JP2008163387A - Aluminum sheet to be molded into cap having superior adhesiveness to resin and corrosion resistance after having been molded, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum sheet to be molded into a cap, in which a paint film containing a large amount of pigment shows superior molding workability even when the paint film is subjected to an extremely severe molding operation, and shows high adhesiveness and corrosion resistance. <P>SOLUTION: This aluminum sheet to be molded into the cap is manufactured by the steps of: subjecting the surface of an aluminum sheet to alkaline degreasing treatment; cleaning the degreased sheet by spraying and jetting a cleaning liquid of 20 to 80°C to the degreased sheet at a rate of 3 to 50 liter/m<SP>2</SP>per second with a jetting pressure of 1.0 to 3.5 kgf/cm<SP>2</SP>; and forming a paint film containing a pigment of 5 mass% or more with respect to a dry weight of the paint film. Thus manufactured aluminum sheet has a chemical conversion coating in which the content of aluminum hydrous oxide is 100 mg/m<SP>2</SP>or less. The cleaning liquid preferably contains a complex-forming substance having such a stability constant (K<SB>A</SB>) with an aluminum ion (Al<SP>3+</SP>) as to satisfy logK<SB>A</SB>≥15 in an amount of 0.05 to 0.5 mol/liter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an aluminum plate coated with a resin coating containing a pigment on at least one side, and more particularly to an aluminum plate for cap molding having excellent resin adhesion and corrosion resistance after molding such as press molding.

  In the present specification, the aluminum plate includes various aluminum alloy plates in addition to an industrial pure aluminum plate.

Aluminum plates are lightweight, have appropriate mechanical properties, and have excellent features such as aesthetics, moldability, corrosion resistance, etc., so they are widely used in various containers, structural materials, mechanical parts, etc. Yes.
The aluminum plate for these uses is often coated with a resin paint and laminated with a resin film on the surface in order to further improve corrosion resistance and elution resistance, improve the appearance, and prevent scratches. At this time, in order to improve the resin adhesion and the corrosion resistance, the aluminum plate is subjected to a base treatment based on existing technology (for example, a chemical-molding base treatment such as phosphate chromate, chromate chromate and zirconium phosphate). It is common. In the case of an aluminum cap, a so-called pre-coating material is often used in which a base treatment and a resin coating are applied to an aluminum plate of the material and then molded.

  Cap-coated pre-coated aluminum alloy sheets require resin adhesion that prevents the resin from peeling even after molding, corrosion resistance that is not affected by corrosive atmospheres, and workability that can withstand advanced molding .

In response to such demands, various proposals have been made from the standpoint of improving coating film adhesion, particularly from the viewpoint of the surface treatment method. For example, in Patent Document 1, after an aluminum plate is subjected to phosphoric acid chromate treatment, the aluminum plate is treated in a solution containing a specific phenol polymer, or the aluminum plate is subjected to phosphoric acid chromate treatment and then subjected to silane treatment. A method has been proposed in which a treated aluminum plate is prepared and coated with a thermoplastic resin to form a resin-coated aluminum plate, which is then drawn and ironed to form a capacitor exterior container. Further, Patent Document 2 includes a base layer in which an anodized film and a silane coupling agent are formed in this order on the inner and outer surfaces of a cap. The film has a porosity of 5% or less, and silicon Si 200 to 50000 ppm, the silane coupling agent is applied to the surface of the film in an amount of 0.5 to 5000 mg / m ² , and the inner surface of the base layer has a size coat layer composed of a polyester / amino resin and a liner adhesive. The cap is provided with a size coat layer composed of a polyester / amino resin on the surface of the outer base layer in this order, a coating layer on the surface of the layer, and a top coat layer covering these layers. is doing.
JP 2001-303273 A Japanese Patent Laying-Open No. 2005-067618

However, the conventional techniques as described above have the following problems.
In other words, aluminum caps used in re-sealable containers such as bottle cans are capacitor cases that are the subject of Patent Document 1 such as deep drawing molding, screw molding, and perforation processing with pilfer proofing. Compared with, it undergoes very severe processing. In addition, a large amount of pigment (often titanium oxide particles and / or silica particles) may be added to the resin coating film due to the appearance and design requirements, which is disadvantageous for coating film adhesion. ing. In particular, when the added amount of the pigment is 5 mass% or more with respect to the dry weight of the coating film, the tendency becomes stronger. Further, in recent years, since bottle cans have been adopted for hot beverages, retort resistance has also been required for the resin coating film of caps.

  Under such conditions, the techniques such as Patent Document 1 and Patent Document 2 have problems such as peeling of the coating film after retorting because the resin adhesion after being subjected to severe processing is insufficient. In addition, since the coating film and the ground are damaged by severe processing, the corrosion resistance to beverages and the like is often lowered.

As a result of repeated studies to solve the above problems, the present inventors have found that the aluminum hydrated oxide formed on the surface of the aluminum material in the pretreatment step of the chemical conversion treatment has a very large adverse effect on the adhesion and corrosion resistance of the coating film after processing. Found to bring. Specifically, when the aluminum hydrated oxide is contained in the chemical film in excess of 100 mg / m ² , the post-processing coating film adhesion and the corrosion resistance to a coating film containing a pigment of 5 mass% or more are significantly reduced. I discovered that.

That is, the invention of claim 1 contains a base material made of an aluminum plate, a chemical conversion film formed on at least one surface of the base material, and a pigment of 5 mass% or more based on the dry weight formed on the chemical conversion film. A resin-coated aluminum plate provided with a coating film, wherein the amount of the aluminum hydrated oxide contained in the chemical conversion film is 100 mg / m ² or less; It is an aluminum plate for cap molding with excellent corrosion resistance.

Further, the invention of claim 2 includes a step of subjecting at least one surface of a substrate made of an aluminum plate to an alkaline degreasing treatment, a step of washing the alkaline degreased surface, a step of subjecting the washed surface to chemical conversion, Forming a coating film containing a pigment of 5 mass% or more on the dry weight on the chemical conversion treatment surface, and a method for producing an aluminum plate for cap molding,
The cleaning treatment step includes spraying a 20 to 80 ° C. cleaning liquid onto the alkaline degreasing surface, the spray injection amount is 3 to 50 liters / m ² per second, and the spray injection pressure is 1. It is a manufacturing method of the aluminum plate for cap shaping | molding excellent in the resin adhesiveness after a shaping | molding process, and corrosion resistance characterized by being 0-3.5 kgf / cm < ² >.

Further, in the invention of claim 3, in the method for producing a cap-molding aluminum plate according to claim 2, a complex forming substance having a stability constant K _A of log K _A ≧ 15 with aluminum ions (Al ³⁺ ) as the cleaning solution is 0. 0.05 to 0.5 mol / liter is specified.

The aluminum plate made according to the present invention is a cap molding because the coating film containing a large amount of pigment has excellent molding processability and exhibits high adhesion and corrosion resistance even when subjected to extremely severe processing. Ideal for use.

  Hereinafter, details of the present invention will be described in order.

A. Aluminum base material As the aluminum plate used in the present invention, a pure aluminum material and an aluminum alloy material are used, and can be appropriately selected according to applications and required characteristics. As the aluminum alloy material, 1000 series, 3000 series, 5000 series and the like are preferably used from the viewpoint of strength and workability.
In the present invention, the term “aluminum” is intended to include both pure aluminum and aluminum alloys, and the term “aluminum substrate” is intended to include both pure aluminum substrates and aluminum alloy substrates. The term “aluminum plate” is intended to include both pure aluminum plates and aluminum alloy plates.

B. Mechanism of Retort Peeling and Corrosion Resistance Degradation Generally, a coating film containing a pigment tends to generate minute cracks having a length of about several tens to several hundreds μm due to strong processing such as cap molding and screw processing. It is substantially difficult to eliminate this crack due to the weak interaction between the pigment particles and the paint resin, and the fact that the paint resin is relatively soft while the pigment is hard.
The cause of the retort peeling is considered to be that hot water enters from the cracks and directly attacks the coating film-chemical conversion film interface in the retort process. Therefore, in order to prevent retort peeling, it is required to form a coating film-chemical conversion film interface that can withstand hot water entering from cracks.

  Moreover, since the coating film-chemical conversion film interface is directly exposed to the corrosive atmosphere due to the crack of the coating film, the chemical conversion film is required to have stricter corrosion resistance in order to prevent the progress of corrosion.

  The inventors of the present invention conducted a cross-sectional observation of the chemical conversion film after intensive processing with a TEM (transmission electron microscope) or the like. As a result, the chemical conversion film formed by the conventional technique has cracks in the horizontal direction, that is, parallel to the plate surface. Found out that it would occur. Although the chemical conversion film having such cracks has a temporary adhesion force due to intermolecular forces in the dry state, when exposed to a hot water atmosphere such as a retort process, the cohesive force in the vertical direction is rapidly increased. lose. At this time, it was found that as a result of the residual stress of the pigment-containing coating film acting in the direction of peeling off the coating film, the coating film peels off from the crack portion of the chemical conversion film. It has also been found that this horizontal crack has a significant adverse effect on corrosion resistance as a result of the extreme loss of the thickness of the chemical conversion film layer that should originally protect aluminum.

As a result of various studies on the cause of the occurrence of cracks in such a chemical conversion film, it was found that cracks are unlikely to occur when the aluminum hydrated oxide contained in the chemical conversion film is 100 mg / m ² or less. That is, if the aluminum hydrated oxide contained in the chemical conversion film is 100 mg / m ² or less, the pigment-containing coating film does not peel off even under severe use conditions such as a retort process after cap molding, and the corrosion resistance is also good. I found it maintained.

This is because when the content of the aluminum hydrated oxide in the chemical conversion film of the resin-coated aluminum plate is 100 mg / m ² or less, the network structure of the chemical conversion film molecules is regularly formed without interposing the aluminum hydrated oxide. This is probably because a strong chemical conversion film is formed. On the other hand, when the content of the aluminum hydrate oxide exceeds 100 mg / m ² , a hard and brittle network structure is formed in which the aluminum hydrate oxide molecules intervene in the network structure of the chemical conversion film molecules. As a result, it is considered that parallel cracks occur in the chemical conversion film during strong processing.

  By the way, most of the aluminum hydrated oxide, which is a problem described above, is formed at the stage of pretreatment prior to chemical conversion treatment. In general, as a pretreatment for the chemical conversion treatment, a degreasing / etching process using an alkaline degreasing agent is performed, and the rolling oil, wear powder, oxide film, and the like on the surface of the aluminum plate are removed. And it turned out that most aluminum hydrated oxide is produced | generated in the washing | cleaning process after completion | finish of this alkali degreasing process, and such aluminum hydrated oxide is taken in in a chemical conversion film during chemical conversion treatment. Therefore, the aluminum hydrated oxide contained in the chemical conversion film can be reduced by suppressing the formation of the aluminum hydrated oxide in the cleaning treatment step.

C. Alkaline degreasing process The alkali degreasing process can apply the degreasing liquid and the degreasing method based on a prior art as it is. The alkaline degreasing solution is a solution in which an alkaline degreasing agent is dissolved or dispersed in a solvent such as water at a concentration of 0.5 to 2.0% by weight, for example, and has a pH of about 9 to 13 having etching properties. Used. The alkaline degreasing agent includes an alkali builder, a surfactant, a chelating agent, and the like. As such an alkaline degreasing agent, for example, trade name “SC-EC370” manufactured by Nippon Paint Co., Ltd. can be used.

  Examples of alkali builders include alkali metal carbonates such as Na carbonate and K carbonate; alkali metal hydroxides such as caustic Na; alkali metal phosphates such as Na phosphate and Na hydrogen phosphate; alkali metals such as Na silicate Silicates or the like; or a mixture thereof is used.

  As surfactants, polyoxyethylene surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers having a HLB (hydrophilic-lipophilic ratio) = about 8 to 11 and higher alcohol surfactants Etc. are used.

As the chelating agent, EDTA · 2Na salt, naphthylamine, or the like is used.
As for the etching amount of the aluminum base-material surface by an alkali degreasing process, about 60-300 mg / m < ² > is preferable. Since the amount of the oxide film on the aluminum base material produced by rolling is in the range of several tens to several hundreds mg / m ² , the oxide film removal is insufficient when the etching amount is less than 60 mg / m ² , and the etching amount is 300 mg / m 2. Exceeding ² is not preferable because not only the effect of removing the oxide film is not improved, but also sludge generation is accelerated.

  The alkaline degreasing treatment is performed, for example, by spraying an alkali degreasing solution at 50 to 80 ° C. on an aluminum substrate for 1 to 20 seconds, or an aluminum substrate for 10 to 60 seconds in an alkali degreasing solution at 50 to 90 ° C. A dipping method is employed.

D. Cleaning process A cleaning process is performed following the alkali degreasing process. As described above, the pH of the alkaline degreasing agent is 9 or higher, and the pH in the vicinity of the surface of the aluminum substrate immediately after completion of the alkaline degreasing is naturally 9 or higher. At this point, aluminum is only dissolved in the degreasing liquid remaining on the substrate surface. However, when the cleaning process is started and the cleaning water comes into contact with the surface of the aluminum substrate, the pH in the vicinity of the surface of the aluminum substrate becomes a weak alkaline region of 8-9. The solubility of aluminum at such a weak alkaline pH is very low. Therefore, when the cleaning treatment is started and the pH in the vicinity of the surface of the aluminum substrate is lowered to a weak alkali of 8-9, aluminum dissolved in a state of pH 9 or higher is precipitated as aluminum hydrated oxide. The aluminum hydrated oxide thus deposited forms a new hydrated oxide layer on the surface of the aluminum substrate. This hydrated oxide layer is incorporated into the chemical conversion film in the chemical conversion treatment step, and as a result, the resin adhesion after processing of the resin-coated aluminum plate is lowered. Therefore, in order to prevent the formation of the aluminum hydrated oxide layer, in the water washing treatment process, “to quickly remove aluminum ions from the vicinity of the aluminum surface” and “to quickly lower the pH in the vicinity of the aluminum surface to 8 or less” It is effective.

  In the cleaning process, in order to achieve the above two requirements, a method of supplying a large amount of cleaning liquid at a predetermined temperature onto the aluminum substrate at a stretch is adopted. Specifically, a method in which the cleaning liquid is sprayed onto the surface of the aluminum substrate is preferably used.

The spray injection conditions are preferably a spray injection amount of 3 to 50 liters / m ² per second and a spray injection pressure of 1.0 to 3.5 kgf / cm ² . If the cleaning liquid spray rate is less than 3 liters / m ² per second, rapid removal of aluminum ions is not achieved, and if the spray spray pressure is less than 1.0 kgf / cm ² , the pH near the aluminum surface is reduced. It cannot be rapidly reduced to 8 or less, and as a result, formation of new aluminum hydrated oxide is promoted, which is not preferable. On the other hand, even if the spraying amount of the cleaning liquid exceeds 50 liters / m ² , the effect of removing aluminum ions is saturated, and the production cost increases as much water is consumed, which is not preferable. Further, when the spray injection pressure exceeds 3.5 kgf / cm ² , it is not preferable because not only the effect of lowering the pH is saturated but also strengthening of piping and the like to withstand high pressure is required, which is uneconomical.

  Although the dipping method may be used as the cleaning treatment method, since the pH lowering rate on the aluminum substrate becomes slow, it is difficult to obtain a rapid pH lowering effect as in the spray injection method, and the cleaning liquid is stirred. Even if a device or the like is provided, it cannot be recommended as a means for satisfying the requirements of the present invention.

  About the temperature of a washing | cleaning liquid, it selects in the range of 20-80 degreeC. This is because if a cleaning liquid exceeding 80 ° C. comes into contact with a fresh aluminum substrate surface that has undergone the degreasing / etching step, the aluminum and water react to generate new pseudo boehmite-like aluminum hydrated oxide, which is inappropriate. Moreover, if it is less than 20 degreeC, the melt | dissolution rate of a degreasing agent will be slow, pH change will become slow, and the temperature of an aluminum base material may fall, and there exists a possibility that precipitation of the aluminum which melt | dissolves in a degreasing agent may arise.

  The cleaning liquid only needs to have water quality that has been conventionally used as industrial water. That is, although distilled water or pure water (deionized water) is preferably used, soft water or industrial water having an electric conductivity of 20 mS / m or less can also be used.

In addition, by using a cleaning solution stability constant log K _A and ^{Al 3+} contains 0.05 to 0.5 mol / liter of complex forming substance is 15 or more, aluminum hydrated than with the distilled water Oxide formation can be greatly suppressed. In other words, such a cleaning solution can trap Al ³⁺ ions on the surface of the aluminum base as a complex in the cleaning process, thereby preventing the precipitation and precipitation of aluminum hydrated oxide. Because it does. Such complexed products with Al ³⁺ include EDTA (ethylenediaminetetraacetic acid), CyDTA (cyclohexane-1,2-diaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), TTHA (triethylenetetraminehexaacetic acid), etc. Examples include organic coordination substances such as chelating reagents and citric acid. The addition concentration of these substances is preferably 0.05 to 0.5 mol / liter. This is because if it is less than 0.05 mol / liter, the effect of sufficiently preventing precipitation and precipitation of aluminum hydrated oxide by forming a complex with Al ³⁺ cannot be obtained. On the other hand, even if it exceeds 0.5 mol / liter, the effect of precipitation / precipitation of the aluminum hydrated oxide is saturated, so that it becomes disadvantageous in terms of cost only by using a large amount.

  The cleaning processing time is appropriately set depending on the configuration of the production line, but is preferably 2 seconds or longer. When the cleaning treatment time is less than 2 seconds, the surfactant contained in the degreasing agent remains without being removed, which may contaminate the chemical conversion treatment solution used in the chemical conversion treatment step. In order to remove the surfactant more reliably, the washing time is preferably 4 seconds or longer.

  On the other hand, the upper limit of the cleaning treatment time is not particularly limited, but it is preferably 30 seconds or less in consideration of the configuration of the production line and the operation speed of the production line. If the cleaning processing time exceeds 30 seconds, a very long cleaning processing line is required, or the operation speed of the cleaning processing line needs to be extremely reduced, resulting in hindering productivity. Because it becomes.

E. The chemical conversion treatment is performed following the chemical conversion treatment cleaning step. As the chemical conversion treatment, a conventional chemical conversion treatment method, that is, a reactive chemical conversion treatment such as a phosphoric acid chromate treatment, a zirconium phosphate treatment, or a titanium phosphate treatment can be employed. Since the formation of aluminum hydrated oxide can be suppressed in the above-described cleaning treatment step, the aluminum hydrated oxide in the chemical conversion film is automatically added to 100 mg / m by simply applying the chemical conversion treatment method based on the conventional technology. ² or less.

F. Coating process An aluminum plate for cap molding that is excellent in resin adhesion and corrosion resistance after molding by providing a coating containing 5 mass% or more of pigment with respect to the dry weight on the chemical conversion treatment surface thus obtained. Can be obtained. In this case, the pigment is, in many cases, titanium oxide particles and / or silica particles as described above. In order to exhibit the coloring effect and the underlying color hiding effect, the pigment is based on the dry weight of the entire coating film. It is almost essential to have a blending amount of 5 mass% or more. In addition, as a resin constituting the main body of the coating film, resins generally used for paints such as polyester resins, epoxy resins and vinyl chloride resins can be used as they are. The paint containing the pigment may be water-soluble or solvent-based. The thickness of the coating film is preferably set to about 1 to 20 μm from the viewpoint of the color forming effect and the base color hiding effect. Moreover, as baking conditions, the temperature and time which accelerate | stimulate hardening of coating resin and do not impair the material strength of aluminum material are set, for example, the method of baking for 10 minutes at 190 degreeC atmosphere in a furnace can be mentioned.

  Further, various ink layers may be provided on the coating film containing the pigment for the purpose of imparting color, and various finishing clear coating films may be provided as a top coat.

  In addition, as a method for measuring the amount of aluminum hydrated oxide contained in the chemical conversion film, FT-IR (Fourier transform infrared spectrophotometer) is preferably used. That is, calibration of the amount of aluminum hydrated oxide at the absorptance of Al-OH vibration (peak appearing in the vicinity of 600 to 800 cm-1; the peak position varies depending on the type of chemical conversion film) by polarization reflection method (p-wave) FT-IR By creating a line, the amount of aluminum hydrated oxide can be determined simply, rapidly and non-destructively.

  Hereinafter, preferred embodiments of the present invention will be described in detail based on examples and comparative examples.

As the aluminum alloy material, a JIS A5151-H39 alloy plate having a plate thickness of 0.25 mm was used. As the alkaline degreasing bath, a commercially available alkaline degreasing agent “EC-370 (Nippon Paint)” was used. The usage conditions are a concentration of 1.0%, a spray pressure of 1.5 kgf / cm ² , a treatment time of 5 seconds, and a bath temperature of 65 ° C. After alkali degreasing, after washing under the conditions shown in Table 1, phosphoric acid chromate treatment was performed as a chemical conversion treatment. The treatment agent was “408/48 (Nippon Paint)”, and the treatment conditions were adjusted so that the coating amount was 10 mg / m ² with metallic Cr. Moreover, only in Example 4, the zirconium phosphate process was performed as a chemical conversion process. The treatment agent was “Surfalcoat 404 (Nippon Paint)”, and the treatment conditions were adjusted so that the coating amount was 10 mg / m ² with metal Zr.

    The following evaluation was performed on the samples thus obtained.

(Application of paint containing pigment)
Commercially available solvent-based paint for cap “White Coaching” (containing titanium oxide pigment (content = 6.3 mass%), polyester resin, coating amount 13 g / m ² , baking temperature = 190 ° C.) Baking time = 600 seconds) was applied to both sides to prepare a coated sample.

(Evaluation of resin adhesion after processing)
Apply 50 mg / m ^{2 of} commercially available silicon lubricant on both sides of the above painted sample, and after drawing with cap molding machine (cap diameter = 38 mm, cap height = 18 mm), then perforation・ Screw processing was performed in this order. With respect to the obtained cap, the film peeling state of the perforation part, the lower end of the cap and the bead part was visually observed after retorting (125 ° C. × 30 minutes). The length of the part where peeling occurred relative to the total length of the perforation part, the cap lower end and the bead part was recorded in units of%.

(Evaluation of corrosion resistance after processing)
Apply 50 mg / m ^{2 of} commercially available silicon lubricant on both sides of the above painted sample, and after drawing with cap molding machine (cap diameter = 38 mm, cap height = 18 mm), then perforation・ Screw processing was performed in this order. The obtained cap was immersed in a model juice test aqueous solution (citric acid monohydrate 1.0% + sodium chloride 0.5%) heated to 70 ° C. for 72 hours to prevent corrosion at the perforation, the lower end of the cap and the bead. The degree was determined visually.

  The results are shown in Table 3.

  As is apparent from Table 3, Examples 1 to 7 satisfy the requirements of the present invention and have high adhesion and corrosion resistance to the titanium oxide pigment-containing paint when subjected to strong processing. The model juice test also showed good results.

  On the other hand, since Comparative Examples 1 to 5 do not satisfy the requirements of the present invention, the adhesion and corrosion resistance to the titanium oxide-containing paint in the case of strong processing are low, and the coating film after retorting and after the model juice immersion Corrosion was conspicuous. Specifically, the spray amount of Comparative Example 1 is insufficient, the spray pressure of Comparative Example 2 is too low, the water temperature of Comparative Example 3 is low, and the water temperature of Comparative Example 4 is too high. As a result of the formation of a large amount of aluminum hydrated oxide at the time when rinsing was completed after degreasing, a large amount of aluminum hydrated oxide was incorporated into the chemical conversion film in the subsequent chemical conversion treatment process, resulting in retort peeling and reduced corrosion resistance after cap processing. I have been invited.

Claims (3)

A resin coating comprising a base material made of an aluminum plate, a chemical conversion film formed on at least one surface of the base material, and a coating film containing 5 mass% or more of pigment with respect to the dry weight formed on the chemical conversion film Aluminum for cap molding having excellent resin adhesion after molding and corrosion resistance, characterized in that the amount of aluminum hydrated oxide contained in the chemical conversion film is 100 mg / m ² or less. Board. A step of subjecting at least one surface of an aluminum plate to an alkali degreasing treatment, a step of subjecting the alkali degreasing treatment surface to a washing treatment, a step of subjecting the washing treatment surface to a chemical conversion treatment, and a chemical conversion treatment surface having a dry weight of 5 mass. A process for forming a coating film containing at least% pigment, and a method for producing a cap-forming aluminum plate,
The cleaning treatment step includes spraying a 20 to 80 ° C. cleaning liquid onto the alkaline degreasing surface, the spray injection amount is 3 to 50 liters / m ² per second, and the spray injection pressure is 1. A method for producing a cap-molding aluminum plate excellent in resin adhesion and corrosion resistance after molding, characterized by being from 0 to 3.5 kgf / cm ² . Wherein the cleaning liquid, as claimed in claim 2, characterized in that the stability constant _{K A} of aluminum ions ^{(Al 3+)} contains 0.05 to 0.5 mol / liter of complex forming substance is a log K _A ≧ 15 Manufacturing method of cap forming aluminum plate.