(12) Patent Application Publication (10) Pub. No.: US 2014/0290802 A1 Morita Et Al

Home , Rustproofing

US 201402908O2A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2014/0290802 A1 Morita et al. (43) Pub. Date: Oct. 2, 2014

(54) SURFACE TREATMENT METHOD AND (30) Foreign Application Priority Data COATING METHOD FOR STEEL MATERIAL, AND METHOD FOR PRODUCING MACHINE Oct. 25, 2011 (JP) ...... 2011-234331 COMPONENT Publication Classification (51) Int. Cl. (75) Inventors: Haruji Morita, Hanno-shi (JP); Tsuneo C23C 8/42 (2006.01) Tate, Setagaya-ku (JP); Akira C23C 8/80 (2006.01) Shiozawa, Okaya-shi (JP) (52) U.S. Cl. CPC. C23C 8/42 (2013.01); C23C 8/80 (2013.01) (73) Assignees: KOMATSU LTD., Tokyo (JP); USPC ...... 148/241; 148/253 NIPPON KAZAI CO.,LTD., Okaya-shi, Nagano (JP); COTEC (57) ABSTRACT CORPORATION, Tokyo (JP) This Surface treatment method comprises a rustproofing step, a rinsing step, and a cleaning step. In the rustproofing step, a (21) Appl. No.: 14/350,724 rustproofing liquid containing orthophosphoric acid and an organic acid is used to perform a rustproofing treatment on the (22) PCT Filed: Sep. 12, 2012 Surface of a steel material. In the rinsing step, a treatment 9 liquid containing an oxoacid salt of a transition metal is used to perform a rinsing treatment on the Surface of the Steel (86). PCT No.: PCT/UP2012/073363 material. In the cleaning step, the Surface of the steel material S371 (c)(1), that has undergone the rinsing step is subjected to a cleaning (2), (4) Date: Apr. 9, 2014 treatment.

(a) Shape of film formed by this surface treatment method (SEM, x10,000) Patent Application Publication Oct. 2, 2014 Sheet 1 of 7 US 2014/0290802 A1

FIG. 1 Patent Application Publication Oct. 2, 2014 Sheet 2 of 7 US 2014/0290.802 A1

‘uluuOy‘O-OG-07

Z Patent Application Publication Oct. 2, 2014 Sheet 3 of 7 US 2014/0290.802 A1

t Concentration

Sodium silicate (Water glass) 20-50

degreasing liquid

diphosphoric acid 0.02-2.00 #5000 (pyrophOSphoric acid)

special modified ionized water 50-70 phosphoric acid 2-60 (orthophosphoric acid)

DL-malic acid 0.02-5

Appre Solution sodium dihydrogen phosphate dihydrate

fluorine-based surfactant 0.01-015 special modified ionized water 37.65-65.45

modified sodium tungstate Trinse special modified ionized water 50-95

FIG. 3

Patent Application Publication Oct. 2, 2014 Sheet 5 of 7 US 2014/0290.802 A1

|z) H ?,ILI |-

H ILI

Patent Application Publication Oct. 2, 2014 Sheet 6 of 7 US 2014/0290.802 A1

U |.|| |- Z # G

|- Zd Patent Application Publication Oct. 2, 2014 Sheet 7 of 7 US 2014/0290.802 A1

FIG. 7A

(a) Shape of film formed by this surface treatment method (SEM, x10,000)

FIG. 7B

(b) Shape of film formed by surface treatment method using zinc phosphate (SEM, x 10,000) US 2014/02908O2 A1 Oct. 2, 2014

SURFACE TREATMENT METHOD AND material, and a method for producing a machine component, COATING METHOD FOR STEEL MATERIAL, with which corrosion resistance and adhesion at least as good AND METHOD FOR PRODUCING MACHINE as those when using a treatment liquid containing Zinc phos COMPONENT phate can be ensured, while the process can be simplified and the cost reduced. CROSS-REFERENCE TO RELATED 0012. The surface treatment method for a steel material in APPLICATIONS accordance with a first exemplary embodiment of the present 0001. This application is a U.S. National stage application invention comprises a rustproofing step, a rinsing step, and a of International Application No. PCT/JP2012/073363, filed cleaning step. The rustproofing step involves using a rust on Sep. 12, 2012. This U.S. National stage application claims proofing liquid containing orthophosphoric acid and an priority under 35 U.S.C. S 119(a) to Japanese Patent Applica organic acid to perform a rustproofing treatment on the Sur tion No. 2011-234331, filed in Japan on Oct. 25, 2011, the face of a steel material. The rinsing step involves using a entire contents of which are hereby incorporated herein by treatment liquid containing an oxo acid salt of a transition reference. metal to perform a rinsing treatment on the Surface of the Steel material. The cleaning step involves Subjecting the Surface of BACKGROUND the Steel material that has undergone the rinsing step to a cleaning treatment. 0002 1. Field of the Invention 0013 The surface treatment method for a steel material in 0003. The present invention relates to a surface treatment accordance with a second exemplary embodiment of the method and a coating method for a steel material, and to a present invention is the surface treatment method for a steel method for producing a machine component. material according to the first exemplary embodiment of the 0004 2. Description of the Related Art present invention, further comprising a degreasing step of 0005. In recent years, the machine components used in using a degreasing liquid to remove oil and grease from the hydraulic excavators and other Such construction machinery surface of the steel material. have been Subjected to various Surface treatments as precoat 0014. The surface treatment method for a steel material in ing preparation to improve the adhesion and corrosion resis accordance with a third exemplary embodiment of the present tance of the coating. invention is the surface treatment method for a steel material 0006 For example, there is a surface treatment method for according to the second exemplary embodiment of the a steel material that involves the use of a treatment liquid present invention, further comprising a first water washing containing Zinc phosphate and that comprises a degreasing step of washing the surface of the steel material that has step, a first waterwashing step, an acid washing step, a second undergone the degreasing step. water washing step, a neutralization step, a third water wash 0015 The surface treatment method for a steel material in ing step, a surface adjustment step, a fourth water washing accordance with a fourth exemplary embodiment of the step, a chemical conversion coating step, a fifth water wash present invention is the surface treatment method for a steel ing step, and a hot water washing step. material according to any of the first to third exemplary 0007. However, a problem is that the treatment liquid con embodiments, further comprising a second water washing taining the Zinc phosphate also contains a large amount of step of using a treatment liquid containing orthophosphoric heavy metal ions, which are harmful to the environment. acid and an organic acid to wash the Surface of the steel Also, because Zinc phosphate itself is a deleterious Substance, material that has undergone the rustproofing step. there is a problem of higher costs required by the need for 0016. The surface treatment method for a steel material in special equipment to perform this treatment (see Japanese accordance with a fifth exemplary embodiment of the present Laid-Open Patent Application 2010-106334 (laid open on invention is the surface treatment method for a steel material May 13, 2010), for example). according to any of the first to fourth exemplary embodi 0008 Accordingly, treatment liquids whose main compo ments, further comprising a spray step of spraying water on nent is malic acid, orthophosphoric acid, or the like have been the Surface of the steel material that has undergone the clean developed as treatment liquids that are more environmentally ing step. friendly and safer for workers to use, and these have been used 0017. The surface treatment method for a steel material in in the Surface treatment of Some parts. accordance with a sixth exemplary embodiment of the present invention is the surface treatment method for a steel material SUMMARY pertaining to any of the first to fifth exemplary embodiments, 0009. However, the following problems were encountered wherein a treatment liquid containing sodium dihydrogen with the above-mentioned conventional surface treatment phosphate dihydrate, a fluorine-based Surfactant, and special method for a steel material. modified ionized wateris used in the rustproofing step and the 0010 Specifically, with a phosphate coating film that gave second water washing step. a fine crystal structure by using orthophosphoric acid as the 0018. The surface treatment method for a steel material in main component and adding malic acid or another Such accordance with a seventh exemplary embodiment of the organic acid, a problem is that because the crystal structure is present invention is the surface treatment method for a steel finer than with a phosphate coating film having a relatively material pertaining to any of the first to sixth exemplary large crystal structure. Such as a conventional Zinc phosphate embodiments, wherein a treatment liquid containing an oxo coating film, the unstable phosphate or electrolyte remaining acid salt of a transition metal and special modified ionized on the crystal Surface in the treatment step tended to have an water is used in the rinsing step. adverse effect on adhesion with the coating and so forth. 0019. The surface treatment method for a steel material in 0011. It is an object of the present invention to provide a accordance with an eighth exemplary embodiment of the Surface treatment method and coating method for a steel present invention is the surface treatment method for a steel US 2014/02908O2 A1 Oct. 2, 2014

material pertaining to any of the first to seventh exemplary 0032 FIG. 7A shows the shape of the coating film formed embodiments, wherein the oxoacid salt of a transition metal on the steel material surface by the surface treatment method contained in the treatment liquid used in the rinsing step is of an exemplary embodiment of the present invention; and either a tungstate, a molybdate, or a Zirconate. 0033 FIG. 7B is a comparative micrograph of the shape of 0020. The surface treatment method for a steel material in the coating film formed on the steel material surface by a accordance with a ninth exemplary embodiment of the Surface treatment method using Zinc phosphate. present invention is the surface treatment method for a steel material pertaining to any of the first to eighth exemplary DETAILED DESCRIPTION OF EXEMPLARY embodiments, wherein rustproofing of the steel material and EMBODIMENTS a phosphate coating treatment are carried out simultaneously 0034. The surface treatment method for a steel material in the rustproofing step. pertaining to an exemplary embodiment of the present inven 0021. The surface treatment method for a steel material in tion will now be described through reference to FIGS. 1 to 4. accordance with a tenth exemplary embodiment of the 0035. Overall Configuration of Steel Material Surface present invention is the surface treatment method for a steel Treatment Method material pertaining to any of the first to ninth exemplary 0036. The surface treatment method for a steel material embodiments, wherein the first water washing step is pertaining to an exemplary embodiment is, for example, a repeated a plurality of times. pretreatment step performed as a coating pretreatment on 0022. The surface treatment method for a steel material in hydraulic lines 11a (FIG. 4) installed on a hydraulic excavator accordance with an eleventh exemplary embodiment of the 1. As shown in FIG. 1, a degreasing step (S1), a first water present invention is the surface treatment method for a steel washing step (S2), a rustproofing step (S3), a second water material pertaining to any of the first to tenth exemplary washing step (S4), a rinsing step (S5), a cleaning step (S6), embodiments, wherein ultrasonic waves or a spray is used in and a spray step (S7) are carried out in that order. After this, a the second water washing step. coating step (S8) is carried out. 0023 The coating method for a steel material in accor 0037 Here, as shown in FIG. 4, for example, the steel dance with a twelfth exemplary embodiments of the present material treated by the surface treatment method for a steel invention involves Subjecting a steel material that has been material of this exemplary embodiment is the hydraulic lines treated by the surface treatment method for a steel material 11a, etc., provided on the cab 10 side of a boom 11 of a work according to any of the first to eleventh exemplary embodi implement 4 installed on the hydraulic excavator 1. ments to a coating treatment. 0038. In the degreasing step (S1), as shown in FIG. 2, the 0024. The method for producing a machine component in material is dipped or sprayed with a 40 to 70° C. degreasing accordance with a thirteenth exemplary embodiment of the liquid. When environmental impact is taken into account, it is present invention involves producing a machine component preferable to use degreasing liquid #5000 (made by Nippon by using a steel material that has undergone a coating treat Kazai) diluted 5 to 10 times. ment by the coating method for a steel material pertaining to 0039. The i5000 degreasing liquid can be a treatment the twelfth exemplary embodiment. liquid containing the components shown in FIG. 3. 0025. The method for producing a machine component in 0040 sodium silicate (waterglass): 20 to 50 wt % (CAS accordance with a fourteenth exemplary embodiment of the Registry Number: 1344-09-8 (American Chemical present invention is the method for producing a machine Society)) component pertaining to the thirteenth exemplary embodi 0041 diphosphoric acid (pyrophosphoric acid): 0.02 to ment, wherein the machine component is a hydraulic line for 2.00 wt % (CAS Registry Number: 2466-09-3 (Ameri a hydraulic excavator. can Chemical Society)) (0.042 special modified ionized water: 50 to 70 wt % BRIEF DESCRIPTION OF DRAWINGS (CAS Registry Number: 7732-18-5 (American Chemi cal Society)) 0026 FIG.1 is a flowchart of the surface treatment method for a steel material pertaining to an exemplary embodiment of 0043. As shown in FIG. 2, in the first water washing step the present invention; (S2), the steel material treated in the degreasing step (S1) is dipped for 1 to 2 minutes in fresh water (well water). 0027 FIG. 2 is a table showing specific examples of the 0044 As shown in FIG. 2, in the rustproofing step (S3), for steps of the surface treatment method of FIG. 1; the purpose of obtaining a fine crystal structure, the Steel 0028 FIG. 3 is a table of the makeup of the treatment material treated in the first water washing step (S2) is dipped liquids used in the various steps of the Surface treatment in a treatment liquid whose main component is orthophos method of FIG. 1; phoric acid and to which an organic acid has been added, or is 0029 FIG. 4 is an overall oblique view of the configura sprayed with this treatment liquid, thereby simultaneously tion of a hydraulic excavator equipped with hydraulic lines removing rust from the Steel material Surface and forming a treated by the surface treatment method of FIG. 1; phosphate coating film. 0030 FIG. 5 is a table of test results for a scratch hardness 0045. The treatment liquid can be, for example, Appre test and an adhesion test of steel materials treated by the HybridTM (made by Nippon Kazai) that has been diluted 5 to surface treatment method of an exemplary embodiment of the 10 times. present invention, as well as comparative example test results; 0046. A treatment liquid containing the components 0031 FIG. 6 is a table of test results for a corrosion resis shown in FIG. 3 can be used as the Appre Hybrid liquid. tance test of steel materials treated by the surface treatment 0047 phosphoric acid (orthophosphoric acid): 2.0 to method of an exemplary embodiment of the present inven 60.0 wt % (CAS Registry Number: 7664-38-2 (Ameri tion, as well as comparative example test results; can Chemical Society)) US 2014/02908O2 A1 Oct. 2, 2014

0048 DL-malic acid: 0.02 to 5 wt % (CAS Registry 0059. The fluorine-based nonionic surfactant is preferably Number: 617-48-1 (American Chemical Society)) contained in a ratio of 0.01 to 0.15 wt %, and more preferably 0049 sodium dihydrogen phosphate dihydrate: 0.01 to in the range of 0.01 to 0.1 wt %. This is because there will tend 5 wt % (CAS Registry Number: 13472-35-0 (American to be no effect if the blend ratio is less than 0.01 wt %, and the Chemical Society)) cost is higher if the ratio is 0.15 wt % or more, which is 0050 fluorine-based surfactant: 0.01 to 0.15 wt % uneconomical. (CAS Registry Number: 68391-08-2 (American Chemi 0060. The sodium dihydrogenphosphate dihydrate con cal Society)) tained in the Appre Hybrid solution functions as a powerful 0051. This liquid is an aqueous solution, and the water that auxiliary for forming the ultrafine structure coating film on is used can be freshwater with an electrical conductivity of 20 the surface of the steel material. Adding this is expected to uS or less, special modified ionized water (CAS Registry further improve rustproofing performance, the effect as a Number: 7732-18-5 (American Chemical Society)), or the coating primer film, the anchoring effect, conductivity char like. acteristics, and so forth. 0052. In addition to the above-mentioned malic acid (DL 0061 The proportion in which the sodium dihydrogen malic acid), the organic acid contained in the Appre Hybrid phosphate dihydrate is added is 0.01 to 5.00 wt %, and pref Solution can be tartaric acid, citric acid, oxalic acid, or the erably 0.02 to 0.50 wt %. like. 0062. In the second water washing step (S4), as shown in 0053. In the course of research and development of the FIG. 2, a 100-times dilution of the Appre Hybrid solution present invention, it was found that Oxalic acid can also be used in the rustproofing step (S3) is used to subject the steel used as the organic acid. When the Surface treatment is per material treated in the rustproofing step (S3) to a water wash formed using malic acid, tartaric acid, or citric acid, it is ing treatment by spraying or with ultrasonic waves. known that an extremely fine crystal structure is obtained. 0063. This enhances the effect in removing unstable iron When oxalic acid is used, on the other hand, the crystals phosphate or the like left on the coating film surface of the become larger, but a crystal structure that has a uniform steel material. crystal shape and is finer than that of a conventional Zinc 0064. When the water washing treatment is performed phosphate coating film can be obtained. Accordingly, it was ultrasonically, the treatment can be carried out, for example, confirmed that the same performance will be obtained as that such that that a vibrator for generating ultrasonic waves of 28 of a fine crystal structure obtained by surface treatment with kHz (not shown) is moved three times back and forth in the malic acid or the like. It was similarly confirmed that using lengthwise direction of the hydraulic lines 11a. this process improves corrosion resistance and adhesion. 0065. When the water washing treatment is performed by 0054 The proportion in which the organic acid is used is spraying, the treatment liquid is preferably sprayed at a pres 0.02 to 5.00 wt %, and more preferably 0.1 to 0.5 wt %. Sure of 0.1 MPa or more. 0055. The higher the proportion in which the organic acid 0066. In this exemplary embodiment, for example, it is is added, the better the rustproofing performance. Rustproof possible to use ultrasonic waves when a dipping treatment is ing performance will decrease if the proportion is less than performed with a tank system, and to use a spray treatment in 0.02 wt %, and if 5.0 wt % is exceeded, the cost increases and other cases. As to the specific products to be treated, pipe is therefore undesirable from an economic standpoint. shaped steel materials, such as the hydraulic lines 11a (FIG. 0056. Using a treatment liquid containing an organic acid, 4), may be subjected to ultrasonic treatment, while flat or Such as the Appre Hybrid solution, for forming a microstruc rod-shaped steel materials may be subjected to spray treat ture coating film on the Surface of the Steel material as in this ment. This allows surface treatment to be carried out reliably exemplary embodiment, locally forms a metal complex and regardless of the shape of the steel material. promotes the elution of the metal, and it is believed that 0067. In the rinsing step (S5), as shown in FIG. 2, the steel phosphate ions react with this eluted metal complex to form a material treated in the second water washing step (S4) is fine crystal structure. dipped for 1 to 2 minutes in a room-temperature T rinsing 0057 Also, the fluorine-based surfactant contained in the liquid (made by Nippon Kazai). above-mentioned Appre Hybrid solution is one in which the 0068 A treatment liquid containing the components hydrogen atoms in an alkyl chain have been Substituted with shown in FIG. 3 can be used as the Trinsing solution used fluorine atoms, and is characterized by being physicochemi here. cally stable and having lower Surface tension thana Surfactant 0069 modified sodium tungstate (transition metal oxo containing no fluorine atoms. Also, if a nonionic Surfactant is acid salt): 5 to 50 wt % (CAS Registry Number: 10213 used, it is believed that the structure of its hydrophilic portion 10-2 (American Chemical Society)) will form a microstructure coating film on the metal Surface, (0070 special modified ionized water: 50 to 95 wt % (CAS and a better rustproofing effective is exhibited. Thus, in this Registry Number: 7732-18-5 (American Chemical Society)) exemplary embodiment, adding a fluorine-based nonionic 0071. In the cleaning step (S6), as shown in FIG. 2, the surfactant to the Appre Hybrid solution promotes permeabil steel material treated in the rinsing step (S5) is dipped for 3 ity and forms a microstructure coating film on the Steel Sur minutes in 40 to 70° C. fresh water (well water). face. 0072. In this cleaning step, 40 to 70° C. freshwater is used 0058. There are no particular restrictions on the fluorine to promote the evaporation of the moisture from the steel based nonionic Surfactant, but one or more types of com surface, but the exemplary embodiments of the present inven pounds are selected from the group consisting of perfluoro tion are not limited to this, and room-temperature water may alkyl ethylene oxide adducts, and oligomers containing be used instead, for example. fluorine groups, hydrophilic groups, and lipophilic groups 0073. In the spraying step (S7), as shown in FIG. 2, the (such as perfluoroalkyl Sulfonic acid compounds and perfluo steel material treated in the cleaning step (S6) is sprayed for roalkyl oxide adducts). about 30 seconds with pure water. US 2014/02908O2 A1 Oct. 2, 2014

0074 To enhance the effect of flushing away the electro Coating Scratch Hardness Test and Adhesion Test lyte or the like left on the surface of the steel material, it is preferable to use fresh water of 20 LS (and more preferably, 0083 FIG. 5 shows the results of a scratch hardness test 10 LS or less). The electrolyte or the like left on the steel and an adhesion test conducted on a steel material that had Surface may also be flushed way by dipping the steel material been treated by the steel surface treatment method of the in this fresh water, rather than by spraying. present invention and then coated. 0075 With the surface treatment method for a steel mate Scratch Hardness Test rial in this embodiment, the Surface treatment of an uncoated steel material is performed by the above steps, which allows 0084 First, a scratch hardness test was conducted accord a microstructure coating film to be formed on the Steel mate ing to JIS K 5600-5-4 (Paint-General Test Methods Part 5: rial surface while entailing fewer steps than in the past. There Mechanical Properties of Coating Films—Section 4: Scratch fore, this Surface is coated, the coating will work its way into Hardness (Pencil Hardness). the microstructure, which improves adhesion through an I0085. The quality required here is at least a pencil hard anchoring effect with the steel. ness of F, in the case of baked-on enamel. 0.076 Also, with the surface treatment method for a steel I0086. As a result, it was found that the PFE-CR test piece material in this exemplary embodiment, a microstructure and the PZ test piece both had scratch hardness equivalent to coating film that contains a dense crystalline structure can be a pencil hardness H or higher. formed on the steel Surface according to the characteristics of I0087. That is, in the scratch hardness test, comparable the various treatment liquids, so foreign matter Such as crys results were obtained with the steel surface treatment method talline water tends not to accumulate inside the crystals, and of the present invention and the conventional Steel Surface excellent thermal properties (heat cycle, etc.) can also be treatment method. obtained. 0077. As a result, coating adhesion and corrosion resis Adhesion Test tance can be ensured that are equal to or better than those of 0088 Next, an adhesion test was carried out as set forth in products that were treated before coating by a conventional JISD 0202 (General Rules of Coating Films for Automobile Surface treatment method using a treatment liquid containing Parts, 3.14 Cross-Cut Adhesion). The number of squares in Zinc phosphate. the adhesion test was 100, and the cut spacing was 2.0 mm. 0078. In the coating step (S8), as shown in FIG. 2, coating I0089. The quality required here was a state in which the is performed on the surface of the steel material treated by the paint did not separate in 95 to 100 of the 100 squares. surface treatment method described above. (0090. As a result, it was found that the PFE-CR test piece 007.9 The effect of the steel material surface treatment and the PZ test piece were similar in that the paint did not method in this exemplary embodiment related to coating separate in any of the 100 squares. adhesion and corrosion resistance will be discussed in the 0091 That is, in the adhesion test, the steel surface treat working examples given below. ment method of an exemplary embodiment of the present invention and the conventional steel Surface treatment WORKING EXAMPLE 1. method both gave comparable results. 0080. The corrosion resistance and the adhesion of a coat Corrosion Resistance Test ing applied to the surface of the steel material treated by the steel surface treatment method described in the above exem 0092. Then, a corrosion resistance test was conducted on the steel material that had been coated after being treated by plary embodiment was examined, the results of which are the steel surface treatment method of the present invention, described through reference to FIGS. 5 to 7. for steel, the results of which are shown in FIG. 6. I0081. The “PFE-CR” displayed in the test results shown in 0093. The test was conducted using the same test pieces FIGS. 5 and 6 indicates the test results for a test piece that had that those use for the above-mentioned scratch hardness test been surface treated by the surface treatment method of an exemplary embodiment of the present invention, using and adhesion test. 0094. The corrosion resistance test here was conducted as SPCC-SD sheet steel (JIS G3141 sheet steel (100x70x0.8 set forth in JIS K 5600-7-1, in which diagonally intersecting mm)). More precisely, PFE-CR is a test piece obtained by first scratches were made 20 mm to the inside of the edges of test performing Surface treatment using the Appre Hybrid Solu pieces using the single blade defined in JIS K 5600-5-6. The tion as described in the above exemplary embodiment, or the resulting test pieces were sprayed with Salt water, and the like, and then applying a single powder coat (Everclad 8010 width of rusted portions and the width of blistered portions Natural, made by Kansai Paint). that occurred on part of the coating were measured after 120, 0082 Meanwhile, “PZ (zinc phosphate coating film) 240, 480, 600, and 720 hours to check for salt water spray indicates the test results for a test piece that had been surface corrosion resistance. treated with a conventional treatment liquid containing Zinc phosphate, using the same sheet steel as that used for the Elapsed Time of 120 Hours PFE-CR test piece (SPCC-SD sheet steel (JIS G3141 sheet steel (100x70x0.8 mm))). More precisely, PZ is a test piece (0095. With the conventional PZ test pieces, the rust width obtained by first performing treatment with industrial-use and blister width after 120 hours had elapsed were both less Zinc phosphate made by Partek, and then applying a single than 1.0 mm. powder coat (Everclad 8010 Natural, made by Kansai Paint), (0096. With the PFE-CR test pieces of an exemplary just as with PFE-CR. embodiment of the present invention, the rust width and blis US 2014/02908O2 A1 Oct. 2, 2014

ter width after 120 hours had elapsed were both less than 1.0 gave results that were comparable to those with a conven mm, which was the same as the test results for the conven tional steel Surface treatment method in a corrosion resistance tional PZ test pieces. teSt. 0097 Thus, the result of the test at an elapsed time of 120 hours was that the test pieces of the present invention gave test Shape of Coating Film results comparable to those of the conventional test pieces, for 0111. In another exemplary embodiment, the coating film all of the test pieces. shown in FIG. 7A is formed on the surface of a steel material by using a rustproofing liquid whose main component is the Elapsed Time of 240 Hours above-mentioned orthophosphoric acid and to which an 0098. With the conventional PZ test pieces, the rust width organic acid has been added. FIG. 7A shows an enlarged after 240 hours had elapsed was 1.4 mm. image (magnified 10,000 times) captured by SEM (scanning electron microscope). 0099. With the PFE-CR test pieces of an exemplary 0112 Meanwhile, FIG. 7B shows an enlarged image embodiment of the present invention, of the five test pieces, (magnified 10,000 times) captured by SEM (scanning elec the rust width and blister width after 240 hours had elapsed tron microscope), of a Zinc phosphate treated film formed by were both less than 1.0 mm for test pieces 1, 2, 4, and 5. The a conventional Surface treatment method. rust width after 240 hours was 1.2 mm for test piece 3. 0113. A comparison of these reveals that when using a 0100 Thus, the result of the test at an elapsed time of 240 treatment liquid whose main component is orthophosphoric hours was that the test pieces of an exemplary embodiment of acid and to which an organic acid has been added, there is less the present invention gave test results Superior to those of the height difference between the peaks and valleys of the coating conventional test pieces, for all of the test pieces. film than with the conventional zinc phosphate treated film, but there are a greater number of portions that are apexes. A Elapsed Time of 480 Hours comparison of actual Surface area shows that a coating film 0101. With the conventional PZ test pieces, the rust width after the surface treatment of an exemplary embodiment of after 480 hours had elapsed was 1.9 mm. the present invention, in which orthophosphoric acid is the 0102. With the PFE-CR test pieces of an exemplary main component and an organic acid has been added, is larger embodiment of the present invention, of the five test pieces, than a conventional Zinc phosphate treatment film. the rust width after 480 hours had elapsed was 1.2, 1.8, 1.6, 0114. Accordingly, when a rustproofing liquid is used in and 1.4 mm for test pieces 2, 3, 4, and 5. The rust width after which orthophosphoric acid is the main component and an 480 hours was 1.4 mm for test piece 1. organic acid has been added, many fine bumps are formed, 0103) Thus, the result of the test at an elapsed time of 480 and it is Surmised that this gives an anchoring effect compa hours was that the test pieces of an exemplary embodiment of rable to that of a conventional zinc phosphate treatment film. the present invention gave test results Superior to those of the 0115 Actually, however, the above-mentioned phosphate conventional test pieces, for all of the test pieces. treatment film in which orthophosphoric acid was the main component and an organic acid was added gave clearly infe Elapsed Time of 600 Hours rior results in terms of adhesion and corrosion resistance. The reason for this is surmised to be that the performance of a 0104. With the conventional PZ test pieces, the rust width phosphate treatment film having a fine crystal structure is after 600 hours had elapsed was 2.5 mm. impaired by unstable crystal components or by iron orphos 0105. With the PFE-CR test pieces of an exemplary phorus ions remaining on the coating film Surface, or that embodiment of the present invention, of the five test pieces, occur on the coating film Surface during the course of film the rust width after 600 hours had elapsed was 2.0, 2.5, 2.3, formation. and 2.5 mm for test pieces 2, 3, 4, and 5. The rust width after 600 hours was 1.9 mm for test piece 1. Consideration 0106 Thus, the result of the test at an elapsed time of 600 0116. The reason why the above-mentioned superior hours was that the test pieces of an exemplary embodiment of results are obtained with the steel surface treatment method of the present invention gave test results Superior to those of the an exemplary embodiment of the present invention was con conventional test pieces, for all of the test pieces. sidered, and as a result the inventors surmised that the effect of the Trinsing liquid used in the surface treatment method of Elapsed Time of 720 Hours an exemplary embodiment of the present invention is a prod 0107. With the conventional PZ test pieces, the rust width uct of reaction promotion and stabilization of iron ions and after 720 hours had elapsed was 3.0 mm. phosphorus ions as oxidants. 0108. With the PFE-CR test pieces of an exemplary 0117 That is, the inventors came to the conclusion that the embodiment of the present invention, of the five test pieces, T rinsing solution used in an exemplary embodiment of the the rust width after 720 hours had elapsed was 2.7, 2.6, 2.5, present invention has the effect of preventing excessive elu and 2.9 mm for test pieces 2, 3, 4, and 5. The rust width after tion of material and Stabilizing the fine crystal structure on the 720 hours was 2.0 mm for test piece 1. surface of the steel material, which results instabilization and 0109 Thus, the result of the test at an elapsed time of 720 promotion of the anchoring effect of the coating film on the hours was that the test pieces of an exemplary embodiment of steel material. the present invention gave test results Superior to those of the conventional test pieces, for all of the test pieces. Other Exemplary Embodiments 0110. As discussed above, the steel surface treatment 0118. An exemplary embodiment of the present invention method of an exemplary embodiment of the present invention was described above, but the present invention is not limited US 2014/02908O2 A1 Oct. 2, 2014

to or by the above exemplary embodiment, and various modi I0134. In this case, for example, whether to use ultrasonic fications are possible without departing from the gist of the waves or a spray as the treatment in the second water washing invention. step may be determined according to the shape of the machine 0119. In the above exemplary embodiment, an example component, etc. was given in which a Trinsing Solution containing a modified Sodium tungstate was used to perform surface treatment of the INDUSTRIAL APPLICABILITY steel material in the rinsing step shown in FIG. 1. However, 0.135 The effect of the surface treatment method for a steel the present invention is not limited to this. material of an exemplary embodiment of the present inven 0120 For example, a T rinsing solution containing a tion is that corrosion resistance and adhesion at least as good molybdate, a Zirconate, or another Such transition metal oxo as those with a conventional steel Surface treatment method acid salt may be used instead of S modified tungstate, includ involving the use of a Zinc phosphate treatment liquid can be ing the above-mentioned modified Sodium tungstate. ensured, while the process can be simplified and the cost 0121. In the above exemplary embodiment, an example reduced. This means that the method of an exemplary was given in which a Surface treatment method including a embodiment of the present invention can be widely applied in degreasing step, a first water washing step, a rustproofing the Surface treatment of uncoated Steel materials. step, a second water washing step, a rinsing step, a cleaning 1. A Surface treatment method for a steel material, com step, and a spray step was performed prior to coating, but the prising: present invention is not limited to this. a rustproofing step of using a rustproofing liquid contain 0122 For example, the degreasing step is not essential to ing orthophosphoric acid and an organic acid to perform the present invention if a steel material is used which does not a rustproofing treatment on the a Surface of a steel mate require degreasing, for example. rial; 0123. Similarly, the first water washing step, the second a rinsing step of using a treatment liquid containing an oxo water washing step, and the spray step are not essential to acid salt of a transition metal to perform a rinsing treat obtaining the effects of the present invention. ment on the surface of the steel material; and a cleaning step of subjecting the Surface of the steel mate 0.124. In the above exemplary embodiment, an example rial that has undergone the rinsing step to a cleaning was given in which the above-mentioned surface treatment treatment. method of the present invention was performed as a pretreat 2. The surfacetreatment method for a steel material accord ment to coating, but the present invention is not limited to this. ing to claim 1, 0.125 For example, the surface treatment method of the further comprising a degreasing step of using a degreasing present invention can be carried out as a pretreatment for liquid to remove oil and grease from the Surface of the performing a plating treatment or the like. steel material. 0126 Here again, a plating treatment with excellent adhe 3. The surfacetreatment method for a steel material accord sion and so forth can be performed because of the anchoring ing to claim 2, effect on the Steel material Surface, just as in a coating treat further comprising a first water washing step of Washing ment. the surface of the steel material that has undergone the 0127. In the above exemplary embodiment, an example degreasing step. was given in which the first water washing step was per 4. The surfacetreatment method for a steel material accord formed one time, but the present invention is not limited to ing to claim 1, this. further comprising a second water washing step of using a 0128. For example, the first water washing step may be treatment liquid containing orthophosphoric acid and an repeated a plurality of times. organic acid to wash the Surface of the steel material that 0129. In the above exemplary embodiment, an example has undergone the rustproofing step. was given in which an aqueous solution whose main compo 5. The surfacetreatment method for a steel material accord nent was tap water or other Such fresh water was used as the ing to claim 1, Appre Hybrid solution for forming a microstructure coating further comprising a spray step of spraying water on the film on the steel surface, but the present invention is not Surface of the steel material that has undergone the limited to this. cleaning step. 6. The surfacetreatment method for a steel material accord 0130 For example, an Appre Hybrid solution made with ing to claim 1, distilled water or the like may be used. wherein a treatment liquid containing sodium dihydrogen 0131 However, in this case, it is preferable in terms of phosphate dihydrate, a fluorine-based Surfactant, and corrosion resistance to use water with an electrical conduc special modified ionized water is used in the rustproof tivity of 20 LS or less. ing step and the second water washing step. 0.132. In the above exemplary embodiment, an example 7. The surfacetreatment method for a steel material accord was given in which the steel material treated with the steel ing to claim 1, surface treatment method of the present invention was the wherein a treatment liquid containing an oxoacid salt of a hydraulic lines 11a used in the hydraulic excavator 1, but the transition metal and special modified ionized water is present invention is not limited to this. used in the rinsing step. 0.133 For example, the invention may be applied to the 8. The surfacetreatment method for a steel material accord coating (manufacture) of other machine components used in ing to claim 1, hydraulic excavators and other such construction machinery, wherein an oxoacid salt of a transition metal contained in or of machine components that undergo a coating treatment the treatment liquid used in the rinsing step is either a and are used in various kinds of vehicles and the like. tungstate, a molybdate, or a Zirconate. US 2014/02908O2 A1 Oct. 2, 2014

9. The surface treatment method for a steel material accord ing to claim 1, wherein rustproofing of the steel material and a phosphate coating treatment are carried out simultaneously in the rustproofing step. 10. The surface treatment method for a steel material according to claim 1, wherein the first water washing step is repeated a plurality of times. 11. The surface treatment method for a steel material according to claim 1, wherein ultrasonic waves or a spray is used in the second water washing step. 12. The surface treatment method for a steel material according to claim 1, further comprising: a coating step of Subjecting the steel material to a coating treatment. 13. The surface treatment method for steel material accord ing to claim 12, further comprising producing a machine component with the steel material following the coating step. 14. The surface treatment method for a steel material according to claim 13, wherein the machine component is a hydraulic line for a hydraulic eXCaVatOr.