JPH0213040B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is applicable to the production of single-sided electroplated steel sheets.
The present invention relates to a post-treatment method for improving the phosphate treatment properties of non-plated surfaces. (Prior Art) As a recent trend in automotive steel sheets, single-sided galvanized steel sheets have been mainly used. This is done by applying a plating surface to areas where the paint does not adhere sufficiently, such as the inside of the car body.
Non-plating surfaces (hereinafter referred to as iron surfaces) are applied to areas that are easy to paint, such as the exterior of the vehicle body, and are assembled and used. This single-sided plated steel sheet is usually manufactured by Zn-based hot-dip plating or electroplating, but the electroplating method is generally used because it allows a high degree of freedom in workability of the original plate. Plated steel sheets used for automobiles and the like are generally subjected to electrodeposition coating, followed by intermediate coating and top coating, and therefore phosphate treatment is usually performed as a base treatment for these coatings. (Problem to be Solved by the Invention) The iron surface of a single-sided electroplated steel sheet corrodes due to contact with a plating bath during the single-sided electroplating process, and as a result, corrosion products are generated on the surface. Not only does this discolor and impair the appearance quality, but also the formation of a phosphate film is inhibited, resulting in a deterioration in coating performance. In response, many methods have been studied for manufacturing iron surfaces. For example, (1) the method of removing plating by brushing after plating has a removal effect, but since plating that is softer than steel plate, such as galvanizing, cannot be removed sufficiently, the quality is only improved to a certain extent. Also,
Not only does the cost of brushing equipment increase, but depending on the degree of polishing, the size of phosphate crystals during phosphate treatment may become uneven, impairing phosphate treatment properties and reducing paintability (finish appearance and corrosion resistance).
adversely affect. (2) After plating, the plating metal and corrosion products are removed by electrolytic pickling in an acid, and then a very small amount of a specific metal such as Ni is dispersed and precipitated on the surface, followed by plating. There are ways to improve processing performance. However, in order to deposit a specific metal only on the iron surface, specific equipment is required, which not only increases costs, but also because an acidic plating bath is usually used. This may cause melting or discoloration of the plated metal, which may greatly reduce the commercial value of the single-sided plated steel sheet. (Example: Tokuko Sho 60
-7713) (3) After plating, there is a method of performing anodic electrolysis treatment in an electrolytic bath to remove plating metals and corrosion products and forming a passive film to improve phosphate treatment properties. However, the passive film is difficult to control under electrolytic treatment conditions (e.g., electrolytic bath composition, current density, electrolytic time, etc.).
Since the film thickness and film composition change depending on the temperature (bath temperature, etc.), the effect of improving phosphate treatment properties is unstable. (Examples: JP-A No. 59-56600, JP-A No. 59-96292) In order to meet the above-mentioned needs, the present invention has been developed in addition to the conventional method of simply removing corrosion products generated on iron surfaces by anodic electrolysis treatment, etc. The present invention provides a method for stably producing a single-sided electroplated steel sheet having an iron surface with good phosphate treatment properties and paintability. (Means for Solving Problems) As a result of intensive studies, the present inventors have developed an extremely excellent electrolytic treatment method. The present invention uses a conductive bath with a pH of 3 to 7 containing a sulfur compound having an arcuate electron pair and a metal oxide ion to coat the iron surface of a single-sided electroplated steel sheet in an electrolytic region where an oxygen energizing reaction occurs. After the corrosion products on the iron surface are removed by anodic electrolysis, the non-plated surface is subsequently brought to a non-charged state in a bath containing the conductive bath, and the products are removed from the non-plated surface by the electrolysis. A method characterized by improving the phosphatability of a steel surface by removing a passive film and adsorbing the sulfur compound onto the steel surface. After that, the above electrolytic treatment is applied to the iron surface. (2) In the production of single-sided electroplated steel sheets, a method in which the steel surface is also plated with a light coating weight to protect the steel surface from corrosion, and the above electrolytic treatment is applied to the steel surface after plating. (3) When performing chromate conversion treatment on the plated surface in the production of single-sided electroplated steel sheets, after applying a light weight plating to the iron surface to prevent contamination of the iron surface by the chromate conversion treatment bath. , is a method of performing the above processing. As a result, a single-sided electroplated steel sheet having an iron surface with good phosphate treatment properties, paintability, and surface appearance can be stably produced. (Function) Next, the contents will be described in detail. In the present invention, any conductive bath may be used as the electrolytic bath, e.g.
Na ₂ SO ₄ , Na ₂ CO ₃ , K ₂ SO ₄ , K ₂ CO ₃ ,
A mixture of NaH ₂ PO ₄ , Na ₂ HPO ₄ , Na ₃ PO ₄ , H ₃ PO ₄ , boric acid, borate, or any other chemicals may be used, but the bath should be carried out in a pH range of 3 to 7. It is necessary. If the pH is less than 3, the dissolution of the iron surface substrate becomes large, and the effect of improving the phosphate treatment properties of the sulfur compound having an erect electron pair becomes small. Also, plated surfaces exposed to the same bath may dissolve and deteriorate quality.
PH3 or higher is required. If the pH exceeds 7, it becomes difficult to remove corrosion products and thin plating on the iron surface, and the automatic reductive dissolution of the passive film described below is difficult to occur, resulting in deterioration of phosphate treatment properties, so the pH should be lower than 7. is necessary. In the anodic electrolysis in the pH range of the present invention, the iron surface of the base material is at a potential in the hyperpassive region, so there is little elution of iron, almost no etching of the iron surface, and almost no deterioration of the bath. Further, corrosion products generated on the iron surface are removed by a slight dissolution reaction of the iron surface and an intense oxygen generation reaction in the overpassive region of the iron surface. Also,
A thin coating for protecting the iron surface is removed from the iron surface by a hyperpassive reaction on the iron surface. The current density varies depending on the composition, pH, temperature, etc. of the electrolytic bath, but a current density of 2 A/dm ² or more is required to make the iron surface hyperpassive. The amount of electricity varies depending on the amount of corrosion products and the amount of thin plating, but 10 clones/dm ² or more is required to clean the iron surface. Next, a sulfur compound having an arc pair of electrons (hereinafter referred to as a sulfur compound) will be described. Sulfur compounds play the most important role in improving the phosphating properties of iron surfaces. Sulfur compounds that improve the phosphate treatment properties of iron surfaces are shown in Table 1.

【table】

[Table] is a compound that has an amino group mercaptans, thiocyanates, sulfides, disulfides, or thiocarbonyl groups (thioureas, thiocarbonyls, dithiocarbamates), and the sulfur element has an arc electron pair. It is characterized by being a compound that has The present inventors have discovered that these sulfur compounds are adsorbed onto iron surfaces, which are clean metal surfaces, and have the effect of significantly improving phosphate treatment properties. However, the adsorption of sulfur compounds onto iron surfaces
In order to chemically adsorb according to the HSAB rule, the iron surface must be a clean metal surface, and the presence of oxides such as passive films inhibits the adsorption of sulfur compounds. Therefore, corrosion products generated on the iron surface are removed by anodic electrolysis treatment,
It is an effective method to purify the iron surface, but as mentioned above, this anodic electrolytic treatment is electrolysis in the hyperpassive region, so a passive oxide film is formed, which must be removed. Become. As a result of various studies, the present inventors found that after anodic electrolysis,
It has been found that the passive film can be most easily removed by keeping it in an uncharged state in the bath. That is, by making the iron surface uncharged in a conductive bath similar to that used in anodic electrolysis, an automatic reductive dissolution reaction of the passive film generated during the anodic electrolytic treatment is caused, and the passive film is removed. This is the most effective method for promoting adsorption of sulfur compounds and improving phosphate treatment properties by providing a clean metal surface. Although the effect of adsorbed sulfur compounds on improving phosphate treatment properties has not been fully elucidated, it is believed to be due to the following reasons. As a pretreatment for phosphate treatment, surface conditioning is performed with a liquid containing titanium colloid. Titanium colloids and the like are adsorbed onto the surface of the steel sheet, serve as precipitation nuclei for phosphate crystals, and have the effect of forming a dense phosphate film. At this time, it is thought that the sulfur compounds adsorbed on the iron surface promote the adsorption of titanium colloids, etc., or that the adsorbed sulfur compounds act as direct nuclei for the precipitation of phosphate crystals. This sulfur compound is one of the compounds shown in Table 1.
Contains a species or two or more species, the concentration of which is 10 ^-5 mol/
If it is less than that, there is no improvement in phosphate treatment properties. Also, from an economic point of view, it is effective even if it exceeds ¹⁰⁰ .
Less than that is desirable. Next, the reason why the anodic electrolytic treatment is followed by an uncharged state is to remove the passive film by causing an automatic reductive dissolution reaction of the passive film. As a result, the iron surface becomes a clean metal surface, and since adsorption of sulfur compounds occurs quickly, stable and good phosphate treatment can be obtained. On the other hand, in cases where the electrolyzer is washed with water immediately after anodic electrolysis, or in the vertical electrolytic cell shown in FIG. When a steel surface is anodically electrolyzed in bath 4, if a current flows around the iron surface after electrolysis as shown in the direction of the arrow and becomes charged, a passive film exists on the iron surface and the sulfur No adsorption of compounds occurs. The time required to reach an uncharged state depends on the automatic reduction dissolution reaction rate of the passive film, the thickness and composition of the passive film, and therefore depends on the metal electrolysis conditions (current density, quantity of electricity).
Although it is affected by the electrolytic bath conditions (PH, temperature, composition), etc., it is usually 0.5 to 10 seconds. The pH in this case is
A lower pH value is advantageous, but a pH lower than 3 is regulated by anodic electrolytic treatment, and a pH higher than 8 requires a long time, which significantly reduces productivity, so a pH lower than that is required. The presence or absence of a passive film can be determined by measuring the immersion potential of the iron surface. In other words, as shown in FIG. 2, the result of measuring the immersion potential of the iron surface after anodic electrolysis is that the immersion potential is high at the beginning of the measurement, but becomes rapidly low after a period of time. This indicates that the passive film (high immersion potential) disappeared and became bare iron (metallic state; low immersion potential). Point A in FIG. 2 indicates the time for the passive film to disappear. Next, the reason for performing cathodic electrolysis treatment after anodic electrolysis treatment is to reduce and remove the passive film generated by anodic electrolysis in the overpassive film area, adsorb sulfur compounds on the iron surface, and produce stable and good phosphoric acid. This is to obtain salt treatment properties. In this case, the current density needs to be 0.1 A/dm ² or more, and if it is less than that, it will take a long time. The amount of electricity required is 0.1 clone/dm2 ^or more,
If it is less than that, the reduction and removal of the passive film will be incomplete and the sulfur compound will not be uniformly adsorbed, resulting in an insufficient improvement in phosphate treatment properties. The reason for adding metal oxide ions is as follows. Generally, when performing electrolytic treatment, (1) the bath is stirred to prevent voltage increase due to gas bubbles generated in the electrolytic reaction; (2) In a continuous production line, the steel strip to be treated moves into the treatment bath, so a relative bath flow rate occurs. etc., a relative bath flow velocity occurs between the iron surface and the conductive bath. When this relative bath flow rate increases, dissolution of iron, which is one of the anodic electrolytic reactions, increases, and as a result, the phosphate film tends to become amorphous and the phosphate treatment properties deteriorate. In order to prevent this phenomenon, it is necessary to suppress the dissolution of iron during anodic electrolysis. As a result of intensive studies, the present inventors found that molybdate ion, titanate ion, tungstate ion, vanadate ion, selenate ion, stannate ion, antimonate ion, zirconate ion, tantalate ion, niobate ion, It has been found that metal oxide ions such as bismuthate ions are effective. These metal oxide ions have the effect of passivating iron during anodic electrolysis, and as a result, the elution of iron is significantly suppressed, so the action of sulfur compounds becomes normal, and it shows good phosphate treatment properties. Become. Among metal oxide ions, chromate ions and manganate ions have a strong effect of passivating iron, so they are generated during anodic electrolysis and the passive film is reduced and removed during the non-electrostatic immersion that follows after anodic electrolysis. This is not suitable because the phosphate treatment becomes difficult and the phosphate treatment deteriorates significantly as a result. As shown in Figure 3, the amount of metal oxide ions is determined by the relationship between flow velocity and phosphate treatment properties, but roughly speaking, when the flow velocity is 0.05 m/s or more,
If it is less than 10 ^-3 mol/mol, the dissolution of iron during anodic electrolysis will be insufficient, resulting in deterioration of phosphate treatment properties, so it is necessary to use 10 ^-3 mol/or more. Also 5×10 ^-1
If the amount exceeds mol/mol, the passive film formed during anodic electrolysis becomes strong, making it difficult to remove the passive film by subsequent immersion in a non-electrostatic state, and as a result, the phosphate treatment property deteriorates significantly. ^10-1
mol/or less is required. In addition, a higher bath temperature is advantageous in shortening the disappearance time of the passive film in the non-electrostatic state, but on the other hand, the stabilization of the passive film by metal oxide ions also occurs, so it is suitably 60°C or lower. is desirable. The amount of thin coating on the non-plated surface according to claim 2 is required to be 0.1 g/m ² to 5 g/m ² . i.e. 0.1
If it is less than g/m ² , the steel surface cannot be protected against corrosion in the plating bath. Moreover, if it exceeds 5 g/m ³ , it is uneconomical because a more than necessary amount of electricity is required during anodic electrolytic treatment to remove it. (Example) Next, an example of the present invention will be described. Embodiment 1 FIG. 4 is an installation layout diagram of an example of the present invention in the production of continuous single-sided electroplated steel sheets. Uncoiler 5
After passing through the degreasing tank 7, washing tank 8, pickling tank 9, and washing tank 8 for pre-plating treatment, the plated steel sheet 2 unwound from After electroplating and washing with water in washing tank 8,
After being subjected to the electrolytic treatment of the present invention and a process to make it uncharged in order to remove the passive film in an electrolytic bath 11 and a non-charged immersion bath 12, it is passed through a washing tank 8 and a dryer 13 and then wound up in a recoiler 14. . Table 2 shows examples and comparative examples of the present invention. Embodiment 2 FIG. 4 is an installation layout diagram of an example of the present invention in the production of continuous single-sided electroplated steel sheets. After passing through the degreasing tank 7, washing tank 8, pickling tank 9, and washing tank 8 for pre-plating treatment, the plated steel plate 6 unwound from the uncoiler 5 passes through the plating tank 10 using an acidic zinc-based plating bath. After applying electroplating to one side and applying a light coating to the iron surface, after washing with water in washing tank 8, electrolytic cell 1
1 and a non-charged immersion tank 12 to perform the electrolytic treatment of the present invention and a process to make the film into a non-charged state in order to remove the passive film, and then passed through a washing tank 8 and a dryer 13 to be wound up in a recoiler 14. Table 3 shows examples and comparative examples of the present invention. Embodiment 3 FIG. 5 is an installation layout diagram of an example of the present invention in the production of continuous single-sided electroplated steel sheets. Uncoiler 5
After passing through a degreasing tank 7, a washing tank 8, a pickling tank 9, and a washing tank 8 for pre-plating treatment, the plated steel plate 6 is rewound from the plating tank 10, where it is coated on one side using an acidic zinc-based plating bath. After applying electroplating to the iron surface and applying plating to a light coating weight on the iron surface, it is washed with water in the washing tank 8, and then chromate treatment is applied to the plated surface in the chemical conversion treatment tank 15. After washing with water, the electrolytic treatment of the present invention is carried out in an electrolytic bath 11 and a non-charged immersion bath 12, and the treatment is carried out to make it into a non-charged state in order to remove the passive film. 14
It is wound up. Table 3 shows examples and comparative examples of the present invention. Note that the electrolytic cell and the non-charged immersion tank used were the apparatus shown in FIG. 6. In the electrolytic bath 11, move the single-sided plated steel plate 2 in the direction of the arrow and remove the conductor roll 1.
is an anode, anode 3 is a cathode, and a conductive bath 4
After the iron surface is subjected to anodic electrolysis treatment, it is subsequently passed through a non-charged immersion tank 12 filled with a conductive bath 4 to remove the passive film and adsorb sulfur compounds, thereby converting the iron surface into phosphoric acid. Improved salt treatment properties. The accumulating bath used in Examples 1 to 3 was (1) ZnSO ₄ 7H ₂ O 200g/L, H ₂ SO ₄ 25g/L,
Na ₂ SO ₄ 100g/L, bath temperature 60℃, line speed
Zn plating of 30 g/m ² was carried out at 100 m/min. (2) ZnSO ₄・7H ₂ O 250g/L, NiSO ₄・6H ₂ O 100
g/L, H ₂ SO ₄ , 15g/L, Na ₂ SO ₄ 100g/L, bath temperature
20g/ ^m2 Zn at 60℃ and line speed 80m/min
-12% Ni plating was performed. (3) ZnSO ₄・7H ₂ O 200g/L, FeSO ₄・7H ₂ O 100
g/L, H ₂ SO ₄ 10g/L, (NH ₃ ) ₂ SO ₄ 20g/L, 20g/m ² at bath temperature 60℃, line speed 80m/min.
Zn−20%Fe plating was performed. Chromate treatment: chromic acid 30g/L, sulfuric acid 0.1
g/L, electricity amount 30 clones/dm ² using bath temperature 40℃
60mg/m ² of chromium on the plating surface after cathodic electrolysis treatment with
Attached. At this time, 8 mg/m ² of chrome was deposited on the thin plating surface applied to the iron surface. The evaluation method for samples in Examples and Comparative Examples is as follows. The evaluation of phosphate treatment properties is easily affected by the surface properties of the steel sheet.Bt 3118 is a spray-type phosphate treatment agent.
(manufactured by Nippon Parkerizing Co., Ltd.). The treatment method is degreaser FC4328A, concentration 15g/L, bath temperature 55
℃, treatment time 120 seconds after spray degreasing, washing with water, and then using Bt3118 with total acidity 15-17 points,
Free acidity 0.4-0.7 points, accelerator concentration 1.5-2.0
A bath prepared with Zn ²⁺ of 1000 to 800 ppm was used. The phosphate film formed on the steel plate by the above treatment is (1)
Film amount: 1.5-2.0g/m ² (2) Crystal size: 10-20 microns
(3) A P ratio of 0.6 or more is good. Paint corrosion resistance was evaluated using the following salt spray test. The phosphate-treated steel plate was manufactured by Nippon Paint Co., Ltd.
Cationic electrodeposition paint Power Top U50 from 20~
After applying a 23 micron electrodeposition coating and baking it at 180℃ for 30 minutes, a cross cut was made to reach the substrate using a sharp knife, and after conducting a 1000 hour salt spray test according to JIS-2371, the cross cut part was peeled off with cellophane tape. The peeling width was measured. The smaller the peeling width,
Paint has good corrosion resistance. Next, the present invention in each example and a comparative example will be compared and explained. Table 2 shows examples related to claim 1. Examples 1, 2, and 3 of the present invention exhibit good performance equivalent to that of the cold rolled steel sheet of Comparative Example 5, whereas Comparative Example 4 to which the present invention is not applied, Comparative Example 1 with a small amount of sulfur compounds, and anodic electrolysis Comparative Example 2, in which the current density and quantity of electricity were low, and Comparative Example 3, in which the electrolytic bath PH was high, the time in the uncharged state was long, and the passive film was incompletely removed, had poor phosphate treatment properties, paint corrosion resistance, and appearance. is inferior. Table 3 is an example regarding claim 2. Inventions 4, 5, 6, and 7 show good performance equivalent to that of the cold-rolled steel sheets in Table 2, whereas Comparative Example 6 has a low pH in the electrolytic bath, and Comparative Example has a short period of uncharged state. No. 7 has poor phosphate treatment properties and paint corrosion resistance. Table 4 is an example regarding claim 3. Inventive Examples 8 and 9 show good performance equivalent to the cold-rolled steel sheets in Table 2, whereas Comparative Example 8, in which the steel surface was contaminated with chromate bath due to the small coating weight, has good phosphate treatment properties. , paint corrosion resistance is poor. Comparative Example 9 Due to the small amount of metal oxide ions,
Part of the phosphate film becomes amorphous, resulting in poor phosphate treatment appearance and slight deterioration in paintability. Comparative Example 10 has a large amount of metal oxide ions, so
Comparative Example 11 had poor phosphate treatment properties and paint corrosion resistance due to the high bath temperature.

【table】

【table】

【table】

【table】

【table】

[Table] (Effects of the Invention) As described above, the present invention allows the iron surface of a single-sided electroplated steel sheet to be subjected to anodic electrolysis treatment in a conductive bath containing a certain amount of sulfur compound and in a specific pH range, and then to be uncharged. By performing post-treatment to condition the iron surface, it removes corrosion products adhering to the iron surface, prevents corrosion of the iron surface in the plating bath, and also prevents chemical conversion of chromate on the plating surface. It is possible to prevent the iron surface from being contaminated during treatment and easily create a clean iron surface, and it is also possible to create an iron surface that exhibits excellent phosphate treatment properties, paint corrosion resistance, and stable appearance. This is an advantageous method for producing single-sided electroplated steel sheets.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view of a vertical electrolytic cell, and FIG. 2 shows the relationship between the immersion potential of the iron surface and time. FIG. 3 shows the relationship between relative bath flow rate and metal oxide ion concentration. FIG. 4 is an equipment layout diagram relating to the present invention in the production of continuous single-sided electroplated steel sheets. FIG. 5 is another installation layout of the present invention in the production of continuous single-sided electroplated steel sheets. FIG. 6 is an explanatory diagram of an electrolytic bath and a non-charged immersion bath. 1... Conductor roll, 2... Single side plated steel strip, 3... Electrode, 4... Conductive bath, 5... Uncoiler, 6... Plated steel plate strip, 7... Degreasing tank, 8... Water washing tank, 9... Pickling tank , 10... plating bath, 11... electrolytic bath, 12... non-charged immersion bath, 13... dryer, 14...
Recoiler, 15...Chemical treatment tank.

Claims (1)

[Scope of Claims] 1. In the production of single-sided electroplated steel sheets, after plating, the non-plated surface is treated with a concentration of 10 ^-5 to 10 ⁰ mol containing one or more sulfur compounds having arcuate electron pairs. PH containing one or more types of / and metal oxide ions at a concentration of 10 ^-3 to 5 × 10 ^-1 mol/
Using a conductive bath of 3 to 7, conduct anodic electrolysis of 10 clones/dm ² or more in an electrolytic region where an oxygen evolution reaction of 2 A/dm ² or more occurs, and then perform anodic electrolysis of 0.5 to 10 clones/dm 2 or more in a bath containing the conductive bath. Leave the non-plated surface uncharged for seconds,
A single-sided electrolytic lamp characterized in that the phosphate treatment property of the non-plated surface is improved by removing the passive film formed on the non-plating surface by the electrolysis and adsorbing the sulfur compound to the non-plating surface. Method for producing steel plate. 2 In the production of single-sided electroplated steel sheets, one side is plated and the other non-plated surface is also plated with a light coating weight, and then the non-plated side is plated with a light coating weight. A concentration of 10 ^-5 to ¹⁰⁰ mol containing one or more sulfur compounds having an arc electron pair/a concentration of 10 ^-3 to 5×10 ^-1 containing one or more metal oxide ions PH3 containing mol/
Using a conductive bath of ~7, conduct anodic electrolysis at 10 clones/dm ² or more in an electrolytic region where an oxygen evolution reaction of 2 A/dm ² or more occurs on the non-plated surface to remove light plating, 0.5~ in a bath containing the conductive bath.
The non-plated surface is left uncharged for 10 seconds to remove the passive film formed on the non-plated surface by the electrolysis,
A method for producing a single-sided electroplated steel sheet, characterized in that the sulfur compound is adsorbed on the non-plated surface to improve phosphate treatment properties of the non-plated surface. 3. In the production of single-sided electroplated steel sheets, one side is plated and the other non-plated side is plated with a light coating weight, then chromate treatment is applied to one side, and the non-plated side is plated. The non-plated surface of the thin-metal plated surface, on which chromate has unavoidably adhered to the thin-metal plated coating, is treated with one or more sulfur compounds having arcuate electron pairs at a pH of 3 to 8. Concentrations ranging from 10 ^-5 to ¹⁰⁰ mol/1 of metal oxide ions
Contains a species or two or more species at a concentration of 10 ^-3 to 5 x 10 ^-1 mol/. Using a conductive bath with a pH of 3 to 7, perform anodic electrolysis at 10 clones/dm ² or more in an electrolytic region where an oxygen generation reaction of 2 A/dm ² or more occurs on the non-plated surface to remove light plating. Then, the non-plated surface is left uncharged in a bath containing the conductive bath for 0.5 to 10 seconds to remove the passive film formed on the non-plated surface by the electrolysis and remove the sulfur compound. A method for producing a single-sided electroplated steel sheet, characterized in that the phosphate treatment properties of the non-plated surface are improved by adsorption to the non-plated surface.