JP3531616B2 - Aluminum alloy plate with excellent corrosion resistance and coating surface treatment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy sheet which is suitable as a coating sheet material for automobile outer panels and the like and which is excellent in corrosion resistance and coating surface treatment.

[0002]

2. Description of the Related Art An aluminum alloy plate used for an automobile outer plate is generally used after being coated, and therefore, it is required to have an excellent coating surface treatment property. In addition, corrosion resistance after painting, especially thread rust resistance is required. The coating undercoating property was imparted by a chromate treatment using chromic acid. However, due to the problem of environmental impact due to the use of chromic acid and the requirement for simultaneous coating and undercoating of cold-rolled steel sheets and aluminum alloy sheets, zinc phosphate treatment is often used at present as in the case of cold-rolled steel sheets. ing. In the simultaneous zinc phosphate treatment with the cold-rolled steel sheet, in order for the surface of the aluminum alloy sheet to be sufficiently pretreated, the property of the aluminum alloy surface becomes a problem.

Al-Mg, which is widely used for automobile outer panels
The system alloy sheet is manufactured by DC casting, homogenizing heat treatment, hot rolling, cold rolling, intermediate annealing, cold rolling, and final annealing as in the usual case. Further, the final annealing has been performed at high temperature in consideration of formability, measures for stretcher strain, and the like. However, in the final annealing, Mg accumulates on the surface and becomes MgO, which impairs the surface treatment property, and adversely affects the corrosion resistance, especially the thread rust resistance.
Particularly, when the Mg concentration on the surface exceeds 20%, the corrosion resistance is significantly deteriorated.

[0004]

In order to suppress an increase in the Mg concentration in the surface layer portion, a method of incorporating a washing step with an acid or an alkali in the manufacturing step is disclosed in JP-A-3-111.
It is disclosed in Japanese Patent No. 532. Even in this case, it is difficult to reduce MgO near the surface because Mg is diffused on the surface of the aluminum alloy plate by the heat treatment and oxidized near the surface.
Further, if cleaning is performed with an acid or an alkali after the final heat treatment is completed, the surface of the product plate may be scratched. Moreover, since an extra washing step is required, it causes an increase in manufacturing cost. Therefore, it is desired to be able to manufacture an aluminum alloy plate that is cheaper and has excellent base treatment properties without a cleaning step if possible.
For this purpose, it is necessary to effectively prevent the segregation of Mg on the surface of the aluminum plate.

Japanese Unexamined Patent Publication (Kokai) No. 3-287739 discloses an aluminum alloy having an Al-Mg-Cu-Cr system in which the crystal structure is refined by equiaxed crystal grains to improve the surface treatment property and the corrosion resistance. There is. However, even in this aluminum alloy, Mg tends to be concentrated in the surface layer portion, so that good undercoating property may not be obtained in some cases. Further, in the case where Mg is extremely concentrated, the corrosion resistance is significantly deteriorated. The present invention has been devised in order to solve such a problem, by suppressing the concentration of Mg on the surface by finely adjusting the contained components, controlling the amount of Mg in the surface layer, and cooling. It is an object of the present invention to provide an aluminum alloy sheet which is excellent in corrosion resistance and coating undercoating property while the solution treatment is applied to the rolled sheet.

[0006]

In order to achieve the object, the aluminum alloy sheet of the present invention which is excellent in corrosion resistance and coating pretreatment is Mg: 2.5 to 5.5% by weight, Cu: 0.
05-0.4 wt%, Mn: 0.005-0.2 wt%, Cr: 0.005-0.1 wt%, Ti: 0.01
~ 0.05 wt%, Si: 0.08 wt% or less, Fe:
0.1% by weight or less and Be: 0.0001 to 0.01
A cold-rolled solution-treated plate having an oxide layer on the surface thereof, the content of which is Mg, containing Mg,
Between Cu and Be, A = Mg% -10 × Cu% -10
A value defined by 00Be% [wt%] has a relation of 4 or less, and the Mg concentration is regulated to 20 wt% or less in the depth direction of the plate surface. This aluminum alloy plate further contains Zr: 0.001 to 0.1% by weight, V: 0.001 to 0.1% by weight, and B: 0.0.
It is also possible to contain one kind or two kinds or more of 001 to 0.01% by weight.

Such an aluminum alloy plate is subjected to a homogenizing treatment of an ingot and is rolled into a cold rolled plate having a predetermined plate thickness by hot rolling and cold rolling. 100 ℃ for this cold rolled sheet
Induction heating is performed at a temperature rising rate of 1 / sec or more, the temperature is kept in the temperature range of 450 to 520 ° C. for 3 seconds or less, and then a solution treatment of cooling to room temperature at a cooling rate of 1 ° C./sec or more is performed. The Mg concentration is reliably suppressed to 20% by weight or less. Following the solution treatment, it is preferable to perform a stabilization treatment of heating at 110 to 160 ° C. for 1 to 3 hours. Aluminum alloy cold-rolled sheet is, for example, 1 to 24 at 430 to 450 ° C.
Homogenization treatment in the first stage of heating for 2 hours, homogenization treatment in the second stage of heating at 480 to 550 ° C for 1 to 12 hours, hot rolling at a hot rolling start temperature of 500 ° C or less and a hot rolling end temperature of 370 to 420 ° C. It is manufactured through cold rolling with a working rate of 70 to 90%. If necessary, intermediate annealing may be performed during the cold rolling.

[0008]

The aluminum alloy plate of the present invention is basically M
It is a material whose strength is improved by utilizing solid solution strengthening by g, and is intended for precipitation hardening by Cu and grain refinement by Mn, Cr and the like. The alloy elements and their contents will be described below. Mg: 2.5 to 5.5 wt% Mg is an alloying element necessary for imparting strength and moldability. However, if the Mg content is less than 2.5% by weight, the improvement in strength is insufficient. On the other hand, if a large amount of Mg is contained in excess of 5.5% by weight, the strength is increased, but the effect on improving the moldability is reduced. As a result, casting cracks during DC casting and edge cracks during hot rolling are likely to occur, and are also susceptible to stress corrosion cracking. Therefore, in the present invention, the content of Mg is set in the range of 2.5 to 5.5% by weight.

Cu: 0.05 to 0.4 wt% Cu is an alloying element which imparts strength like Mg,
In particular, the effect of improving the yield strength by the precipitation of the Al-Cu-based compound in the paint baking step is great. Further, it also effectively acts to improve the stress corrosion cracking resistance and suppresses the diffusion of Mg to the material surface during solution treatment. Such an effect is remarkable when the Cu content is 0.05% by weight or more. However, when a large amount of Cu exceeding 0.4% by weight is contained, the yarn rust resistance tends to deteriorate. Therefore, in the present invention, the Cu content is 0.0
The range was set to 5 to 0.4% by weight.

Mn: 0.005 to 0.2 wt% Mn has the function of making the grain structure after annealing fine and controlling the recrystallization texture. If the Mn content is 0.01% by weight or less, this effect is usually not remarkable. However, when performing rapid cooling at 100 ° C./sec or more, the action of Mn is sufficiently exerted even if the Mn content is 0.005 wt% or more. On the other hand, when a large amount of Mn exceeding 0.2% by weight is contained, a coarse intermetallic compound is likely to be generated, resulting in deterioration of formability. Therefore, in the present invention, Mn
The content was set in the range of 0.005 to 0.2% by weight.

Cr: 0.005 to 0.1% by weight Cr is also effective for refining the crystal grain structure, like Mn, but if it is less than 0.005% by weight, the effect is small. On the other hand, when a large amount of Cr exceeding 0.1% by weight is contained, the moldability decreases. Therefore, in the present invention, Cr
The content range was set to 0.005 to 0.1% by weight. Ti: 0.01 to 0.05% by weight Ti is an alloying element which, together with B, makes the crystal grain size of the ingot fine and prevents casting cracks. However, 0.
If the Ti content is less than 01% by weight, the effect is small.
On the contrary, when the Ti content exceeds 0.05% by weight, Al ₃ T
It tends to produce coarse particles of i and deteriorate moldability. Therefore, in the present invention, 0.01 to
The Ti content was set in the range of 0.05% by weight.

Fe: 0.1% by weight or less Fe is a harmful impurity which causes deterioration of ductility and deteriorates moldability such as bendability and overhanging property. Therefore, in consideration of applications requiring particularly high moldability such as automobile outer panels, in the present invention, the upper limit of the Fe content is set to 0.1% by weight.
Stipulated in. Si: 0.08 wt% or less Si is also an impurity element that hinders formability depending on the amount added, and its upper limit is set to 0.
It was defined as 08% by weight. Further, in the present invention, since the hardening in the coating baking step is expected to be the precipitation of the Al—Cu-based compound instead of Mg ₂ Si, Si is 0.08.
The required strength is ensured even if the amount is reduced to less than or equal to weight%.

Be: 0.0001 to 0.01 wt% Be prevents the oxidation and disappearance of Mg during the melting of an aluminum alloy and the oxidation of Mg diffused from the inside of the material to the surface. It is an effective alloying element. The oxidation consumption of Mg is effectively prevented when the Be content is 0.0001% by weight or more. Further, the addition of 0.0001% by weight or more of Be also improves the yarn rust resistance. However, Be content exceeding 0.01% by weight tends to deteriorate molding processability such as overhanging property.

The aluminum alloy of the present invention may also contain B, V and Zr as optional components.
The action of these alloy elements is as follows. B: 0.0001 to 0.01% by weight B is an alloying element which, like Ti, makes the grain size of the ingot fine and prevents casting cracks. But,
When the content of B is less than 0.0001% by weight, the effect is small. On the contrary, when the B content exceeds 0.01% by weight, Al
Coarse particles such as B ₂ and TiB ₂ are generated to reduce the ductility and hinder the moldability. Therefore, when B is contained, its content is set in the range of 0.0001 to 0.01% by weight.

V: 0.001 to 0.1% by weight V has the function of controlling the work structure and improving the formability of the final plate, like Mn and Cr. This effect is small when the V content is less than 0.001% by weight, and decreases the formability when it exceeds 0.1% by weight. Therefore, when V is contained, its content is set in the range of 0.001 to 0.1% by weight. Zr: 0.001 to 0.1% by weight Zr has the function of controlling the work structure during hot rolling and improving the formability of the final plate. This effect is small when the Zr content is less than 0.001% by weight, and when the Zr content exceeds 0.1% by weight, the generation of coarse particles causes a decrease in elongation. Therefore, when Zr is contained, its content should be 0.00
It is set in the range of 1 to 0.1% by weight.

In the present invention, the following relationships are maintained among the above alloying elements. This relationship is empirically determined from a large number of experiments by the present inventors,
This is an effective index for preventing Mg from concentrating on the surface layer. First, A = (Mg%)-10 × (Cu%)-
The components of Mg, Cu and Be are adjusted so that the A value defined by 1000 × (Be%) is 4 or less. Here, (Mg%), (Cu%) and (Be%)
Is a numerical value indicating each content by weight%. C
u and Be are elements that suppress the diffusion of Mg into the surface of the material, and when the relationship of A ≦ 4 is maintained, the diffusion of Mg to the surface of the material during solution treatment is suppressed in the alloy of this system, and MgO Growth is suppressed.

Further, B = [Mg%] at a position where the Mg concentration has a peak in the depth direction of the material surface after the solution treatment.
B value defined by / ([Al%] + [O%]) is 0.3
It is necessary to keep below. [Mg%],
[Al%] and [O%] are numerical values representing the respective contents in atomic%. M so that B ≦ 0.3 holds
By balancing g, Al and O, the Mg amount becomes 20 wt% or less at the position where the Mg concentration is maximum in the depth direction, and the thread rust resistance and coating adhesion of the coating material are improved. It For example, Test No. 1 used in Examples described later has Al, Mg and O distributed in the concentration distribution shown in FIG. As a result of investigating similar concentration distribution curves for alloys having various compositions, when A ≦ 4 and B ≦ 0.3 are satisfied, the oxidation of Mg is prevented and the maximum Mg concentration in the depth direction is 20. It was clarified that the amount can be suppressed to less than or equal to weight%.

[0018]

The aluminum alloy plate of the present invention is formed into an ingot by, for example, ordinary DC casting. After the ingot is homogenized, it undergoes the steps of hot rolling, cold rolling, intermediate annealing, and cold rolling, and is finally heat-treated in a continuous annealing furnace. The homogenization treatment homogenizes the distribution of elements such as Mg segregated during casting, and controls the shape of the crystallized product generated during casting, thereby improving the strength and forming workability of the product sheet. For this homogenization treatment, it is preferable to employ low-temperature first-stage heating and high-temperature second-stage heating. In the first stage heating, Mg ₂ Al ₃ formed during casting is melted into the matrix as much as possible under the condition that the β phase is not locally melted (burning) when the temperature is raised. So in the first stage,
Conditions for heating to 430 to 450 ° C. for 1 to 24 hours are adopted. In the second stage heating, Mg was completely solutionized and Al ₆
Formability is improved by controlling the shape of the intermetallic compound such as Fe. In this regard, in the second stage, 4
The condition of heating at 80 to 550 ° C. for 1 to 12 hours is adopted.

The homogenized ingot is hot-rolled to a desired plate thickness by a conventional method. Hot rolling preferably has a hot rolling start temperature of 500 ° C. or lower and a hot rolling finish temperature of 370 to 420 ° C. in order to prevent hot cracking. After hot rolling, cold rolling is performed to a desired plate thickness by a usual method. At this time, the cold working rate affects the recrystallized grains during the final annealing. In order to make the recrystallized grains fine, it is preferable to set the working rate in the entire cold rolling process to 70 to 90%. In cold rolling with a working rate of less than 70%, recrystallized grains may become coarse. On the other hand, the processing rate of cold rolling is 90%
If it exceeds, recrystallized grains become too fine and stretcher strain marks are likely to occur.

Further, the aluminum alloy plate work-hardened by cold rolling softens the work structure by recrystallization and
Intermediate annealing is performed as necessary to control the formability of the final plate. For the intermediate annealing, either a batch type annealing furnace or a continuous type annealing furnace can be used. For the intermediate annealing, annealing conditions that take into account the balance between the r value and the elongation are adopted so that the required deep drawability can be obtained. When performing intermediate annealing in a batch type annealing furnace, the conditions of heating at 320 to 350 ° C. for 1 to 10 hours are adopted. If the annealing temperature is lower than 320 ° C., segregation of Mg tends to be promoted, and 350 ° C.
If it exceeds, the oxidation of the plate surface will become active. When intermediate annealing is performed in a continuous annealing furnace, 400 to 520 ° C in a short time within 3 seconds
The condition of heating to is adopted. When the heating temperature during continuous annealing exceeds 520 ° C, segregation of Mg is promoted, and when it is less than 400 ° C, sufficient recrystallization is not performed. When the intermediate annealing is performed, cold rolling is further performed to a predetermined plate thickness.

In order to improve the coatability and the corrosion resistance of the Al-Mg alloy for coating, it is important to prevent the segregation of Mg generated during the solution treatment of the aluminum alloy cold-rolled sheet. The solution heat treatment also has an effect of recrystallizing a worked structure generated during cold working. Concentration of Mg in the surface layer portion can be suppressed by sufficiently shortening the heating time so as not to give a time for Mg to diffuse over a long distance during solution treatment. Concentration of Mg to the surface layer portion also occurs in the hot rolling step, but the Mg concentrated layer containing MgO and the like on the surface is destroyed by the hot rolling and therefore does not adversely affect the product characteristics. However, Mg concentrated on the surface layer during solution treatment
Has an adverse effect on the coating surface treatment property, corrosion resistance, and the like. In order to perform sufficient solution treatment by heating for a short time, it is effective to heat to a high temperature in a short time by performing eddy current heating from the inside using an induction heater and then cool sufficiently quickly. When using other heating methods such as heat transfer, infrared rays, hot air blowing, etc. from the surface, the heating time for solution heat treatment becomes long, the increase of the Mg concentration on the surface is unavoidable, and a short time is sufficient. In many cases, the effect of solution treatment cannot be obtained.

In order to carry out recrystallization and solution treatment without concentrating Mg on the plate surface, rapid heating to a temperature range of 450 to 520 ° C. is performed at a heating rate of 100 ° C./sec or more. When the temperature rising rate is slower than 100 ° C./sec, easily diffusible Mg is accumulated on the surface layer of the aluminum alloy plate, and the coating undercoating property,
Deteriorates corrosion resistance. If the solution temperature is lower than 450 ° C., sufficient recrystallization and solution treatment cannot be achieved within a practical processing time. On the contrary, solution treatment for a long time of more than 3 seconds or 5
At a solutionizing temperature of higher than 20 ° C., defects such as Mg concentration and surface oxidation are likely to appear. The solution-treated aluminum alloy plate is cooled at a rate of 1 ° C./sec or more because a phenomenon in which Mg diffuses is observed even in the temperature lowering process. For example, an aluminum alloy plate is rapidly cooled by spraying or dipping cold water, hot water, cold air or the like into a quenched state.

The solution treated aluminum alloy plate is
For example, a tensile leveler is used to apply a tensile deformation of about 0.2 to 1% to remove the thermal strain generated in the solution treatment. However, the straightening may reduce the ductility of the aluminum alloy plate and deteriorate the formability. So, after straightening the aluminum alloy plate,
It is preferable to perform a stabilizing treatment of heating to 160 ° C. for 1 to 3 hours. The stabilization process removes the strain and restores the original elongation. To do this, the stabilization process
It is necessary to heat to a temperature of ℃ or more for 1 hour or more.
However, when the heating temperature is higher than 160 ° C. or the heating time is longer than 3 hours, precipitation of S ′ phase, S phase and the like is observed and the strength is improved but the workability tends to be deteriorated. The aluminum alloy plate prepared in this way is
Coating baking is performed by heating to 0 to 180 ° C. for 20 to 30 minutes. During this heating, the S phase and S'phase composed of an Al-Cu-Mg-based intermetallic compound or the like are precipitated, and a coated plate material having the required strength and hardness can be obtained.

[0025]

EXAMPLES Example 1: Various aluminum alloys having the compositions shown in Table 1 were melted, and DC was formed on a slab having a thickness of 400 mm.
Cast. This slab has 440 ° C for 10 hours and 52
After carrying out a two-step soaking treatment at 5 ° C for 1 hour, hot rolling was performed at a hot rolling start temperature of 450 ° C to obtain a hot rolled sheet having a sheet thickness of 7 mm.
The hot rolling end temperature was set to 400 ° C. After cold-rolling the obtained hot-rolled sheet to a sheet thickness of 1.3 mm, it is heated to 340 ° C. for 1 hour in a batch type annealing furnace, and the sheet thickness is 1.0 mm.
Cold rolled until.

[0026]

The temperature rise rate of the cold-rolled sheet is 150 ° C. in the atmosphere.
After heating rapidly at a heating rate of 1 / sec and holding at 480 ° C for 3 seconds, cooling water is sprayed on the surface of the cold rolled sheet to reduce the temperature to 400 ° C.
/ Sec to room temperature. When the Mg concentration in the surface layer portion of the solution-treated plate material was measured by Auger analysis, the Mg concentration in the surface layer was between the A value and the B value.
Had a relationship shown in. Further, the Al, Mg, and O concentrations in the plate material of test number 1 fluctuated from the surface toward the inside, as seen from the Auger analysis result of FIG. The horizontal axis of FIG. 1 represents the sputtering time (minutes), and corresponds to the depth of the sample at a ratio of 1 minute≈170 Å. On the other hand, the vertical axis represents the concentration of each element expressed in atomic%.

A 70 mm × 150 mm test piece was cut out from each plate and subjected to chemical conversion treatment, electrodeposition coating, intermediate coating and top coating under the conditions shown in Table 2. 40 ° C for each test piece after painting
After dipping in pure water for 24 hours, the adhesion of the coating film was determined by counting the number of the remaining coating film in a test using a grid having 100 2 mm squares.
When the judgment results were sorted by the Mg concentration of the surface layer, as shown in Table 3, the adhesion was significantly different at the boundary of the Mg concentration of 20% of the surface layer. That is, when the Mg concentration was maintained at 20% or less, no squares were observed in which the coating film peeled off, whereas when the Mg concentration exceeded 20%, at least 5
The squares where the individual coating films were peeled off were counted. The excellent adhesion of the coating film obtained in the examples of the present invention is derived from the fact that a base having a high affinity for the coating film was formed by the chemical conversion treatment.

[0029]

Example 2 The aluminum alloy of test No. 1 shown in Table 1 was hot-rolled and cold-rolled in the same manner as in Example 1 to form a cold-rolled sheet having a thickness of 1.0 mm, and then Table 3 Solution treatment was performed under the conditions shown in. In the examples of the present invention and Comparative Examples 6 and 7, the temperature was raised to the solution treatment temperature at a temperature rising rate of 150 ° C./second, and after the solution treatment, the temperature was lowered to room temperature at a temperature lowering rate of 400 ° C./second. In Comparative Example 8, the temperature rising rate is 10 ° C. /
The temperature was raised to the solution treatment temperature in seconds, and after the solution treatment, it was cooled to room temperature at a temperature decrease rate of 150 ° C./sec.

Each solution-treated test piece was coated through the same steps as in Example 1, and chemical conversion treatability, corrosion resistance, coating adhesion and the like were investigated. The chemical conversion treatability was evaluated by observing the surface of the test piece after the zinc phosphate treatment with a scanning electron microscope, investigating the deposition state and density of zinc phosphate crystals, and evaluating the weight of the zinc phosphate coating. Those of 5 g / m ² or more were accepted. Corrosion resistance is measured by using a cutter to scratch a test piece that has been coated up to the top and forming a cross cut that reaches the base material.
The salt spray test was conducted in accordance with S Z2371. The salt spray is continued for 24 hours, and then exposed to a constant temperature and constant humidity layer maintained at a temperature of 40 ° C. and a relative humidity of 80% for 1500 hours, and the length from the cross cut of the filamentous corrosion generated on the test piece is measured. The corrosion resistance was determined by.

The coating film adhesion was examined by a cross-cut test as in Example 1, and was expressed by the number of cross-cuts on which the coating film remained out of 100 cross-cuts. As is clear from Table 3 showing the investigation results, in the example of the present invention in which the solution treatment of heating at 450 to 520 ° C. for a short time within 3 seconds was performed, the Mg concentration of the surface layer was 20.
%, Which was excellent in terms of chemical conversion treatability, corrosion resistance, and coating adhesion. On the other hand, in Comparative Example 6 heated for a long time, Comparative Example 7 heated at a high temperature, and Comparative Example 8 heated at a relatively low temperature rising rate, a large amount of Mg exceeding 20% was concentrated in the surface layer, and thus the chemical conversion was performed. All of the processability, corrosion resistance and coating adhesion were inferior.

[0033]

[0034]

As described above, according to the present invention, by balancing the alloy components, the concentration of Mg that is easy to concentrate on the surface of the aluminum alloy sheet that has been solution-treated after cold rolling is 20% or less. Is suppressed. Further, the Mg concentration of the surface layer is surely suppressed to 20% or less even under the solution treatment conditions including the rate of temperature rise, the rate of temperature decrease, and the like.
An aluminum alloy plate with suppressed Mg concentration exhibits excellent properties such as chemical conversion treatability, corrosion resistance, and coating adhesion, and has the necessary strength and hardness after coating baking, making it a suitable plate material for automobile outer panels, etc. .

[Brief description of drawings]

FIG. 1 Concentration distribution of Mg, Al and O from the surface of solution treated material to the inside

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Suzuki 1-11-1 Koike, Inazawa City, Aichi Japan, Nagoya Works, Nippon Light Metal Co., Ltd. (56) Reference JP-A-4-214835 (JP, A) HEI 4-154934 (JP, A) JP HEI 2-57656 (JP, A) JP-B-62-54855 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C22C 21 / 00-21/18 C22F 1/00-1/057

Claims (2)

(57) [Claims] 1. Mg: 2.5 to 5.5% by weight, Cu:
0.05-0.4 wt%, Mn: 0.005-0.2 wt%, Cr: 0.005-0.1 wt%, Ti: 0.0
1 to 0.05 wt%, Si: 0.08 wt% or less, F
e: 0.1 wt% or less and Be: 0.0001 to 0.
A cold-rolled solution-treated plate having an oxide layer on the surface thereof, which comprises 01% by weight and the balance is substantially Al, and contains M
Between g, Cu and Be, A = Mg% -10 × Cu%-
The A value defined by 1000Be% [wt%] has a relationship of 4 or less, and the Mg concentration is 2 in the depth direction of the plate surface.
An aluminum alloy plate excellent in corrosion resistance and coating surface treatment, characterized by being regulated to 0% by weight or less . 2. Mg: 2.5 to 5.5% by weight, Cu:
0.05-0.4 wt%, Mn: 0.005-0.2 wt%, Cr: 0.005-0.1 wt%, Ti: 0.0
1 to 0.05 wt%, Si: 0.08 wt% or less, F
e: 0.1 wt% or less and Be: 0.0001 to 0.
01 wt%, Zr: 0.001-0.1 wt%, V: 0.001-0.1 wt% and B: 0.0
001 to 0.01% by weight of one or more,
A cold-rolled solution-treated plate having an oxide layer on the surface, the balance being substantially Al, containing Mg, Cu, and Be.
Between A = Mg% −10 × Cu% −1000Be% [wt%] has a relationship of 4 or less, and the Mg concentration is regulated to 20 wt% or less in the depth direction of the plate surface. An aluminum alloy plate with excellent corrosion resistance and coating surface treatment.