JPH05195241A - Heat resistant and corrosion resistant superposedly coated steel product - Google Patents

Abstract

PURPOSE:To enhance the adhesion between a black nickel electroplating layer and a chromic acid film deposited and superposed on the surface of iron and steel products by forming the chromic acid film on the electroplating layer. CONSTITUTION:The black nickel electroplating layer 3 is deposited and superposed on the plating layer of the zinc-nickel alloy applied on the surface 1' of the iron and steel products 1. Further, the chromic acid film 4 is provided on the electroplating layer 3. As a result, the adhesion on the mutually deposited and superposed surfaces formed of the plating layer consisting of the zinc-nickel alloy and the electroplating layer consisting of the black nickel increases, by which the coated steel products improved in corrosion resistance and heat resistance are obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various parts around an engine in an internal combustion engine or members thereof.
A plate that is used in a heated atmosphere below about ℃,
The present invention relates to a polymer-coated steel material that is required to have heat resistance and corrosion resistance at the same time, which is formed on the surface of a steel material such as a pipe, a rod, or a wire material.

2. Description of the Related Art Conventionally, as various parts used around the engine or as a steel material having a heat-resistant and corrosion-resistant coating structure as these members, zinc on the surface of a steel material formed by an electroplating method or a dipping method is generally used. On the plating layer, either a normal chromate coating may be simply provided, or a black chromate coating may be formed on the zinc plating layer on the surface of the steel material in connection with the requirement of quality value in appearance. And put it to practical use.

[0003]

However, in these prior arts, both the chromate coating and the black chromate coating are generally short due to the thermal effect of continuous or intermittent repetition from the engine due to running for a long time. There is a problem that heat resistance is still not fully satisfied, such as discoloration with time, strong disappearance, peeling, etc., and at the same time, deterioration of heat resistance also deteriorates corrosion resistance and causes deterioration. Therefore, the present situation is such that improvement is widely desired.

The present invention addresses the above-mentioned problems of the prior art, especially zinc-
Adhesion between the plating layer of nickel alloy and the electroplating layer of black nickel on the surface to be adhered to each other is remarkably improved, and a chromic acid film is further formed on the outer surface to form each of the plating layer, electroplating layer and chromium layer. A heat-resistant / corrosion-resistant polymer-coated steel material that can be effectively solved in relation to the corrosion resistance of an acid coating and can satisfy both heat resistance and corrosion resistance even under use in a heating atmosphere at a temperature lower than the above temperature. It is intended to be provided.

[0005]

According to the present invention, a zinc-nickel alloy plating layer is formed on a surface of a steel material as a lower layer, and an electroplating layer of black nickel is formed on the surface of the plating layer as an upper layer to perform polymerization.
Further, the gist is a heat-resistant and corrosion-resistant polymer coated steel material having a chromic acid coating on the surface of the electroplated layer.

[0006]

In order to form the polymer coating of the corrosion-resistant polymer-coated steel material according to the present invention, a zinc-nickel alloy plating layer is formed by electroplating on the surface of a steel material that has been pretreated by degreasing, derusting, etc. , Further on the surface of the zinc-nickel alloy plating layer,
A black nickel electroplating layer is formed by an electroplating method, and then the surface of the black nickel electroplating layer is subjected to a chromic acid treatment consisting of a series of dipping with a chromic acid aqueous solution, water washing and drying once or more to form a chromic acid film. Form. Alternatively, the chromic acid coating is formed by performing the above-mentioned chromic acid treatment one or more times of these series of treatments including immersion in a chromic acid aqueous solution, drying and heating. Furthermore, the chromic acid treatment is performed by chromic acid treatment consisting of a series of dipping in chromic acid aqueous solution, washing and drying at least once, and then once again in the series consisting of dipping in chromic acid aqueous solution, drying and heating. The above process is performed to form a chromic acid film.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

1 and 2 are both plate materials as heat-resistant and corrosion-resistant polymer-coated steel materials constructed according to the present invention (FIG. 1).
FIG. 2 is an enlarged cross-sectional view of a main part of the pipe and the pipe material (FIG. 2) partially cut away, in which (1) is a zinc-plated surface (1 ′) that has been pretreated by degreasing, rusting, or the like. − A steel material with a plating layer (2) made of a nickel alloy, (3) is zinc −
A black nickel electroplating layer deposited and polymerized on the surface (2 ') of the nickel alloy plating layer (2) by the electroplating method, and (4) is further formed on the surface (3') of the black nickel electroplating layer (3). It is a chromic acid coating.

The zinc-nickel plating layer is applied by an electroplating bath containing zinc chloride, nickel chloride and ammonium chloride as the main components and having a pH of 5.8 to 6.8, and 7% by weight to 15% of nickel. It is formed in a state of being contained in the range of wt%, and naturally, heat resistance and corrosion resistance are made effective by containing these nickel. On the other hand, for the deposition polymerization of the black nickel electroplating layer (3), it is possible to use an electroplating bath comprising nickel sulfate, zinc sulfate, nickel ammonium sulfate and potassium thiocyanate and having a pH of 5.6 to 5.9, and zinc is used in an amount of 30 A nickel-zinc alloy layer contained in an amount of 50% by weight to 50% by weight, which is formed to have a black appearance and is deposited by a similar metal composition similar to that of the lower zinc-nickel plating layer. Therefore, the adhesion between the surfaces to be adhered and polymerized is significantly improved. At the same time, since the electroplating bath having a pH in the range of 5.6 to 5.9, which is used for the deposition polymerization, is used, pretreatment in the middle thereof is not limited, and these treatment operations are simplified, and adhesion is improved. Adhesive polymerization with sufficient heat resistance, and synergistic effect with the chromic acid film (4) formed on the surface (3 ') of the black nickel electroplating layer (3) to exert sufficient corrosion resistance. Can be done.

In forming the chromic acid film (4), the adhered and polymerized steel material (1) is immersed in an aqueous solution of chromic anhydride for about 20 to 60 seconds, washed with water and then at room temperature to 15
Drying is performed in the range of 0 ° C., and a series of treatments of dipping, washing with water and drying is performed once or more, or the steel material (1) is similarly dipped in an aqueous solution of chromic anhydride, and after pulling up, it is left as it is. It is dried in the state, and then heated at about 300 ° C. or lower for 1 minute to 5 minutes, and then subjected to a series of treatments of dipping, drying and heating one or more times, or alternatively, dipping, washing and drying. After the treatment (1) is performed once or more, the series of treatments including the dipping, drying and heating is performed once or more again.

The concentration of chromic anhydride is 20 g /
A range of 1 to 900 g / l is desired, and 2
If it is less than 0 g / l, the coating effect is poor, and 900 g / l
The reason for this is that the viscosity of the aqueous solution increases and the workability is remarkably lowered, and at the same time, it becomes uneconomical.

As described above, the present invention is based on the above-mentioned polymerized coating structure. Therefore, the electroplating layer of black nickel in which metallic zinc is co-deposited in nickel sulfide is added to the plating layer (2) made of a zinc-nickel alloy. (3) is adhered and polymerized to exhibit excellent adhesiveness, and the black nickel electroplating layer (3), which is the upper layer, is used to form 250
As a result, the heat resistance under a heating atmosphere of ℃ or below and the corrosion resistance at the same time as the heat resistance and the corrosion resistance can be exhibited by the lower plating layer (2) made of zinc-nickel alloy. Since the treatment is carried out within the range of the pH value of the electroplating bath during the deposition polymerization of, the pretreatment in the middle thereof is extremely simple, and therefore the productivity can be improved and the cost can be reduced. The surface (3 ') of the electroplated layer (3) of (1) suppresses the generation of white rust by the chromic acid coating (4) related to the above series of treatments, and the chromium compound generated by the reaction between zinc and chromic acid In addition to sealing the existing pinholes, it also forms a passivation film on the surface to stabilize and improve the corrosion resistance, and at the same time discolor, disappear or peel off the chromic acid film (4). Results that also reduce or prevent It is made of. Example 1-Steel material ... A material having a material of STPG38, an outer diameter of 10.0 m / m, a wall thickness of 0.7 m / m, and a length of 500 m / m is subjected to a pretreatment for degreasing and derusting by a conventional method.

· Zinc-nickel alloy plating treatment: pH of zinc chloride 45 g / l, nickel chloride 75 g / l, ammonium chloride 250 g / l, boric acid 20 g / l
Using a plating bath of 5.8, using the tube material as a cathode, while using a nickel plate as an anode, and a bath temperature of 38 ° C. and a cathode current density of 2 A /
After energizing at dm ² for 10 minutes, it was washed with water to obtain a zinc-nickel alloy plating layer having a layer thickness of 5 μm.

Pretreatment in the middle: Immersed in a 10% sulfuric acid aqueous solution for 5 seconds and then washed with water.

・ Black nickel electroplating process ... Nickel sulfate 7
Using a galvanizing bath having a composition of 5 g / l, zinc sulfate 38 g / l, nickel ammonium sulfate 45 g / l, and potassium thiocyanate 15 g / l and having a pH of 5.6, the tube material having the zinc-nickel alloy plating layer was used as a cathode. On the other hand, with a nickel plate as the anode, the bath temperature was 50 ° C, and the cathode current density was 1 A / d.
After energizing at m ² for 5 minutes, washing with water was carried out. As a result, a black nickel electroplating layer having a thickness of 4 μm was deposited and polymerized on the plating layer.

Chromic acid treatment: Chromic anhydride 750 g /
immersing the adhered and polymerized tubing in an aqueous solution of 1 for 30 seconds,
After washing with water, it was dried at 50 ° C., and a chromic acid film was formed by these series of treatments. Example 2 • Steel material ... Same as in Example 1.

Zinc-nickel alloy plating treatment: zinc chloride 60 g / l, nickel chloride 85 g / l, ammonium chloride 200 g / l, ammonia water 50 ml / l, boric acid 20
A plating bath having a composition of g / l and having a pH of 6.5 was used, and the tube material was used as a cathode, while a nickel plate was used as an anode and the bath temperature was 4
After applying current for 8 minutes at 0 ° C. and a cathode current density of 2.5 A / dm ² , a zinc-nickel alloy plating layer having a layer thickness of 5 μ was obtained.

Pretreatment in the middle ... Same as in the first embodiment.

Black nickel electroplating process: Same as in Example 1.

Chromic acid treatment: Chromic anhydride 50 g / l
The tube material subjected to the adhesion polymerization was dipped in the aqueous solution for 40 seconds, washed with water, dried in an oven at 120 ° C., and a series of these treatments was performed twice to form a chromic acid film. Example 3 The steel material, zinc-nickel alloy plating treatment, intermediate pretreatment, and black nickel electroplating treatment were all the same as in Example 1.

Chromic acid treatment: Chromic anhydride 500 g /
immersing the adhered and polymerized tubing in an aqueous solution of 1 for 30 seconds,
After drying at 90 ° C., it was heated at 260 ° C. for 5 minutes, and a chromic acid film was formed by these series of treatments. Example 4 The steel material, zinc-nickel alloy plating treatment, intermediate pretreatment, and black nickel electroplating treatment were all the same as in Example 1.

Chromic acid treatment: Chromic anhydride 250 g /
immersing the coating-polymerized tubing in an aqueous solution of 1 for 25 seconds,
After drying at room temperature, it was heated at 230 ° C. for 5 minutes, and a series of these treatments was performed twice to form a chromic acid film. Example 5 The steel material, zinc-nickel alloy plating treatment, intermediate pretreatment, and black nickel electroplating treatment were all the same as in Example 1.

Chromic acid treatment: Chromic anhydride 750 g /
immersing the adhered and polymerized tubing in an aqueous solution of 1 for 30 seconds,
After washing with water, drying at 60 ° C and chromic anhydride 2 again
It was immersed in an aqueous solution of 50 g / l for 30 seconds, dried at 60 ° C., and then heated at 250 ° C. for 3 minutes to form a chromic acid film. Comparative Example Using the same steel material as in Example 1, a plating bath having a composition of 30 g / l of zinc oxide, 50 g / l of soda blue and 60 g / l of caustic soda was used, and the tube was used as a cathode, while the zinc plate was used as an anode. As a cathode current density of 3 A / dm ² at room temperature for 15
After energizing for a minute, it was washed with water to obtain a zinc-plated layer having a layer thickness of 9 μ, immersed in a black chromate bath at room temperature for 20 seconds, then washed with water and dried to obtain a black chromate film.

The results of comparative characteristics of the products of the present invention (Examples 1 to 5) and the conventional product (Comparative Example) in the heat and corrosion resistance tests are shown in Tables 1 and 2 below.

Results of heat resistance test: After constant heating at 200 ° C. in a heating atmosphere for 24 hours, the temperature is allowed to cool to the atmospheric temperature and the temperature is lowered to the atmospheric temperature.
Table 1 shows the results obtained by visually observing the appearance states of each of the samples, which were continuously heated at a constant temperature of 50 ° C. for 24 hours under constant heating.

[0026]

[Table 1] -Corrosion resistance test results Table 2 shows the results obtained by the salt spray test method according to JIS Z-2371 for the samples after the heat resistance test at 200 ° C for 24 hours.

[0027]

[Table 2] In Table 2, W indicates white rust spots, R indicates red rust spots, WW indicates flow white rust, RR indicates flow red rust, and the numbers attached to the above-mentioned products are the average number of occurrences at the time of recording. The value and the surface area% of the generated part are shown respectively, and if R is generated,
Only R was recorded regardless of occurrence of W and WW, and if RR was generated, only RR was recorded regardless of occurrence of R.

[0028]

As described above, the heat-resistant and corrosion-resistant polymer-coated steel material according to the present invention has the mutual zinc-nickel alloy plating layer (2) and black nickel electroplating layer (3), and each of them is heated. Heat resistance and corrosion resistance under atmospheric conditions can be satisfied at the same time, and the adhesion between these adhered polymerization surfaces is remarkably good, and the surface (3 ') of the black nickel electroplated layer (3) is further improved. The chromic acid film (4) associated with a series of treatments suppresses the generation of white rust and promotes the sealing of pinholes existing by the chromium compound generated by the reaction between zinc and chromic acid. By the synergistic effect of forming and stabilizing a passivation film on the surface, the corrosion resistance is further improved, and at the same time, discoloration, disappearance or peeling of the chromic acid film itself can be reduced or prevented. In the covering treatment, the productivity can be improved and the manufacturing cost can be made relatively low by simplifying the intermediate pretreatment related to the use range of the pH value of the electroplating bath, and the black nickel applied as the second layer. It is a very useful heat-resistant and corrosion-resistant polymer-coated steel material having many features, such as that the electro-plated layer causes the polymer coating on the surface of the steel material to appear black, which improves heat dissipation.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a plate member with a heat-resistant and corrosion-resistant polymerized coating according to an embodiment of the present invention, with a partial cutout.

FIG. 2 is an enlarged cross-sectional view of a main part of the pipe material, which is partially cut away.

[Explanation of symbols]

 1 Steel material 1'Surface 2 Zinc-nickel alloy plating layer 2'Surface 3 Black nickel electroplating layer 3'Surface 4 Chromic acid coating

Claims (1)

[Claims] 1. A surface (1 ') of a steel material (1) having a plating layer (2) made of a zinc-nickel alloy as a lower layer, and a surface of the plating layer.
The black nickel electroplating layer (3) is deposited and polymerized on (2 ') as the upper layer, and the chromic acid coating (4) is further formed on the surface (3') of the black nickel electroplating layer (3). Characteristic heat resistant and corrosion resistant polymer coated steel.