JPS62274090A - Al-mn alloy plated metallic material - Google Patents

Abstract

PURPOSE:To obtain an Al-Mn alloy plated metallic material having superior corrosion resistance by regulating the amount of Fe among impurities in an Al-Mn alloy layer contg. a specified amount of Mn formed by plating to a specified value or below. CONSTITUTION:An Al-Mn alloy layer consisting of 10-30wt% Mn and the balance Al essentially is formed on the surface of a metallic material by plating. At this time, the amount of Fe among impurities in the Al-Mn alloy layer is regulated to <=1wt%, preferably <=0.5wt%. Thus, superior corrosion resistance is provided to the Al-Mn alloy layer so that the plated metallic material shows superior corrosion resistance even at the edge and a part on which a film is defective.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an Al alloy plated metal material with excellent corrosion resistance, particularly a metal material such as steel provided with an Al-Mn alloy plating layer. Regarding.

(Prior Art) It is well known that M or Al alloy plated metal materials have many advantages such as excellent corrosion resistance, beauty, and non-toxicity. However, this Al or Al alloy plating Since electrodeposition from an aqueous solution is impossible1, it is carried out by molten metal immersion method, vacuum evaporation method, electroplating method using organic solvent bath or molten salt electrolytic bath, etc.Currently, currently, molten metal immersion method is mainly used. Although the law is used,
In this method, the target is almost single Al plating, and furthermore, thinning is difficult, and since the processing temperature exceeds 700° C., there are problems such as formation of an alloy layer and adverse effects on the base material.

Therefore, in recent years, attention has been focused on the latter method of Al electroplating using a molten salt electrolytic bath, and Q-Mn has superior corrosion resistance.
Alloy plating has been proposed (Special Publication No. 43-18245)
issue).

According to this, the Al-Mn alloy plating layer is made of zinc and Al.
The inventors of the present invention have similarly proposed (
When Q-Mn alloy plating was performed on a steel plate without controlling the iron content (described later), it was confirmed that it had excellent corrosion resistance. It was necessary that there be no defects. In other words, as an example of general use of plating materials, if the end face of the plating layer is exposed or if there is a defect in the plating layer due to processing etc.
Red rust occurred in about 1 day in the salt spray test and in about 10 days in the air exposure test. This was due to the fact that the corrosion potential of the plating film was higher than that of the steel sheet, that is, there was no sacrificial corrosion protection at all.

(Problems to be Solved by the Invention) An object of the present invention is to provide Al-Mn alloy plating that improves bare corrosion resistance, particularly corrosion resistance at the end faces or defective areas of the Al-Mn alloy plating layer. An object of the present invention is to provide a Mn alloy plated metal material.

(Means for Solving the Problems) ゛ As a result of intensive study on a method to improve this serious drawback of Al-Mn alloy plating, the present inventors found that Al-Mn alloy plating
It was discovered that iron, an impurity in the alloy plating film, is significantly involved in the corrosion potential.

Figure 1 shows a cold-rolled steel plate as a base material, Al-20%Mn
Fe content in the plating film when alloy is plated and 4
The graph shows the relationship between the corrosion potential in a 5% NacQ solution at 0°C.0 The corrosion potential of normal steel is approximately -0.6
Considering that V (vs, Ag/AgC2),
It is clear that if the amount of iron in the coating exceeds about 0.5% by weight, the potential of the plating coating will be higher than the corrosion potential of the steel base material, so sacrificial corrosion protection cannot be expected.

Unlike other impurities, iron as an impurity is extremely easily mixed in, not only when it is mixed in the raw salt, but also when it is leached from the plating cell material, and even when it is leached from the steel material that is the base metal. It's also big.

Figure 2 shows a plating current density of 10 using a steel plate as the base material.
A/cls", 20A/d+s"? ! )h is a graph showing the relationship between the iron concentration in the molten salt electrolytic bath and the iron concentration in the plating film after treatment. As shown in Figure 2, only 20-30 ppm in the plating bath.
Considering the severe relationship that just Fe content is 0.5% by weight in the plating film, it is extremely difficult to obtain the desired plating film with excellent corrosion resistance, especially if iron removal is not performed. Conceivable.

Here, in the broadest sense, the present invention is an A9 alloy plated metal material in which an Al-Mn alloy plating layer is provided on a part or the entire surface of a base metal, which has sacrificial corrosion protection ability for the base metal of the metal material. It is a metal material with excellent corrosion resistance characterized by limiting the iron content in the coating to a range having .

More specifically, the gist of the present invention is to apply an Al material on the metal surface, with Mn: 10 to 30% by weight, the remainder being substantially A12, and Fe in the impurities being 1% by weight or less.
-Al-M characterized by having a Mn alloy plating layer
It is an n-alloy plated metal material.

The metal material constituting the base metal is not particularly limited, and includes ordinary steel, chromium steel, stainless steel, and the like. Further, the shape thereof may be any shape such as a plate material, a wire material, or a bar material.

Furthermore, although the alloy plating film in the present invention is formed by a so-called molten salt electroplating method, sufficient iron removal may be performed after preparing the desired Al-Mn alloy plating bath. Baths may typically be prepared using molten chloride baths.

It is common knowledge that such a molten chloride bath normally contains 50 ppm or more of Fe ions, and in particular, when steel materials are plated, the Fe ions eluted from the bath can reach a concentration of 100 ppm or more. In the present invention, by adding aluminum powder as described later,
This Fe ion content is reduced to 20 ppta or less.

Thus, according to the present invention, an Al=Mn alloy plated metal material is provided which has excellent corrosion resistance and sacrificial corrosion resistance, and thus has excellent corrosion resistance even on end faces and film defects.

(Function) Although the Mn content in the plating film of the plated metal material of the present invention is not particularly limited, it is difficult to form a beautiful plating film when the Mn content is 10% by weight.
Further, if it exceeds 30% by weight, the processability of the film deteriorates, so the content is usually 10 to 30% by weight.

Further, the iron content of the plating film of the plated metal material of the present invention should be limited to an amount that does not affect the corrosion potential of the plating film based on the corrosion potential of the base metal.

The corrosion potential of the base metal differs slightly depending on the type, so it is difficult to limit it, but the corrosion potential at 40°C
% corrosion potential of normal steel in saline solution is -0.6V
(vs, Ag/^gcQ), so in that case, it is desirable that the amount is 0.5% by weight or less in the film.

In other words, the Fe1l in the plating layer only needs to be within the range that provides sacrificial corrosion protection, but since the potential of the steel material changes somewhat depending on the environment in which it is used, the Fe1l that provides sacrificial corrosion protection actually changes, but the plating In the general usage environment of steel materials,
-0.6, so by setting the Fe content to 1% or less, preferably 0.5% or less, the effect of sacrificial corrosion protection will be enhanced in all usage environments.

Next, the method for producing an Al-Mn alloy plating film according to the present invention is preferably electroplating using a molten salt bath, but usually a binary or multicomponent bath of AlC2sXO2 (X: alkali metal). h ion is added. In addition, in order to limit the iron content in the film according to the present invention, it is necessary to sufficiently remove iron before plating, and when plating is performed continuously, it is necessary to perform iron removal continuously. This is because the amount of iron contained in normal industrial chemicals exceeds the limit iron content of the present invention, and the amount of iron eluted during normal plating processes cannot be ignored. Any method may be used to remove iron, but for example, a method of removing iron by electrolysis or a method of displacement precipitation using metal aluminum powder are excellent. The Fe ion content in the molten salt electrolytic bath is preferably suppressed to several ppm or less.

In addition, in order to further improve electrodeposition properties and corrosion resistance, and to prevent iron from being leached from the base metal, the surface may be plated with Zn or the like in advance.

Example A flow cell (made of Inconel 600) exclusively for molten salt was created, an Al plate with a purity of 99.8% was installed as an anode in the flow channel, and various steel plates with a thickness of 0 and 8n+m as the material to be plated were used as a cathode. The following various plating tests and characteristic tests of the obtained steel sheets were conducted under the conditions shown in Table 1. The plated area of the 0W4 board was 0.7do+'', which was degreased with an organic solvent as a pretreatment, electrolytically degreased in 10% sodium orthosilicate, pickled with 10% HCQ, and then treated with 100% ethanol. It was soaked in water and dried with warm air.

l Bath composition: AlCQx-NaCQ- with α(AlC2*
: 62+mo1%, NaC2:20mo1%, CQ
: 1B + mo1%) Bath temperature = 200°C Additives: Mn: Mna 2g (ion concentration in bath 50
~6000ppm) Fe: 5~200ppm ■ Contains from raw material salt as an impurity.

■From the plating base material, cell, and anode Contamination and natural increase.

■Added by anodically melting Fe plate.

Iron removal method: Al powder (distributed through a column packed with 100 meshes) - Bath flow rate: 20.5 mm/see Current density: 40 A/da+" These results are summarized in Table 2.

Samples 1111L1 to 1111L1 to 5 were not subjected to any iron removal, and it is thought that iron was contained as an impurity in the raw material salt. If the Mn content in the film is less than 10% (Nal, 2), the plating properties will be poor and the corrosion resistance will be insufficient. On the other hand, when the Mn content exceeds 10% by weight, the corrosion resistance is significantly improved, but due to the iron contained as an impurity, the corrosion potential of the plating film is higher than that of the steel Fi base material, and when the end face is exposed, Red rust will develop within a day.

1', 5 to 12 are cases where iron was removed using Al powder. When the iron content is about 0.5% by weight or less, the corrosion potential of the plating film is less noble than that of the steel sheet base material, and it has sacrificial corrosion protection.

Therefore, even if the end face is exposed for Na9 to Na12,
The generation of red rust can be prevented for 12 to 14 days.

In addition, if the Mn content in the film exceeds 30% by weight (fish products 2
), cracks occur in the coating due to processing such as bending.

Magnets 13 to 18 are cases in which a base material having a somewhat negative corrosion potential is used. In this case, after preparing the plating bath, iron was sufficiently removed using aluminum powder, and then iron was naturally increased without any particular iron removal. The first sample is magnetic 13 and thereafter 10
Every piece! 11a14, 15, 16, 17, and 18, a total of 50 sheets were plated. As is clear from Table 2,
At only the 10th sheet (Ilh14), the iron content reached 0.77% by weight, and the corrosion potential was now comparable to that of the steel plate base material.
In the 20th sheet (llh15), the corrosivity of the end face has significantly deteriorated due to the corrosion potential of the base metal.

The above results indicate that, especially if the amount of iron content is not controlled, the corrosion potential of the film easily shifts to the negative side and sacrificial corrosion protection is lost.

(Effects of the Invention) As described above, according to the present invention, Al-Mn alloy plating has excellent corrosion resistance, beauty, and non-toxicity inherent to it, as well as excellent corrosion resistance at the end faces of plating layers or plating defects. A -Mn alloy plated metal material is obtained, which exhibits excellent effects particularly as a material used in severe corrosive environments for building materials and automobiles.

Conventionally, the corrosion resistance mechanism of AO, -Mn alloy plating was thought to be due to a simple barrier effect, but it has been found that it has been given sacrificial corrosion protection ability, and that Fe is used to achieve this.
The present invention, which has been achieved by reducing impurities, is an excellent invention that contributes to the development of this field also due to its excellent corrosion resistance improvement effect as described above.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the Fe content in the plating film and corrosion potential; and FIG. 2 is a graph showing the relationship between the Fe concentration in the plating bath and the Fe content in the plating film. Figure 1 0 1.0 2. O Ll Air Fξ Look '4-11 (W+-i) Figure 2 Sea cP Fugi 1 (pPp9L)

Claims (1)

[Claims] On the metal surface, Mn: 10 to 30% by weight, the balance being substantially A.
Al having an Al-Mn alloy plating layer consisting of L and containing 1% by weight or less of Fe in impurities.
-Mn alloy plated metal material.