, it is essential to contain Zn and Mg, and preferably, Mg is in the range of 0.05 to 30% by mass with respect to Zn. If the content of Mg is less than 0.05% by mass, high corrosion resistance cannot be obtained.
If it exceeds 300, the plating layer becomes brittle, and cracks tend to occur during bending.

The lower Fe—Al alloy layer is made of Fe—Zn.
It has the effect of suppressing the formation of a brittle layer of the alloy and is effective in maintaining the workability of plating. The composition of the Fe—Al alloy layer is such that the ratio of Al to the total amount of Fe and Al is 4%.
The content is preferably 9% by mass or more, and if it is out of this range, the layer itself becomes brittle. When reheating after plating,
The content of Al may change to an Fe-Al alloy layer having a content of less than 49% by mass. For example, an alloy layer containing about 70 to 80% by mass of Fe and about 20 to 30% by mass of Al is relatively flexible and has good workability, but has a large Fe content, and thus has very poor corrosion resistance.

In order to individually determine the metal composition in the lower layer and the upper layer, a chemical analysis method is preferable because it can be measured with the highest accuracy, but it is simple because separation of each layer is difficult and errors are likely to occur. The measurement is preferably performed by an instrumental analysis method using a GDS having a beam diameter of about 4 mm. This Fe-
The thickness of the Al-based alloy layer is preferably 90% or less of the total plating thickness. If it exceeds 90%, Zn-Al
-Not only the original corrosion resistance of the Mg-based alloy plating cannot be obtained, but also the gloss of the plating surface is impaired, which is not preferable.

Further, the total plating thickness of the lower layer and the upper layer together is 100 to 8 in terms of the amount of adhesion converted to the mass of Zn.
00 g / m ² is preferred. If it is less than 100 g / m ² , flaws are likely to occur due to mechanical impact on plating.
On the other hand, if it exceeds 800 g / m ² , the uniformity of plating appearance may be impaired. Zn-Al-M as described above
g-based alloy plating includes equilateral angle steel, unequal angle iron, unequal thickness angle steel, flat steel, H-shaped steel, I-shaped steel, steel pipe, tapered pipe, different diameter pipe, steel plate, bolt, nut, washer , Rivets and the like. Of course, there is no problem even if it is used for steel materials other than these. Then, one or more of these Zn-Al-Mg-based alloy-plated steel materials may be used as a member to make a pillar material or a member constituting a pillar. In the members constituting the pillars, the plated steel material may be used partially or entirely.

Further, an equilateral angle iron, an unequal angle iron, an unequal thickness angle iron, an H-shaped steel, an I-shaped steel, a flat steel, a steel pipe, a tapered pipe, a different diameter pipe, a steel sheet, a bolt, a nut, a washer, Of the rivets, at least one or more types of steel materials are used to assemble the pillars or members constituting the pillars in advance, and then the Zn
-Al-Mg based alloy plating may be applied. The above Zn-
Al-Mg based alloy plating has good corrosion resistance even in a strongly alkaline environment. Therefore, in places where a part or all of steel material is in contact with or buried in an alkaline material such as concrete, such as a pillar base. Can also be used.

Next, a plating method used for applying the above-mentioned Zn-Al-Mg-based plating will be described. First, a plating bath composed of Mg, Al, Zn and unavoidable impurities is used. If Mg in the bath is less than 0.05%, the Zn-Mg based intermetallic compound phase does not precipitate, and if it exceeds 7%, the Zn-Mg based intermetallic compound phase is 50% of the plating layer.
Precipitates more than. If the Al content in the bath is less than 0.01%, the Fe-Zn alloy layer is not formed, but the Fe-Zn alloy layer is formed. If the Al content exceeds 20%, the Al-Zn alloy phase is 80% of the plating layer. Precipitates more than.

As described above, any of these causes a reduction in the corrosion resistance and workability of the plating. Therefore, as a plating bath, Mg: 0.05 to 7% by mass, Al: 0.
It is preferable to use a plating bath containing each of 0.01 to 20% by mass and the balance consisting of Zn and unavoidable impurities.
The contents of Mg and Al must satisfy at least the following two relational expressions at the same time. That is, [Mg] <(7 [Al] +28) /9.8 (1) [Mg] <(25 [Al] +0.4) /1.8 (2) In these equations, [Mg] And [Al] represent the contents of Mg and Al in mass%, respectively.

When the contents of Mg and Al are out of the range defined by the formula (1), the formation of oxides on the plating bath surface is promoted. , So that the working efficiency is greatly reduced. This requires caution when plating in a batch manner, such as in a section steel or steel pipe. In other words, in the case of continuous plating such as wire rods, immediately after the steel material is discharged from the plating bath, the steel material is passed through a sand bath or the like for the purpose of adjusting the amount of adhesion. Can be removed at the same time, so the relationship between the Mg and Al contents is relatively insignificant. However, in the case of batch plating, since it is difficult to provide a step of removing foreign matter, strict attention must be paid to the generation of oxides on the plating bath surface which causes foreign matter adhesion, and Mg and Al The relationship of the contents becomes extremely important. To avoid oxide formation, use Mg
It is necessary that the addition amount of Al and Al satisfy the relationship of the above equation.

When the contents of Mg and Al are out of the range defined by the equation (2), even if the oxide on the bath surface is sufficiently removed and plated, the plating layer becomes over time. Cracks occur over a wide area, making it easy to peel. In order to further impart chemical and / or physical properties to the plating layer, one of a typical metal element belonging to IA to VA group, a transition metal element belonging to IB to VIII group, and a misch metal in the bath. More than one type of metal can be added. However, these addition amounts are 0.001 to 5% by mass for the typical metal element and 0.001 to 5% by mass for the transition metal element.
10% by mass, 0.001-5% by mass for misch metal
If the ratio is out of this range, problems such as poor appearance such as non-plating and an increase in bath temperature are likely to occur.

The specific plating method is as follows. After the steel material is degreased and pickled, the steel material is pre-treated with a flux and the Zn-M
A method of plating in one stage by immersing in a g-Al-based alloy bath is adopted. The flux used here may be selected from those having the following compositions. That is, in mass%,
(Flux _{-1) (1) ZnCl 2:} 60~95%,
(2) One or more of alkali metal hydrides, alkaline earth metal hydrides, alkali metal silicates, and alkaline earth metal silicates in total: 0.1 (3) at least one of fluorides of alkali metal elements, fluorides of alkaline earth metal elements, chlorides of alkali metal elements, and chlorides of alkaline earth metal elements: % And (4) at least one of Sn, Pb, In, Tl, Sb, and Bi chlorides in total: 0.1 to 10%. It is a flux that is dissolved or dispersed and the total concentration is adjusted to 10 to 60 (mass / volume%).

(Flux-2) (1) ZnCl
₂ : 60 to 95%, (2) at least one kind of alkali metal element fluoride or alkaline earth metal element fluoride: 0.1 to 10%, (3) alkali metal element chloride Or one of the alkaline earth metal element chlorides
It is a composition containing 1 to 30% in total of more than one kind, and it is possible to dissolve or disperse this composition in water and use a flux whose total concentration is adjusted to 10 to 60 (mass / volume%). Good. This flux may become a suspension depending on the concentration and temperature. In such a case, the pH may be adjusted to 6 or less. Note that Sn, Pb, In, Tl, S
b, at least one of chlorides of Bi in total of 0.1 to 1
It is also possible to add 0% by mass. This improves the plating properties, but makes it unwieldy to produce precipitates.

If the composition of the flux is out of the above-mentioned range, the appearance becomes inferior plating containing a large amount of dross adhesion, non-plating, pinholes, etc., and cannot be put to practical use. The minimum temperature of the plating bath cannot be specified unconditionally because it varies depending on the plating composition.
0 ° C. or higher, preferably 450 ° C. or higher. If the temperature is lower than 420 ° C., the plating bath may be solidified when the concentration of Mg or Al in the bath is high. The upper limit of the plating bath temperature is not particularly specified, but when the strength of the steel material is required, 500 ° C. or lower is an essential condition.

Further, even when the strength is not strictly required, if the temperature exceeds 500 ° C., the Fe—Al-based alloy layer easily grows at the interface between the base iron and the plating, and depending on the plating time, Fe accounts for the entire plating thickness. -The thickness of the Al alloy layer is 90
%, The corrosion resistance and the surface gloss are likely to decrease. Therefore, a temperature not exceeding 500 ° C. is preferred.

The immersion time of the steel material in the plating bath is 1 to 60.
0 seconds is preferred. If the time is less than 1 second, non-plating occurs and the adhesion of plating decreases. On the other hand, if it exceeds 600 seconds,
The growth of the Fe-Al-based alloy layer is promoted, and the thickness of the alloy layer tends to be so large as to exceed the thickness limit of 800 g / m ² for obtaining a good plating appearance as described above. Also,
Since the growth of the Fe—Al alloy layer is based on the supply of Fe from the ground iron to the plating layer, the content of Fe in the alloy layer increases, and the Al content relatively decreases. The ratio of Al to the total amount of Fe and Al is 49% by mass.
, Causing embrittlement of the plating layer. When the Al concentration in the plating bath is low, Fe-Al
An Fe—Zn alloy layer may be formed instead of the alloy layer, and in such a case, the corrosion resistance is greatly reduced.

The steel material plated in this manner is heated at a rate of 0.1 to 50 ° C./sec until the plating layer reaches at least the melting point.
Preferably, cooling is performed at a rate of 1 to 30 ° C./sec on average. When the cooling rate is less than 0.1 ° C./sec, Al in the plating bath
When the addition amount of Fe is large, the Fe-Al-based alloy layer grows more than necessary, and the thickness ratio of the Fe-Al alloy layer to the total plating thickness increases.

When the amount of Al added is small, F
An Fe-Zn alloy layer may be generated instead of the e-Al-based alloy layer, and in any case, the corrosion resistance is reduced. On the other hand, when the cooling rate exceeds 50 ° C./sec, unnecessary growth of the Fe—Al alloy layer and generation of the Fe—Zn alloy layer are suppressed, but at the same time, the upper Zn—Mg layer is formed.
The alloy phase is easily refined. In particular, when the Zn—Mg alloy phase is the η phase, the distance between adjacent η phases partially falls below 0.05 μ, so that high corrosion resistance cannot be obtained. By the way, since the growth of the Fe-Al-based alloy layer is fast, the thickness of the Fe-Al-based alloy layer greatly varies depending on the temperature of the plating bath and the immersion time. And this affects the variation in the thickness of the entire plating. When Si is added to the plating bath, the formation of the Fe-Al-based alloy layer is suppressed, so that the plating thickness can be easily controlled. The amount of Si added is 10% by mass or less based on the Al content in the plating bath. Even if it is added in excess of this, only the island-like Si phase is formed in the plating layer, and the effect of suppressing the formation of the Fe-Al-based alloy layer is no longer improved. The lower limit of the amount of Si added is not particularly specified, but is usually preferably about 0.1 to 0.5% by mass with respect to the Al content in the plating bath.

The pillars and the members constituting the pillars manufactured as described above may be used by applying an organic synthetic resin paint on the entire plating surface or partially. Further, when a flaw or peeling occurs partially on the plated surface when assembling the member, it is desirable to paint that part.
Further, the life can be further prolonged by painting a portion where water easily accumulates, such as a joint with concrete, a path of rainwater, and a vicinity of a drain port. Further, in the present invention, even when the members after plating are joined by welding,
There is no structural problem. However, at the welded portion, it is not possible to secure the anticorrosion function by plating, so it is desirable to paint for the purpose of repair. As the paint, acrylic, chlorinated rubber, vinyl chloride, polyurethane, polyester and various commercial products can be used,
Select an appropriate paint in consideration of the corrosive environment and landscape.
It is important that the required coating film thickness be individually determined in consideration of the corrosive environment of the steel material and the like, and thus is not particularly limited here. However, in order to have anticorrosion properties, the thickness of the coating film is preferably at least 5 μm or more.

A chemical conversion coating such as chromate, phosphate, organic zirconium salt, organic titanium salt, zirconium salt may be interposed between the Zn—Mg—Al alloy plating layer and the organic synthetic resin coating. Good. When performing the chemical conversion treatment, it is preferable to perform the degreasing after the plating surface is sufficiently degreased. As a chemical solution used for degreasing, a volatile organic solvent or a dedicated commercial product can be used.
The immersion method, the spray method, or any other appropriate method may be used.

[0044]

Next, the present invention will be described in detail with reference to examples. (Example 1) 150x degreased with a commercially available alkaline degreaser
A steel sheet of 75 × 1 mmt was immersed in 10% sulfuric acid at 60 ° C. for 1 minute and pickled, then ZnCl ₂ : 85% by mass, N
It was immersed in a flux consisting of aF: 1.5% and NaCl: 10%, and adjusted to a total concentration of 25% by mass / volume. The temperature of the flux was 80 ° C., and the immersion time was 5 seconds. Immediately after immersion, it was left in an oven set at 150 ° C. for 5 minutes to be dried.

Next, this steel sheet was subjected to a plating bath (bath temperature 47) containing Mg and Al at arbitrary concentrations and the balance being Zn.
(0 ° C.) for 30 seconds. Then, the steel sheet was pulled up while controlling the pulling speed so that the plating layer had a constant thickness, air-cooled to 200 ° C. at 5 ° C./sec, and then water-cooled.
The thickness of the plating was 3
It was about 00 to 400 g / m ² . EP for plating section
When analyzed using MA (plane analysis, 1000 times),
The plating had a two-layer structure, and the lower layer was an Fe-Al alloy layer containing about 50 to 60% by mass of Al, and the thickness was 15 g / m ² or less in terms of the amount of deposited Zn. In addition, the upper layer showed a different morphology depending on the plating bath composition.

The corrosion resistance was as follows:
mm, and the cut surface is sealed with a sealant.
(1) A salt spray test (hereinafter abbreviated as SST) was performed for 10
00 hours, (2) Dry / wet repeated test (3% NaC at 40 ° C)
(1) After immersion in an aqueous solution for 16 hours, left in an oven at 60 ° C. for 8 hours) for 60 days, (3) Combined cycle test (pure water spray:
4 hours → 70 ° C drying: 4 hours → 49 ° C x 95% RH: 4
Time → -20 ° C freezing: 4 hours, interval between modes: 2 hours), 30 cycles, (4) hot water immersion test (4
(0 ° C. pure water) for 2000 hours, and (5) alkali immersion test (pH 12-13, 40 ° C. aqueous solution) for 2000 hours to measure corrosion loss.

The bending workability is as follows.
A steel bar having a thickness of φ was bent along the circumferential direction (5T bending), and the plating appearance at that time was evaluated. Table 1 shows the test results. From this table, it can be seen that the corrosion resistance is improved by the presence of a Zn—Mg based intermetallic compound phase, whether a continuous or an island phase, in the upper layer of plating. However, when the Zn-Mg-based intermetallic compound phase occupies more than 50% by volume in the entire plating layer, cracking and peeling of the plating easily occur by 5T bending. Also, Al
It can be seen that when the proportion of the -Zn alloy phase in the entire plating layer exceeds 80%, the corrosion resistance decreases.

In order for the upper layer of the plating to form the above-mentioned structure, the contents of Mg and Al in the plating bath should be within the ranges of 0.05 to 7% by mass and 0.01 to 20% by mass, respectively. It turned out that there should be anything.

[0049]

[Table 1]

[Table 2] (Embodiment 2) 150 pre-processed in the same manner as in Embodiment 1
× 75 × 1 mmt steel sheet, Mg: 3% by mass, Al: 1
It was immersed in a plating bath containing 0% by mass and the balance being Zn. At this time, the temperature of the plating bath and the plating time were arbitrarily changed.

Next, the steel sheet is pulled up at an arbitrary pulling rate, and air-cooled to 200 ° C. at a cooling rate of 5 ° C./sec.
Water cooled. A part of the thus prepared plating sample was analyzed by EPMA (1000 times, surface analysis) and GDS, and the layer structure, metal composition and the like were specified. The corrosion resistance was determined by cutting the plated steel sheet to 100 × 50 mm, sealing the cut surface with a sealant, and performing SST for 1000 hours to measure the corrosion weight loss. In addition, 5mmφ
Bend along the circumference of a steel bar with a thickness of (5T bending)
The bending workability was evaluated from the plating appearance at that time.

Table 2 shows the results. From this table,
Depending on the plating bath temperature and plating time, the lower layer (Fe-Al
It can be seen that the metal composition and thickness of the alloy layer) change.
And it turns out that corrosion resistance, bending workability, and appearance change by it. That is, the following can be understood. (1) When the proportion of Al in the lower Fe-Al layer relative to the total amount of Fe and Al is less than 49% by mass, cracking due to bending tends to occur, and the corrosion resistance is also reduced. (2) If the thickness of the lower layer exceeds 90% of the total plating thickness, bending workability, corrosion resistance, and appearance (especially, gloss) deteriorate. (3) When the adhesion amount (in terms of Zn) is less than 100 g / m ² , red rust is easily generated, while when it exceeds 800 g / m ² , the plating appearance is significantly impaired.

From the above results, Fe and A
The ratio of Al to the total amount of l is 49% by mass or more,
It has been found that the thickness is preferably 90% or less of the total plating thickness. It has also been found that the total thickness of the lower layer and the upper layer is preferably 100 to 800 g / m ² in terms of Zn equivalent.

[0053]

[Table 3]

[Table 4] Example 3 An equilateral angle iron having a cross-sectional size of 50 × 50 × 4 mm and a length of 300 mm was degreased with a commercially available alkaline degreasing agent, and was then quenched with 10% sulfuric acid at 60 ° C. using 0.2% of peracid washing inhibitor. (% By volume)) and pickled by immersion until the oxide film on the surface was completely removed.

Then, after washing thoroughly with water, ZnCl ₂ : 85%, NaF: 1.5%, NaC
The sample was immersed in a flux consisting of 1: 10% and SnCl ₂ : 2% and adjusted to a total concentration of 25% by mass / volume. The temperature of the flux was 80 ° C., and the immersion time was 5 seconds. Immediately after immersion, it was left in an oven set at 150 ° C. for 5 minutes to be dried.

Next, this equilateral angle iron was used for (a) Mg and A
(a bath temperature of 450 ° C.) containing 0.5% and 0.2% by mass of Zn and the balance being Zn, or (b) Mg and Al at 3% by mass and 10% by mass, respectively. % With the balance being Zn (bath temperature 470 ° C.). Also, for comparison, (c) a plating bath (bath temperature 450 ° C.) containing 0.2% by mass of Al and the balance being Zn, and (d) a plating bath containing 10% by mass of Al and the balance consisting of Zn. A plating bath (bath temperature 450 ° C.) was also used. The immersion time was 100 seconds in each case. Then, the steel sheet was pulled up at a speed of 200 mm / sec, air-cooled to 200 ° C at a cooling rate of 1 ° C / sec, and then water-cooled.

The thickness of the plating varied depending on the portion of the sample.
It was 00~750g / m ^2. Both ends of the plated material thus produced were cut off by 50 mm each to obtain a sample having a length of 200 mm, and both cut ends were sealed with epoxy paint. Two such samples were prepared for each of the plating baths (a) to (d) and connected by bolting, and then one end was buried in concrete to produce a test body as shown in FIG.

In the test piece of FIG. 1, bolts and nuts were also used by plating in the plating baths (a) to (d). In addition, the bolt holes are formed in advance in consideration of the fact that the connection test pieces are finally formed, and the inner surfaces of the holes are also plated. Separately, a connection test specimen bolted before plating was prepared and plated in the plating baths (a) to (d) described above, and one end was buried in concrete. Specimens of dimensions and shapes were prepared.

For these specimens, a combined cycle test ([SST: 4 hours] → [70 ° C. drying: 4 hours] →
[49 ° C x 95% RH: 4 hours] → [-20 ° C freezing: 4
Time], an interval between modes: 2 hours) was performed for 30 cycles, and the appearance was observed. The results are shown below.

(1) Of the test pieces plated in bath (a), those which were bolted after plating showed slight red rust at the joints, but the plating was entirely good.
After plating, almost no red rust was observed. The concrete part was destroyed and the plating material inside was observed, but no corrosion product was found. (2) In the sample plated in the bath (b), red rust was not observed in both of the sample plated with bolts after plating and the sample plated with bolts. Also, no corrosion products could be confirmed inside the concrete.

(3) In the test specimen plated in bath (c), remarkable red rust was observed in both the specimens which were bolted after plating and the specimens which were plated after bolting.
In particular, the corrosion of the bolts and nuts was severe, and almost no plating remained. Also, inside the concrete,
The corrosion products were slightly spotted. (4) The sample plated in the bath (d) had a corrosion state substantially equivalent to that of the test piece plated in the bath (a) at a portion exposed to the atmosphere. However, since cracks were observed from the upper surface to the side surface of the concrete portion, the cracks were broken, and the plating material inside was observed. As a result, a corrosion product of black-black-brown color was observed over a wide range.

From the above results, a steel product formed into a structure using the plated steel material of the present invention, or a steel product obtained by assembling a steel material in advance to form a structure, and then performing the plating of the present invention,
All were found to show excellent corrosion resistance. It was also found that when used as a composite with concrete, good corrosion resistance was exhibited. (Example 4) A steel wire having a diameter of 7 mm and a length of 200 mm was degreased with a commercially available alkaline degreaser, followed by pickling with 10% sulfuric acid at 60 ° C, followed by flux treatment. The flux treatment was carried out by preparing fluxes of various compositions as trials, immersing steel wires in a 10 to 40% by mass aqueous solution (80 ° C.) for 5 seconds. Then, the steel wire was kept in an electric oven at 120 ° C. for 4 minutes to completely dry the flux.
It was subjected to plating.

The flux-treated steel wire was immersed in a hot-dip Zn—Mg—Al plating bath (450 ° C.) containing 1% by mass of Mg and 5% by mass of Al for plating for 30 seconds. Then, the steel sheet is pulled up at a speed of 200 mm / sec, and air-cooled to 200 ° C. at a cooling rate of 5 ° C./sec.
Water cooled. Appearance after plating, unplated, pinhole,
Judgment was made based on the presence or absence of defects such as dross adhesion and unevenness. The results are shown in Tables 3 and 4.

As is clear from these tables, when the flux of the present invention is used, plating having a smooth surface can be obtained without defects such as non-plating, pinholes, dross adhesion, and irregularities. When a flux out of the range is used, the generation of defects or a decrease in the smoothness of the plated surface becomes remarkable.

[0064]

[Table 5]

[Table 6]

[0065]

[Table 7]

[Table 8] (Embodiment 5) 150 pre-processed in the same manner as in Embodiment 1
A × 75 × 1 mmt steel plate was immersed for 30 seconds in a plating bath (bath temperature 450 to 500 ° C.) obtained by dissolving an alloy lump containing Mg and Al at arbitrary concentrations and the balance substantially consisting of Zn. Then, the steel sheet is pulled up while controlling the pulling speed so that the plating layer has a predetermined thickness.
After air cooling at a rate of ° C./sec, it was cooled with water.

The appearance of the plated steel sheet thus produced was visually observed. These results are shown in FIG. From this figure, it is understood that it becomes difficult to obtain good plating as the content of Mg increases. This is because oxides are liable to be generated on the plating bath surface, and as a result, the oxides may adhere to the plating surface to deteriorate the appearance and may cause cracks in the plating. However, when a certain amount or more of Al coexists in the bath,
Plating with good appearance and no cracks can be easily obtained.

Equations (1) and (2) express this as mathematical expressions with the contents of Mg and Al as [Mg] and [Al], respectively. Of these, equation (1) is a condition for obtaining a good appearance, and equation (2) is a condition for not causing cracking. That is, [Mg] and [A
It has been found that, when l] is within the range determined by these formulas, good plating can be obtained relatively easily. [Mg] <(7 [Al] +28) /9.8 (1) [Mg] <(25 [Al] +0.4) /1.8 (2)

Example 6 A 150 × 75 × 1 mmt steel sheet degreased with a commercially available alkaline degreasing agent was immersed in 10% sulfuric acid at 60 ° C. for 1 minute and pickled. This steel sheet was washed with water and immersed in a flux. As flux, ZnCl ₂ :
A composition consisting of 215 g, 3.5 g of NaF, 25 g of NaCl, and 5 g of SnCl ₂ was dispersed in 1 liter of pure water to give a total concentration of 22.85 mass / vol%.
Was prepared. The temperature of the flux is 80 ° C,
The immersion time was 5 seconds. Immediately after immersion, it was left in an oven set at 150 ° C. for 5 minutes to be dried.

Next, the above steel sheet was subjected to (a) Mg and A
(a bath temperature of 450 ° C. and a melting point of 380 ° C.) containing 0.5% and 0.2% by mass of Zn and the balance of Zn, respectively, or (b) 3% by mass of Mg and Al, respectively. % And 10% by mass, with the balance being Zn for 1 minute in a plating bath (bath temperature: 470 ° C., melting point: 420 ° C.).

Then, the steel sheet was pulled up at a speed of 200 mm / sec and cooled under arbitrary conditions. The temperature of the plated steel sheet during the cooling process was measured by a thermocouple attached to the steel sheet. The amount of plating is 400 to 500 g in terms of Zn.
/ M ² . The plating cross section was determined by EPMA (surface analysis, 10
(00 ×), the plating had a two-layer structure consisting of a lower layer containing Fe and an upper layer mainly composed of Zn.

The corrosion resistance of the plated steel sheet was 100 × 50
mm, and the cut surface is sealed with a sealant.
The SST was performed for 500 hours, and the corrosion loss was measured. Table 5 shows the results when the plating bath (a) was used, and Table 6 shows the results when the plating bath (b) was used. A summary of what can be learned from these tables is as follows. (1) In the case where the steel sheet after plating is cooled in the air until the temperature of the steel sheet becomes equal to or lower than the melting point, high corrosion resistance is easily obtained when the cooling rate is 0.1 to 50 ° C./sec. In particular, when the cooling rate is 1 to 30 ° C./sec, the effect of improving the corrosion resistance becomes remarkable.
The plating cross section at this time has a two-layer structure including a lower layer, which is a thin Fe—Al alloy layer having a thickness of about several g / m ² or less, and a thick upper layer mainly composed of Zn, in terms of an adhesion amount converted to Zn. , Zn-Mg based intermetallic compounds were present. (2) In the cooling method of the above (1), the cooling rate is 0.5.
If it is less than 1 ° C./sec, the corrosion resistance is reduced. The plating section is composed of a lower layer containing Fe and having a thickness of more than 90% of the whole,
A two-layer structure consisting of a thin upper layer consisting mainly of n
Was hardly recognized. The lower layer is bath (a)
Is used, it is an Fe—Zn alloy layer, and the bath (b)
In the case where was used, it was a Fe-Al alloy layer. (3) In the cooling method of the above (1), the cooling rate is 50
Even when the temperature exceeds ℃ / sec, the corrosion resistance decreases. In this case, the plating cross section of each of the bath (a) and the bath (b) is such that the lower layer, which is a thin Fe—Al alloy layer having a deposition amount of about several g / m ² in terms of Zn, and the fine Zn—Mg metal layer It had a two-layer structure consisting of a Zn-based thick upper layer in which the compound phase was uniformly dispersed. In this upper layer, the distance between adjacent Zn-Mg intermetallic compound phases is short, and particularly when bath (b) is used,
Frequently, portions close to 0.05 μm were observed. (4) When the temperature of the plated steel sheet was higher than the melting point and it was immersed in water and rapidly cooled, a number of fine projections were generated on the plated surface. This is because bubbles generated by immersion quenching stayed inside the plating, and red rust was preferentially generated from this portion.

From the above results, it was found that the structure of the plating layer changed significantly depending on the cooling conditions, and the corrosion resistance changed accordingly. Then, in order to obtain plating having high corrosion resistance, 0.1 to 50 ° C./sec, preferably 1 to 30 ° C./sec, until the plating layer reaches at least the melting point.
It turned out that cooling at a rate of seconds was necessary.

[0073]

[Table 9]

[Table 10]

[0074]

[Table 11]

[Table 12]

(Example 7) A 150 × 75 × 1 mmt steel sheet pretreated in the same manner as in Example 1 contains 3% by mass of Mg, 2 to 10% by mass of Al, and Si at an arbitrary ratio.
The remainder was immersed in a plating bath composed of Zn, respectively. At this time, the temperature of the plating bath was 470 ° C., and the plating time was 5 minutes. Then, the steel sheet is pulled up at an arbitrary pulling speed, and 2
After air cooling to 00 ° C. at a cooling rate of 5 ° C./sec, it was water cooled. The cross section of the plating sample thus prepared was E
Observed by PMA (1000 times, area analysis). The plating exhibited a two-layer structure including a lower layer of an Fe-Al alloy and an upper layer in which an island-like η phase was dispersed in a Zn matrix. EPMA
3 shows the results of measuring the thickness of the lower layer from the secondary electron image of FIG. From FIG. 3, it is understood that as the amount of Si added with respect to the Al content in the plating bath increases, the thickness of the lower layer decreases. However, when the content exceeds 10% by mass with respect to the Al content, it hardly decreases. From this, it was found that the amount of Si added should be 10% by mass or less based on the Al content in the plating bath in order to stabilize the plating thickness. (Example 8) A steel pipe having a thickness of 9 mm and an outer diameter of 300 mm was cut into a length of 2000 mm, and a flat steel sheet of 9 mm and a reinforcing material were welded to one side to form a lower member. The other end was welded with a flanged member. Column members were manufactured by combining flanged steel pipes of the same size. Degreasing these components together with bolts and nuts with a commercially available alkaline degreasing agent,
After being immersed in 10% sulfuric acid at 60 ° C. (addition of a peracid washing inhibitor) for 5 minutes and pickling, ZnCl ₂ : 85% by mass, Na
The sample was immersed in a flux consisting of 1.5% F and 10% NaCl and adjusted to a total concentration of 25% by mass / volume.
The flux temperature was 80 ° C., and the immersion time was about 30 seconds. Immediately after immersion, it was dried with warm air. this,
Mg is 3% by mass, Al is 10% by mass, Si is 0.5% by mass.
It was immersed for about 5 minutes in a plating bath containing Zn, with the balance being Zn and having a bath temperature of 470 ° C. After raising,
It was immersed in warm water at 80 ° C. and cooled to produce a plated member. The stud bolt was set up on the seawall concrete at the seashore, and an exposure test piece of the pillar was manufactured. For the sake of comparison, the same position member manufactured by galvanization was also exposed, but in an exposure test for about 1.5 years, the galvanized member partially showed a reddish appearance due to corrosion of the iron zinc alloy layer. However, the Zn—Mg—Al alloy of the present invention remained metallic luster, demonstrating its high corrosion resistance. (Embodiment 9) A steel plate having a thickness of 6 mm has a maximum outer diameter of 150 mm.
And the end was welded to produce a 5 m long tapered steel pipe. This was plated under the conditions shown in Example 8 to produce a plated steel pipe column. At the same time, a branch material for installing a member of the steel pipe head and a wire for wiring, and a bolt and nut for joining were manufactured under the same plating conditions. These were erected at a depth of 1 m into a drilled hole having a diameter of 500 mm and solidified with mortar to obtain a steel pipe column. The upper part of the steel pipe column was welded on site after plating the steel pipe head member and the wiring member, then ground with a grinder, and painted with zinc rich paint. FIG. 4 shows the appearance. No change in external appearance was observed even after 9 months from the upsetting, and it became clear that the plated material according to the present invention is suitable for application to actual members and is also suitable for on-site welding and repair. .

[0076]

The column material made of zinc alloy plating according to the present invention has been subjected to hot-dip Zn-Mg-Al alloy plating. This plating layer has a two-layer structure, the lower layer is an Fe-Al-based alloy layer, and the upper layer is a layer mainly composed of Zn. The Zn—Mg intermetallic compound (MgZn ₂ , Mg ₂ Zn)
₁₁ ) The phases are mixed. By applying this plating, excellent corrosion resistance that can withstand a wide range of corrosive environments such as coastal areas with high chloride ion concentration, rivers and mountainous areas with low chloride ion concentration, and strong alkaline environments Can be imparted to steel products. In addition, the steel column member can be used for a long time, particularly as an iron column for lighting or an iron column for overhead wire.

Further, by using the plating bath, the flux and the plating method included in the present invention, the above-mentioned steel column member can be easily subjected to quality control and is economically advantageous in a one-stage dry brazing method. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a view showing a test body used in Example 3.

FIG. 2 is a diagram showing the effect of the contents of Al and Mg in a plating bath on plating.

FIG. 3 shows that the amount of Si added to the Al content in the plating bath is
FIG. 4 is a diagram showing an effect on a thickness of an Fe—Al alloy layer.

FIG. 4 is a diagram showing the appearance of a pillar manufactured in Example 9.

[Explanation of symbols]

1 ... equilateral angle iron (50 x 50 x 4 mmt) 2 ... equilateral angle iron (50 x 50 x 4 mmt) 3 ... bolt 4 ... concrete 5 ... concrete 6 ... tapered steel pipe after plating (6 mm thick, maximum 150 m)
7 ... bolts and nuts after plating 8 ... steel pipe head members after plating 9 ... branch materials for wiring after plating

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Akihiro Miyasaka 20-1 Shintomi, Futtsu-shi, Chiba F-term in the Technology Development Division of Nippon Steel Corporation (reference) 4K027 AA05 AA07 AA08 AA12 AA15 AA22 AB05 AB14 AB32 AB35 AB44 AC03 AC72

Claims (13)

[Claims] 1. A steel column or a member constituting the column, having a plating layer containing Zn, Mg, and Al as main components, and a Zn—Mg intermetallic compound phase in the plating layer. Wherein the proportion of Zn-Mg based intermetallic compound phase in the entire plating layer is 50% or less by volume. 2. In a plating layer containing Zn, Mg and Al as main components, a Zn—Mg based intermetallic compound has a θ (M
The zinc alloy-plated column material according to claim 1, wherein the column material is a g ₂ Zn ₁₁ ) phase and forms a continuous phase along the Zn grain boundary. 3. In the plating layer containing Zn, Mg and Al as main components, a Zn—Mg based intermetallic compound is η (M
The zinc alloy-plated column material according to claim 1, wherein the column material is a gZn ₂ ) phase, forms an island phase, and a distance between adjacent η phases is 0.05 µ or more. 4. In the plating layer mainly composed of Zn, Mg and Al, the Al—Zn alloy phase forms a dendritic or island-like phase, and the proportion of the Al—Zn alloy phase in the entire plating layer is volume. The zinc alloy-plated column material according to claim 3, wherein the percentage is 80% or less. 5. A plating layer containing Zn, Mg, and Al as main components, wherein at least Fe and Al are contained immediately above a steel material surface, and a ratio of Al to the total amount of Fe and Al is 49% by mass or more. A certain lower layer and at least Z
It exhibits a two-layer structure composed of n and an upper layer containing Mg, wherein the lower layer has a thickness of 90% or less of the total plating thickness, and the total thickness of the lower layer and the upper layer is 1 in terms of Zn equivalent.
2. The amount is from 100 to 800 g / m < ² >.
The zinc alloy-plated column material according to any one of Items 1 to 4. 6. The steel column is an equilateral angle steel, an unequal angle iron, an unequal thickness angle iron, a flat steel, an H-shaped steel, an I-shaped steel, a steel pipe, a tapered pipe, a different diameter pipe, a steel sheet. 6. A column made of zinc alloy plating according to any one of claims 1 to 5, wherein the column is a steel column made by deforming, further joining, and combining some of them. . 7. A member constituting the column is an equilateral angle steel,
Unequal angle iron, unequal thickness angle iron, flat steel, H-shaped steel, I
Shaped steel, steel pipes, tapered pipes, different diameter pipes, steel plates, bolts, nuts, washers, rivets, and these are steel members made by deforming, further joining, and combining some of them. The zinc alloy-plated column material according to any one of claims 1 to 5. 8. The steel column or steel member according to claim 6, wherein the steel plate and the steel member are entirely or partially coated with an organic coating. The column material made of zinc alloy plating described. 9. The method according to claim 6, wherein a part or all of the plating surface has a portion in contact with the concrete.
9. The zinc alloy-plated column material according to any one of items 8 to 8. 10. A ZnCl ₂ content of 60 to 95% by mass.
%, A total of 0.1 to 10% of any one or more of a fluorinated fluoride or a silicofluoride of an alkali metal element or an alkaline earth metal element, and a fluoride or chloride of an alkali metal element or an alkaline earth metal element 1 to 30% in total, and Sn, P
any one of chlorides of b, In, Tl, Sb or Bi
A flux containing 0.1 to 10% in total of more than one kind and a total concentration of 10 to 60 (mass / volume%). 11. ZnCl _{2 in an amount} of 60 to 95% by mass.
%, At least one of fluorides of an alkali metal element or an alkaline earth metal element in a total amount of 0.1 to 10%,
A flux comprising at least one kind of chlorides of alkali metal elements or alkaline earth metal elements in total of 1 to 30%, and a total concentration of 10 to 60 (mass / volume%). . 12. The steel material surface is degreased and pickled, then the steel material is immersed in the flux according to claim 10 or 11, and the flux attached to the steel material surface is dried. 0.05 to 7%, Al: 0.01 to
20%, the balance consisting of Zn and unavoidable impurities,
Mg content ([Mg]) and Al content ([Al])
Is immersed in a hot-dip galvanizing bath that simultaneously satisfies the relations [Mg] <(7 [Al] +28) /9.8 and [Mg] <(25 [Al] +0.4) /1.8 by mass% And thereafter cooling the steel material at a rate of 0.1 to 50 ° C./sec until the temperature of the steel material surface reaches at least the melting point of the plating layer. . 13. The production of a zinc alloy plating column material according to claim 12, wherein a hot-dip plating bath to which 10% by mass or less of Si is added to the Al content is used in the hot-dip plating bath. Method.