JPS6140315B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to composite galvanized coatings having novel compositions, and more particularly to novel electroplating baths and methods useful for producing zinc-cobalt alloy galvanized coatings on non-flat substrates. British Patent Application No. 2070063 discloses a method for the continuous electrogalvanizing of steel strips from a zinc, cobalt and chromium bath in which the electrolyte flows at high speed in the direction opposite to the movement of the steel strip as a cathode. has been done. In this specification, in this combination, the so-called " It is taught that "bare" corrosion resistance and corrosion resistance after passivation treatment can be maintained with improved water purity. Therefore, in the temperature range 35-60°C, the cobalt content lies between 0.7 and 0.8% (although at 30°C it is about 1.1% and at 70°C it is 3.2%). Current density 5ASD and 40ASD at temperature 50℃
The variation in cobalt content between is only about 0.5% and 0.8
It is between %. If the flow velocity is 0.5 m/s and the cobalt in the bath is 5
The variation in cobalt content in the film when varying from ~35 g/s is about 0.05 to about 0.9%, while the variation in cobalt content when the flow rate is only 0.1 m/s is about 0.5% and 5.2 %. Cobalt content in the bath is 5g/30~
In the case of a current density of 40ASD (bath temperature 50℃)
At flow rates above 0.5 m/s, the cobalt content in the film is approximately 0.2%, which is 20% of the cobalt content in the bath.
g/, the cobalt content in the film is about 0.8% by weight at a flow rate of about 0.5 m/sec. According to the UK patent application mentioned above, at least
It has been shown that chromium/cobalt coatings containing 0.3% cobalt have improved bare corrosion resistance, but when containing 1.0% or more cobalt, the coating becomes blackish. The teachings of this patent application are based on sulfate baths containing acetate, and the examples are all sulfate baths, although the possibility of using zinc chloride is mentioned. Moreover, the method of the UK application does not require the presence of chromium in the coating, and the examples all relate to plated coatings with a cobalt content of 0.7% or 0.8%. Although there are some comparative or reference examples described in the specification of this British patent application, these are cases of pure zinc or contain both cobalt and chromium, and
Limited to cobalt content below 0.08%. In addition, the corrosion resistance test in this British patent application specification is for a chromate-treated product,
The details of the chromate treatment conditions are not clear. This same method using the same type of bath is used by Nippon Kokan.
Kaigai Technical Report No. 26 (1979, p. 10-16) and
Sheet Mental Industries International
Dec.1978, p.73-79 and old published in 82 magazines,
Here, phosphate-treated electrogalvanized steel strips containing approximately 0.5% cobalt and approximately
There is mention of something containing 0.05% chromium. The inventors have identified discontinuous sheet parts, such as washers, screws, clips, and other parts, that are flat in shape with cut-out or brochure edges, recessed, or non-flat. or to improve the corrosion resistance of parts such as housings, such as windshield wiper automobile housings, which are not in the form of a continuous sheet and which have significant differences in current density conditions from place to place over their surface. I have been interested in the problem of achievement. These items have a high current density (HCD) at their edges or projection edges, a low current density (LCD) at the cutouts, recesses or bends, and at the same time also medium current density areas. also exists. The present inventors are interested in not only improving corrosion resistance, but also being able to simultaneously achieve a finish with a semi-gloss or glossy appearance, and provide consumers with parts that have a good appearance while maintaining corrosion resistance. interested in providing. According to the inventors, sulfate-type baths such as those described in the above-mentioned British patent application are unsuitable for providing semi-gloss or gloss continuous coatings on parts of the type of interest to the inventors. I found out. Moreover, commercially available zinc acid chloride baths, even if they were doped with cobalt, were not suitable prior to the invention of the novel dosing system according to the present invention. The only thing the inventors were able to do at the time was to deposit a zinc-cobalt alloy containing less than 1% cobalt to compete economically with the commonly used 10% nickel-containing zinc-nickel alloy, but still. It seems that an industrially viable system has not yet been constructed. Such zinc cobalt coatings also have built-in ductility problems such as susceptibility to embrittlement. From a sulfate bath containing acetate, the bath temperature is 50℃, PH4.2,
J.Electrochem.Soc. reported that a zinc-cobalt alloy film containing about 0.1% to about 1.5% cobalt was deposited on steel sheets at a current density of 30 ASD.
Described in Vol. 128 No. 10 p. 2081-2085 (Oct. 1981). However, there is no mention of chromate treatment or passivation treatment of these films. We have experimented with this type of bath, but it remains unsuitable for types of articles such as parts with recesses where there are significant differences in current density across the surface. It was hot. For spectroscopic analysis of zinc cobalt, see J.
Electrochem.Soc.Vol.128 No.7 p.1456-1459
(July.1981). This experiment uses a sulfate bath containing cobalt doped with cobalt-57 and traces of chromium and acetate. In this report 0.68-9.90% cobalt; 0.12
~0.24% cobalt; 0.08-0.12% cobalt;
and 0.03-0.1% cobalt and 0.008-0.014
% cobalt; there are descriptions of plating films containing about 0.5%, about 0.75% and about 2% cobalt. There is no mention of chromate treatment or passivation treatment for any of the coatings. The present inventors have found that the novel acidic chloride zinc cobalt plating bath of the present invention can be used to form zinc-cobalt films on various parts made of discontinuous sheet-like substrates, and that the film can be applied over a wide range of currents. It has been found that it has semi-gloss to gloss properties over a range of densities. The inventors found that about 0.10%, especially 0.21%, especially 0.25%
% cobalt to 0.8%, in particular 0.7%, more preferably 0.67% and most preferably 0.65%, the corrosion resistance prior to passivation treatment is significantly improved; Cobalt content in the range, especially 0.1-0.4%,
It has been found that, especially at cobalt contents of 0.15 to 0.35%, passivation, for example by commercially available dichromate passivating solutions, provides improved corrosion resistance over the entire surface. Thus, according to the invention, having a non-flat surface,
The surface contains up to about 5% cobalt, usually up to about 1% cobalt, typically between 0.1% and 0.8% cobalt, particularly between 0.1% and 0.7% cobalt, preferably
0.15-0.65%, more preferably 0.21-0.35%,
Parts can be provided having a continuous semi-gloss or glossy zinc-cobalt alloy electroplated film with good adhesion, most preferably containing 0.22 to 0.30% cobalt. The film thickness in this case is at least 1 micron, for example at least 2 micron, in particular from 2 to 20
microns, more preferably 3 to 15 microns, such as 5 to 10 microns. The term "flat" refers to a surface that is flat and free of crevices, cuts, depressions, or corrugations. The term "non-flat" refers to cases other than the above-mentioned "flat". The cobalt content in the zinc-cobalt film is routinely determined by dissolving the film in dilute hydrochloric acid and using induced conjugated plasma atomic emission spectroscopy (ICP analysis). An advantage of the coatings according to the invention is that they can also be passivated using known dichromate dip passivation solutions. According to another aspect of the invention, there is provided an article comprising a substrate having a non-planar electrically conductive outer surface, the surface of which is effective for providing sufficient resistance to salt spray testing (as per ASTM-117). It is possible to provide an article having a zinc-cobalt plating layer containing a sufficient amount of cobalt and a thin zinc flash plating having a thickness such that it can be converted into an adherent, continuous zinc passivation film. . In the present invention, it has been found that the best results in terms of total corrosion resistance are obtained when the cobalt content is in the range of 0.1 to 0.4% by weight, particularly 0.15 to 0.35% by weight. An advantage of the present invention is also a continuous, well-adhered passivated zinc-cobalt alloy plating containing 0.1 to 0.4% by weight, preferably 0.15 to 0.35% by weight of cobalt, the plating film preferably having a low 1 micron, such as at least 2 micron thick, with
In particular, a surface coated with an alloy plating of 2 to 20 microns, more preferably 3 to 15 microns, such as 5 to 10 microns thick, such that the surface is preferably semi-gloss to glossy. This can be extended to products that have The article in this proposal of the invention may be a part with a non-flat surface or may even be flat. According to another proposal of the invention, cobalt 0.1-0.8
% by weight, in particular from 0.15 to 0.65% by weight, the plating bath comprises component A as a source of zinc ions; component A as a source of cobalt ions; Component B as a chloride ion source (which may be the same as or different from A or B); Component D, which is an optional boric acid, and further comprises benzoic acid, salicylic acid, nicotinic acid or component E which is a compatible alkali metal or ammonium salt of these;
Component F which is benzylidene acetone; N-allylthiourea or the following general formula Here, R ₁ represents an alkyl group having 1 to Y carbon atoms, or an alkyl group having 1 to Y carbon atoms, at least one of which is substituted with a hydroxyl group; and R ₂ or R ₃ or both are hydrogen. Atom or alkyl group having 1 to Y carbon atoms or 1 to Y carbon atoms
is an alkyl group, at least one of which is substituted with a hydroxyl group or an amino group, and R ₂ and R ₃ are the same or different, and R ₂ and R ₃ are the same or different from R ₁ . and Y is an integer from 2 to 6, preferably 2, 3 or 4, and preferably R ₁ , R ₂ and
At least one of R ₃ is an alkyl group substituted with a hydroxyl group, component G; and polyoxyethylene long-chain acetylenic alcohol or alkylamine ethoxylate or polyethylene glycol, preferably Such baths contain at least one, preferably at least two, especially at least three, most preferably all, selected from the group consisting of component H, which is a compound with particle densification effect, e.g. H) or (G and F) or (G and E), or (G, H and F) or (G, H and E); or (F and H) or (E, F and H) A plating bath for zinc-cobalt plating is provided, the bath having a pH of 3 to 6, for example 4 to 5. In a broad sense, component H has a molecular weight of about 100 to about
polyethers in the range of 1,000,000; polyalkylene glycols such as polyethylene glycol or polypropylene glycol; polyglycidols; polyoxyethylene phenols, polyoxyethylene naphthols; acetylenic glycol ethoxylates; olefin glycol ethoxylates; polyoxyethylene alkyl amines or these consisting of a mixture of Component G is triethanolamine or N- _{allylthiourea} such that _R1 = _R2 = _R3 = _-CH2CH2OH . Although component G can be omitted in low current density plating such as barrel plating, it is strongly desired to be present in high current density plating such as easy plating. Component A is 40-120g/, for example 60-100g/,
It is particularly preferred to supply it with zinc chloride at a zinc ion concentration of 70 to 90 g/, for example 33 to 43 g/. Component B is cobalt sulfate or cobalt chloride,
For example 20-60g/i.e. 30-50g/, especially 35
Preferably, it is supplied as a sulfate salt of ~45 g/(e.g. 7-10 g/cobalt ion). Component C is an alkali metal chloride or ammonium chloride, such as sodium chloride, in an amount of 80 to 245 g/
, in particular in a concentration of 100 to 200 g/, in particular 150 to 180 g/, for example 90 to 100 g/, or in the case of component A being a preferred component such as zinc chloride, 125 to 165 g/ of chloride ions ( ZnC
₂ 70-90 g/and NaC 150-180 g/reference) concentration. Potassium chloride can also be used in place of sodium chloride, in which case there are benefits from the cloud point aspects of anionic and nonionic wetting agents. Component D, boric acid, is an optional component, but it is 15~
Preferably it is present in a concentration of 45g/eg 20-40g/, especially 25-35g/. Component E is sodium salicylate or sodium nicotinate or sodium benzoate in an amount of 2 to 12 g/e.g. 3 to 10 g/, especially 4 to 6
Preferably it is present at a concentration in the range of g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g of the Component F benzylidene acetone is 0.05~05g/
For example, a concentration of 0.07 to 0.2 g/g is preferred. Component G is 0.5 in the case of triethanolamine
~5ml/e.g. 0.7~3ml/ amount is used,
Preference is given to an amount of N-allylthiourea of 0.01 to 1 g/eg 0.05 to 0.5 g/. Component H is one or more, e.g.
6, especially ethoxylated long-chain acetylenic alcohols having 6 to 15 carbon atoms, such as 8 to 12 carbon atoms, especially 10 carbon atoms, substituted with four side chains, such as methyl, and 20 to 40 moles per mole, such as 25 to 35 moles, especially
Preferably it is a reaction product of 30 mol of ethylene oxide, especially polyoxyethylenetetramethyldecynediol (EO 30:1, 30 mol of ethylene oxide adduct) in an amount of 1 to 10 g/e.g.
It is preferably used in a concentration of 8 g/, especially about 4 to 6 g/; or the alkyl group preferably has a carbon number of
10 to 30 polyoxyethylene long-chain alkylamines having a carbon number of, for example, 16 to 20, in particular 18, the reaction product of 10 to 100 mol, such as 40 to 60 mol, in particular 50 mol, of ethylene oxide per mol of alkylamine. and especially polyoxyethylene ( _C18 alkyl)amine (EO 50:1) at 0.1 to 10 g/e.g.
It is preferred to use a concentration of 0.5 to 5 g/, especially 1 g/; or polyethylene glycol with a molecular weight of 1000 to 6000, e.g.
It is advisable to use amounts of ~10g/eg 1-5g/, especially 4g/. A preferred embodiment of the invention is a bath for bright zinc cobalt plating, preferably containing 0.1 to 1.0% cobalt, wherein ZnC as component A
₂ 40-120g/e.g. 60-100, especially 70-90g/
and; 20 to 60 g/CoSO ₄ 7H ₂ O as component B.
e.g. 30-50 g/, especially 35-45 g/; sodium chloride as component C 60-245 g/e.g.
100-200 g/, in particular 150-180 g/; 15-45 g/e.g. 20-40 g/ of boric acid as component D;
in particular from 25 to 35 g/; sodium benzoate as component E from 2 to 12 g/e.g. 3 to 10 g/, in particular from 4 to 6 g/; benzylideneacetone as component F from 0.05 to 0.5 g/e.g. and;
0.5-5 ml/for example 0.7-3 ml/of triethanolamine as component G; polyoxyethylenetetramethyldecynediol (EO 25-
35:1) in an amount of 1 to 10 g/, in particular 4 to 6 g/, and a pH of 3 to 6, for example 4 to 5, is provided. Another preferred embodiment according to the invention is a plating bath for producing bright zinc-cobalt plating, preferably containing 0.21% or more of cobalt, the _bath containing 40 to 120 g/e.g. ~
100g/, especially 70-90g/; as component B
CoC _{2.7H 2} O 20-60g/e.g. 25-45g/
85 to 245 g/e.g. 100 to 200 g/, especially 30 to 40 g/ of potassium chloride as component C;
150~180g/; boric acid as component D: 15~
45g/e.g. 20-40g/, especially 25-35g/;
1 to 12 g of sodium benzoate as component E/
For example, 2 to 8 g/, especially 2 to 4 g/; benzylidene acetone as component F, 0.05 to 0.5 g/
For example, 0.07 to 0.2 g/; N-allylthiourea as optional component G: 0.1 to 1 g/for example, 0.05 to
Amount of 0.5 g/polyoxyethylenetetramethyldecynediol-EO 25-35 as component H:
1 to 10g/particularly 6g/or polyoxyethylene ( _C16-20 alkyl)amine EO (40 to
60:1) in an amount of 0.1 to 10 g/for example 0.5 to 5 g/or polyethylene glycol with a molecular weight of 2500 to 4500.
A plating bath with a pH of 3 to 6, such as 4 to 5, containing 0.1 to 10 g/eg 1 to 5 g/or mixtures thereof is provided. The filling bath according to the proposal of this invention preferably has a pH of 4 to 5, a bath temperature of 15 to 30°C, and a current density of 1 to 30°C.
Used under the condition of 5ASD (ampere/square decimeter). Mechanical stirring is preferred. Also, pure zinc anodes are used. Zinc passivation films are applied, for example, by chromate or dichromate passivation using an immersion passivation bath. The coated parts or substrates can then be used without further treatment and have an excellent gloss or semi-gloss appearance and are optionally coated with organic coatings such as lacquers, waxes or paints. As mentioned above, it is preferable that this zinc-cobalt plating film be subjected to a conventional passivation treatment to form a passivation film with good adhesion. A preferred passivation is a dichromate passivation treatment, which provides very effective corrosion resistance. Of course, the use of other passivation techniques may also be considered within the scope of the present invention. The invention can also be extended to a multi-stage system in which the zinc cobalt plating film is overlaid with a substantially pure zinc flash electroplated layer, and the zinc flash film is then applied with a zinc passivation film. converted into. This zinc flash is essentially pure zinc, e.g.
Preferably, the zinc cobalt has a purity of 99.90% or 99.95% or higher and is substantially cobalt-free, but at least 10% of the amount in the zinc-cobalt layer, such as 5% or less, especially 1% or less. is preferred. The thickness of the zinc flash is such that, although not as bright as the zinc cobalt layer prior to flashing, it still retains the shiny appearance of the zinc cobalt layer. Usually this zinc flash layer is less than 1 micron, e.g.
The thickness is less than 0.7 microns, and in some cases less than 0.5 microns. The lower limit of the thickness is calculated from the fact that it is a thickness that allows a sufficient zinc passivation film with good adhesion to be applied during the passivation treatment. A preferred passivation treatment is dichromate passivation, especially immersion dichromate passivation, which gives significantly better corrosion resistance results. This passivation dissolves most of the pure zinc flash and forms a zinc passivation film in its place. The thickness of this passive film is greater than the thickness of the initial zinc flash plating. This zinc flat plating requires 40 to 120 g/e.g. 60 to 100 g/, especially 70 to 90 g/of extruded zinc,
80-245g/e.g. 100-200g/, especially 150-180
g/ of sodium chloride and 15-45 g/e.g. 20
Electrolytically briefly for 5 to 40 seconds, e.g. It can be generated by contacting. The zinc flash is then subjected to a chromate or dichromate passivation treatment using, for example, an immersion passivation bath at a bath temperature of 22° C. for a time insufficient to dissolve all the zinc flash, e.g. 20 to 30 seconds. Preferably, it is converted to a zinc passive film. The parts or substrates coated in this way have an excellent glossy appearance and are ready for use without further treatment (aside from washing and drying) and, if necessary, an organic coating. Thus, according to the present invention, a corrosion-resistant composite plating can be applied to a non-flat substrate where the current density varies significantly over a wide range, for example, from high current density such as 0.1 to 8 or 9 ASD to low current density. It is possible to give structure. Although this invention can be carried out in various ways, it will be explained in detail in the following examples.
All parts and percentages are by weight unless otherwise stated. Example 1 Production of Zinc Cobalt Electroplating A bath with the following composition was prepared. Component A Zinc chloride (ZnC ₂ ) 80g/ 40g/(zinc) Component B Cobalt sulfate (CoSO ₄ 7H ₂ O) 38.4g/ 8g/ Component C Sodium chloride 165g/ 100g/(chlorine ion) Total chlorine ion 142g/ component D Boric acid 30g/ Component E Sodium benzoate 4.75g/ Component F Benzylideneacetone (C ₆ H ₅ CH=CHC=OCH ₃ ) 0.1g/ Component G Triethanolamine 1ml/ Component H 2,3,7,9-tetra Methyl-5-decyne-
4,7-diol ethoxylate (EO 30:1) 4.8g/PH 4.5 A mild steel flat specimen was cleaned and activated as known using conventional galvanized steel procedures. Next, it was immersed in the above bath and plated for 10 minutes at a current density of 2 ASD and a bath temperature of 23° C. under mechanical stirring to obtain a plated film of 10 microns. The coating is glossy, contains 0.6-0.8% by weight of cobalt, and exhibits excellent corrosion resistance when subjected to a neutral salt spray test according to ASTM-117. Example 2 Production of Zinc Cobalt Electroplating A bath with the following composition was prepared. Component A Zinc chloride (ZnC ₂ ) 80g/ Component B Cobalt chloride (CoC _{2.6H 2} O) 32.5g/ Component C Sodium chloride 165g/ 78.6g/ (chlorine ions) Total chlorine ions 128g/ Component D Boric acid 30g/ Component E Sodium benzoate 3.0g/ Component F Benzylideneacetone (C ₆ H ₅ CH=CHC=OCH ₃ ) 0.1g/ Component G N-allylthiourea 0.1ml/ Component H 2,3,7,9-tetramethyl-5- Decine
4,7-diol ethoxylate (EO 30:
1) 1.0g/ polyoxyethylene (C ₁₈ alkyl) amine (EO 50:1) 1g/ polyethylene glycol (MW4000) 4g/ PH 4.5 One mild steel flat plate specimen was cleaned and compared to normal galvanized steel. Activation was performed as known in the art using a known technique, followed by immersion in the bath described above and plating under mechanical stirring for 10 minutes at a current density of 2 ASD and a bath temperature of 23°C to give a film thickness of 10 microns. The coating is glossy, contains 0.2-0.4 weight cobalt, and exhibits excellent corrosion resistance when subjected to a neutral salt spray test according to ASTM-117. Example 3 Production of Zinc Cobalt Electroplating A bath with the following composition was prepared. Component A Zinc chloride (ZnC ₂ ) 80g/ Component B Cobalt chloride (CoC _{2.6H 2} O) 32.5g/ Component C Potassium chloride 165g/ 78.6g/ (chlorine ions) Total chlorine ions 128g/ Component D Boric acid 30g/ Component E Sodium benzoate 3.0g/ Component F Benzylideneacetone (C ₆ H ₅ CH=CHC=OCH ₃ ) 0.1g/ Component G None Component H 2,3,7,9-tetramethyl-5-decyne-
4,7-diol ethoxylate (EO 30:
1) 1.0g/polyoxyethylene ( _C18 alkyl) amine (EO 50:1) 1g/polyethylene glycol (MW4000) 4g/PH 4.5 This bath has been shown to give satisfactory results at low current densities such as barrel plating. As it turns out, component G is only needed for high current density plating. A steel screw was barrel plated using the above bath, and the plating conditions were a bath temperature of 27 to 29℃ and an average current density.
0.5-1.0 ASD (e.g. 100 ampere current for a load with a surface area of 100 square decimeters),
The barrel rotation speed was 6R.PM. The film, approximately 10 microns thick, is shiny and contains 0.2-0.4% by weight of cobalt, and showed excellent corrosion resistance in the ASTM-117 neutral salt spray test. Example 4 Formation of Passive Film A commercially available yellow dichromate passivation bath was used, which contained 4 g of chromic acid, 1 g of sodium sulfate, and 3 to 4 ml of concentrated nitric acid, and had a pH of 1.4 to 1.4.
It was 1.8. The soaking time was 20-30 seconds at 25°C. The product of Example 1 was rinsed with cold water and then immersed in this passivation bath for 35 seconds at 22°C for passivation. The passivated electroplating was rinsed with cold water, rinsed with hot water, and dried and still had an excellent gloss appearance. Example 5 A test piece similar to that used in Example 1 was plated with pure zinc using a known plating bath having the following composition. ZnSO ₄・7H ₂ O 500g/ Na ₂ SO ₄・7H ₂ O 50g/ Sodium acetate 12g/ PH 4.0 The plating conditions were a current density of 15 ASD, a bath temperature of 50° C., and a plating time of 2 minutes. Example 6 The product of Example 5 was rinsed with cold water and then passivated as in Example 4 for 20 seconds. The products of Examples 1, 4, 5 and 6 were subjected to ASTM-
Table 1 shows the results of the 117 neutral salt spray test. Buffers other than boric acid can also be used, but boric acid is preferred. The presence of component D is preferred but may not be necessary in all cases.

[Table] Examples 7 to 23 Steel Hull Cell specimens (plated area 1 dm ² ) were plated in 30 square tanks under the conditions of marsupial zinc anode, filtration, current density 2ASD, and air agitation from the bottom of the tank. did. The cobalt content in the soaking bath used varied within the following range, and the exact values for each example are shown in Table 2. Solution composition Component A ZnC ₂ 78.0g/ Component B CoC ₂ 3.25-32.5g/ (as 0.8 to 8.0g/Co) Component C Potassium chloride 165g/ Component D Boric acid 30g/ Component E Sodium benzoate 4g/ Component F Benzylidene acetone 0.05g/ Alkylnaphthalene sulfonate 0.2g/ Diethylene glycol monoethyl ether
0.2g/Component H 2,3,7,9-tetramethyl-5-decyne-
4,7-diol ethoxylate (EO 30:
1) 1.2g/ Polyoxyethylene ( _C18 alkyl)amine (EO 50:1) 1.2g/ Polyethylene glycol (MW 4000) 3.6g/

[Table] In Table 2, the cobalt content is given in g/Co(B) and is determined by the bath PH and bath temperature, agitation, the cobalt content of the coating (measured in the area shown in Figure 1 as discussed later) and The film thickness (microns) at the same position is displayed. Cobalt content is shown in LCD and HCD in Figure 1.
Sample portions (1 cm x 2 cm each) were cut out, dissolved in dilute hydrochloric acid, and analyzed for cobalt and zinc by ICP. Examples 24 and 25 In Example 24, Examples 7 to 23 were prepared using the following bath composition.
The method was repeated. Component A ZnC ₂ 80g/ Component B CoC ₂ 32.5g/ Component C NaC 165g/ Component D Boric acid 30g/ Component E Sodium benzoate 5g/ Component F Benzylidene acetone 0.05g/ Alkylnaphthalene sulfonate 0.2g/ Diethylene glycol monoethyl ether
0.2g/Component H 2,3,7,9-tetramethyl-5-decyne-
4,7-diol ethoxylate (30:1)
0.48 g/ bath of Example 25 was the same as Example 24 except that 1 ml/ of triethanolamine (Ingredient G) was added.
It was the same. Table 3 shows the same data as Table 2 obtained in Examples 7-22.

[Table] The products of Examples 7 to 25 were then subjected to ASTM-B117
A 5% neutral salt spray test was conducted in accordance with the following. The percentage of red rust at various test times is shown in Table 4. For comparison, Table 4 also includes the results obtained using a standard 100% galvanized test piece having a similar film thickness (8 microns) (Example 26).

【table】

[Table] Examples 27-39 These examples illustrate the use of the method of the present invention in barrel plating. The barrel load was 150 steel nuts and the average surface area per unit load was 10 dm ² . The procedure for the plating operation was as follows: cold water rinse/normal acid activation/cold water rinse/zinc cobalt plating using the bath of Example 3/cold water rinse/acid treatment before passivation (10 seconds, 0.5-1%
v/v aqueous nitric acid solution) / Cold water rinse / Conventional yellow dichromate passivation using the bath described in Example 4 (room temperature, no air agitation, immersion time 40 seconds, transfer time 15 seconds) / Cold water rinse / Drying Bath capacity 30, filtered, anode Marsupial zinc, bath temperature 30
℃, PH4.4~5.0, barrel rotation 10~30RPM,
Current: 5-10 amperes, plating time: Examples 27-34
In Examples 35 to 37, the bath temperature was 37℃ and the pH was 20 to 40 minutes.
4.4 to 5.10, the plating time was 20 to 40 minutes under the same barrel rotation conditions and a current of 5 to 10 amperes. Table 5 shows PH, plating current (ampere), barrel agitation (volts), plating time (minutes), average plating film thickness (microns), and weight percent of cobalt in the film.
The average value of a large number of nuts and the appearance at the final stage are shown. The cobalt value is the average value of the values obtained by dissolving the plating product in dilute hydrochloric acid and analyzing it by ICP.

【table】

[Table] As is clear from Table 5, plating current 0.5A/d
m ² , 30° C., and pH 4.4 to 5.0, a glossy plating was obtained, and only slight haze was observed in the low current density area. Cobalt content is from 0.22
It was within the range of 0.25, and no problems associated with passivation were observed. Cobalt content of 0.3% or more (Examples 35-37)
can be achieved by raising the bath temperature, increasing the current density or loosening the agitation. Approximately 0.4%
At a cobalt content of , dark blue spots initially appeared in the yellow passivated areas, followed by heavy dark blue "blots". In Examples 32 and 37, the same operations as in Examples 38 and 39 were repeated using a conventional blue dichromate passivating solution. The corrosion resistance results of Example 38 and Example 39 are shown in Table 6. It was found that this blue passive film tends to emphasize the defective areas of the zinc-cobalt plating, while the yellow passive film reduces defects and has a masking effect. Next, a neutral salt spray test was carried out in the same manner as in Examples 7 to 25, and the qualitative test results for the materials passivated by the blue passive film are shown in Table 6. Table 7
Quantitatively shows the percentage of area where black rust or white rust occurs after a certain exposure period of a material passivated with a yellow dichromate passivation film.

【table】

[Table] Example 40 Production of Zinc Cobalt Electroplating A bath having the following composition was prepared. Component A Zinc chloride (ZnC ₂ ) 78g/ Component B Cobalt chloride (CoC _{2.6H 2} O) 33g/ Component C Sodium chloride 170g/ 103.2g/ (chlorine ion) Total chlorine ion 153.7g/ Component D Boric acid 30g/ Component E Sodium benzoate 4.0g/ Component F Benzylidene acetone 25ml/ Component G Pear Component H 2,3,7,9-tetramethyl-5-decyne-
4,7-diol ethoxylate (EO 30:
1) 2.0g/Polyethylene Glycol (MW1500) 5g/PH 5.0 A mild steel flat specimen was cleaned and activated as known using techniques for conventional galvanized steel. Next, using the above bath, plating was carried out for 10 minutes at a bath temperature of 50° C. under mechanical stirring at a current density of 2ASD to obtain a plated film with a thickness of 10 microns. The film is glossy and contains approximately 1.5% by weight of cobalt.
It showed excellent corrosion resistance when subjected to a neutral salt water test in accordance with ASTM-117. On the other hand, alloy coatings containing more than about 1% cobalt can be used, but such alloys may be less amenable to passivating bath compositions in some cases and are also less desirable from an economic standpoint. . Example 41 Production of Zinc Cobalt Electroplating A bath with the following composition was prepared. Component A Zinc chloride (ZnC ₂ ) 80g/ 38.3g/ (zinc) Component B Cobalt sulfate (CoSO ₄ 7H ₂ O) 38.4g/ 8g/ (cobalt) Component C Sodium chloride (NaC) 165g/ 100g/ (chlorine ion ) Total chlorine ions 142g/ Component D Boric acid 30g/ Component E Sodium benzoate 4.75g/ Component F Benzylideneacetone (C ₆ H ₅ CH=CHC=OCH ₃ ) 0.1g/ Component G Triethanolamine 1ml/ Component H 2, 3,7,9-tetramethyl-5-decyne-
4,7-diol ethoxylate (EO 30:
1) 4.8g/PH 4.5 A mild steel flat specimen was cleaned and activated as known using conventional galvanized steel procedures. Next, it was immersed in the above bath and plated for 10 minutes at a current density of 2 ASD and a bath temperature of 23° C. under mechanical stirring to obtain a plated film with a thickness of 10 microns. The coating was glossy, contained 0.6-0.8% by weight of cobalt, and showed excellent corrosion resistance in a neutral salt spray test according to ASTM-117. Example 42 Production of Zinc Flash Film A bath containing 80 g/zinc chloride (ZnC ₂ ), 165 g/sodium chloride, and 30 g/boric acid at a pH of 4.5 was prepared. The product of Example 41 was subjected to a cold water rinse and then cathodically immersed in this bath for 30 seconds to deposit a zinc flash layer approximately 0.1-0.5 microns thick. The plating conditions were the same as in Example 41. The appearance of this plating was still glossy. Example 43 Passivation of Zinc Flash A commercially available yellow dichromate passivation bath was used.
The product of Example 42 was passivated by rinsing in cold water and immersing in the passivating bath at 22° C. for 20-30 seconds to avoid complete dissolution of the zinc flash. The passive electroplated film was rinsed with cold water, then rinsed with hot water, and dried, still retaining a good glossy appearance.

[Brief explanation of the drawing]

Figure 1 shows Examples 7 to 23 (and Example 24 and Example
25) is a plan view of the Hull cell test piece used in 25).

Claims (1)

[Scope of Claims] 1. An aqueous acidic electroplating bath for producing zinc-cobalt alloy electroplating, comprising component A.
is zinc ion; component B is cobalt ion; component C
is a chloride ion; component E is benzoic acid, salicylic acid, or nicotinic acid, or a bath-compatible alkali metal salt or ammonium salt thereof; component F is benzylidene acetone; component G is N-allylthiourea; and the general formula Here, R ₁ represents an alkyl group having 1 to Y carbon atoms or an alkyl group having 1 to Y carbon atoms, at least one of which is substituted with a hydroxyl group; and R ₂ or R ₃ or both is a hydrogen atom, an alkyl group having 1 to Y carbon atoms, or an alkyl group having 1 to Y carbon atoms, at least one of which is substituted with a hydroxyl group or an amino group, and are R ₂ and R ₃ the same? or different, and R ₂ and R ₃ are the same as or different from R ₁ , and Y is an integer from 2 to 6; and component H is a polyoxyethylene long-chain acetylenic alcohol or a polyoxy Ethylene alkylamine or molecular weight 100
~1000000 polyether or polyalkylene glycol or polyglycidol or polyoxyethylene phenol or polyoxyethylene naphthol or polyoxyethylene olefin glycol or polyoxyethylene acetylene glycol or a mixture thereof, preferably having particle densification effect when the plating bath consists of a component A in an amount of 40 to 120 g/calculated as zinc chloride;
20 calculated as cobalt sulfate or cobalt chloride
A plating bath containing components B and C in an amount of ~60 g/m and further comprising at least one of components E, F, G and H. 2. The plating bath according to claim 1, further comprising a buffer as component D. 3. The plating bath according to claim 1, which contains at least two of components E, F, G, and H. 4. The plating bath according to claim 1, which contains at least three of components E, F, G, and H. 5. The plating bath according to claim 1, which contains components E, F, G, and H. 6. The plating bath according to claim 1, wherein the plating bath has a pH of 3 to 6. 7. Plating bath according to claim 1, characterized in that component C is supplied by 85 to 245 g/alkali metal chloride or ammonium chloride. 8. The plating bath according to claim 2, wherein component D is boric acid and its bath-soluble and bath-compatible salts present in an amount of 15 to 45 g. 9. The plating bath according to claim 1, characterized in that component E is contained in an amount of 2 to 12 g/l. 10. The plating bath according to claim 1, characterized in that component F is contained in an amount of 0.05 to 0.5 g/. 11 Component G consists of N-alkylthiourea,
The plating bath according to claim 1, characterized in that the plating bath is contained in an amount of 0.01 to 1 g/. 12 Component G consists of triethanolamine,
The plating bath according to claim 1, wherein the plating bath is contained in an amount of 0.5 to 5 ml. 13. The plating bath according to claim 1, characterized in that component H consists of the polyoxyethylene long-chain acetylenic alcohol and is contained in an amount of 1 to 10 g/l. 14. The plating bath according to claim 1, wherein component H consists of the polyoxyethylene alkylamine and is contained in an amount of 0.1 to 10 g/l. 15 An aqueous acidic electroplating bath for producing a zinc-cobalt alloy electroplating bath, in which component A is zinc ion; component B is cobalt ion; component C is chlorine ion; component E is benzoic acid, salicylic acid or Nicotinic acid or a bath-compatible alkali metal salt or ammonium salt thereof; Component F is benzylidene acetone; Component G is N-allylthiourea and the general formula Here, R ₁ represents an alkyl group having 1 to Y carbon atoms or an alkyl group having 1 to Y carbon atoms, at least one of which is substituted with a hydroxyl group; and R ₂ or R ₃ or both is a hydrogen atom, an alkyl group having 1 to Y carbon atoms, or an alkyl group having 1 to Y carbon atoms, at least one of which is substituted with a hydroxyl group or an amino group, and are R ₂ and R ₃ the same? or different, and R ₂ and R ₃ are the same as or different from R ₁ , and Y is an integer from 2 to 6; and component H is a polyoxyethylene long-chain acetylenic alcohol or a polyoxy Ethylene alkylamine or molecular weight 100
~1000000 polyether or polyalkylene glycol or polyglycidol or polyoxyethylene phenol or polyoxyethylene naphthol or polyoxyethylene olefin glycol or polyoxyethylene acetylene glycol or a mixture thereof, preferably having particle densification effect when the plating bath consists of a component A in an amount of 40 to 120 g/calculated as zinc chloride;
20 calculated as cobalt sulfate or cobalt chloride
A substrate is immersed in a plating bath containing components B and C in an amount of ~60 g/, and further contains at least one of components E, F, G, and H, and the substrate is used as a cathode. Semi-bright or bright zinc-cobalt on a conductive substrate comprising the step of passing an electric current between the anode and the substrate for a period of time sufficient to form the desired thickness of the zinc-cobalt alloy plating film. Method for producing plating film. 16. The method according to claim 15, further comprising the step of controlling the pH of the bath within the range of 3 to 6. 17 Claim 1 further includes a step of controlling the bath temperature within 15°C to 30°C
The method described in Section 5. 18. The method of claim 15, wherein the conductive substrate is non-flat. 19. The process according to claim 15, further comprising the step of withdrawing the substrate having the zinc-cobalt alloy plating from the bath and then applying a passive film on the zinc-cobalt alloy plating. Method. 20 Further, removing the substrate having the zinc-cobalt alloy plating from the bath and immersing the substrate in a second bath to provide a substantially pure zinc flash plating on the surface of the zinc-cobalt alloy plating. 16. A method according to claim 15, characterized in that it comprises: 21 The claimed invention further comprises the step of controlling the thickness of the zinc flash plating to be sufficient to convert the zinc flash into a cohesive and substantially continuous zinc passivation film. The method according to scope item 20. 22. The method of claim 20, further comprising withdrawing the substrate having a zinc flash plating on the surface from the second bath and then applying a passive film on the zinc flash.