JP4635638B2 - Phosphate-treated electrogalvanized steel sheet with excellent corrosion resistance and blackening resistance - Google Patents

Description

The present invention relates to a suitable surface treatment steel sheet for building materials and home appliances such as, in particular, of a preferred phosphating galvanized steel sheet as a paint substrate steel sheet.

Zinc-based galvanized steel sheets that have been subjected to surface treatment such as galvanization or zinc alloy plating are used in parts that require corrosion resistance in the use of building materials, home appliances, and the like. These galvanized steel sheets are rarely used as they are, and are usually used after being painted. When coating is performed, chemical conversion treatment such as phosphate treatment and chromate treatment is performed as a pretreatment.
Phosphate treatment is a treatment in which an acidic solution containing phosphate ions and a zinc-based plated steel sheet are brought into contact with each other and reacted to form a crystalline film mainly composed of zinc phosphate on the plating surface. Adhesion with the paint and stable paint base performance for various types of paint. For this reason, the zinc-based plated steel sheet to which the phosphate treatment has been applied has been widely used as a base steel sheet for coating for building materials, home appliances and the like.

  However, since the phosphate treatment alone has insufficient corrosion resistance, a sealing treatment called “sealing treatment” has been usually performed after the phosphate treatment. This sealing treatment is a treatment in which a hexavalent chromium-containing aqueous solution is brought into contact with the steel plate by a method such as spraying or dipping, and then dried without washing with water. This treatment improves the corrosion resistance. However, since hexavalent chromium is an environmentally regulated substance, there has been a demand for measures for improving the corrosion resistance of the phosphate-treated film instead of the “sealing treatment” using this hexavalent chromium-containing aqueous solution.

  In response to such a demand, for example, Patent Document 1 discloses a corrosion resistance having a crystalline phosphate-based chemical conversion coating layer on the surface of the zinc-based plating layer and an amorphous phosphate-based coating thereon. An excellent surface-treated steel sheet has been proposed. Patent Document 2 discloses that a zinc phosphate-treated film is formed on the surface of a zinc-containing plated steel sheet, and an upper layer thereof includes at least one metal compound selected from a copper compound, a titanium compound, and a zircon compound. Or a non-chromium with excellent corrosion resistance and paint adhesion having a sealing film obtained by applying and drying a liquid composition containing a polycondensation resin compound of bisphenol A, amines and formaldehyde, and water A zinc phosphate-treated steel sheet has been proposed. The techniques described in Patent Document 1 and Patent Document 2 are sealing processes that do not use chromium at all.

Patent Document 3 discloses a film made of a phosphate compound containing a Zn-based plating layer formed on the surface of a metal material and further containing 0.1 wt% or more, preferably 5 wt% or less of Mg on the plating layer. A formed surface-treated steel sheet has been proposed. In the technique described in Patent Document 3, the corrosion resistance is improved by adding 0.1 wt% or more of Mg in the phosphate film.
Patent Document 4 discloses that the zinc phosphate coating contains Mg of 2% or more, 0.01 to 1% of one or more elements selected from Ni, Co and Cu, and an adhesion amount of 0.7 g / m ^2. A zinc phosphate-treated zinc-based plated steel sheet having excellent corrosion resistance and color tone as described above has been proposed.
JP 2000-313967 A JP 2004-143475 A Japanese Unexamined Patent Publication No. 1-312081 JP 2002-285346 A

  However, the techniques described in Patent Documents 1 and 2 are sealing treatments that do not use chromium at all. In either case, in the process of forming the uppermost layer film, a water-soluble chemical solution is applied, followed by baking by heating. This is an economic problem in that in addition to the existing phosphatized galvanized steel sheet manufacturing equipment, new coating equipment and baking equipment for applying these chemicals are required, leading to an increase in manufacturing costs. Was leaving.

  On the other hand, in the techniques described in Patent Document 3 and Patent Document 4, the corrosion resistance of the phosphating film itself can be improved without sealing treatment. However, in the technique described in Patent Document 3, since the upper layer film contains Mg, the surface may turn black when exposed to a high-temperature and high-humidity environment. It was. Further, in the technique described in Patent Document 4, the surface of the zinc phosphate film may change to black when exposed to a high-temperature and high-humidity environment by containing a large amount of Mg. At the same time, there is a problem that the color tone of the zinc phosphate coating becomes dark when Ni, Co, and Cu are contained in the zinc phosphate coating at a high concentration.

The present invention is conventionally in view of the art problems, without performing a sealing treatment using chromium, it has a conventional sealing process and corrosion resistance equivalent to, yet good phosphating galvanized steel sheet blackening resistance The purpose is to propose.

  In order to achieve the above-described problems, the present inventors diligently studied factors that affect the corrosion resistance and blackening resistance of a phosphate-treated galvanized steel sheet. As a result, as a phosphate-treated galvanized steel sheet that can achieve the above-mentioned problem, in the specification of Japanese Patent Application No. 2004-240782, a galvanized layer comprising a single phase of η phase containing a predetermined amount of Ni on the steel sheet surface And a phosphate-treated galvanized steel sheet having a phosphate-treated layer containing a predetermined amount of Mg as an upper layer. This phosphate-treated galvanized steel sheet has excellent corrosion resistance and excellent blackening resistance, but it is necessary to form a galvanized layer consisting of a single phase of η phase containing a predetermined amount of Ni on the steel sheet surface. is there. Such a galvanized layer can be easily formed by adding an appropriate amount of Ni ions to the plating solution when formed by electrogalvanizing, but is formed by hot dip galvanizing. In some cases, there was a problem that it was not so easy.

  Therefore, the present inventors have intensively studied various factors affecting the corrosion resistance and blackening resistance of the phosphate-treated galvanized steel sheet. As a result, they have come up with a small amount of Ni adhesion between the galvanized layer and the phosphate-treated layer. After forming a galvanized layer on the surface of the steel plate, a surface on which a small amount of Ni adhesion is formed on the surface of the galvanization layer, and a phosphate treatment layer containing a predetermined amount of Mg is further formed on the Ni adhesion By adopting a treatment layer structure, both corrosion resistance and blackening resistance are improved, without requiring a sealing treatment, and without containing Ni in the galvanized layer, phosphorus having excellent corrosion resistance and blackening resistance. It was newly found that an acid-treated galvanized steel sheet can be obtained.

The present invention has been completed based on the above findings and further studies. That is, the present invention is a phosphate treated galvanized steel sheet having a phosphate treatment layer on at least one surface as an upper layer of the galvanized layer and the electro-galvanized layer of the steel sheet, the galvanized layer When characterized by being obtained by forming a Ni deposition of 0.1 to 500 mg / m ² in the middle of the phosphating layer, it is a phosphate treated galvanized steel sheet excellent in corrosion resistance and blackening resistance the phosphating layer you containing 0.1% by mass to less than 2.0 mass% of Mg. In the present invention also adhesion amount of the zinc plating layer, 1 g / ^{m 2} or more 100 g / ^{m 2} Ru der below. In the present invention, the amount of the phosphate treatment layer deposited is preferably 0.2 g / m ² or more and 3 g / m ² or less.

Moreover, the manufacturing method of the phosphating galvanized steel sheet of the present invention includes a galvanizing process step for forming a galvanized layer on at least one surface of the steel sheet, and a galvanized layer formed in the galvanizing process step. As a top layer, a phosphating treatment step of forming a phosphating treatment layer in order, a method of manufacturing a phosphating galvanized steel sheet, after the galvanizing treatment step and before the phosphating treatment step The steel sheet on which the galvanized layer is formed is brought into contact with an aqueous solution containing Ni ions to displace and precipitate Ni on the surface of the galvanized layer, or more actively, the steel sheet on which the galvanized layer is formed is used as a cathode. Including a Ni adhering portion forming treatment step of forming a trace amount of Ni adhering portion on the surface of the galvanized layer by electrolyzing in an aqueous solution containing Ni ions and precipitating Ni on the surface of the galvanized layer. The salt treatment step uses a phosphate treatment solution in which the ratio of Mg ion concentration to Zn ion concentration and Mg ²⁺ / Zn ²⁺ exceeds 0.05, and the steel sheet subjected to the Ni adhering portion formation treatment step is treated with the phosphate. Phosphoric acid containing Mg in an amount of 0.1% by mass or more and less than 2.0% by mass on the Ni adhering portion as an upper layer of the galvanized layer by immersing in the treatment solution or spraying the phosphate treatment solution on the steel plate It is preferable to provide a method for producing a phosphate-treated galvanized steel sheet, which is a step of forming a salt-treated layer.

Further, in the method for producing a phosphate-treated galvanized steel sheet of the present invention, the Mg ions are preferably obtained by adding Mg nitrate, and in the present invention, the galvanizing treatment step is an electrogalvanizing treatment step or It is preferable that it is a hot dip galvanizing treatment step. In the present invention, the amount of the galvanized layer is preferably 1 g / m ² or more and 100 g / m ² or less. It is preferable that the average Ni adhesion amount of the adhesion part is 0.1 to 500 mg / m ² , and in the present invention, the adhesion amount of the phosphating layer is 0.2 g / m ² or more and 3 g / m ² or less. It is preferable.

According to the present invention, without performing a sealing treatment, it has a conventional phosphating galvanized steel sheet equal to or higher than corrosion resistance, yet the phosphating galvanized steel sheet having the same blackening easily In addition, it can be manufactured at a low cost and has a remarkable industrial effect. Further, according to the present invention, to prevent an adverse effect on the environment, there is also an effect that can be produced phosphating galvanized steel sheet.

  The phosphatized galvanized steel sheet of the present invention has a galvanized layer and a phosphatized layer as an upper layer of the galvanized layer on at least one surface of the steel sheet as a substrate. It is a galvanized steel sheet in which a Ni adhering portion is interposed in the middle of the treatment layer. The steel plate used as a board | substrate should just be a steel plate applicable as a galvanized steel plate, and the kind in particular is not limited. What is necessary is just to select suitably according to a use.

In the present invention, the galvanized layer formed on the steel plate as the substrate is formed by electrogalvanizing treatment . Moreover, although the adhesion amount of a galvanization layer can be suitably selected according to a use, it is preferable to set it as 1 g / m < ² > or more from a corrosion-resistant viewpoint. However, when the adhesion amount exceeds 100 g / m ² , the plating peel resistance decreases. In addition, More preferably, they are 5 g / m < ² > or more and 70 g / m < ² > or less.

In the present invention, the Ni adhesion portion is formed on the surface of the galvanized layer and is interposed between the phosphating layer, which is the upper layer of the galvanized layer. Thereby, the blackening resistance is improved. In this invention, the Ni average adhesion amount of the Ni adhesion part interposed in the middle of a galvanization layer and a phosphate treatment layer shall be 0.1-500 mg / m < ² >. The Ni adhesion portion provided on the surface of the galvanized layer may exist as a uniform layer as long as it satisfies the above-mentioned range of the average adhesion amount, and adheres in a microscopically discontinuous form. It may be what you did. Here, the average adhesion amount is a value quantified in accordance with an adhesion test stipulated in JIS H 0401-1999 as described later, and the measurement area is an area stipulated in JIS H 0401-1999. It is the average value of the amount of adhesion. If the average amount of Ni deposited on the Ni deposit is less than 0.1 mg / m ² , prevent blackening that occurs particularly in high-temperature and high-humidity environments when a phosphate-treated layer containing Mg is formed in the upper layer. I can't. In addition, since the effect of preventing blackening becomes more certain as the amount of Ni attached increases, the average amount of attached Ni is preferably 1 mg / m ² or more, more preferably 5 mg / m ² or more. On the other hand, if the average adhesion amount of Ni exceeds 500 mg / mm ² and increases too much, corrosion resistance deteriorates, so 500 mg / mm ² is the upper limit. In addition, Preferably it is 100 mg / m < ² > or less, More preferably, it is 20 mg / m < ² > or less.

  Moreover, the phosphate-treated galvanized steel sheet of the present invention has a phosphate-treated layer on the above-described Ni adhesion portion as an upper layer of the galvanized layer. In the phosphate-treated galvanized steel sheet of the present invention, the phosphate-treated layer contains Mg in an amount of 0.1% by mass or more and less than 2.0% by mass. By including Mg in the phosphate treatment layer, it is possible to delay the time until white rust is generated in the salt spray test, and the corrosion resistance of the phosphate-treated galvanized steel sheet can be reduced without applying a sealing treatment. Can be improved. By making the Mg content in the phosphating layer 0.1% by mass or more, the above-mentioned effect becomes remarkable, and the corrosion resistance substantially equivalent to the corrosion resistance of the phosphating galvanized steel sheet subjected to the conventional sealing treatment, It can be ensured without applying a sealing process. On the other hand, even if 2.0% by mass or more of Mg is contained, the effect of improving the corrosion resistance is saturated, and further, the blackening resistance tends to deteriorate as the Mg content in the phosphate treatment layer increases. For this reason, the upper limit of the Mg content in the phosphate treatment layer is less than 2.0% by mass. In addition, Mg is preferably 1.4% by mass or less, more preferably 0.5 to 1.0% by mass from the viewpoint of blackening resistance.

Further, in the phosphate treatment layer, other cations contained in the phosphate treatment solution, for example, Ni, Mn, Co, etc. may be contained as inevitable impurities if they are about 0.01 to 0.4% by mass. There is no problem.
Further, the adhesion amount of the phosphating layer is preferably 0.2 g / m ² or more, more preferably 1.0 g / m ² or more, and further preferably, in order to ensure corrosion resistance and sufficient paint adhesion. 1.5 g / m ² or more. In addition, since the above-mentioned effect by the increase in adhesion amount is saturated at 3 g / m ² or more, it is preferable to set 3 g / m ² as the upper limit.

Below, the preferable manufacturing method of the phosphating galvanized steel plate of this invention is demonstrated.
In the present invention, a galvanizing process for forming a galvanized layer on at least one surface of the steel sheet, and a Ni-attached part forming process for forming a small amount of Ni-adhered part on the surface of the galvanized layer. And a phosphate treatment step of forming a phosphate treatment layer on the Ni deposit as the upper layer of the galvanized layer.

Needless to say, as the pretreatment, if necessary, electrolytic degreasing, pickling, etc. and water washing are performed to clean the steel plate surface, and then the galvanizing treatment step is performed.
Examples of means for forming the galvanized layer in the galvanizing process include vacuum deposition, hot dipping, and electroplating. In the galvanizing process of the present invention, electroplating is performed using electroplating. Let it be a plating process . Hereinafter, the case where the electroplating method is used will be described as an example.

In the galvanizing treatment step of the present invention, any electroplating method using a normal plating bath composition can be suitably used.
As the zinc plating bath, a zinc sulfate solution, a zinc chloride solution, etc., which are normal zinc plating baths for forming a pure zinc plating layer, can be suitably used, and there is no particular limitation. Needless to say, the energization conditions such as the current density are adjusted according to the amount of the galvanized layer deposited. In addition, it is preferable from a viewpoint of corrosion resistance and plating peeling resistance that the adhesion amount of a zinc plating layer shall be the range of 1-100 g / m < ² >.
In the present invention, the Ni adhering portion forming treatment step is performed after the galvanizing treatment step and before the phosphate treatment step. In the Ni adhering part forming treatment process, the steel sheet on which the galvanized layer is formed by the galvanizing process is brought into contact with an aqueous solution containing Ni ions to displace and deposit Ni on the surface of the galvanized layer, or more aggressively. In particular, it is preferable to form a small amount of the Ni-adhered portion by electrolysis in an aqueous solution containing Ni ions using the steel sheet on which the galvanized layer is formed as a cathode, and substituting and depositing Ni on the surface of the galvanized layer. An aqueous solution such as nickel chloride or nickel sulfate can be used as the aqueous solution containing Ni ions used in the Ni adhering portion forming process. It is preferable to change the Ni concentration in the aqueous solution, the liquid temperature, the contact time, the electrolysis conditions, or the like as appropriate in accordance with the amount of Ni attached.

The steel sheet that has been subjected to the Ni adhering portion forming treatment step is then subjected to a phosphate treatment step. In the phosphate treatment step, a phosphate treatment layer containing 0.1% by mass or more and less than 2.0% by mass is formed on the Ni adhesion part. The phosphating layer is preferably formed by bringing the steel sheet subjected to the Ni adhering portion forming process and the phosphating solution into contact with each other by a conventional method such as spraying or dipping. In order to contain Mg in the phosphating layer, in the present invention, a phosphating solution that satisfies the mass ratio of Mg ion concentration to Zn ion concentration, Mg ²⁺ / Zn ²⁺ exceeds 0.05, preferably 5 or less. Use. Note that the amount of Mg taken into the phosphate treatment layer is influenced by the Zn concentration, solution temperature, pH, and the like in the treatment solution, in addition to the Mg ²⁺ / Zn ²⁺ ratio in the treatment solution. The range of Mg ²⁺ / Zn ²⁺ described above is particularly preferable under the conditions under which ordinary chemical conversion treatment is performed, for example, when the Zn concentration is 0.5 to 5 g / L, the liquid temperature is 30 to 70 ° C., and the pH is 1.0 to 2.5. .

When Mg ²⁺ / Zn ²⁺ is 0.05 or less, a phosphating layer containing 0.1 mass% or more of Mg may not be obtained. On the other hand, if Mg ²⁺ / Zn ²⁺ exceeds 5 and becomes too high, the amount of Mg in the phosphating layer may be outside the proper range. In order to set Mg ²⁺ / Zn ²⁺ in the phosphating solution to an appropriate level, it is necessary to dissolve the Mg salt at an appropriate concentration. For this reason, selection of the anion which becomes a pair with Mg becomes important. When Mg hydroxide, Mg carbonate, Mg sulfate, or the like is used as the Mg ion source, there is a tendency that sufficient solubility cannot be obtained. Mg chloride has sufficient solubility, but simultaneously with Mg ions, a high concentration of chlorine ions may be mixed into the phosphating solution and adversely affect the formation of the phosphate film. For this reason, Mg nitrate is suitable as the Mg ion source.

As the phosphate treatment solution used in the present invention, a commercial treatment solution containing zinc ions, phosphate ions, and further containing an accelerator, for example, trade name “PB3312M” manufactured by Nippon Parkerizing Co., Ltd. In addition, a further addition of a predetermined amount of the above-mentioned Mg ion source can be suitably used. Moreover, it is preferable to adjust the adhesion amount of a phosphate process layer to the range of 0.2-3.0 g / m < ² > by the conventional method which controls the contact time of a steel plate and a phosphate process liquid.

In addition, it is preferable to perform the surface adjustment process of the steel plate surface which gave the Ni adhesion part formation process process prior to a phosphate process process. The surface adjustment of the steel sheet surface that has been subjected to the Ni adhering portion forming treatment step is preferably performed by spraying using a titanium colloidal active treatment agent. As a titanium colloid type active treating agent, Nippon Parkerizing Co., Ltd. prevalene ZN (brand name) can be illustrated, for example.
Next, the present invention will be described in more detail based on examples.

A test plate having a size of 210 × 100 mm was taken from a cold-rolled steel plate having a thickness of 1.0 mm. These test plates were first pretreated. Pretreatment, ortho sodium silicate (60 g / L) added alkaline degreasing solution (liquid temperature: 70 ° C.) in the counter electrode and a stainless steel plate, the current density: at 5A / dm ² 30 seconds electrolytic degreasing, electrolytic degreasing After washing with water, it was further immersed in a 30 g / L sulfuric acid aqueous solution (liquid temperature: 30 ° C.) for 5 seconds, pickled, and then washed with water. After performing this pretreatment, the test plate was subjected to electrogalvanizing treatment, and a zinc plating layer having an adhesion amount of 5 to 40 g / m ² was formed on one surface of the test plate.

The electrogalvanizing treatment was as follows.
A zinc plating solution to which 440 g / L of zinc sulfate heptahydrate was added was used as a zinc plating bath. The zinc plating solution was adjusted to pH 1.5 by adding sulfuric acid. The bath temperature of the galvanizing bath was 50 ° C. In the galvanizing bath described above, the iridium oxide-coated Ti plate electrode is used as a counter electrode, the counter electrode is placed in parallel with the test plate at a distance of 10 mm, and the plating solution is circulated at a flow rate of 1.5 m / s between the electrodes. And energized at a current density of 70 A / dm ² .

After forming a galvanized layer on the surface of the test plate in this way, a Ni adhesion portion forming process for forming Ni on the surface of the galvanized layer is performed. On the galvanized layer, the adhesion amount: 0.1 to 500 mg A Ni adhesion portion of / m ² was formed.
The Ni adhesion part formation process was as follows.
A test piece with a galvanized layer formed on the surface is immersed in a 10 g / L nickel sulfate aqueous solution (40 ° C.) for 1 to 10 seconds, or an iridium oxide-coated Ti plate electrode is used as a counter electrode, and the counter electrode and the test piece Were placed in parallel, energized at a current density of 5 A / dm ² , and electrolyzed to deposit a predetermined amount of Ni to form a Ni-adhered portion. Note that the Ni adhesion amount was adjusted by changing the dipping time or electrolysis time.

Thus, after forming a Ni adhesion part on a galvanization layer, it washed with water, and then gave phosphate treatment. In addition, as a pretreatment for phosphating, a steel sheet with a Ni deposit on the galvanized layer was subjected to a surface conditioning treatment using a surface conditioning agent (Nippon Parkerizing Co., Ltd., trade name “Plenpalen Z”). did.
Phosphate treatment is a zinc phosphate treatment solution (Nihon Parkerizing Co., Ltd .: trade name “PB3312M” with Mg nitrate added to steel sheet with a Ni deposit on the galvanized layer; Zn concentration: 3.5g / L, liquid temperature: 60 ° C, pH: 2.2) sprayed and contacted, washed with water and dried to form a phosphate treatment layer, between the galvanized layer and phosphate treatment layer A phosphate-treated galvanized steel sheet (test plate) with a Ni adhering portion interposed was used. The amount of Mg in the phosphating layer was changed by changing the amount of the Mg source added to the phosphating solution. Moreover, the adhesion amount of the phosphate treatment layer was changed by changing the contact time with the phosphate treatment solution.

  As a comparison, a pure galvanized layer was formed using a normal galvanizing bath, and a phosphate-treated layer containing no Mg was formed using a normal phosphating solution, and chromic anhydride (V1) was added. Using an aqueous solution (manufactured by Nippon Parkerizing Co., Ltd .: trade name “LN62”) as a main component, a sealing treatment was performed to obtain a phosphate-treated galvanized steel sheet (test plate) (test plate No. 26). A phosphate-treated galvanized steel sheet (test plate) without sealing treatment was also produced (test plate No. 24).

About the obtained test plate, the adhesion amount, corrosion resistance, and blackening resistance of the galvanized layer, the Ni adhesion portion, and the phosphate treatment layer were investigated. The investigation surface was a surface on which the galvanized layer and the phosphate treatment layer of the obtained test plate were formed. The survey method was as follows.
(1) Adhesion amount of galvanized layer, Ni adhering portion, and phosphate treatment layer The amount of adhering plating in the galvanized layer and the adhering amount of Ni adhering portion formed on the galvanized layer are determined after galvanizing treatment. The zinc plating layer with Ni deposited and deposited on the surface was dissolved in a hexamethylenetetramine solution in accordance with the adhesion amount test method specified in JIS H 0401-1999, and the plating layer was dissolved. The solution was obtained by analyzing with an electric heating type atomic absorption spectrometer specified in JIS K 0121-1993. The adhesion amount of the phosphate treatment layer was determined by a weight method after dissolving with an aqueous ammonium dichromate solution. The Mg content in the phosphate treatment layer was determined by dissolving the phosphate treatment layer with an ammonium dichromate aqueous solution and analyzing the solution by ICP analysis (inductively coupled plasma emission analysis).
(2) Corrosion resistance A test piece (size: 100 x 50 mm) is cut out from the obtained test plate, the end and back of the test piece are tape-sealed, and then sprayed with salt water in accordance with JIS Z 2371-2000. The test was conducted. During the test, the surface of the test piece was regularly observed, and the time until the white rust generation area became 5% of the total evaluation area of the test piece (white rust generation time) was examined to evaluate the corrosion resistance. The case where the white rust occurrence time was 24 hours or more was rated as ◎, the case where it was less than 24 hours and 8 hours or more, ○, the case where it was less than 8 hours and 4 hours or more, and the case where it was less than 4 hours, and ×.
(3) Blackening resistance A test piece (size: 100 × 50 mm) was cut out from the obtained test plate, and the initial L value of the test piece was first measured using a spectroscopic color difference meter SQ2000 (Nippon Denshoku). (Lightness) was measured. Next, the test piece was left in a constant temperature and humidity chamber at a temperature of 80 ° C. and a humidity of 95% RH for 24 hours. After standing, the L value of the test piece was measured in the same manner, and the change amount ΔL of the L value from the L value (initial value) was obtained. When ΔL is −1 or more, ◎, less than −1, −2 or more, ○, less than −2 to −4 or more, Δ, and less than −4, x is evaluated as blackening resistance. did.

  The obtained results are shown in Table 1.

All of the examples of the present invention are phosphate-treated galvanized steel sheets having corrosion resistance equivalent to or higher than that of conventional phosphate-treated steel sheets and equivalent blackening resistance without performing sealing treatment. On the other hand, in a comparative example that is out of the scope of the present invention, either corrosion resistance or blackening resistance is deteriorated.

Claims (1)

A phosphating galvanized steel sheet having a phosphate treatment layer on at least one surface as an upper layer of the galvanized layer and the electro-galvanized layer of the steel sheet, the galvanized layer and the phosphating layer Ri Na and middle to form an Ni deposition of 0.1 to 500 mg / m ² of the deposition amount of the electro-galvanized layer, 1 g / m ² or more 100 g / m ² or less, the phosphate treatment layer but corrosion resistance and excellent phosphating galvanized steel sheet blackening resistance, characterized in that it contains less than 0.1 wt% to 2.0 wt% of Mg.