JP2009242815A - Surface treated steel sheet, and method for producing the same - Google Patents

Abstract

The present invention provides a cold-rolled steel sheet having an initial rust prevention property for a long period of time without applying a rust prevention oil even in a harsh environment where dry and wet conditions are repeated in the presence of chlorine ions.
A rust preventive film based on Zn, which is an amorphous oxide layer of Zn, P and Si, is formed on the surface of a cold rolled steel sheet.
[Selection figure] None

Description

  The present invention relates to a surface-treated steel sheet having excellent initial rust prevention properties suitable for use in automobiles, home appliances, building materials and the like, and a method for producing the same, particularly in a severe environment in which dry and wet conditions are repeated in the presence of chlorine ions. However, it is intended to prevent the occurrence of rust without applying rust-preventing oil during the period from immediately after production to processing such as painting at the customer site.

In order to prevent rust (hereinafter referred to as initial rust) from occurring immediately after production until use at the customer's site, cold rolled steel usually has about 1 to ² g / m ² of rust preventive oil per side of the steel plate. Applied. In addition to the original anti-rust effect, the anti-rust oil also has an effect as a lubricant in press molding or the like, but is generally removed by a degreasing process prior to a process such as painting at a customer site. Since the omission of this degreasing treatment is effective for environmental protection and cost reduction, there has been a demand for a steel sheet having excellent initial rust prevention properties that does not generate initial rust without using rust preventive oil.

Conventionally, the following are proposed as a steel plate excellent in initial rust prevention.
In Patent Document 1, components such as C and S are obtained by continuously annealing a steel sheet having a defined composition such as C and S in a reducing atmosphere composed of nitrogen gas containing 0.5 to 10 vol% of hydrogen. A cold-rolled steel sheet is disclosed in which a very thin dense carbide or sulfide layer is formed by gently segregating the surface layer.
Patent Document 2 discloses an automatic reduction time (an index indicating the stability of the oxide film formed on the steel sheet surface) by water washing after removing the oxide film on the steel sheet surface by, for example, pickling at the downstream side of the continuous annealing process. A steel sheet is disclosed in which an oxide film is regenerated with a disintegration time of the oxide film in the neutral salt bath of interest for 40 seconds or longer.
In Patent Documents 3 and 4, steel sheets for automobiles having excellent perforation resistance in extremely severe environments where dry and wet conditions are repeated in the presence of chloride ions caused by snowmelt salt scattered on North American and Scandinavian roads are disclosed. It is disclosed.
Patent Document 5 discloses a steel sheet in which an aqueous solution mainly composed of lithium silicate is applied to a steel sheet and dried to form a barrier film.
Patent Document 6 discloses a steel sheet in which a phosphate ion or a phosphate compound is applied to a surface-treated steel sheet and dried to form a chemical conversion film.
Patent Document 7 discloses a steel sheet in which a barrier film containing P is formed on the steel sheet surface by bringing the solution containing P into contact with the annealed cold-rolled steel sheet after defining the component composition of the steel sheet. Yes.
Patent Document 8 discloses a steel sheet in which a barrier film containing Si is formed on the surface of a steel sheet by bringing the Si-containing solution into contact with the annealed cold-rolled steel sheet after defining the composition of the steel sheet. Yes.
Japanese Patent Laid-Open No. 2001-348621 JP 2004-269919 A Japanese Patent Laid-Open No. 11-293346 JP 2000-34544 A Japanese Examined Patent Publication No. 4-69235 JP 2000-144444 A JP 2007-84868 JP 2007-113108 A

However, all of the above-described conventional techniques have the following problems.
The steel sheets described in Patent Document 1 and Patent Document 2 are said not to rust even when left indoors for 1 to 14 days in an oil-free state, but in severe exposure environments containing a relatively large amount of salt. The film deteriorated due to the wet state persistence due to the adhering salt and the influence of chlorine ions, etc., and sufficient initial rust preventive properties could not be obtained with carbides, sulfides and oxides formed on the surface layer.

  The steel plates described in Patent Literature 3 and Patent Literature 4 define the component composition of the steel plate, densify rust formed on the surface layer of the steel plate and suppress pitting corrosion, and have a small inhibitory effect on initial rust.

  The steel sheet described in Patent Document 5 needs to have a thick rust preventive film in order to ensure sufficient initial rust preventive property, but on the other hand, increasing the film thickness deteriorates the adhesion of the film and causes peeling. The initial rust resistance was rather lowered because it was easier to do.

  The steel sheet described in Patent Document 6 needs to have a thick rust preventive film in order to ensure sufficient initial rust resistance, and the same problem as the steel sheet described in Patent Document 5 has occurred.

  The steel sheets described in Patent Document 7 and Patent Document 8 have improved corrosion resistance in comparison with the steel sheets described in Patent Documents 1 to 6, but have an environment with more adhered salt and a length exceeding one month. There was a problem with the corrosion resistance during storage over a period of time.

  The present invention advantageously solves the above-mentioned problem, and even in a harsh environment where the drying and wetting is repeated in the presence of chloride ions, the initial rust prevention is performed for a long period of one month or longer without applying the rust prevention oil. An object of the present invention is to provide a cold-rolled steel sheet capable of maintaining the properties together with its advantageous manufacturing method.

In order to achieve the above-mentioned object, the inventors have studied a method for suppressing the generation of initial rust over a long period of time even in a harsh environment where chlorine ions exist, and obtained the following knowledge.
(1) The amorphous oxide layer of Zn, P and Si formed by combining high barrier type oxide containing P or Si with Zn on the outermost layer of the steel plate is the rust preventive property of the steel plate. Is greatly improved.
(2) However, when a barrier type oxide is combined with Zn, Zn is formed by a method in which Zn ions or Zn compounds are mixed in advance with a treatment solution containing P and Si necessary for oxide formation. The effect of improving rust prevention is small in the oxide layer of P, Si and Si.
(3) In this regard, first, Zn is deposited on the surface of the steel sheet to form a metal Zn layer, and then a treatment liquid containing P and Si is brought into contact with the steel sheet, so that Zn and the treatment liquid present on the surface of the metal Zn layer are removed. An amorphous oxide layer containing Zn, P and Si formed by sufficiently reacting exhibits excellent rust prevention.
(4) Further, by containing one or more selected from Ca, Zr, Ti, V, Mn, Al and Mg, the rust prevention property is further improved.

The present invention has been completed by further studies based on the above-described findings, and the gist of the present invention is as follows.
1. A surface-treated steel sheet having a rust preventive film based on Zn on the surface of the steel sheet, wherein the outermost layer of the rust preventive film is composed of an amorphous oxide layer of Zn, P and Si. steel sheet.

2. The ratio of Zn, P, and Si in the amorphous oxide layer satisfies P: 2 to 30 and Si: 2 to 30 with respect to Zn: 100 by mass ratio. The surface-treated steel sheet described.

3. The amorphous oxide layer further contains one or more selected from Ca, Zr, Ti, V, Mn, Al and Mg in a mass ratio of 0.1 to 3.5 with respect to Zn: 100. The surface-treated steel sheet according to 2 above, which is contained at a ratio of

4). 4. The surface-treated steel sheet according to any one of 1 to 3, wherein the amorphous oxide layer has a thickness of 10 to 1000 nm.

5. On the surface of the cold-rolled steel sheet, Zn is electrolyzed to deposit 100 to 7000 mg / m ^{2 in} terms of metal Zn to form a metal Zn film, and then a treatment solution containing P and Si is brought into contact with the metal Zn film and a unit area. : By reacting 10 to 100 mg of P with 10 to 100 mg of Si per 1 m ^2, the outermost layer of the metal Zn film has a mass ratio of Zn: 100, P: 2 to 30 and Si: 2 A method for producing a surface-treated steel sheet, comprising forming an amorphous oxide layer composed of Zn, P and Si containing ~ 30.

6). The treatment liquid further contains one or more selected from Ca, Zr, Ti, V, Mn, Al and Mg, and the metal Zn film and unit area: 1 to ²⁰ mg per 1 m ² By reacting with one or more selected from Ca, Zr, Ti, V, Mn, Al and Mg, the mass ratio of Zn: 100 in the amorphous oxide layer One or two or more selected from Ca, Zr, Ti, V, Mn, Al, and Mg: 0.1 to 3.5, The method for producing a surface-treated steel sheet according to 5 above.

  According to the present invention, the occurrence of initial rust can be prevented over a long period of one month or longer without applying a rust preventive oil even in a harsh environment where drying and wetting are repeated in the presence of chlorine ions. Furthermore, in a mild corrosive environment such as indoors, it can be used without coating.

The present invention will be specifically described below.
First, the rust preventive film in the surface-treated steel sheet of the present invention will be described.

The outermost layer of Zn-based anticorrosion film: Amorphous oxide layer of Zn, P and Si When salt is present on the steel sheet, the electrical conductivity of condensed water and surface water film due to salts increases, the same water Steel sheets are easily corroded by complex effects such as promotion of iron ion diffusion due to complex formation in the film, destruction of the oxide film due to adsorption of chlorine ions, and persistence of moisture (condensation) due to chemical condensation. In particular, as in coastal areas, salt is likely to adhere due to the influence of incoming sea salt, and corrosion is likely to occur in a very short time in an environment where the wet and dry conditions are repeated due to changes in the temperature of day and night.

  In order to eliminate the influence of such adhering salinity, it is effective to prevent the attack of chlorine ions on the outermost surface layer of the steel sheet and to form a stable barrier film even if chlorine ions are present. In the present invention, an amorphous oxide layer of Zn, P and Si is used as the barrier film.

  As a method for forming an amorphous oxide layer of Zn, P and Si, it is conceivable to bring a steel plate into contact with a treatment liquid containing Zn, Si and P. However, with this method, a dense amorphous oxide layer cannot be formed, and the expected barrier effect cannot be expected. This is considered to be because the reactivity between the treatment liquid containing Zn, Si and P and the steel sheet surface is not good.

  Therefore, in the present invention, a metal Zn layer is formed on a steel plate in advance, and then contacted with a treatment liquid containing Si and P, whereby a dense Zn, P and Si amorphous material is formed on the outermost layer of the metal Zn layer. A quality oxide layer was formed. This is because the treatment liquid containing Si and P is rich in reactivity with metal Zn as compared with the steel sheet surface, and when contacted with the treatment liquid, the reaction can be finished uniformly and in a short time. This is because the obtained amorphous oxide layer of Zn, P, and Si has a uniform and dense layer thickness and composition.

  The oxide layer of Zn, P and Si needs to be amorphous. A crystalline film such as a zinc phosphate crystal typified by a zinc phosphate film does not necessarily have a local film, or a very thin area of the film is formed. Progress. On the other hand, the film of the amorphous oxide layer as in the present invention is homogeneous because it is amorphous, and exhibits excellent corrosion resistance.

  The metal Zn layer formed first is dissolved in the outermost layer portion by reaction with a treatment solution containing Si and P to form an amorphous oxide layer of Zn, P, and Si. It is necessary to leave the Zn layer at the interface with the steel plate. The thickness of the metal Zn layer excluding the outermost layer is preferably 10 to 700 nm. If the thickness of the metal Zn layer is less than 10 nm, red rust is likely to occur and the corrosion resistance is poor. On the other hand, if the thickness of the metal Zn layer exceeds 700 nm, Zn is excessively used, which is uneconomical and tends to cause white rust in a wet environment.

  The thickness of the outermost amorphous oxide layer is preferably 10 to 1000 nm. This is because when the thickness of the amorphous oxide layer is less than 10 nm, sufficient corrosion resistance cannot be obtained, whereas when the thickness of the amorphous oxide layer exceeds 1000 nm, the film is easily formed by bending or the like. It is because the result which peels will be caused.

Ratio of Zn, P and Si in the amorphous oxide layer: P: 2 to 30, Si: 2 to 30 with respect to Zn: 100 in mass ratio
P is believed to elute a trace amount from the amorphous oxide layer in a corrosive environment and form a dense compound with iron ions eluted by the corrosion to form a dense protective layer and suppress corrosion.
When P is less than 2 with respect to Zn: 100, sufficient corrosion resistance cannot be obtained. On the other hand, when P exceeds 30 with respect to Zn: 100, it results in easy peeling of the film by bending or the like.

In the same corrosive environment as Si, Si also elutes a trace amount from the amorphous oxide layer and is contained in the protective layer made of a compound of P and iron ions, so that the protective layer becomes denser, It seems to have an effect of improving the blocking effect and stability.
When Si is less than 2 with respect to Zn: 100, sufficient corrosion resistance cannot be obtained. On the other hand, when Si exceeds 30 with respect to Zn: 100, the film becomes thick, resulting in the result that the film is easily peeled off by bending or the like.

Ratio of additive component in the amorphous oxide layer: with respect to Zn: 100 by mass ratio, a total of one or more selected from Ca, Zr, V, Mn, Al and Mg: 0.1 to 3.5
By adding one or more components selected from Ca, Zr, V, Mn, Al and Mg to the amorphous oxide layer containing Zn, P and Si, the corrosion resistance is further improved. Can be improved. When the total of one or more selected from Ca, Zr, V, Mn, Al and Mg is less than 0.1 with respect to Zn: 100, no improvement effect is observed. On the other hand, when the total of one or more selected from Ca, Zr, V, Mn, Al, and Mg exceeds 3.5 with respect to Zn: 100, the film becomes thick and the film peels off due to bending, etc. It becomes easy to do. Therefore, the ratio of the additive component in the amorphous oxide layer is a total of one or more selected from Ca, Zr, V, Mn, Al and Mg with respect to Zn: 100 by mass ratio. The range was 0.1 to 3.5. Preferably it is the range of 0.1-2.0.

  In the present invention, the upper layer of the above-described amorphous oxide layer is further composed of an organic resin layer, an inorganic compound containing a resin component, and an inorganic component only for the purpose of improving lubricity, adhesion to a paint, and corrosion resistance. It does not deny forming a film layer or the like.

Next, the manufacturing method of the surface treatment steel plate of this invention is demonstrated.
There is no restriction | limiting in particular about the manufacturing method of the cold rolled steel plate which is a raw material of this invention, What is necessary is just to follow a conventional method.

Zn is deposited by electrolysis on the surface of a cold-rolled steel sheet manufactured by a conventional method to form a metal Zn layer. When Zn deposited is less than 100 mg / m ^2, the thickness of the metal Zn layer remaining after contact with the treatment solution containing P and Si and the amount of Zn in the amorphous oxide are insufficient, and red rust is likely to occur, resulting in corrosion resistance. to degrade. On the other hand, if Zn to be deposited exceeds 7000 mg / m ² , Zn is excessively used, which is uneconomical. Accordingly, Zn to be deposited is in the range of 100 to 7000 mg / m ^{2 in} terms of metal Zn. In addition, since the metal Zn layer remaining after the treatment tends to cause white rust in a wet environment when the thickness exceeds 700 nm, the thickness is preferably 700 nm or less.

Although there is no particular limitation on the method of forming the metal Zn layer by electrolysis, a method of electrodepositing metal Zn in an aqueous solution of sulfuric acid or the like containing a predetermined amount of Zn ions using a cold-rolled steel plate that has been pickled in advance as a cathode is suitable. is there. At this time, the anode is not particularly limited, but a Zn anode, an oxide-coated insoluble anode, or the like can be used. Electric current density of the analysis time is preferably in the range of 1~200A / dm ^2. When the current density range is less than 1 A / dm ² , a good metal Zn layer cannot be obtained. On the other hand, when the current density exceeds 200 A / dm ² , it is necessary to perform electrolysis for a very short time in order to deposit Zn with a low adhesion amount defined in the present invention, and control during operation is difficult. It becomes. Moreover, although electrolysis time changes also with current densities, the range of 0.5 to 60 second is preferable.

  Next, the contact reaction with the treatment liquid containing P and Si performed after electrolysis will be described. The treatment liquid is preferably an aqueous solution in which a substance containing P and a substance containing Si are mixed. Substances containing P include primary phosphates, water-soluble organic phosphonic acids, etc., and substances containing Si include sodium silicate aqueous solution, lithium silicate, hexafluorosilicate aqueous solution, silica sol, silane coupling Although an agent etc. are preferable, it is not limited to these.

The amount of P to be reacted with the metal Zn is in the range of 10 to 100 mg per unit area: 1 m ² . When the amount of P per unit area is less than 10 mg, there is a problem that sufficient corrosion resistance cannot be obtained. On the other hand, when the amount of P per unit area exceeds 100 mg, there is a problem that the film is easily peeled off by bending or the like.
The amount of Si to be reacted with metal Zn is in the range of 10 to 100 mg per unit area: 1 m ² . When the amount of Si per unit area is less than 10 mg, there is a problem that sufficient corrosion resistance cannot be obtained. On the other hand, when the amount of Si per unit area exceeds 100 mg, there is a problem that the film is easily peeled off by bending or the like.

In order to further improve the corrosion resistance, Ca, Zr, Ti, V, Mn, Al, and Mg are added to the above-mentioned treatment liquid, primary phosphate, carbonate, oxygenate ion, oxide sol, chelating agent. You may mix in the state of. In that case, the total amount of Ca, Zr, Ti, V, Mn, Al and Mg to be reacted with the metal Zn is preferably in the range of 1 to ²⁰ mg per unit area: 1 m ² .

  In addition to these substances, it is more preferable to further contain components such as fluorine ions and phosphoric acid in the treatment liquid. This is to enhance the etching of Zn and make it easy to incorporate as a component of the amorphous oxide layer.

  The method for contacting the treatment liquid is not particularly limited, but is dried after contacting the steel sheet surface by coating, spraying, dipping, or the like. Before drying, the thickness of the liquid film may be controlled by a method such as roll squeezing or gas squeezing as necessary. Further, when the treatment liquid is insolubilized by reaction, the soluble component may be washed with water before drying.

In mass%, C: 0.0011%, Si: 0.004%, Mn: 0.1%, P: 0.007%, S: 0.007%, Cu: 0.01%, Ni: 0.01%, Cr: 0.02%, Al: 0.025%, Nb : Cold-rolled steel sheet composed of components containing 0.002% and Ti: 0.03% Degrease, then use sulfuric acid (concentration: 98% by mass): 50g / l, humidity: 50 ° C, immersion: 10 seconds After pickling with an experimental plating device, zinc sulfate heptahydrate in a 400 g / l aqueous solution (50 ° C), with the steel plate as the cathode and the current density in the range of 5-10 A / dm ² Various changes were made to deposit Zn by electrodeposition to form a metal Zn layer. The amount of precipitation was controlled by the electrolysis time.
Next, after applying the treatment liquid shown in Table 1 to the Zn-deposited steel sheet, it was dried to form an amorphous oxide layer (some comparative examples are crystalline oxide layers, hereinafter the same). . The drying was performed using a drying furnace under the conditions of reached steel plate temperature (PMT): 110 ° C. (furnace temperature: 390 ° C., maintained for 7.7 seconds).

The properties and various properties of the coating on the steel sheet thus obtained were evaluated by the following methods.
Zn deposition amount After forming the metal Zn layer, cut out a part of the steel sheet before contacting with the treatment liquid, and wet analysis (dissolving with acid and analyzing the amount of Zn in the dissolution liquid by ICP analysis using the calibration curve method) The amount was determined. Since the amorphous oxide film (including the comparative example) according to the present invention is formed by applying the treatment liquid, the amount of Zn in the film does not change before and after the treatment. The total amount of Zn after forming the physical layer ([Zn amount in the metal Zn layer] + [Zn amount in the amorphous oxide layer]) is equal to the Zn precipitation amount. Therefore, the Zn precipitation amount was defined as the total Zn amount after the amorphous oxide layer was formed.

The thickness of the amorphous oxide layer and the thickness of the metal Zn layer The surface layer of the steel sheet was cut out by FIB processing so as to include the anticorrosion film, and the amorphous oxide layer was observed by TEM observation at any three points in the cross section And the thickness of each metal Zn layer was measured, and the average value was obtained.

Zn content in the amorphous oxide layer The Zn content in the amorphous oxide layer is the total Zn content ([Zn content in the metal Zn layer] + [in the amorphous oxide layer] The amount of Zn in the metallic Zn layer] was subtracted from the amount of Zn in the metallic Zn layer. The [Zn amount in the metal Zn layer] was calculated from the thickness of the metal Zn layer and the specific gravity of Zn (7.13 g / cm ³ ).

P and Si contents in the amorphous oxide layer Wet analysis of P and Si contents in the amorphous oxide layer in advance (dissolved with acid, and calibrate the P and Si contents in the solution) It was measured by fluorescent X-ray analysis by comparison with a calibration curve obtained by ICP analysis by the linear method.

Content of Ca, Zr, Ti, V, Mn, Al and Mg in amorphous oxide layer Content of Ca, Zr, Ti, V, Mn, Al and Mg components in amorphous oxide layer With a calibration curve obtained by wet analysis (ICP analysis of each content of Ca, Zr, Ti, V, Mn, Al, and Mg in the solution by using a calibration curve method) By comparison, it was measured by fluorescent X-ray analysis.

Proportions of Zn, P and Si in the amorphous oxide layer The proportions when the Zn content in the amorphous oxide layer was 100 were determined by mass ratio for P and Si, respectively.

Ratio of Ca, Zr, Ti, V, Mn, Al, and Mg in the amorphous oxide layer The ratio when the Zn content in the amorphous oxide layer is 100 is expressed as Ca, Zr, Ti, V, It calculated | required by mass ratio about Mn, Al, and Mg, respectively.

Crystallinity of amorphous oxide layer The oxide layer on the surface of the steel sheet was identified by X-ray diffraction. If there was no peak indicating a crystalline compound other than Fe and Zn, the oxide layer was judged to be amorphous.

Initial Rust Resistance A steel plate was sheared to a size of 70 mm × 70 mm, one of the four end faces and the coating surface was sealed, and a red rust generation test was conducted. The test procedure and evaluation criteria are as follows.
Artificial sea salt was dissolved in ion-exchanged water to make an aqueous solution with a concentration of 0.035% by mass, sprayed onto the steel plate after sealing, and dried to adhere a salt content of 100 mg / m ² . Next, this steel sheet was put in an environmental test machine, and dried (temperature: 60 ° C, relative humidity: 35%): 3 hours → wet (temperature: 40 ° C, relative humidity 95%): corrosion test with 3 hours as one cycle. went. The transition time of drying → wetting or wetting → drying is set to 1 hour, and 3 cycles of drying and drying are repeated per day, and the number of days until the area where red rust occurs reaches 5% of the exposed area is investigated. It was evaluated as follows.
◎: 30 days or more ○: 10 days or more and less than 30 days △: 5 days or more and less than 10 days ×: Less than 5 days

Film adhesion The state of the film was investigated by bending the sample (OT bending) and observing the bent part with SEM. If the film is cracked but is attached to the steel sheet, ◎, if the film is cracked but almost attached to the steel sheet, ○, the film is broken and slightly lifted In some cases, the evaluation was Δ, and in the case where the film was broken and floated, the evaluation was ×.

  The results are shown in Tables 2-1 and 2-2. In the table, the type of treatment liquid used for the production of each sample is shown using the symbols in Table 1.

As shown in the table, according to the present invention, the surface-treated steel sheet in which an amorphous oxide layer of Zn, P, and Si is formed on the outermost layer of the Zn-based anticorrosion film is 10 The occurrence of red rust was not observed over the above-mentioned long period, and good initial rust preventive properties were exhibited.
In contrast, the comparative examples of Samples Nos. 2, 4, 13, 28 and 29 have a low content of P or Si in the amorphous oxide layer, and Sample No. 32 has the amorphous oxide layer. The sample thickness was less than 10 nm, and Sample No. 33 did not show sufficient initial rust prevention properties because the oxide layer was crystalline.
Samples Nos. 3, 5, and 15 have a comparative example in which the content of P or Si in the amorphous oxide layer and the ratio of P and Si when Zn in the amorphous oxide layer is 100 Since it was small, the adhesion was not satisfied.
The comparative examples of Samples 30 and 31 are those in which the metal Zn layer is not present or very thin, and the treatment liquid containing Zn, P and Si is directly contacted without precipitating Zn on the steel plate surface in advance. Although it was, it was remarkably inferior to initial rust prevention property compared with the invention example.
In Sample No. 15, since the thickness of the amorphous oxide layer exceeded 1000 nm, the film was easily peeled off by bending.
For reference, a conventional example having only a metal Zn layer and no oxide layer is also shown as sample No. 34 in the same table, but its initial rust prevention property was a Δ level in 5 days. Moreover, although the conventional example which formed the barrier film containing P and Si on the steel plate surface according to patent documents 7 and 8 was written together in the same table as sample No. 35-38, the initial rust prevention property is △ in 5 days. It was a level.

Claims (6)

  A surface-treated steel sheet having a rust preventive film based on Zn on the surface of the steel sheet, wherein the outermost layer of the rust preventive film is composed of an amorphous oxide layer of Zn, P and Si. steel sheet.   The ratio of Zn, P, and Si in the amorphous oxide layer satisfies P: 2 to 30 and Si: 2 to 30 with respect to Zn: 100 by mass ratio. The surface-treated steel sheet described in 1.   The amorphous oxide layer further contains one or more selected from Ca, Zr, Ti, V, Mn, Al and Mg in a mass ratio of 0.1 to 3.5 with respect to Zn: 100. The surface-treated steel sheet according to claim 2, wherein the steel sheet is contained in a proportion of   The surface-treated steel sheet according to any one of claims 1 to 3, wherein the amorphous oxide layer has a thickness of 10 to 1000 nm. On the surface of the cold-rolled steel sheet, Zn is electrolyzed to deposit 100 to 7000 mg / m ^{2 in} terms of metal Zn to form a metal Zn film, and then a treatment solution containing P and Si is brought into contact with the metal Zn film and a unit area. : By reacting 10 to 100 mg of P with 10 to 100 mg of Si per 1 m ^2, the outermost layer of the metal Zn film has a mass ratio of Zn: 100, P: 2 to 30 and Si: 2 A method for producing a surface-treated steel sheet, comprising forming an amorphous oxide layer composed of Zn, P and Si containing ~ 30. The treatment liquid further contains one or more selected from Ca, Zr, Ti, V, Mn, Al and Mg, and the metal Zn film and unit area: 1 to ²⁰ mg per 1 m ² By reacting with one or more selected from Ca, Zr, Ti, V, Mn, Al and Mg, the mass ratio of Zn: 100 in the amorphous oxide layer One or more selected from Ca, Zr, Ti, V, Mn, Al, and Mg: 0.1 to 3.5. The method for producing a surface-treated steel sheet according to claim 5.