JP2001087707A - Coating method, coating material and coated composite material excellent in corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method, a coating material and a coated composite material excellent in corrosion resistance even if the performance of zinc phosphate treatment on a steel material or an Al alloy material side is degraded. SOLUTION: At the time of coating the steel material and the Al alloy material in the same treating process after phosphating, the coating is performed with the coating material containing no lead based pigment but containing calcium phosphate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a steel material and an aluminum alloy material with excellent corrosion resistance, a paint and a composite material.

[0002]

2. Description of the Related Art An Al alloy has characteristics that its specific gravity is 1/3 that of steel, that it has excellent energy absorption, and that it has a high degree of freedom in its sectional shape. Therefore, it is possible to comply with safety standards and to improve vehicle body performance without increasing the vehicle body weight of vehicles such as vehicles, motorcycles, and automobiles. In addition, it is effective in regulating exhaust gas amount and improving fuel efficiency by reducing the weight of a vehicle body in response to recent environmental problems such as exhaust gas.

[0003] For this reason, Al-Mg-based materials are used for door beams and side members as vehicle door reinforcing members, body reinforcing members (vehicle protection members) such as bumpers and bumper stays, and the like.
Si-based AA to JIS 6000-based Al alloys and Al-Zn-Mg-based 7000 series
Extruded shapes such as Al alloys are used.

In addition, structural materials having complicated shapes and thick portions, such as motorcycles, automobile wheels, suspension parts such as knuckles, lower arms, and upper arms, include:
Inexpensive Al alloy castings and forgings having the necessary strength and toughness (these are collectively referred to as cast forgings in the present invention) are used. As a casting material, 6.5
A typical example is an Al-Si-Mg-based Al alloy containing up to 7.5% (mass%, the same applies hereinafter). As a forged material, a 6000 series Al alloy or the like is typical.

[0005] Further, as a member for a vehicle such as a panel material such as a door, a fender or a bonnet of an automobile, or a wheel, a 5000 series or 6000 series aluminum alloy rolled plate is used. Among them, the 6000 series Al alloy has a low yield strength at the time of press forming and can secure the formability, and can be hardened by age hardening at the time of baking coating after the press forming to improve the proof strength and can secure the necessary strength as a panel material. Further, when scrap is reused as a raw material for dissolving an Al alloy, there is also an advantage that the alloy amount is relatively small, the original 6000 series Al alloy ingot is easily obtained, and the recyclability is excellent.

[0006] However, when various Al alloy materials such as these plate materials, profiles, cast materials, and forged materials are used for, for example, an automobile body, most of the automobile bodies except for a part of an all-aluminum vehicle are used. A steel material such as a steel plate, which has been conventionally used, and an Al alloy material are often used as a composite material.
For example, a reinforcing member such as an aluminum alloy door beam or an energy absorbing material is formed into a composite material by mechanical joining such as welding or bolting to a steel material such as a door or a side arm and attached to a vehicle body.

On the other hand, in an ordinary production line for transport equipment such as automobiles, the molded and assembled vehicle bodies are subjected to a coating base treatment such as zinc phosphate treatment, and then subjected to cationic electrodeposition coating, intermediate coating, top coating, etc. Various coatings (including baking hardening) are applied. The processing conditions of each step in this production (surface treatment) line basically correspond to the conditions of steel materials used so far.
This is because the amount of Al alloy material used is not as large as that of steel material yet, and the surface treatment of Al alloy material is not required to provide a new surface treatment step (line) dedicated to Al alloy material. This is because it is often carried out using the processing steps as they are.

Accordingly, for example, an Al alloy material used for an automobile body is made of zinc phosphate on the surface in the same processing step or under the same processing conditions as a steel material, even as a composite material with a steel material or as a single member. Processing and painting will be performed.

[0009] The problem of zinc phosphate treatability on the side of the Al alloy material. As described above, when the Al alloy material is subjected to the zinc phosphate treatment in the same processing steps or conditions as the steel material, the Al alloy material is inferior in the zinc phosphate treatment property to the steel material. There is a problem that it is difficult to secure a uniform and appropriate amount of a zinc phosphate film. If the phosphatability is poor, the adhesion of a coating film formed by coating afterwards is reduced. As a result, there is a problem that rust-like corrosion and swelling of the coating film occur after coating, and the corrosion resistance and appearance of the automobile are deteriorated.

[0010] In order to improve the phosphatability of this Al alloy material, the phosphating bath has been conventionally improved. A typical example is to add a high concentration of free fluorine (F) ions of about several tens to several hundreds ppm to a phosphating bath.

The problem of zinc phosphate treatability on the steel side. The addition of the free fluorine (F) ions certainly improves the phosphatability of the Al alloy material. However, the formation of a phosphate film on the surface of the Al alloy material is promoted by the elution of Al ions from the surface of the Al alloy material. Al
The elution amount of ions increases. When the elution of Al ions increases, a new problem arises in that the phosphatability of the important steel material is significantly impaired.

For example, when a steel material is usually subjected to a phosphate treatment, a phosphophyllite having granular crystals is formed on the surface of the steel material. The phosphophyllite also has good electrodeposition coating properties as a coating base, and can guarantee corrosion resistance such as coating film adhesion and appearance. However, when a large amount of Al ions is contained in the phosphate bath, a whipite having plate-like crystals is formed on the surface of the steel material. The Hopite has poor electrodeposition coating properties, and cannot guarantee corrosion resistance such as coating film adhesion and appearance.

In this regard, in order to improve the zinc phosphate treatability of the steel material, it is conceivable to positively remove Al ions accumulated in the bath due to the elution of the Al ions from the zinc phosphate treatment bath. However, the loss of the phosphate bath solution accompanying this removal and the increase in the cost of the bath solution for removing Al ions are large, making it very practical for automobile production lines where energy saving and efficiency are strictly pursued. Not a solution.

Further, in order to prevent the elution of Al ions from the surface of the Al alloy material, a surface treatment of the Al alloy material which can insulate the zinc phosphate bath from the surface of the Al alloy material before the zinc phosphate treatment. It is conceivable to provide a coating. For example, as a surface treatment of an Al alloy material, a well-known anodic oxidation treatment or an oxide film of Al by surface oxidation, a so-called dacro film treatment combining zinc and chromium, a chromate treatment film, a resin film (such as a vinyl sheet) Lithium salt, magnesium salt,
Films such as cerium salt and calcium salt, and potassium permanganate film.

However, these conventional surface treatments or surface coatings impair the phosphatability of the Al alloy material and the adhesion (paintability) of the coating film when the actual application is taken into consideration. There is a problem that it deteriorates. In addition, there is a practical problem that the cost increases due to an increase in the number of surface treatment steps.

Therefore, as described above, when the Al alloy material and the steel material are subjected to the zinc phosphate treatment (and the coating) under the same processing step (line) or the same processing conditions, both the Al alloy material and the steel material are treated. At the present time, it is difficult to solve both problems of the zinc phosphate treatment property at the same time.

For this reason, when a composite material of a steel material and an Al alloy material is treated with zinc phosphate in the same treatment step,
When the aluminum alloy material is separately treated with zinc phosphate in the same processing step, the adhesion amount and the throwing power of the zinc phosphate film on the surface of either material or either material are inferior (each material is used alone). It is unavoidable that this is unavoidable (compared to zinc phosphate treatment).

Problems on the paint side. As described above, when the zinc phosphate treatment property of the steel material and the Al alloy material is reduced, the coating is performed with the coating undertreatment insufficient, and inevitably, after the steel material and the Al alloy material are coated. This results in lowering of corrosion resistance or adhesion of the coating film.

On the other hand, cationic electrodeposition coating, intermediate coating,
At present, paints containing lead-based pigments such as lead red, lead oxide, basic lead chromate, cyanamide lead, calcium leadate and the like are used as rust preventive pigments.
If the paint contains these lead-based pigments, even if the zinc phosphate treatability described above is reduced or insufficient, the paint and the steel material and the aluminum are treated by the effect of the lead-based pigment. It is possible to compensate for the deterioration of the corrosion resistance and the adhesion of the coating film after coating of the alloy material to some extent.

[0020]

However, recently, from the viewpoint of environmental protection and the like, the paint side also eliminates the lead-based pigment contained in the paint and is free of lead (no lead or lead pigment). There is a tendency to move to paints containing rust-preventive pigments as a substitute. However, when the transition to lead-free rust preventive pigment, this lead-free rust preventive pigment, as described below,
With the decrease in zinc phosphate treatability of the steel material and the Al alloy material,
A new problem arises in that the deterioration of the corrosion resistance and the adhesion of the coating film after coating cannot be compensated.

Various lead-free rust preventive pigments have been conventionally proposed. For example, in Japanese Patent Application Laid-Open No. 5-339004, a white rust-preventive pigment composed of zinc calcium phosphite with no pollution, low toxicity and emphasizing the rust-preventive effect is coated with a zinc compound in Japanese Patent Application Laid-Open No. 6-200192. JP-A-8-41374 discloses a rust-preventive pigment composed of titanium oxide, and discloses a white rust-preventive pigment composed of zinc cyanamide and calcium phosphate. In addition, rust preventive pigments such as barium borate are also known.

However, all of these rust-preventive pigments replacing the lead-based pigments are intended for zinc phosphate treatment and painting of steel (steel plate), and the composite of the steel of the present invention and an Al alloy is treated with zinc phosphate. When processing, steel material and Al alloy material are not targeted for zinc phosphate treatment in the same processing step
(Not intended). In other words, these pigments that substitute for the lead-based pigments are intended only for the coating treatment in the case of a steel sheet that has been successfully zinc-phosphorated.

Therefore, the rust-preventive pigments that can replace these lead-based pigments are the corrosion resistance and the adhesion of the coating film when the steel material and the Al alloy material are not zinc-treated well. Does not consider the decline in sex. For this reason, when these rust-preventive pigments are used in place of the lead-based pigments, the effect of improving the adhesion of the target coating film and the corrosion resistance after coating is reduced for a steel sheet that has been subjected to zinc phosphate treatment. For steels and Al alloys, or composites of these, which can be effectively used but have not been successfully treated with zinc phosphate, the effect is completely unknown or effective. Can not.

This problem is more serious due to the tendency that the composite material of the steel material and the Al alloy material is much more likely to be corroded than when each is used alone for transportation or the like. Becomes That is, first, when a steel material and an Al alloy material are used as a composite material, corrosion, so-called electrolytic corrosion, is likely to occur on the Al alloy material side, and thread rust is also likely to occur. This is because the Al alloy is a metal that is more noble than steel, so when the steel member and the Al alloy material come into contact, a battery is formed between the two metals, and the corrosion current easily flows through the Al alloy material,
This is because it causes electrolytic corrosion.

Further, the transport machine is often used in an environment corroded with salt water such as seawater, which is more than the case where the composite material of the steel material and the Al alloy material is used alone. It is a cause of corrosion. In addition, the composite material is more likely to be corroded when used under a certain stress load state or a state where stress is easily concentrated, such as a structural material. This is because the use in a corrosive environment under this stress load significantly promotes the occurrence of the electrolytic corrosion (reduces the electrolytic corrosion resistance). Further, even when a high-strength element such as Zn or Cu is added in order to further increase the maximum load and bending stiffness of the Al alloy material, the corrosion sensitivity of the Al alloy material itself is increased.

As described above, when the painted steel material and the Al alloy material are compounded and used for a transport machine or the like, the steel material and the Al alloy material are more severe after the painting than when each is used alone. Corrosion resistance will be required. However, in spite of this, when a steel material and an Al alloy material are combined, the zinc phosphate treatability of the steel material and the Al alloy material is necessarily reduced. Even on the side of paints that should exhibit corrosion resistance by compensating for this, there is a major problem that rust preventive pigments that can replace conventional lead-based pigments cannot compensate for the corrosion resistance after coating as much as lead-based pigments.

The present invention has been made in view of such circumstances, and its object is to reduce the corrosion resistance after severe coating even if the zinc phosphate treatability on the steel or Al alloy material side is reduced. An object of the present invention is to provide a coating method, a coating material, and a coated composite material having excellent corrosion resistance that meet the demand.

[0028]

In order to achieve this object, the gist of the coating method of the present invention is to provide a method for coating a steel material and an aluminum alloy material after phosphate treatment in the same processing step. The coating is performed using a paint containing calcium phosphate as a rust preventive pigment without a lead pigment (corresponding to claim 1).

Preferred embodiments of the coating method of the present invention include:
The steel material and the aluminum alloy material are formed into a composite material before the phosphate treatment (corresponding to claim 2). Further, the coating method of the present invention is preferably applied to steel and aluminum alloy materials for use in transport vehicles, and further to steel and aluminum alloy materials for use in automobiles among transport devices (corresponding to claims 3 and 4). .

The gist of the paint of the present invention is that it is a paint used in the above-mentioned coating method of the present invention and contains calcium phosphate as a rust-preventive pigment without containing a lead-based pigment (corresponding to claim 5). .

Further, the gist of the composite material of the present invention is a composite material of a steel material and an aluminum alloy material which has been previously made into a composite material, and which has been subjected to a phosphate treatment and coating. That is, it was coated with a paint containing calcium phosphate without pigment (corresponding to claim 6).

According to the present invention, when only calcium phosphate among the conventional lead-free rust preventive pigments is used as the lead-free rust preventive pigment, the zinc phosphate treatability of the steel or Al alloy material is reduced. Even if it does, it has been found that it is possible to meet the demanding characteristics of the strict or more advanced coating film adhesion and corrosion resistance after coating when a steel material and an Al alloy material are combined.

Among the conventional lead-free rust preventive pigments, phosphoric acid
Only calcium is treated with zinc phosphate on the steel or Al alloy side.
Even if the reason is lowered, the higher adhesion and coating
The reason why the required characteristics of corrosion resistance after mounting can be met
Is not certain. However, phosphoric acid calcium contained in the coating film
Cium protects against corrosion of Al alloy material due to damage and deterioration of coating film.
Al and Mg and phosphate ions in the Al alloy eluted by corrosion
React, for example, Al ³⁺+ PO_Four ^3-→ AlPO_Four Or 3Mg²⁺+
2PO_Four ^3-→ Mg_Three(PO_Four)_TwoAs shown in the reaction example, AlPO_FourAnd Mg_Three(P
O_Four)_TwoInsoluble compounds such as
It is presumed to be coated. Also, calcium phosphate
Is the tip of the corrosion, Ca_Three(PO_Four)_Two+ 2H⁺→ 2CaHPO_Four + Ca
²⁺Slows down the phenomenon of pH that promotes corrosion
It is presumed that there is also an effect of summing.

However, the positive rust-preventing function of these calcium phosphates is similarly exerted on the surface of the coated steel material,
Even if the zinc phosphate treatability on the steel or Al alloy material side is reduced, the demands for stricter paintability (coating film adhesion) and corrosion resistance after coating when steel and Al alloy materials are combined On the other hand, it is presumed that corrosion resistance can be improved. By the way, the positive rust-prevention function of the calcium phosphate is similar to the rust-prevention function in the case of lead, which is why calcium phosphate exerts an excellent effect compared to other rust-prevention pigments. It can be said that

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION (Calcium phosphate rust preventive pigment) In the present invention, calcium phosphate contained in a paint as a rust preventive pigment is represented by a general formula of Ca ₃ (PO ₄ ) ₂ described in a dictionary of physics and chemistry. tricalcium phosphate represented (tribasic calcium phosphate), general formula, dicalcium phosphate (dibasic calcium phosphate) and represented by CaHPO _4, hydrates thereof each of which is illustrated.

The content of the calcium phosphate in the paint as a rust preventive pigment is preferably about 0.5 to 2.5 g / m ² as the content in the coating film. Is less than 0.5 g / m ^2, the effect as a rust-preventive pigment calcium phosphate not exhibited, even zinc phosphate treatment of the side of the steel or Al alloy is decreased, composite of the steel material and an Al alloy material Stricter paintability and corrosion resistance requirements after painting,
Corrosion resistance cannot be improved. On the other hand, when it exceeds 2.5 g / m ² , the ratio of the resin paint decreases, and the adhesion of the coating film decreases.

The content of calcium phosphate in the paint as a rust-preventive pigment may be determined in the case of a cation-type electrodeposition paint, a middle coat or a top coat, which is commonly used for painting an automobile body. It may be performed appropriately in the paint. But,
Electrodeposition coating, like the current lead-based pigments, is used in cases where the appearance of the coating is impaired by being included in the paint for intermediate coating or top coating, or when the anticorrosion effect is to be exerted on the side closer to steel and Al alloy materials. It is preferable to include it in a paint for use.

(Resin paint) As the resin paint used in the paint of the present invention, a known resin paint for electrodeposition coating usually used for an automobile body or a transportation machine can be appropriately used. That is, as a usual paint for cationic electrodeposition coating after zinc phosphate treatment, or as a paint for intermediate coating or top coating, 140 to 2
Acrylic resin coatings such as aminoalkyd resin coatings such as melamine alkyd, polyester melamine resin coatings, and polymethyl methacrylate, which have baking curability (thermal condensation properties) by baking treatment at about 00 ° C. × 5 to 30 minutes, Epoxy resin paints such as bisphenol type and novolak type,
Known resin paints such as a phenolic resin paint and a polyester resin paint can be used. And these,
As it is or modified with silicon or the like, a single paint system or a plurality of paint systems are appropriately mixed or laminated for use.

The paint of the present invention can use known additives such as coloring pigments, stabilizers and emulsifiers in addition to the rust preventive pigment of calcium phosphate and the resin paint.

Next, the Al alloy to which the present invention is applied is a rolled sheet material, an extruded shape material, or a forged material as AA to JIS 3000 series, 5000
Al alloys with component specifications of 6000 series, 6000 series, and 7000 series can be appropriately applied. For casting materials, Al-Cu-Si based AC2A, AC
2B, AC3A of Al-Si system, AC4A, AC4C, AC4CH of Al-Si-Mg system
, Al-Si-Cu AC4B, Al-Si-Cu-Mg AC4D, Al-Si-N
An i-Cu-Mg-based Al alloy such as AC8A, AC8B, or AC8C can be used as appropriate. Further, even with Al alloys other than these standards, Al alloys satisfying the required characteristics of the intended use such as the transport aircraft of the present invention are also used.
All alloys are subject to the present invention. For example, it is permissible to appropriately change the component composition in order to further improve the characteristics or add other characteristics.

Further, the Al alloy material according to the present invention is manufactured as a sheet material or an extruded material by rolling, extruding, or the like by a conventional method. That is, the molten aluminum alloy melted and adjusted within the component standard range is cast by appropriately selecting a normal melting casting method such as a continuous casting rolling method and a semi-continuous casting method (DC casting method, hot top casting method). I do. Next, the ingot is subjected to a homogenizing heat treatment, and hot rolling, cold rolling, tempering (solution treatment and quenching and age hardening), extrusion, tempering, hot forging, tempering. An Al alloy material having a desired cross-sectional shape such as a plate material, a shape material, a forged material, or the like is formed by a cast material-tempering process or a combination thereof.

Further, the steel material is also a JIS G 3141 SPC which is a cold-rolled steel sheet for forming work which is usually used in this kind of field.
C, SPCD, SPCE, JIS G 3125 SPA-C, low yield point steel sheet,
High tensile strength or high strength (high tensile) of ultra-deep drawn steel sheets and other low carbon steels and low alloy steels, nitrogen-added steels, APFC 40-60, phosphorus-added steels, and dual-phase steels (ferrite + martensite) JIS G 31 which is a hot rolled steel sheet for forming work
13 SAPH32-45, JIS G 3131 SPHC, SPHD, SPHE, etc. can be used basically. In addition, zinc-plated surface-treated steel sheets can be used for the purpose of rust prevention.

The steel material can also be manufactured by a normal steel plate manufacturing method. That is, the steel is produced by continuous casting or ingot-making method, and then subjected to cold rolling after hot working such as slab rolling, hot forging, and thick plate rolling, thereby producing a predetermined product sheet thickness. These processing conditions and conditions for cooling and heat treatment after the processing are appropriately determined according to requirements and specifications of mechanical properties such as strength of the steel material.

The Al alloy material and the steel material are formed, for example, as members or parts of a transport machine, respectively.
The steel member and the Al alloy member are made into a composite material by mechanical joining such as welding or bolting, and attached to the transport as a transport composite material member or composite part.

[0045]

Embodiment 1 Next, an embodiment of the present invention will be described. According to the above-mentioned conventional method, various types of cold-rolled steel sheets having the specifications shown in Table 1 and rolled sheets, extruded shapes (plates), forged materials (plates), and cast materials (plates) also having the specifications shown in Table 1 Prepare an Al alloy material having the shape of the above, each Al alloy material is 1.0mm in thickness, 70mm × 150mm
And a cold-rolled steel plate of the same size, cut them together and join them with steel bolts at the four corners to produce a composite specimen of steel and Al alloy. did.

The lubricant on the surface of the test piece (test material) of the composite material was completely degreased to remove the lubricant, and thereafter, in both the invention examples and the comparative examples, a colloidal dispersion of titanium phosphate (colloidal titanium solution: Nippon Parker Co., Ltd.) Rising Co., Ltd., product name PBL3020 system, temperature 25 ° C, immersion for 1 minute) treatment and zinc phosphate treatment (free fluorine ion amount 50ppm, temperature 42)
° C, immersion for 2 minutes). At this time, the zinc phosphate adhesion amount (g / m ² ) of the steel test piece and the Al test piece was measured. In addition, about the zinc phosphate of the steel test piece, observed with an electron microscope of 1000 times,
The evaluation was evaluated as ○ when the sample consisted only of granular phosphophyllite having excellent electrodeposition coatability, and as x when part of leaf-like whipite having poor electrodeposition coatability was generated. Table 2 shows the results. Also, for reference when zinc phosphate treatability is good, only cold-rolled steel sheets of the specifications shown in Table 1 (Comparative Example
No. 17) and only the rolled aluminum alloy sheet of the specifications shown in Table 1 (Comparative Example No. 18) were treated with a colloidal dispersion of titanium phosphate and a zinc phosphate treatment under the same conditions as above. The zinc oxide adhesion amount (g / m ² ) was measured. Table 2 also shows these results.

Next, as shown in Table 1, the test pieces of the composite materials subjected to the chemical conversion treatment were subjected to the calcium phosphate of the present invention (Examples Nos. 1 to 11 and Nos. 1 to 7 were tricalcium phosphate,
Nos. 7 to 11 are dicalcium phosphates) and, as comparative examples, various rust preventive pigments such as lead pigments, zinc calcium phosphite, titanium oxide, zinc cyanamide, barium borate (Comparative Examples Nos. 12 to 16) Cationic electrodeposition paint containing
In each case, a 20 μm-thick electrodeposition coating was performed using a power top U-80 (trade name, manufactured by Corporation). Then, thereafter, as a middle coat and a top coat (two coats, two bake coats), various coats shown in Table 1 having a thickness of 30 μm each in the middle coat and the top coat were provided in each case. Each baking hard (baking hardening) treatment condition was 170 ° C. × 20 minutes.

(Corrosion Resistance Test after Painting) Then, the coating test specimens of the composite materials of the invention examples and the comparative examples were subjected to a rust resistance evaluation test under the same conditions. Table 2 also shows the results of these evaluations.
The rust resistance evaluation test was performed by applying a 7 cm cross-cut to both surfaces of a painted test piece of Al alloy material and steel material, followed by 5% at 35 ° C.
NaCl aqueous solution (brine) is sprayed for 24 hours, and then
It was left for 1440 hours in an atmosphere of constant temperature and humidity of% RH. After the standing, the maximum length L (distance in the vertical direction from the cross cut) of the thread rust generated on the surface (painted surface) of each of the Al alloy material and the steel material of the composite material was measured. And the maximum length L of the thread rust is
○ for L ≦ 1mm, △ for 1mm <L ≦ 3mm, L>
3 mm was evaluated as x. At the same time, as the evaluation of the coating film adhesion, the blistering (peeling) of the coating film was also evaluated. .

As is evident from the results in Table 2, Invention Examples Nos. 1 to 11 using calcium phosphate as a rust preventive pigment had a small amount of zinc phosphate adhering to the steel material or Al alloy material side and had a small amount of zinc phosphate on the steel material surface. Even if the zinc phosphate treatability such as formation of Hopite is lower than that of the steel or Al alloy alone of Comparative Examples Nos. 17 and 18, the corrosion resistance of the coating film (yarn rust resistance )
And the adhesion of the coating film (peelability of the coating film) are excellent as in the case of the lead-based rust-preventive pigment and in the case of the steel materials of Comparative Examples Nos. 17 and 18 and the aluminum alloy material alone.

However, Invention Example No. 4 having a relatively low content of calcium phosphate has a rust resistance of the coating film, and Invention Example No. 3 having a relatively high content of calcium phosphate has an adhesion property of the coating film. It is inferior to other invention examples, and supports the significance of the preferable content of calcium phosphate.

On the other hand, Comparative Examples Nos. 12 to 16 in which lead pigments, zinc calcium phosphite, titanium oxide, zinc cyanamide, and barium borate were used as rust-preventive pigments, exhibited a lower resistance to steel and Al alloy materials. If the zinc phosphate treatment property is low, such as the amount of zinc phosphate adhered to the surface and the formation of whipite on the steel surface is low, the coating will have rust resistance and adhesion.
(Removability of the coating film) is significantly inferior to the invention examples and also compared to the case of the lead-based rust preventive pigment or the steel material of Comparative Examples Nos. 17 and 18 and the aluminum alloy material alone. ing.

Therefore, the above facts support the critical significance of the present invention and the significance of preferred conditions.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

According to the present invention, even if the zinc phosphate treatability of the steel material or the Al alloy material is reduced, severe or more advanced coating is required when the steel material and the Al alloy material are combined. It is possible to provide a coating method for a steel material and an aluminum alloy material, a coating material for a composite material, and a coated composite material that can meet required properties of corrosion resistance and corrosion resistance after coating. Therefore, the use of the Al alloy material for transportation equipment such as automobiles, vehicles, ships, and the like can be expanded, and thus has a great industrial value.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 201/00 C09D 201/00 C23C 22/07 C23C 22/07 (72) Inventor Takenori Nakayama Takatsuka, Nishi-ku, Kobe-shi No. 1-5-5 Kobe Steel Works Kobe Research Institute F-term (reference) 4D075 BB75X CA33 DA06 DA23 DB02 DB07 DB64 DC08 DC11 EC01 EC15 4J038 HA416 KA08 NA03 PC02 4K026 AA02 AA07 AA09 AA22 BA03 BA04 BA12 BB06 BB06 BB08 CA16 CA23 CA28 EB08

Claims (6)

[Claims] When a steel material and an aluminum alloy material are subjected to a phosphate treatment in the same treatment step and then painted, the paint is a paint containing calcium phosphate without a lead-based pigment as a rust preventive pigment. A coating method with excellent corrosion resistance, characterized by being carried out according to: 2. The coating method according to claim 1, wherein the steel material and the aluminum alloy material are formed into a composite material before the phosphate treatment. 3. The coating method having excellent corrosion resistance according to claim 1, wherein the use of the steel material and the aluminum alloy material is for a transport machine. 4. The coating method having excellent corrosion resistance according to claim 3, wherein the use of the steel material and the aluminum alloy material is for an automobile. 5. A paint used in the coating method according to claim 1, wherein the paint contains calcium phosphate without a lead-based pigment as a rust preventive pigment. 6. A composite material of a steel material and an aluminum alloy material which has been previously made into a composite material, and which has been subjected to a phosphate treatment and coating, wherein calcium phosphate is used as a rust preventive pigment without a lead-based pigment. A composite material characterized by being coated with a paint containing the same.