JPH0347987A - Structure of heat and corrosion resistant plating film - Google Patents

Abstract

PURPOSE:To improve heat and corrosion resistances at high temp. by forming a Zn-based plating film as an upper layer on a Co- or Ni-based plating film or further forming a chromate coating film. CONSTITUTION:The plating film has a structure obtd. by forming a Zn-based plating film as an upper layer on a Co- or Ni-based plating film as an underlayer formed on the surface of a base material. A chromate coating film may further be formed on the upper layer (Zn-based plating film). The plating film has superior corrosion resistance, especially heat and corrosion resistances at high temp.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to the application of a multilayer structure to the surface of plates, pipes, joints, clamps, bolts, nuts, etc. mainly made of steel used in automobiles and various other mechanical devices. The present invention relates to a plating film structure having heat resistance and corrosion resistance, in which a multilayer plating film is formed, and the desired level of heat resistance and corrosion resistance can be set by forming a plating film and controlling the thickness of the lower plating film.

(Prior art) Plates, pipes, joints, clamps, bolts, nuts, etc., which are mainly made of steel and used in automobiles and other mechanical devices, have traditionally been coated with zinc, zinc-based alloys, or other zinc-based plating. When a film is formed and even higher corrosion resistance is required, zinc-nickel,
Formation of alloy plating films such as tin-zinc has been carried out, and furthermore, chromate films have been formed on these plating films.

(Problems to be Solved by the Invention) However, although the conventional plating films described above can improve corrosion resistance in a corrosive environment at room temperature, for example, in an engine room, etc.
In environments with high temperatures such as before and after, there are problems in that oxidation of zinc progresses and the sacrificial corrosion effect deteriorates, and corrosion resistance deteriorates as destruction of the chromate film progresses.

The object of the present invention is to obtain a plating film structure that has not only high performance corrosion resistance but also heat resistance, and which can achieve desired levels of these properties.

(Means for Solving the Problems) In order to solve the above problems and achieve the above objects, the present inventors have made extensive research to solve the above problems and achieve the above objectives. A plating film structure in which a plating film of lulin, nickel-boron, etc. (hereinafter referred to as nickel-based) is formed as the lower layer, and a plating film of zinc, zinc-based alloy, etc. (hereinafter referred to as zinc-based) is formed on top of that. As a result, the present invention was completed based on the discovery that the object could be achieved by forming a plating film structure in which a chromate film was formed on top of these films. That is, the first aspect of the present invention
The second embodiment is a heat-resistant and corrosion-resistant plating film structure consisting of a cobalt-based or nickel-based plating film formed on the surface of the material and a zinc-based plating film formed on the plating film, and is the second embodiment. This is a plating film structure having heat resistance and corrosion resistance, in which a chromate film is further formed on the plating film of the first embodiment.

The materials used in the present invention are mainly steel plates, pipes, joints, clamps, bolts, nuts, etc.
In particular, it can be effectively applied to relatively small-diameter pipes with an outer diameter of about 10 mm used for automobile oil pressure and fuel piping.

In this case, a double-wound steel pipe having a copper layer for welding between the surface and the polymerization surface may be used, and an excellent effect can be exhibited.

Next, the cobalt-based or nickel-based plating film formed as the lower layer preferably has a film thickness of 0.2 to 10 μm. This is because if the film thickness is less than 0.2 μm, the ability to cover the material will be poor, and the effect of improving heat resistance and corrosion resistance will not be seen much.If the film thickness is more than 10 μm, it will be difficult to press, bend, etc. This is because peeling, cracking, etc. are likely to occur, and improvement in corrosion resistance cannot be expected even though the thickness of the plating film is increased.

The cobalt-based plating film is made of cobalt chloride 15, for example.
Using a bath with 0g7Q, boric acid 50g/ρ, and pH 5, a cobalt plating film with a thickness of 5 μm was obtained at a bath temperature of 60°C, a current density of 5A/dm2, and a time of 6 minutes, and the cobalt-nickel alloy plating film was For example, nickel sulfate 14
0g/N, cobalt sulfate 110g/g, boric acid 30g
/β, potassium chloride 15 g/ρ, pH 4.5, a cobalt-nickel alloy plating film of about 5 μm can be obtained at a bath temperature of 45° C., a current density of 2 A/dm2, and a time of 5 minutes. As a nickel-based plating film, the nickel plating film is preferably treated using a Watts bath so that the film has a predetermined thickness in the range of 0.2 to 10 μm,
For example, Nippon Kanigen's nickel phosphorus plating film is
Using a 5-fold diluted solution of the product name [Schumer S-780] as a bath, a nickel-phosphorus plating film of approximately 5 μm was obtained at a bath temperature of 90°C for 15 minutes, and a nickel-boron plating film was obtained, for example, on top material. Industrial ■ Product name rBEL-8
Using a 01J bath, a nickel-boron plating film of about 3 μm can be obtained at a bath temperature of 65° C. in 30 minutes.

Next, as a zinc-based plating film, a zinc plating film can be formed by an electroplating method using a known cyanizing bath or a sulfuric acid bath, and a zinc-based alloy plating film, for example, a zinc-nickel plating film, Ebara Nishi Light■ ZIN-L
Using the OY process bath, the current density was 3 at a bath temperature of 35°C.
A zinc-nickel plating film with a thickness of about 5 μm is obtained in 6 minutes at A/dm2, and the zinc-tin alloy plating film can be obtained by applying a current density of 25°C at a bath temperature of A zinc-tin alloy plating film of about 6 μm can be obtained at 2 A/dm 2 for 10 minutes.

This zinc-based plating film can exhibit its effects by forming it to a film thickness of at least 3 μm or more.

Furthermore, the chromate film can be formed using a commercially available chromate treatment solution for zinc-nickel plating (for example, Ebara Nishilite®).
ZN-80YMU) or a commercially available chromate treatment solution for zinc plating (for example, Z-49 from Dipsol ■)
3> can be formed by dipping treatment.

By forming a multi-layer plating film in this manner, the multi-layer plating film structure of the present invention has excellent corrosion resistance, especially at high temperatures and at bent portions subjected to bending. This is because even if the underlying cobalt-based or nickel-based film does not deteriorate due to heat, and even if the upper zinc-based plating film deteriorates due to heat, the sacrificial corrosion effect on the steel material remains. This is thought to be because the anticorrosion effect is sufficient to protect only minute portions such as pinholes in nickel or cobalt coatings. Note that such heat resistance and corrosion resistance can be set to desired levels by controlling the film thickness of the lower plating film.

(Example> Next, examples of the present invention will be described.

Example 1 1) Fabrication of M-diameter pipe (ERW pipe) Using 5TPG-38 material as the steel material, a pipe diameter of 8 mm, wall thickness of 0.7 mm, and length of 380 mm was made by a normal method. Manufactured.

2) Formation of lower layer plating film (cobalt plating) Cobalt plating film as the lower layer is coated with 150 g/I of cobalt chloride.
J, 50 g of boric acid, /Q, using a pH 5 bath,
The film was treated at a bath temperature of 60°C and a current density of 5 A/dm2 for 3 minutes to form a film with a thickness of 3 μm.

3) Formation of zinc-based plating film (zinc-nickel alloy plating) On the cobalt plating film obtained in 2), use Ebara Nishilite ■'s ZIN-LOY process bath to reduce the bath temperature to 35%.
℃, treated for 6 minutes at a current density of 3 A/dm2, and 5 μm
A zinc-nickel alloy plating film was formed as the upper layer with a film thickness of .

4) Formation of chromate film ZN-80YHU (manufactured by Ebara Nishilite ■) 50+
ne/, 1! A chromate film is formed on the zinc-nickel alloy plating film by immersion treatment for 20 seconds at a liquid temperature of 50° C. to obtain a multilayer plating film.

5) Preparation of heat resistance/corrosion resistance test (salt spray test) sample:
A straight pipe section with a length of 250 mm and a continuous bending process (
It was formed into a cane-like shape with a center radius of 25 mm), and the ends were covered with synthetic resin caps to prevent rust from progressing from the cut surfaces of both ends, and a clean soft cloth soaked in ethyl alcohol was used. The oil and fat content was wiped off using a paper towel, and the sample was dried.

6) The heat resistance and corrosion resistance of the multi-layer plated steel pipes obtained from the test results were evaluated by heating for 24 hours at different heating temperatures.
A salt spray test was carried out according to the test method of IS Z 2371, and the time until red copper was generated was measured. The results are shown in Figure 1.

Example 2 1) Production of small diameter pipe (ERW pipe) An electric resistance welded tube similar to that in Example 1 was manufactured.

2) Nickel plating for forming the lower layer plating film> Apply the nickel plating film as the lower layer using a Watts bath at a bath temperature of 55%.
℃, 6 minutes of current density 3 A/dm2, 3 μm
The film was formed with a thickness of .

3) Formation of zinc-based plating film (zinc-nickel alloy plating) In the same manner as in Example 1-3), a zinc-nickel alloy plating film having a thickness of 5 μm was formed as an upper layer on the nickel plating film.

4) Formation of chromate film Furthermore, in the same manner as in Example 1-4), a chromate film was formed on the zinc-nickel alloy plating film to obtain a multilayer plating film.

5) Heat resistance/corrosion resistance test Regarding the obtained multilayer plating coated steel pipe, Example 1-5)
, 6), heat resistance and corrosion resistance were determined by measuring the red copper generation time. The results are shown in Figure 1.

Comparative example 1 1) Production of small diameter tube An electric resistance welded tube similar to that in Example 1-1) was manufactured.

2) Zinc-nickel alloy plating film A zinc-nickel alloy plating film having a film thickness of 8 μm was formed in the same manner as in Example 1-3).

3) Formation of chromate film A chromate film was formed on the zinc-nickel alloy plating film in the same manner as in Example 1-4).

4) Heat resistance/corrosion resistance test Heat resistance/corrosion resistance was determined in the same manner as in Examples 1-5) and 6). The results are shown in Figure 1.

From these results, when unheated to 100°C, when there is a nickel-based or cobalt-based plating film in the lower layer as in the present invention, there is a small amount of thermal diffusion between zinc and nickel or cobalt, resulting in a decrease in corrosion resistance. There are few, and 200 to 25
At 0°C, the zinc-nickel single layer of the comparative example loses practical corrosion resistance, but when it has a nickel-based or cobalt-based plating film as the lower layer as in the present invention, sufficient corrosion resistance is achieved. Moreover, the effect of the present invention is clearly recognized, as it exceeds the unheated zinc-nickel single layer.

Example 3 1) Production of small diameter tube An electric resistance welded tube similar to that in Example 1-1) was manufactured.

1 2) Formation of lower layer plating film (cobalt-nickel alloy plating) Nickel sulfate 140g/j, cobalt sulfate 110g/j
, 11, Hovic acid 30g/, 1), Potassium chloride 15
g7.1! , 1) Using a 84.5 bath, bath temperature 45℃
, and a current density of 2 A/dm2 for 15 minutes to form a cobalt-nickel alloy plating film (CO/N1=65/35) as a lower layer with a film thickness of 5 μm.

3) Formation of zinc-based plating film (zinc plating) 28g of zinc oxide on the lower cobalt-nickel alloy plating film.
/ρ, sodium cyanide 50g/, I! , using a bath containing 80 g of sodium hydroxide/11, treated at a bath temperature of 25°C and a current density of 3 A/dm2 for 15 minutes, resulting in a film thickness of 8 μm.
Form a galvanized film of m as an upper layer.

4) Formation of chromate film Z-493 (manufactured by Dipsol ■) 10 m, l! on the galvanized film. 7.1! Using liquid, liquid temperature 25
A chromate film was formed by immersion treatment at ℃ for 15 seconds to obtain a multilayer plating film.

2 5) Heat resistance/corrosion resistance test Regarding the obtained multilayer plating coated steel pipe, Example 1-5)
, 6), heat resistance and corrosion resistance were determined by measuring the red copper generation time. The results are shown in Figure 2.

Example 4 1) Production of small diameter tube An electric resistance welded tube similar to that in Example 1-1) was manufactured.

2) Nickel-phosphorus alloy plating for forming the lower layer plating film) As the lower layer, a 5-fold diluted solution of Schumer 3-780 (trade name, Nippon Kanizen ■) was used, and the bath temperature was 90℃ for 15 minutes.
The mixture was treated for minutes to form a nickel-phosphorus alloy plating film with a thickness of 5 μm.

3) Formation of zinc-based plating film (zinc plating) On the lower layer formed in 2), a zinc plating film having a film thickness of 8 μm was formed as an upper layer in the same manner as in Example 3-3).

4) Formation of chromate film A chromate film was formed on the upper galvanized film in the same manner as in Example 3-4) to obtain a multilayer plating film.

5) Heat resistance/corrosion resistance test Regarding the obtained multilayer plating coated steel pipe, Example 1-5)
, 6), heat resistance and corrosion resistance were determined by measuring the red copper generation time. The results are shown in Figure 2.

Comparative example 2 1) Production of small diameter tube An electric resistance welded tube similar to that in Example 1-1) was manufactured.

2) Formation of galvanized film A galvanized film having a film thickness of 13 μm was formed in the same manner as in Example 3-3).

3) Formation of chromate film A chromate film was formed on the zinc plating film in the same manner as in Example 3-4).

4) Heat resistance/corrosion resistance test Heat resistance/corrosion resistance was determined in the same manner as in Examples 1-5) and 6). The results are shown in Figure 2.

These results show that all four exhibit similar deterioration at temperatures between unheated and 100°C, but this is because the outermost layer is the zinc-plated chromate film that does not easily lose crystal water due to heat. At 100 to 200°C, the sacrificial corrosion effect of a single layer of zinc decreases due to thermal deterioration of the film itself, but in the case of the present invention with a nickel-cobalt or nickel-phosphorus lower layer, the above-mentioned Thus, it is sufficient that the sacrificial corrosion action that protects only the minute defect portions in the lower layer remains, and it is thought that there is little deterioration in corrosion resistance.

Example 5 1) Production of I-diameter pipe (double-wound steel pipe) Using 5pcc material with a welded steel plating layer of approximately 3 μm on the surface during pipe manufacturing, the same dimensions (wall thickness) as in Example 1-1) were prepared. Thickness is 0.7mm)
Manufacture double-wound steel pipes.

2) Formation of lower layer plating film (cobalt plating) 3) Formation of zinc-based plating film (zinc-nickel alloy plating) 4) Formation of chromate film These are all the same as in Examples 1-2), 3), and 4). A multilayer plating film was obtained.

5 5) Heat resistance/corrosion resistance test Regarding the obtained multilayer plating coated steel pipe, Example 1-5)
, 6), heat resistance and corrosion resistance were determined.

The results show that the red rust generation time was 3,800 hours when unheated, and 3,000 hours after heating to 200° C. for 24 hours.

Example 6 1) Manufacturing of small diameter pipes (double-wound steel pipes) A double-wound steel pipe similar to Example 5-1) was manufactured.

2) Formation of lower layer plating film (cobalt-nickel alloy plating) 3) Formation of zinc-based plating film (zinc plating) 4) Formation of chromate film These are all the same as in Examples 3-2), 3), and 4). A multilayer plating film was obtained.

5) Heat resistance/corrosion resistance test Regarding the obtained multilayer plating coated steel pipe, Example 1-5)
, 6), heat resistance and corrosion resistance were determined.

The results showed that the time for red rust to occur when unheated was 100 hours, and after heating to 200° C. for 24 hours, it was 550 hours.

Example 7 1) Production of small diameter pipe (ERW pipe) An electric resistance welded tube similar to that in Example 1-1) was manufactured.

2) Nickel plating for forming the lower plating layer) Example 2-
Using the same bath as in 2) for forming the nickel plating film,
Nickel plating films with various film thicknesses were formed by varying the electrolysis time.

3) Formation of zinc-based plating film (zinc-nickel alloy plating) A zinc-nickel alloy plating film was formed on each nickel plating film in the same manner as in Example 23) to form a multilayer plating film.

4) Heat resistance/corrosion resistance test The heat resistance/corrosion resistance of each of the obtained multilayer plated steel pipes was determined by measuring the red rust generation time in the same manner as in Examples 1-5) and 6).

These results are shown in the table below.

7 8 This shows that it is possible to obtain desired levels of heat resistance and corrosion resistance depending on the thickness of the underlying nickel plating film.

(Effects of the Invention) The present invention has a cobalt-based or nickel-based plating film formed as a lower layer, a zinc-based plating film formed thereon as an upper layer, and a chromate film further formed thereon. Because it is a material, it is possible to improve corrosion resistance, especially heat resistance and corrosion resistance at high temperatures, and by controlling the thickness of the lower plating film, it is possible to set the heat resistance and corrosion resistance to the desired level, and a remarkable effect is recognized. .

[Brief explanation of drawings]

1 and 2 are graphs showing the test results of each example of the present invention, with the horizontal axis representing the heating temperature (° C.) and the vertical axis representing the red rust generation time (Hr).

Claims (2)

[Claims] (1) A heat-resistant and corrosion-resistant plating film structure comprising a cobalt-based or nickel-based plating film formed on the surface of a material and a zinc-based plating film formed on the plating film. (2) It is characterized by consisting of a cobalt-based or nickel-based plating film formed on the surface of the material, a zinc-based plating film formed on the plating film, and a chromate film formed on the zinc-based plating film. Plated film structure with heat resistance and corrosion resistance.