DE3418884A1 - SURFACE TREATED STEEL SHEET WITH TRIPLE COATING AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Description

The invention relates to a surface-treated one Sheet steel with atis-marked weldability and excellent corrosion resistance as well as a method for its Manufacturing.

In particular, the invention relates to a surface-treated one Steel sheet with three layers consisting of a base layer (the layer closest to the base steel) made of chrome metal,. an intermediate layer of tin metal or a tin-nickel alloy and a top layer (the layer furthest from the base steel) of chromium oxide hydrate insist on a basic steel. The invention also relates to a method for producing the surface-treated Sheet steel, which is marked with tin plating using a tin plating electrolyte with a low concentration of tin (II) ions or by Tin-Fickel alloy plating using a known tin-Kickel alloy plating electrolytes, which has a low Stromwirlcungsgrad for the tin or Tin-nickel alloy plating, or by tin- or using tin-nickel alloy plating a known tin or tin-nickel alloy plating electrolyte after removal of hydrate of chromium oxide formed during the chrome plating of the base steel has, using an acidic solution with a "pH."

30 _from 0.5 to 2.0.

Using this surface-treated steel sheet, welded can bodies can be welded at high speed without removing the clad layer in the welded area.

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In recent times there has been a rapid change from expensive electro tin sheet to cheaper tin-free steel (TE ¹ S-CT) with a double layer of a lower layer of chromium metal and an upper layer of chromium oxide hydrate, as well as a decrease in the coating weight of the tin.

laminating electro tin sheets in the field of food cans instead of. The reason for this is the high price of the tin necessary for making tinplate as well concerns about depletion of tin deposits. . 10

Ordinary metal cans, with the exception of drawn cans, • consist of two can ends and a single can body. In the pail of tinplate, the seam of the can body becomes common made by soldering. However, in the soldering process, the weight of the tin coating on the tinplate

2
should not be reduced below 2.8 g / m, as the stabilizing

tion of the soldering process is difficult with a tin weight below 2.8 g / m. Because of the lead content regulations in the soldering material used for seaming the tinplate can bodies, the seaming of tinplate can bodies in the food can field has been carried out on a large scale by electric welding. In More recently, for seaming tinplate can bodies, an overlapping seam welding, for example the Soudronic process carried out. In this procedure there is one A reduction in the tin coating weight in the tinplate is desirable. However, the weldability of tinplate is at a lowering of the tin coating weight is bad.

On the other hand, seaming of TPS-CT can bodies is commonly done with nylon adhesives using Procedures such as Toyo Seam or Mira Seam carried out. Another method of seaming can bodies is also known from TPS-CT by electric welding.

In the pail of the seam formation of a TPS-CT can body

However, electric welding must mechanically weld the chrome metal and chrome oxide hydrate layers from the surface of the TFS-CT or chemically removed to allow easy high speed welding of the TIS-CT can body enable. The corrosion resistance of the welded part of the can body is significantly worse, even if this welded area is coated with a lacquer after welding.

On the basis of the foregoing it can be recognized that There is a need in the food can art to develop a can material that is cheaper than Tinplate is and can be easily welded at high speed without removing the clad layer.

Recently, various surface-treated steel sheets have been proposed as a can material that is easy to use can be welded at high speed without removing the clad layer. For example, the following are

20 surface-treated steel sheets known:

a) Sheet steel (LTS) thinly coated with tin with a

Tin application of less than about 1.0 g / m after tin plating melted or not melted; see JP-ASen'56-3440, 56-54070 and 57-55800 and JP-OS 56-75589, 56-130487, 56-156788, 57-101694, 57-185997, 57-192294, 57-192295 and 55-69297.

b) LTS pre-plated with nickel with a tin application of less than about 1.0 g / m ² ; See JP-A-57-23091, 57-67196, 57-110685, 57-177991, 57-2ΟΟ592 and 57-203-797.

c) Kickel-plated sheet steel with a chromate or phosphate film; See JP-A-56-116885, 56-169788, 57-2892, 57-2895, 57-2896, 57-2897, 57-35697 and 57-35698.

d) TFS-CT with double layers on a lower layer of chromium metals, an upper layer of chromium oxide hydrate, which is obtained by certain special processes, v / ie cold rolling after TFS treatment; see JP-OS 55-4-8406, porous Chrome plating; see JP-OS 55-31124-, and a. Cathode treatment of a steel sheet in a chromic acid electrolyte with fluoride, but without anions such as sulfate, nitrate and Chloride; see JP-OS 55-18542.

However, LTS and LTS pre-plated with nickel, denoted by • (a) and (b) above, are slightly more expensive than TFS-CT. Plus, not only do they have a narrower current range for flawless / than tinplate, but also poorer paint adhesion compared with TFS-CT, even if they can be welded without removing the clad layer. The reason that the current range when error-free Welding with LTS and with nickel pre-clad Lü? S is tighter than with tinplate, is probably due to the fact that the Amount of free tin in these sheets is less than in tinplate and as a result of the conversion of free tin into Iron-tin alloy when heated to harden the paint decreases even further.

Nickel-plated sheet steel with a chromate or phosphate film according to explanation (c) above also has a narrower available current range for faultless welding as LTS 'or LTS pre-plated with nickel. Also, the corrosion resistance of nickel-plated steel sheet is worse than that of TFS-CT, although the paint adhesion on nickel-plated sheet steel is good. In particular, can Furrow corrosion at paintwork imperfections on nickel-plated sheet steel is easy as a result of acidic foods, like 'tomato juice, occur because the electrochemical Nickel's potential is nobler than that of steel base and chrome metals.

^{Welding the Ti 1} S-CT discussed in (d) above without removing the TFS-CT film is considered very difficult at high speed because of the high electrical resistance oxide films caused by oxidation of the chrome metal and exposed base steel form the pores of the plating and dehydration of the chromium oxide hydrate during heating to harden the lacquer on the TFS-CT can body, although the TB ¹ S-CT illustrated in (d) can be welded if it is not heated prior to welding.

. The various surface-treated steel sheets as described in (a), (b), (c) and (d) thus have different ones Disadvantages in terms of manufacturing cost and its properties as a can material that does not need to be removed of the clad layers can be welded at high speed.

The invention is based on the object of a surface-treated Steel sheet with excellent weldability without removing the clad layer Can be welded at high speed and excellent corrosion resistance after painting, such as

Ti ¹ S-CT. 25th

Another object of the invention is to provide a method for continuously producing a surface-treated steel sheet excellent in weldability.
30th

These tasks are accomplished by providing a surface treated Sheet steel with three layers on the base steel, consisting of a base layer of metallic Chromium, an intermediate layer made of metallic tin or a tin-Hickel alloy and a top layer Chromium oxide hydrate exist, dissolved.

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The subject of the invention is thus a surface-treated steel sheet, consisting of a base steel with three Layers on top in the following order: a base layer of 30 to JOO mg / m chrome metal, an intermediate layer

10 to 500 mg / m ² tin metal or 10 to 500 mg / m ^2. Tin-nickel alloy with a content of 20 to 60 percent by weight nickel, and a top layer of chromium oxide hydrate in

an amount of 2 to 18 mg / m as chromium.

The steel sheet of the invention can be made by zirin-r or tin-nickel alloy plating are made on the chrome-plated base steel. In detail is the procedure of the invention characterized by tin or tin-nickel plating on the chrome-plated base steel, wherein

t5 the tin or tin-nickel plating at the same time as the removal of the ophthalmic oxide hydrate formed during the chrome plating is carried out. A tin plate is used for this electrolyte with low tin (II) ion concentration or a known tin-nickel alloy plating electrolyte used. These electrolytes have a low current efficiency for tin or tin-nickel plating. Another embodiment of the method of the invention is by tin or tin-nickel alloy plating marked on the chrome plated base steel, being a well known tin or tin-nickel plating electrolyte after the removal of the chromium oxide hydrate formed during the chrome plating by a cathodic treatment with an acidic solution with a

pH 0.5 to 2.0 is used. 30th

The surface-treated steel sheet of the invention can used in areas where excellent weldability, i.e. easy welding without removing the clad layer at high speed is required, such as food can body, aerosol can body and various Can bodies that are painted, except in the

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1 areas to be welded.

The surface treated base steel of the invention can also Can be used for applications that do not require paint coating as it has excellent weldability having. Finally, the surface-treated steel sheet can be used in areas as well as for can bodies where excellent post-painting corrosion resistance is required, such as can ends, drawn cans and drawn— · gene and re-drawn cans (DR cans).

^{Any cold rolled steel sheet commonly used for the manufacture of electro tin sheet or Ti 1} S-CT can be used for the manufacture of the surface treated steel sheet of the invention. A base steel for electrical tinplate according to ASTM A 625/76 (1977); (standard specification of the general requirements for rolled tin products) is preferably used. The base steel preferably has one

Thickness from 0.1 to 0.35mm-20

The surface-treated steel sheet of the invention is produced by the following methods:

(1) Degreasing with alkali and pickling with an acid - ^ Rinse with water - ^ chrome plating -> Rinse with water - ^ tin or tin-nickel alloy plating

-> Rinsing with water -> Chromate treatment -> Rinse with water - * dry, or

(2) Degreasing with alkali and pickling with an acid - rinsing with water -> ghrome plating - 5 rinsing with water - > removal of the chromium oxide hydrate by cathodic treatment with an acidic solution - rinsing with water - * tin or tin-nickel- Alloy plating - £ rinse with water -? Chromate treatment

Rinse with water -> dry. 35

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When using the methods (1) and (2) Three layers are made up of a base layer of chrome metal, an intermediate layer of tin metal or tin-nickel alloy and a top layer of chromium oxide hydrate is created on the base steel. According to the invention is the weight each layer is of great importance in order to achieve the excellent weldability that is achieved with the invention is strived for.

First, the amount of chrome metal that is in the surface treated Steel sheet of the invention represents the lower layer, ranging from 30 to 300 »preferably 70 to

ο
mg / m are maintained. When the amount of chrome metal is below

30 mg / m 2, excellent weldability and excellent corrosion resistance are not obtained. The reason. this is probably due to the insufficient coverage of the surface of the base steel with deposited chromium metal. As a result, a larger part of the subsequently deposited tin or the tin-nickel alloy is converted into a Iron-tin alloy or iron-tin-nickel alloy with high electrical resistance during heating Lacquer hardening around. The amount of chrome metal is economical

-scientific and technical aspects to 300 mg / m limited, although the oxidation of the base steel and the ENT: - stehung of iron-tin or iron-tin-nickel alloy 'are prevented from chromium metal during heating even with an increase in the amount.

The amount of metallic tin or tin-nickel alloy that forms the intermediate layer of the surface-treated steel sheet of the invention is in the range of 10 to

500, preferably 10 to 150 mg / m. With a lot of tin metal or tin-nickel alloy on the chrome

2 plated base steel below 10 mg / m will not be an excellent one Weldability achieved because chromium oxide has a high electrical resistance due to oxidation of the metallic

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Chromium is formed during heating to harden the paint, too if the base steel is prevented from oxidizing by a sufficient amount of chromium metal. On the other hand is the crowd on deposited tin or tin-nickel alloy from host

2 from an economic point of view limited to 500 mg / m, too if the effect of the tin metal or the tin-nickel-

Alloy does not change with a quantity above 500 mg / m

In the present invention, the term "tin-nickel - Alloy "not always, tin-nickel alloys with ötochiometric Composition with a constant ratio of tin to nickel, as in the compounds NiSn, Ni-, Sn, Ni-zSng and Ni, Sn ^. Rather, it means the joint separation of tin and nickel in different proportions of tin to nickel. Tin and nickel deposited at the same time however, yields tin-nickel alloy at room temperature or during heating.

In the pail of tin-nickel alloy plating on top of the chrome-plated Base steel, the nickel content is preferably 20 to 60 percent by weight based on the total deposited tin and nickel. It takes the. Weldability with an increase in the deposited nickel in the Tin-nickel alloy plating. Still shows but also the surface-treated steel sheet of the invention in which a tin-nickel alloy is chrome-plated on the Base steel is deposited, has excellent weldability compared to that of TFS-CT. at more than 60 weight percent or less than 20 weight percent nickel in the tin-nickel alloy is true Excellent weldability and corrosion resistance compared to TFS-CT, stable cladding with a Tin-nickel alloy with less than 20 weight percent or more than 60 weight percent nickel on the chrome plated Base steel using a tin-nickel alloy plating electrolyte however, is difficult since

the nickel or tin content in the tin-nickel alloy changes with small changes in the plating conditions already changed a lot.

In particular, the surface-treated steel sheet of the invention, in which a tin-nickel alloy is applied to the chrome-plated base steel, is characterized by excellent corrosion resistance in sulphite-containing environments exercise, which can often occur inside cans, when eating certain protein foods, such as fish and Meat, in lacquered tinplate cans, unpainted tinplate cans or lacquered, nickel-plated tin cans.

Various processes are used to produce surface-treated steel sheet with excellent weldability for the deposition of layers from an alloy or joint deposition in question, such as joint deposition of tin and zinc, the joint deposition of tin and cobalt, one, nickel plating after tin plating, Tin plating after nickel plating, zinc plating after tin plating and tin plating after zinc plating on chrome-plated base steel. However, these methods are for the production of surface treated steel sheet with excellent weldability because of the complexity of the process or because of the need for a, not suitable for special electrolytes.

As explained, the presence of chrome metal as the base layer and of tin metal or a tin-nickel alloy absolutely necessary as an intermediate layer in the surface-treated steel sheet of the present invention, for excellent weldability after heating.

to reach. 35

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Further, in the present invention, there is the presence of a small amount of chromium oxide hydrate as a top layer essential to prevent oxidation of exposed base steel or exposed chrome metal after tin or tin-nickel alloy plating during heating to the. Prevent paint hardening and provide excellent corrosion resistance and paint adhesion.

The most favorable range for the amount of chromium oxide hydrate

is from 2 to 18, preferably from 4 to. 12 mg / m as chromium.

If the amount of chromium oxide hydrate is less than 2 mg / m as chromium, corrosion resistance and paint adhesion become poor.

When the amount of chromium oxide hydrate is over 18 mg / m, it deteriorates The weldability is noticeable because chromium oxide hydrate is dehydrated during heating for hardening paint in chromium oxide with. high electric

Resistance is converted. 20th

The following are the conditions of each process step for producing the surface-treated steel sheet the invention explained.

For the production of a chrome metal layer as a base layer of the surface-treated steel sheet of the invention, a known chrome plating electrolyte can be used, for example the Sargent bath or a chromic acid electrolyte that contains additives such as fluorine compounds that are used in the Manufacture of TFS-CT with a lower layer of chromium metal and an upper layer of chromium oxide hydrate used will.

In the present invention, the following conditions are electrolytic Chrome plating for the production of a metali- ' see chrome layer on the base steel preferred: '

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Chromic acid concentration: 30 - 300 g / liter preferably 80-300 g / liter

Concentration of additives: 1.0 - 5.0 wt .- ^ preferably 1.0-3.0% by weight

5 the chromic acid concentration;

Additions: at least one fluorine compound or one sulfur compound; Temperature of the electrolyte: 30 - 60 ° C. Cathode current density: 10 - 100 A / dm.

In general, the amount of chromium oxide hydrate deposited during chromium plating decreases with an increase in the chromic acid concentration in the appropriate weight ratio of additives to chromic acid. The use of an electrolyte with a chromic acid concentration below 30 g / liter for chromium plating is not preferred because the current efficiency / the deposition of metallic chromium is markedly decreased. A chromic acid concentration is above 300 g / l is also not suitable for economic reasons ²⁰ ·.

The presence of additives such as fluorine and / or sulfur compounds in the chrome plating electrolyte is essential for uniform chrome deposition. If the amount of additives in percent by weight to chromic acid is less than 1.0 or more than 5.0, the current efficiency for the deposition of metallic chromium _{decreases markedly y} and the evenness of the deposited chrome metal layer also decreases. In particular, a value below 1.0 for the amount of additives in percent by weight of chromic acid prevents

the insoluble chromium oxide hydrate formed clearly the Creation of a uniform metallic tin or tin-nickel alloy layer in the subsequent tin or tin

Mekel plating. . 35

At least one fluorine compound is preferably used as an additive such as! hydrofluoric acid, fluoroboric acid, fluorosilicic acid, ammonium bifluoride, alkali metal bifluoride, ammonium fluoride, Alkali metal fluoride, ammonium fluoroborate, alkali metal fluoroborates, ammonium fluorosilicate, alkali metal fluorosilicates and aluminum fluoride, as well as sulfur compounds, such as sulfuric acid, ammonium sulfate, alkali metal sulfates, Chroasulfate, aluminum sulfate, phenol sulfdic acid, ammo nium phenolsulphonate, alkali metal phenolsulphonates, phenol disulphonic acid, Ammonium phenol disulfonate, alkali metal phenol disulfonate, Ammonium sulfite, alkali metal sulfites, ammonium thiosulfate or alkali metal thiosulfates are used.

The amount of hydrate of chromium oxide formed during chrome plating decreases as the temperature of the electrolyte increases. An electrolyte temperature above 60 ⁰ C is, however, unsuitable from a technical point of view, since the current. Efficiency for the separation of chromium metal decreases noticeably. An electrolyte temperature below 30 ^° C. is also unsuitable, since a long time is necessary for the removal of the large amount of chromium oxide hydrate which is produced in the course of the chrome plating.

With an increase in the cathode current density, the current efficiency increases for the deposition of chromium meta? 1, and the amount of chromium oxide hydrate formed during the chrome plating decreases. According to the invention is a cathode current density for the deposition of chrome metal from 10

2 2

up to 100 A / dm, preferably from 40 to 80 A / dm suitable, since almost no chromium metal is deposited below 10 A / dm current density and the current efficiency for the deposition

generation of chrome metal at a current density of over 100 A / dm; "almost no longer increases.

The conditions for chrome plating where a good Current efficiency for the separation of chromium metal

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is obtained and only a small amount of chromium oxide hydrate is formed, should be set according to the invention, since the presence of chromium oxide hydrate the formation of a uniform tin or tin-nickel alloy layer in the following Tin or tin-nickel alloy plating prevented .

However, chromium oxide hydrate always forms on a deposited Chrome metal layer in chrome plating. With a higher chromic acid concentration, higher current density and higher electrolyte temperature is the. Amount of chromium oxide hydrate, which forms on the deposited chrome metal,

about 3 to 10 mg / m (as chromium>. In contrast, with lower Chromic acid concentration, lower current density and

ο t5 lower electrolyte temperature about 10 to 50 mg / m than

Chrome.

If a large amount of hydrate of chromium oxide during chrome plating has arisen, its amount can be reduced by leaving the chrome-plated base steel for a few seconds is left in the chromium plating electrolyte. However, there remains chromium oxide hydrate in an amount of $ to

5 mg / m as chromium on the surface of the chrome-plated Base steel, even if the chromium-plated base steel with the chromium oxide hydrate in the chromium plating electrolyte for a long time is left.

According to the invention, these chromium oxides have to hydrate before the following tin or tin-nickel alloy plating be removed because the presence of chromium oxide hydrate the deposition of a uniform tin or tin-Hickel alloy layer on the chrome metal layer prevented.

To remove the chromium oxide hydrate on the deposited Chrome metal layer, the following processes are possible:

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(A) Immersing the chrome-plated steel before the Dry in a highly concentrated alkali solution, such as an alkali metal hydroxide or alkali metal carbonate at high Temperatures from 70 to 90 ° C. Such a process is technically difficult to carry out because the alkali solution in the following tin or tin-nickel alloy plating electrolytes can get.

(B) dipping the chrome plated base steel prior to the

Dry in an acid solution such as sulfuric acid or hydrochloric acid. This method is for the present invention unsuitable because the chromium oxide hydrate formed during the chrome plating was briefly immersed in a acidic solution is not sufficiently dissolved.

(C) Mechanical removal of the chromium oxide hydrate by a roller brush or a wiper in an alkaline solution or acidic solution before drying the chrome plated base steel. The one created on the deposited chrome metal layer However, chromium oxide hydrate is not removed uniformly in this process.

Processes such as those explained above under (A), (B) and (C) are therefore for removing the chromium oxide hydrate before the subsequent tin or tin-nickel alloy plating not suitable.

According to the invention, therefore, to remove the on the Chromium oxide hydrate formed by the chromium metal layer preferred the following methods. In one procedure, the Chrome-plated base steel cathodically in an acidic solution, such as sulfuric acid or hydrochloric acid, with a pH value from 0.5 to. 2.0 before the tin or tin-nickel alloy plating is performed. After another The process is tin or tin-nickel alloy plating at the same time as the removal of the

metal layer formed chromium oxide hydrate using a tin-plating electrolyte with a low concentration of stannous ions or a tin-nickel alloy plating electrolyte carried out, whereby the electrolytes have a low current efficiency for the deposition of Ziniir- or tin-nickel alloy.

The conditions for removing the chromium oxide hydrate by the former method are as follows: solution; an acidic solution which contains at least one acid from the group consisting of sulfuric acid, hydrochloric acid, hydrofluoric acid, fluoroboric acid and fluorosilicic acid and has a pH of 0.5 to 2>O;
Temperature of the solution: 30 to 7O ⁰ C;

Cathode current density: 2 to 50 A / dm; Treatment time: 0.5 to 5 »0 seconds.

Even if the main component of the solution is an acid such as sulfuric acid or hydrochloric acid, if the pH of the solution remains between 0.5 and 2.0, there may be various oils that are not deposited on the surface of the chrome plated base steel or the surface of the chrome-plated base steel do not oxidize, be contained in the solution * Precise control of the temperature of the solution is not necessary if it is kept between 30 and 70 ° C. At a temperature of the solution above 70 ⁰ C, the evaporation of water to increase. · At a temperature below 3O ⁰ C requires the cathodic treatment, for sufficient removal of the Chromoxidhydrats long time.

At a current density below 2 A / dm, the chromium oxide hydrate is not removed sufficiently, even if the chromium-plated one Base steel is treated cathodically for a long time. The upper limit for the current density is set at 50 A / dm, since the effect of the treatment at a higher current

1 density is not improved.

If the treatment time is less than 0.5 seconds, the chromium oxide is hydrate not sufficiently removed from the chrome metal layer even if a higher current density is applied. A treatment time over 5.0 seconds is in view of the high speed production of the surface treated Steel sheet of the invention not suitable.

to The conditions for the second procedure, in which the Tin or Tin-Mckel alloy plating at the same time with the removal of the chromium oxide hydrate formed on the chromium metal layer are as follows:

The following conditions are preferred for tin plating: Concentration of tin (II) ions: 2 to 10 g / liter Electrolyte pH: 0.5 to 3.0

Electrolyte temperature: 30 to 60 ° C

Cathode current density: 3 to 50 A / dm

Generally, a tin plating electrolyte such as a Perrostan bath or a halogen bath with about 20 to 40 g / liter Tin (II) ions used for the technical production of electrical tinplate. The application of this tin-plating electrolyte for tin plating on the chrome-plated base steel without removing the material during the chrome plating Chromium oxide hydrate formed by the latter process is not suitable because it is chromium-plated Base steel does not produce a uniform tin layer and the coarse and dendrite-like deposited tin from the chrome-plated Base steel can be peeled off. However, these tin plating electrolytes can be used for tin plating after the removal of the chromium oxide hydrate from the chrome-plated base steel by cathodic treatment in an acidic

³⁵ solution can be used.

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In the second embodiment, the tin plating is done with removal of the chromium oxide hydrate formed during the chrome plating. This embodiment is illustrated by the Use of a tin plating electrolyte with a low tin (II) ion concentration of 2 to 10 g / liter. It has a low current efficiency for the deposition of tin.

The reason why there is no uniform layer of tin on the Chromium-plated base steel is formed when known tin-plating electrolytes with high tin (II) ion concentration is used, is that a larger part of the amount of electricity for the tin deposition, not but is consumed for the removal of the chromium oxide hydrate.

A reduction in the tin (II) ion concentration to below 10 g / liter is therefore desirable according to the invention in order to. to obtain an even layer of tin on the chrome-plated base steel.

However, a tin (II) ion concentration below 2 g / liter is also unfavorable according to the invention, since the current efficiency for the tin deposition decreases noticeably. she is also unfavorable due to the presence of small amounts of foreign ions, such as chromium and iron ions, which dissolve from chromium oxide hydrate and basic steel in the electrolyte accumulate.

Tin (II) ions are mainly produced by adding tin (II) sulfate, tin (II) chloride, tin (II) fluoride or tin (II) fluoroborate or provided by dissolving a soluble tin anode,.

The pH value of the electrolyte is necessary for tin plating on the chrome-plated base steel with simultaneous de-

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removal of the chromium oxide hydrate formed during the chrome plating is very important according to the invention. The pH value of the electrolyte should be in the range from 0 _y 5 to 3.0 · In the ferrostane bath, which contains sulfuric acid or phenol sulfonic acid, there is a pH value of 0.5 to 1.5 and in the halogen bath, the Contains tin (II) chloride, sodium fluoride, potassium bifluoride and sodium chloride, of which 2 to 3 are preferred.

At a low pH such as 0.5 to 3 »0, the surface becomes of the chrome-plated base steel is activated evenly, since that created during the chrome-plating Chromium oxide hydrate easily from chrome plated base steel by evolving a large amount of hydrogen during of dissolving is removed by acid. Therefore, a uniform tin layer is created on the chrome metal layer. A According to the invention, a pH value below 0.5 is not desirable, since part of the chromium metal would otherwise dissolve. A pH value over 3.0 is also not desirable, as there is a uniform tin layer on the chrome metal layer as a result insufficient solution of chromium oxide hydrate does not form in a short time. In addition, stable manufacture of the surface-treated steel sheet of the invention is difficult because the pH of the electrolyte changes little the concentration of tin (II) ions and acid is considerable

²⁵ fluctuates.

The pH value of the electrolyte is essentially determined by adding sulfuric acid, phenolsulfonic acid, hydrochloric acid, hydrofluoric acid, Fluoroboric acid, fluorokia be acid and its alkali metal salts - controlled. Different ions that the tin plating and the chromium oxide hydrate solution do not can be contained in the electrolyte if its pH value is kept in the range of 0.5 to 3? ^ will.

Additives such as ethoxylated Λ-naphtholsulfonic acid, ethoxy-

lated © ^ -naphthol, ß-naphthol and gelatin, which are known in Tin plating electrolytes, such as ferrostane bath or halogen bath, used to make electro tin sheet can be used to improve the evenness of

5 deposited tin layer can be added.

According to the invention, the suitable range for the cathodic current density is 3 to 50 A / dm, preferably 10 to

2 2

30 A / dm. At a current density below 3 A / dm, the Current efficiency for the tin plating so low that a long time is required for the deposition of: the amount of tin is necessary .. At a current density above 50 A / dm, no Tin layer obtained with excellent adhesion to the chrome-plated base steel.

The most favorable range for the electrolyte temperature ranging from 30 to 60 ⁰ C, preferably from 30 to 50 ⁰ C. At a temperature below 3O ⁰ C, the hydrated chromium oxide does not dissolve sufficiently, so that no uniform layer of tin is deposited on the chrome plated metal base steel. At a temperature above 60 ° C, part of the chromium metal is dissolved together with the chromium oxide hydrate.

In tin-nickel alloy deposition with removal of the chromium oxide hydrate formed during the chrome plating The following two types of electrolyte are used. The first type of electrolyte is a pyrrophosphate bath, which consists of an alkali metal pyrrophosphate, Tin (II) chloride, nickel chloride and additives. The second type of electrolyte is a Halogen bath made from tin (II) halide, nickel halide, an alkali metal halide and additives.

When using the first type of electrolyte, the following conditions are used for tin-nickel alloy plating cheap:

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Tin (II) ion concentration: 2 to 40 g / liter

Nickel ion concentration: 4 to 20 g / liter

Concentration ratio of tin (II) -

to nickel ions: 0.1 to 3

5 alkali metal pyrophosphate concentrate

tration: 80 to 300 g / liter

Electrolyte pH: 8 to 10

Electrolyte temperature: 40 to 60 ^{0 C}

ο Cathode current density: "1 to 30 A / dm

When using the second type of electrolyte, the following conditions are used for tin-nickel alloy plating cheap:

Tin (II) ion concentration: 2 to 70 g / liter Nickel ion concentration: 4 to 80 g / liter concentration ratio of

Tin (II) - to nickel ions; 0.1 to 0.8. • pH value of the electrolyte: 0.5 to 3

Electrolyte temperature: 30 to 60 ° C

Cathode current density: 1 to 30 A / dm

With tin-nickel alloy plating on the chrome plated Base steel with simultaneous removal of the chromium oxide hydrate using an alkaline pyrrophosphate bath or acidic halogen bath, it is of great importance that the concentration ratio of tin (II) ions to keep nickel ions within the range described above to provide a uniform tin-nickel alloy layer with a content of 20 to 60 percent by weight nickel on the chrome-plated base steel to obtain.

With tin-nickel alloy plating, the nickel content increases generally under the conditions of higher current density, lower electrolyte temperature, lower concentrations of tin (II) and nickel ions, low concentration

tration ratio of tin (II) ions to kickel ions, and higher pH of the electrolyte.

Below the lower limit of the tin (II) and nickel ion concentration the current efficiency for the simultaneous deposition of tin and nickel decreases noticeably. Concentrations over the upper limit of tin (II) and nickel ions are not suitable for economic reasons, since tin and nod! losses increase. If the concentration loss

ratio of tin (II) - to nickel ions below the lower limit or above the upper limit, deposits of tin-nickel alloys with 20 to 60 percent by weight are produced Nickel hardly survived on the chrome-plated base steel.

The tin (II) and nickel ions are mainly produced by the addition of YQn ZinnClI ^ chloride and nickel chloride or by
Dissolution of soluble tin and nickel anodes supplied.

The pH of the electrolyte is mainly determined by the addition of hydrochloric acid and alkali metal chlorides in the acidic
Halogen bath or by adding pyrrophosphoric acid, alkali metal pyrr © phosphates, hydrochloric acid, alkali metal chlorides and alkali metal hydroxides in the alkaline pyrrophosphate

25 phat bath controlled.

Additives such as glycine and ethylene glycol used in ordinary Tin-nickel alloy plating electrolytes are used can also be used in the present invention to improve the uniformity of the deposited tin-nickel alloy layer to be used.

Cathodic treatment in an acidic solution with a. A pH of 0.5 to 2.0 is also used with tin or tin-nickel plating with removal of the

plating resulting chromium oxide hydrate according to the above

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Γ - 29 - ** * Π

of the description was carried out on the dried chrome-plated base steel under the same conditions.

In the case of tin or tin-nickel alloy plating After the chromium oxide hydrate has been removed by cathodic treatment in an acidic solution, the tin or tin-nickel plating is achieved using the same electrolyte and plating conditions.

In this case, a well-known tin-plating electrolyte, such as a ferrostane bath or a halogen bath with a high concentration of tin (II) ions, for example a ferrostane bath from 30 g / liter tin (II) sulfate (as tin (II) ions), 30 g / liter phenolsulfonic acid (60 $ solution) and 6 g / liter ethoxylate from cc-naphtholsulfonic acid or a halogen bath 30 g / liter of tin (II) chloride (as tin (II) ions), 30 g / liter Sodium fluoride, 50 g / liter sodium chloride and 3 g / liter gelatin for tin plating after removing the chromium oxide hydrate used on the chrome plated base steel.

For the production of the chromium oxide hydrate layer, which is the top layer of the surface-treated steel sheet of the invention, known electrolytes such as that for Post-treatment of tinplate used acidic chromate electrolyte or a small amount of additives, such as fluorine or Chromic acid electrolyte containing sulfur compounds are used to produce TFS-CT with a lower layer of chrome metal and an upper layer

from "Chromxidhydrat is used. 30th

According to the invention, two types of electrolytes are used for production of chromium oxide hydrate used. The first type of electrolyte consists of an acidic chromate electrolyte without Addition of additives such as fluorine or sulfur compounds. The second type of electrolyte consists of a chromic acid electrolyte with additives such as fluorine and sulfur compounds.

For the production of chromium oxide hydrate in an amount from 2 to

18 mg / m as chromium are suitable when using the first type of electrolyte the following conditions:

Concentration of hexavalent chromium ions: 5 to 30 g / l

Temperature of the electrolyte: 30 to 70 ⁰ C

Cathode current density : Λ to 20 A / dm

Amount of electricity: 1 to 4-0 C / dm ²

If the concentration of hexavalent chromium ions is less than 5 g / liter, because of the higher electrical Resistance of the electrolyte results in a loss of electrical energy. The concentration of hexavalent chromium ions is limited to 30 g / liter for economic reasons, though the effect of the treatment is not worsened at higher concentrations.

The electrolyte must be acidic. In the case of an alkaline electrolyte, the effectiveness is the formation of Chromium oxide hydrate so low that it takes a long time for enough chromium oxide hydrate to develop. Electrolytes, which contain only a chromate of an alkali metal or of ammonium are therefore not used in accordance with the invention. ■

In the above case, the electrolyte should therefore be added. must be acidified by chromic acid. Also the addition of an alkali metal hydroxide or ammonia to the chromic acid electrolyte is possible as long as it remains in the acidic range.

Therefore, at least one chromate from the group of chromic acid, chromates and dichromates of alkali metals, ammonium chromate and ammonium dichromate is used in this first type of electrolyte in the acidic range. The temperature of the electrolyte does not have to be set precisely, as long as it is kept between 30 and 70 ^° C. If the electrolyte ^{temperature is above 70 °} C., the evaporation of the water is too strong.

L J

2 Below a current density of 1 A / dm is a long time for the

satisfactory

Formation of / chromium oxide hydrate required. At a Strόπιο

If the density exceeds 20 A / dm, it can be difficult to control the amount of chromium oxide hydrate formed, although it is satisfactory Chromium oxide hydrate is formed for a short time on cathodic treatment.

ο When the amount of electricity is below 1 coulomb / dm, the generation

a suitable amount of chromium oxide hydrate difficult. at

an amount of current of more than 4-0 coulomb / dm, the • Weldability of the surface-treated steel sheet of the "invention due to the formation of a thicker chromium oxide hydrate layer bad.

If an electrolyte of the second type is used, it is advantageous the following conditions are used for the production of chromium oxide hydrate:

Chromic acid concentration: 10 to 50 g / liter Concentration of additives for

Chromic acid: 0.2 to 1.0% by weight

Additions: Sulfur and / or fluorine compounds: Electrolyte temperature: 30 to 60 ° C

Cathode current density: 1 to 10 A / dm

25th

Under the conditions explained above, the amounts of additives to the chromic acid are in percent by weight and the current density of great importance, since with a larger amount added to the chromic acid and higher. Current density metallic Chromium is deposited on the base steel plated with tin or tin-nickel alloy, which has an adverse effect has on weldability. The amount of additives to chromic acid .wird therefore to 1.0 percent by weight and the

Cathode current density limited to 10 A / dm. However, if the amount of additives to chromic acid is below 0.2 percent by weight is, the weldability becomes poor because there is a thick

Chromium oxide hydrate layer forms. With a current density below 1 A / dm is a long time to produce satisfactory Chromium oxide hydrate necessary. In addition, the range of the chromic acid concentration, the amount of electricity and the (temperature of the electrolyte for the same reasons as the first Type of electrolyte limited.

The same additives can be used as for the chrome plating electrolytes.
10

When treating using the second type of electrolyte, the choice of conditions is of great importance, among which no metallic chromium is deposited on the tin or tin-mckel alloy plated surface will. However, if chromium metal is deposited under certain conditions, the maximum amount of metallic chromium should be used

be limited to 10 mg / m. In the cheapest pail, however, should no metallic chromium is deposited.

The examples illustrate the invention. . -

In Examples 1 to 5, cold-rolled steel sheet with a thickness of 0.22 mm is after electrolytic degreasing in a solution of 70 g / liter sodium hydroxide solution, rinsing in water, pickling in a solution of 100 g / liter sulfuric acid and then rinsing in water treated with the following processes: Chrome plating - * ■ »rinsing with water - * tin or tin-nickel alloy plating (with removal of the chromium oxide hydrate formed during chrome plating) - * rinsing with water - * chromate treatment - * rinsing with water —Hl · drying .

In Examples 6 and 7, the same type of steel sheet, pretreated as in Examples Λ to 5 », is treated according to the following procedure

Chrome plating - * rinsing with water - »removal of the

1 Hydrogen oxide formed during chrome plating

by cathodic treatment in an acidic solution -> rinsing with water - > tin plating --J> rinsing with water --J · chromate treatment - ^ rinsing with water - l · drying. 5

example 1

Conditions for ghrome plating Composition of the electrolyte

CrO ₅ 120 g / liter

HBP ^ 0.8 g / liter

H ₂ SO ^ 0.5 g / liter

Electrolyte temperature 60 ° C

2 cathode current density 50 A / dm

Tin Plating Conditions • Composition of the electrolyte

SnSO ^ 10 g / liter as Sn ²⁺

Rienolsulfonic Acid ($ 60 solution) 20 g / liter

ethoxylated ". -naphthol-

sulfonic acid 5 g / liter

pH 1.1

Electrolyte temperature ^{40 0 C}

2 cathode current density 5 A / dm

Chromate treatment conditions

CrO ₅ 50 g / liter

o. 0.1 g / liter

Electrolyte temperature 55 C

ο cathode current density 3 A / dm

Example 2

Conditions for chromium plating Composition of the electrolyte CrO,. 250 g / liter

3 g / liter

Electrolyte temperature 45 ° C

Cathode current density 20 A / dm

Conditions for tin plating Composition of the electrolyte

SnSO ^ 3 g / Idter than Sn ²⁺

Phenolsulfonic acid ($ 60 solution) 20 g / liter ethoxylated c ^ -naphtholsulfonic acid 3 g / liter pH value 0.9

Electrolyte temperature 45 ° C

Cathode current density 8 A / dm

Conditions for .the chromate treatment

Na ₂ Cr ₂ Or ₇ ^ H ₂ O 60 g / liter

Electrolyte temperature ^{40 0 C}

Cathode current density 20 A / dm

Example 3

Conditions for chrome plating Composition of the electrolyte

CrO ₅ 50 g / liter

NaF 2 g / liter

Electrolyte temperature ^{55 0 C}

Cathode current density 40 A / dm

Conditions for tin-nickel alloy plating Composition of the electrolyte

^L 2

SnCl ₀ 50 g / liter as Sn ²⁺

6H ₂ O 75 g / liter as Ni ²⁺

₂₂ ³⁰ ethylene glycol

HCl

Ratio of Sn ⁺ to Ni ⁺

PH value

Electrolyte temperature ³⁵ cathode current density

80 g / liter 30th g / liter 0, 67 O, 5 45 ^{C 1} C 10 A / dm ²

Conditions for chromate treatment Composition of the electrolyte

Na ₂ Cr ₂ O ₇ .2H ₂ O 30 g / liter

Electrolyte temperature 40 ° C

ρ cathode current density 10 A / dm

Example 4

Conditions for the, chrome plating composition of the electrolyte

CrO, 100 g / liter

■ HF 3 g / liter

Electrolyte temperature 6O ⁰ C

Cathode current density 30 A / dm

15 conditions for tin-nickel alloy plating; Composition of the electrolyte

SnCl ₂ 26 g / liter as Sn ²⁺

-OH ₂ O 60 g / liter as Ni ²⁺

₂ 'x 35 g / liter

NaP - 28 g / liter

Ratio of Sn ²⁺ to Ni ²⁺ 0.43

PH value . 2.9

Electrolyte temperature ^{40 0 C}

Cathode current density 2 A / dm

Conditions for chroma treatment Composition of the electrolyte

K ₂ Cr ₂ O ₇ 50 g / liter

Electrolyte temperature 55 ° C

Cathode current density 5 A / dm

Example5

Conditions for chrome plating Composition of the electrolyte

CrO ₅ 200 g / liter

NaB ¹ 6 g / liter

Na ₉ SiSV 1 g / liter

C.

■ 6

L J

Electrolyte temperature. Cathode current density

50 ° c 4-0 A / dm ^£

Tin-nickel alloy plating conditions

Composition, of the electrolyte SnCl ₂

₂ -6H ₂ O glycine K ₄ P ₂ O ₇ .3H ₂ O

Ratio of Sn ²⁺ to Ni ²⁺ pH value Electrolyte temperature Cathode current density

15 g / liter as Sn ²⁺ 7 g / liter as Ki ²⁺ 28 g / liter g / liter

8.1 50 ⁰ C 5 A / dm

Conditions of chromate treatment Composition of the electrolyte

CrO, 7

Electrolyte temperature, cathode current density

30 g / liter

0.3 g / liter 55 ° C 10 A / dm ²

Example 6 Conditions for Chrome Plating

Composition of the electrolyte 100 g / liter CrO ₅ 3 g / liter HF 60 ⁰ C Electrolyte temperature ' 80 A / dnr Cathode current density Chromium oxide hydrate s Conditions for. the removal of the Composition of the electrolyte Value 0.5 H ₂ SO ₄ pH 60 ⁰ C Electrolyte temperature 20 A / dni Cathode current density 0.5 seconds Duration of treatment

Tin Plating Conditions

Composition of the electrolyte

SnSO ₄ 30 g / liter as Sn ²⁺

Phenol disulfonic acid ($ 60 solution) 25 g / liter

ethoxylated (X.-Naphthol 6 g / liter

pH value 0.8

Electrolyte temperature 4-0 ⁰ C Cathodermic current density 15th A / dm ² Conditions for chromate treatment Composition of the electrolyte K ₂ Cr ₂ O ₁₇ 20th g / liter Electrolyte temperature 4-0 ⁰ C Cathode current density 5 A / dm ²

Example?

Conditions for chrome plating Composition of the electrolyte

CrO ₅ 4-0 g / liter

NaB ¹ ■ 1.5 g / liter

Electrolyte temperature 55 ° C

Cathode current density 30 A / dm

Conditions for that. Removal of the chromium oxide hydrate

Composition of the electrolyte

HCl pH 1.5

Electrolyte temperature 4-5 ° C, cathode current density 5 A / dm

Treatment duration 3 seconds

Conditions for tin plating Composition of the electrolyte

SnCl ₂ 28 g / liter as Sn ²⁺

NaS ¹ 30 g / liter

NaCl 50 g / liter

Gelatin 3 g / liter

pH value 2 ", 5

1 electrolyte temperature ^{60 0 C}

Cathode current density 15 A / dm

Conditions for chromate treatment 5 Composition of the electrolyte

Na ₂ Cr ₂ Or ₇ ^ H ₂ O. 30 g / liter

Electrolyte temperature 60 ⁰ G

Cathode current density 3 A / dm

10 Comparative Example 1

The same type of steel sheet, pretreated as in Example Λ , is treated under the following conditions, and then rinsed with water and dried.

^15th Chromic acid electrolytic treatment conditions

Composition of the electrolyte 80 g / liter CrO ₃ 0.5 g / liter HBF ₄ 0.5 g / liter H ₂ SO ₄ 45 ⁰ C Electrolyte temperature 20 A / dnr Cathode current density

Comparative example 2

The same kind of steel sheet pretreated as in examples ²⁵ Game 1, is plated with tin under the following conditions.

Tin Plating Conditions 30

Composition of the electrolyte 30th g / liter as Sn ⁺ SnSO ₄ 20th g / liter ■ phenolsulfonic acid (60 $ solution) 5 g / liter ethoxylated Oi -naphthol ,8th PH value 4-0 ^{c 3} C Electrolyte temperature 8th k / dm Cathode current density

After rinsing with water, the tin-plated steel sheet becomes "Treated under the following conditions and then rinsed with water and dried.

5 Conditions of chromate treatment Composition of the electrolyte

Na ₂ Cr ₂ O ₇ .2H ₂ O 30 g / liter

Electrolyte temperature ^{60 0 C}

Cathoder current density '10 A / dm .10

■ Comparative example 3

The same kind of steel sheet pretreated as in Example Λ is plated with tin under the same conditions as in Comparative Example 2. After rinsing with water, the tin-plated steel sheet is treated under the same conditions as in Comparative Example 1, and then rinsed with water and dried.

The weldability, paint adhesion and corrosion resistance of those treated according to the examples and comparative examples Steel sheets are tested according to the following test method evaluated according to which the amounts of metallic chromium, metallic tin, metallic nickel and chromium in the chromium oxide hydrate were measured by fluorescence analysis. The results are summarized in Table I.

(1) weldability

The weldability is determined by the range of secondary current available when welding according to the report of N.T. Williams (Metal Construction, Apr 1977, pp. 157-160) rated, i.e. the wider the range of the secondary current when welding, the better the weldability. the

1 Upper limit of the available secondary current range corresponds to the welding conditions in which certain errors, such as spraying, appear. The lower limit corresponds to the welding conditions at which the tensile test shows a break in the weld

5 part occurs.

Large amounts of samples are required to obtain data showing the available area of the secondary current when Welding is determined in each sample.

Therefore, the weldability is increased by an electric Contact resistance evaluated according to the following method, since the electrical contact resistance has a salient relationship with the available area that has secondary current when welding; see the report by T. Fujimura (Journal of The Iron and Steel Institute of Japan, Vol. 69, No. 13, September 1983, p. 181), i.e. the lower the electrical contact resistance, the wider the secondary current range during welding. So when the electrical contact resistance is lower, is

20 the weldability better.

First of all, after hardening for 20 minutes at 210 ^° C., the sample treated on both sides is cut to a size of 20 × 100 mm.

² ^ The electrical contact resistance of the sample is calculated from the change in voltage: η a pair of copper disk electrodes (diameter: 65 mm, thickness 2 mm) to which 5 amperes of direct current are applied and which are loaded with 50 kg if two test pieces are between a pair of the copper disk electrodes rotating at a speed of 5 m / min.

(2) Paint adhesion

2 After coating with 60 mg / dm epoxy-phenol lacquer, the sample is ^{cured at 210 °} C. for 12 minutes. Then the coated sample is made into a circular blank with a punch press

cut with a diameter of 80 mm, which leads to it is deep-drawn in a cup.

The paint film on the inside of the cup is peeled off with an adhesive tape - the adhesion of the paint film is divided into five evaluation levels, namely 5 = excellent,
4 = good, 3 = satisfactory, 2 = inadequate and 1 = bad.

(3) Corrosion resistance after painting
After coating with 60 mg / dm ² epoxy-phenol lacquer, the ^{sample is cured at 210 °} C. for 12 minutes. The coated sample is then 7 days at 50 ⁰ C in a solution with a
Content of 1.5% citric acid and 1.5% sodium chloride
immersed. After that, the surface of the coated
Scratch the specimen crosswise with a razor. the

Corrosion in the scratched part of the coated sample is divided into five assessment levels, namely 5 = »excellent, 4 - good, 3 = satisfactory, 2 = inadequate and 1 = bad.

co ..cn

IO

cn

! O O

cn

Table I.

, Example,
1 Ex.
2 Ex
3 .Ex
4th Ex
5 Ex
6th Example,
7th Cf.
Example 1 Cf.
Example 2 4th * 3
Cf.
Example 3 4th * 1
procedure A. A. A. A. A. B. B. - - - $ 2 OP
Amount of Cr (mg / m)
(Base layer; 33 120 105 7 8 151 281 115 121 - 128 Amount of Sn + Ni (mg / m)
(Intermediate layer) Sn
49 2
Ni
O Sn
35
Ni
O Sn
324
Ni
8 6 Sn
64
Ni
42 Sn
6th
Ni
7th Sn
15th
Ni
0 Sn
31
Ni
0 - Sn
38
Ni
0 Sn
34 y
Ni
o ^: * ² amount of Cr ^ox (mg / m ² )
(Top layer) 18th 8th 12th 8th 6th 4th 10 8th 7th 8th Electric contact
resistance C «nQ) 5 ' 2 10 18th 15th 1 4th 321 150 301 Paint adhesion 4th 4th 5 5 5 5 4th 5 4th 5 'Corrosion resistance 4th 5 5 5 5 5 5 5

3418684 - ^

Remarks:

". £ 1 Procedure A: Chrome plating - ^ rinsing with water - ^

Tin or tin-Mckel alloy plating -> rinsing with water - ^ chromate treatment ---} rinsing with water -> drying chrome plating - 9- rinsing with water - ^ cathodic treatment in acidic solution - ^ tin or tin-nickel alloy plating - γ rinsing with water - ^ chromate treatment -> rinsing with water - £ · drying chromium metal, Cr = Cr in chromium oxide hydrate In comparative example 3, the base layer is metallic tin and the intermediate layer is metallic chromium.

Method B:

Cr ⁰ =

20th 25th 30th 35

Claims (1)

VOSSlUS · VOSSIUS -TAUCH N ^ R- "HE: U N'E MJK K N · RAUH SIEBERTSTRASSE A- 8OOO MUNICH 86 · PHONE: (089) 47 40 75 CABLE: BENZOLPATENT MUNICH TELEX 5-29 453 VOPAT D 5 ET: T 024 (Ha / H) May 21, 1984 Case: TOTO KGHAH CO., LTD. Tokyo, Japan "Surface treatment of sheet steel with triple coating and method of its manufacture " Claims (1 / Surface-treated sheet steel, consisting of a Base steel with three layers on it in the following series 20 episode: 2 a base layer of 30 to 300 mg / m chrome metal, an intermediate layer of 10 to 500 mg / m tin metal ο
or 10 to 500 mg / m of tin-wound alloy with a content of 20 to 60 percent by weight nickel, and a top layer of chromium oxide hydrate in an amount of 2 to 18 mg / m as chromium. 2. Steel sheet according to claim 1, characterized in that the amount of chromium metal in the base layer 70 to 150 mg / m, the amount of tin metal or tin-Hickel ~ Le- yment 50 to 3OO mg / m and the amount of chromium oxide hydrate 4 to 12 mg / m as chromium in the top layer. 3. Process for the continuous production of surface-treated Sheet steel, consisting of a base steel with a triple coating of a base L- J layer of chrome metal, an intermediate layer of tin metal or tin-nickel alloy and a top layer of chromium oxide hydrate, characterized in that one a) a base steel for creating a layer of chrome metal and chromium oxide hydrate on it, chromium-chrome plated, b) the chromium-plated base steel with a tin or tin-nickel alloy plating solution under sufficiently acidic conditions ζ inn- or tin-nickel alloy-plated to substantially dissolve ^{the chromium oxide hydrate in this Ιοί 0 solution, and} c) a layer of chromium oxide hydrate on the tin or tin-nickel plated, chrome plated base steel the stage b) generated. * ⁵ 4-. Process for the continuous production of a surface-treated steel sheet, consisting of a base steel with a triple coating of a base layer made of chromium metal, an intermediate layer; of tin metal or tin-nickel alloy and a top layer of chromium oxide hydrate, characterized in that one a) a base steel for producing a layer of chromium metal and chromium oxide hydrate chrome-plated on it, b) the chromium oxide hydrate formed on the chrome-plated base steel by cathodic treatment with ^{25 of} an acidic solution removed, c) the chrome-plated base steel tin or tin-nickel alloy plated, and d) on the tin- or tin-nickel-plated, chrome-plated base steel of stage c) a layer ³⁰ generated chromium oxide hydrate. . 5. The method according to claim 3 or 4, characterized in that that the chrome plating on the base steel at a temperature of JO to 60 C and a cathode current density carries out from 10 to 100 A / dm in an electrolyte, der.30 to 300 g / liter of chromic acid and at least L J an additive from the group consisting of fluorine compounds and sulfur compounds contains, wherein the additive is present in an amount of 1 to 5 percent by weight, based on chromic acid. 6. The method according to claim 5? characterized in that the fluorine compound at least one compound from the group of hydrofluoric acid, fluoroboric acid, fluorokie · * · acidic acid, ammonium bifluoride, alkali metal bifluoride, "Ammonium fluoride, alkali metal fluoride, ammonium fluoroborate, Alkali metal fluoroborates, ammonium fluorosilicate, Alkali metal fluorosilicates and aluminum fluoride. 7. The method according to claim 5, characterized in that .15 the sulfur compound is at least one compound from the group consisting of sulfuric acid, ammonium sulfate, alkali metal sulfates, phenolsulfonic acid, ammonium phenol sulfonate, alkali metal phenol sulfonate, phenol disulfonic acid, ammonium phenol disulfonate, alkali metal sulfate, ammonium metal sulfate, ammonium metal sulfate, ammonium metal sulfate, ammonium metal sulfate, ammonium metal sulfate, ammonium metal sulfate, ammonium metal sulfate, aluminum sulfate, aluminum thiosulfate, ammonium metal sulfate, alkali metal sulfate, alkali metal sulfate, alkali metal sulfate, alkali metal sulfate, alkali metal sulfate, alkali metal sulfate, alkali metal sulfate, alkali metal sulfate, alkali metal sulfate, alkali metal sulfate, alkali metal sulfate is. 8. The method according to claim 4-, characterized in that ■ the tin plating on the chrome-plated base steel with removal of the chromium oxide hydrate formed on the chrome-plated base steel at a temperature of 30 to 60 ⁰ C under a current density of 3 to 50 A / dm in one Performs tin plating electrolytes with a pH of 0.5 to 3.0 containing 2 to 10 g / liter of tin (II) ions. 9. The method according to claim 4, characterized in that the removal of the chromium oxide hydrate formed on the chrome-plated base steel at one temperature from 30 to 70 ° C and below a cathode current density of 2 to 50 A / dm and a treatment time of 0.5 to L _! Seconds in an acidic electrolyte, which performs at least an acid selected from the group consisting of sulfuric acid, hydrochloric acid, fluoroboric acid, fluorosilicic acid and hydrofluoric acid and has a pH of 0.5 to 2.0. 10. The method according to claim 3 or 4, characterized in that the tin-nickel alloy plating on the chrome-plated base steel at a temperature of up to 60 ⁰ C and under a cathode current density of 1 to 50 p
A / dm in a tin-nickel alloy plating electro- lytes with a concentration of 2 to 40 g / liter tin (II) ions and 4 to 20 g / liter of nickel ions and a con- ζentration ratio of tin (II) ions to nickel ions from 0.1 to 3 and a concentration of 80 to 300 g / Lii-5 . ter alkali metal pyrophosphate and a pH of 8 to 10. 11. The method according to claim 3 or 4, characterized in that the tin-nickel alloy plating on the chrome-plated base steel at a temperature of 30 to 60 ⁰ C and under a cathode current density of 1 to 30 A / dm in a tin-nickel alloy plating electrolyte with a concentration of 2 to 70 g / liter tin (II) ions and 4 to 80 g / liter of nickel ions and a concentration ratio clones from tin (II) to nickel ions from 0.1 to 0.8 and a pH of 0.5 to 3. 12. The method according to claim 4, characterized in that the tin plating on the chrome plated base steel at a temperature of 30 to 60 C and below a Cathode current density from 3 to 50 A / dm in a tin plating electrolyte with a pH of 0.5 to 3> 0 and a concentration of 2 to 40 g / liter tin (II) ions performs. L. · ■ J Γ <5 / .1ßafU -5- 13- method according to claim 3 or 4, characterized in, that the chromium oxide hydrate is plated on the tin or tin-nickel alloy Basic steel produced by cathodic treatment in an acidic electrolyte, the at least one compound from the group consisting of chromic acid, chromates or dichromates of alkali metals, ammonium chromate and ammonium dichromate. 14-. Process according to claim 13, characterized in that the cathodic treatment is carried out at a temperature of 30 to 70 ⁰ C, a cathode current density of 1 to 20 A / dm and an amount of electricity of 1 to 40 coulombs / dm in an acidic electrolyte which is 5 up to 30 g / liter contains 6-valent chromium ions. 15th 15. Method according to claim 3 or 4, characterized in that that the chromium oxide hydrate was plated on the tin or tin-nickel alloy Base steel produced by cathodic treatment in an acidic electrolyte of 10 to 50 g / liter of chromic acid and at least one additive from the Group contains fluorine compounds and sulfur compounds, the amount of additives from 0.2 to 1.0 percent by weight the chromic acid is. 16. The method according to claim 15, characterized in that the cathodic treatment at a temperature of 30 to 60 ° C, a cathode current density of 1 to 10 A / dm and an amount of current of 1 to 20 coulombs / dm. 17. The method according to claim 15? characterized in that the fluorine compound at least one compound from the Group hydrofluoric acid, fluoroboric acid, fluorosilicic acid, ammonium bifluoride, alkali metal bifluorides, . Ammonium fluoride, alkali metal fluoride, ammonium fluoroborate and alkali metal fluoroborates. 18. The method according to claim 15 »characterized in that the sulfur compound at least one compound from the group consisting of sulfuric acid, ammonium sulfate, alkali metal sulfates, Phenolsulfonic acid, ammonium phenolsulfonate, alkali metal phenolsulfonates, Phenol disulfonic acid, ammonium phenol-. sulfonate, alkali metal phenol disulfonate, ammonium sulfite, Alkali metal sulfites, ammonium thiosulfate, alkali metal thiosulfates and is chromium sulfate. 19 · The method according to claim 3, characterized in that the clad basic steel after step a) and before Stage b) as well as after stage b) and before stage c) rinses with water. 20. The method according to claim 4-, characterized in that the clad basic steel after stage a) and before stage b), after stage b) and before stage c) as well as after Stage c) and before stage d) flush with water. 20 25 30 35