JPS60262976A - Heat and corrosion resistant multiply coated steel material and formation of multilayered coat - Google Patents

Abstract

PURPOSE:To obtain a multiply coated steel material having superior heat and corrosion resistances by successively coating the surface of a steel material with a Zn-Ni alloy layer by electroplating, a black Ni layer by electroplating and a chromate film. CONSTITUTION:The surface 1' of a steel material 1 is pretreated by degreasing and derusting, and a Zn-Ni alloy layer 2 is formed on the surface 1' by electroplating. The Ni content of the layer 2 is regulated to about 7-15wt%. A black Ni layer 3 is formed on the surface 2' of the layer 2. The Zn content of the layer 3 is regulated to about 30-50wt%. The plated steel material 1 is then immersed in an aqueous soln. of chromic acid anhydride for about 20-60sec, and it is taken out, wached, and dried at ordinary temp. - about 150 deg.C. The immersing, washing and drying stages are carried out once or more to form a chromate film 4 on the surface 3' of the layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to various parts surrounding an internal combustion engine, for example, and plates used as these members in a heated atmosphere of about 250°C or less. The present invention relates to a polymer coated steel material which is applied to the surface of a steel material such as a pipe, rod, wire rod, etc. and which requires heat resistance and corrosion resistance at the same time, and a method for forming the polymer coat.

[Problems with conventional technology]

Conventionally, various parts used around the engine, such as steel materials with a heat-resistant and corrosion-resistant coating structure, are simply coated on a zinc plating layer on the surface of the steel material, which is generally formed by electroplating or dipping. It has been put into practical use either by having a normal chromate coating, or by forming a black chromate coating on the zinc plating layer on the surface of the steel material in connection with the requirement for quality value in terms of appearance. .

However, with these conventional products, both the acid and black chromate coatings generally discolor in a short period of time due to heat effects from continuous or intermittent cycles from the engine during long-term running, etc. However, it is still not possible to fully satisfy the requirements for heat resistance due to problems such as disappearance and peeling. The current situation requires improvement.

[Purpose of the invention]

The present invention solves the above-mentioned conventional problems by significantly improving the tightness of the mutual adhesion between a zinc-nickel alloy plating layer and a black nickel electrolytic plating layer, and furthermore, a chromic acid coating is applied to the outer surface. The problem is effectively solved in connection with the corrosion resistance of each of the above-mentioned plating layer, electroplating layer and chromic acid coating, and the simple polymerization coating formation method, and under the usage conditions in a heated atmosphere below the above-mentioned temperature. The object of the present invention is to propose a heat-resistant/corrosion-resistant polymer coated steel material and a method for forming a polymer coat that can satisfy both heat resistance and corrosion resistance.

[Structure of the invention]

The invention is to significantly improve the adhesion of a zinc-nickel alloy plating layer and a black nickel electrolytic plating layer to each other on the surface of the steel material, and to form a chromic acid film on the outer surface. , the corrosion resistance of each of the above-mentioned plating layer, electroplating layer and chromic acid coating, and the simple polymerization coating formation method have been effectively solved, and the corrosion resistance has been effectively solved under the conditions of use in a heated atmosphere below the temperature I. Another object of the present invention is to propose a heat-resistant/corrosion-resistant polymer coated steel material and a method for forming a polymer coat that can satisfy both heat resistance and corrosion resistance.

[Structure of the invention]

The present invention significantly improves the adhesion between a zinc-nickel alloy plating layer and a black nickel electrolytic plating layer on the surface of a steel material, and also forms a chromic acid film on the outer surface. , the corrosion resistance of each of the plating layer, electrolytic plating layer and chromic acid coating, and the simple polymerization coating formation method have been effectively solved, and even when used in a heated atmosphere below the above-mentioned temperature, The object of the present invention is to propose a heat-resistant/corrosion-resistant polymer coated steel material and a method for forming a polymer coat that can satisfy both heat resistance and corrosion resistance.

[Structure of the invention]

In the present invention, a zinc-nickel alloy plating layer is placed as a lower layer on the surface of a steel material, a black nickel electroplating layer is deposited and polymerized as an upper layer on the surface of the plating layer, and a chromic acid coating is further applied to the surface of the electroplating layer. In addition, as a method for forming the polymer coating of the polymer coated steel, zinc-nickel is coated on the surface of the steel material, which has been pretreated by degreasing, derusting, etc., by electroplating. forming a plating layer of the alloy, further forming a black nickel electroplating layer by electroplating on the surface of the zinc-nickel alloy plating layer, then immersing the surface of the black nickel electroplating layer in an aqueous chromic acid solution;
A chromic acid film is formed by performing a chromic acid treatment consisting of a series of water washing and drying one or more times, or the chromic acid treatment is performed once by a series of chromic acid treatment consisting of immersion in an aqueous chromic acid solution, drying, and heating. Either the above is applied to form a chromic acid film, or alternatively, the chromic acid treatment is performed one or more times, consisting of a series of immersion in an aqueous solution of chromic acid, washing with water, and drying, and 1. 6D, the present invention will be explained below based on the drawings. The following is an example.

Figures 1 and 2 both show a part of the main parts applied to a plate material (Figure 1) and a pipe material (Figure 2), respectively, as heat-resistant and corrosion-resistant polymer coated steel materials constructed by the polymer coating forming method of the present invention. It is an enlarged cross-sectional view with a notch, and (1) shows a surface of a steel material that has been previously subjected to pretreatment such as degreasing and derusting (one is a steel material on which a plating layer (2) made of a zinc-nickel alloy is formed by electroplating, (3) is a black nickel electroplated layer that is polymerized by electroplating on the surface (2) of the zinc-nickel alloy plating layer (2), and (4) is the surface of the black nickel electroplated layer (3). (This is a chromic acid coating formed in three parts.

The zinc-nickel plating layer is an electrolytic plating layer with a pH of 5.8 to A8 whose main components are zinc 1 chloride, nickel chloride, and ammonium chloride.
It is formed in a state in which the content of nickel is in the range of 15% by weight, and naturally the heat and corrosion resistance is effectively achieved by the content of nickel. On the other hand, when depositing and polymerizing the black nickel electroplating layer (3), it is possible to use an electroplating layer of lH5.6 to 5.9 (composed of nickel sulfate, zinc sulfate, nickel ammonium sulfate, and potassium thiocyanide), and Zinc from 30% by weight to 5% by weight
It is formed with a black appearance and is made of a nickel-zinc alloy layer containing V in the range of 0% by weight, and is formed by depositing and polymerizing a composition of the same kind of metal similar to the lower zinc-nickel plating layer. Therefore, the adhesion between the mutually adhered and polymerized surfaces is significantly improved. At the same time, since an electroplated layer having a pH in the range of 5.6 to 5.9 is used during adhesion polymerization, there are no restrictions on pretreatment in between, which simplifies these treatment operations and improves adhesion. The surface of the black nickel electroplated layer (3) is coated with sufficient heat resistance, and the chromic acid coating (4) is formed into three layers.
K works synergistically to fully exhibit corrosion resistance.

When forming the chromic acid coating (4), the polymerized steel material (1) is immersed in an aqueous solution of chromic acid anhydride for about 20 to 60 seconds, washed with water, and then dried at a temperature ranging from room temperature to 150°C. Then, the steel material is subjected to a series of immersion, water washing, and drying processes one or more times, or it is immersed in an aqueous solution of chromic acid anhydride in the same manner as the steel material (1) k above, pulled up, and then dried in that state. Heating is performed for 1 to 5 minutes at about 300°C or less, and the series of treatments consisting of dipping, drying, and heating is performed one or more times, or the series of treatments of dipping, washing, and drying are performed once. - After the above treatment, the series of treatments consisting of dipping, drying and heating is performed once or more again.

In addition, the concentration of chromic anhydride is 20 f/l to 90 f/l.
0? A range of /l is desired, and if it is less than 20f/l, the coating effect will be poor, and if it is less than 900f/l, the coating effect will be poor. This is because if it exceeds ./l, the viscosity of the aqueous solution will increase, significantly reducing workability and at the same time making it uneconomical.

[Action of the invention]

The present invention provides a plating layer (2) made of a zinc-nickel alloy, the gist of which is the above-mentioned polymerized coating structure and method of forming the same.
) and the black nickel electroplated layer (3) on the polymerized surface, the upper black nickel electroplated layer (3)
This results in heat resistance under heated atmosphere conditions below 250°C, and the lower plating layer (2) made of zinc-nickel alloy provides both heat resistance and corrosion resistance. Since the electroplated layer is treated within a range of pi (values) during deposition and polymerization of layer (3), the pretreatment in between is extremely simple, and therefore it is of course possible to improve productivity and form it at low cost. In particular, the surface of the black nickel electroplated layer (3) (the chromic acid coating (4) associated with these methods formed by applying the above-mentioned series of treatments) suppresses the occurrence of white rust and inhibits the formation of zinc. The chromium compound formed by the reaction with chromic acid seals the pinholes that exist, and also forms a passive film on the surface and exhibits a stabilizing effect, further improving corrosion resistance. This results in the reduction and prevention of discoloration, disappearance, peeling, etc. in (4).

[Embodiments of the invention]

Example 1 - Steel material - Material 5TPG3 & outer diameter 1 (10%, wall thickness 0.
7. The tube material of 500% length is pre-treated by degreasing and denitration using conventional methods.

・Zinc-nickel alloy plating treatment ・Zinc chloride 45”i/l
, nickel chloride 759/l, ammonium chloride 250?
/L, using a plating bath consisting of boric acid 20Vt p m (5,8), using the tube as the cathode and the nickel plate as the anode, at a bath temperature of 38°C and a cathode type flow tightness If 2A/d- of 10 After applying electricity for a minute, washing was performed to obtain a zinc-nickel alloy plating layer having a layer thickness of 5 μm.

・Intermediate pretreatment: After immersing in a 10% sulfuric acid aqueous solution for 5 seconds, washing with water is performed.

・Black nickel electroplating treatment...nickel sulfate 751/1
．． Zinc sulfate 389/L, nickel ammonium sulfate 45
9/l, potassium thiocyanide 15 Vt, pH 5.6, the electrolytic plated layer of the zinc-nickel alloy was used, the tube material was used as a cathode, while the nickel plate was used as an anode, and the bath temperature was 50°C. After applying current at a cathode current density of IA/d- for 5 minutes and washing with water, a black nickel electrolytic plating layer having a layer thickness of 4 μm was deposited and polymerized on the plating layer.

- Chromic acid treatment: The coated and polymerized pipe material was immersed in an aqueous solution of 750 t/l of chromic anhydride for 30 seconds, washed with water, and then dried at 50°C. Through this series of treatments, a sifuronic acid coating was formed.

Example 2 ・Steel material: Same as Example 1.

・Zinc-nickel alloy plating treatment・・Zinc chloride 60f/l
, nickel chloride 859/l, ammonium chloride 200f
/l, ammonia water 50d/l, boric acid 20? Using a plating bath with a pH of 65 and a composition of /l, using the tube material as a cathode and the nickel plate as an anode, current was applied for 8 minutes at a bath temperature of 40°C and a cathode current density of 25Vd-, resulting in a zinc-nickel layer with a layer thickness of 5μ. An alloy plating layer was obtained.

- Intermediate pretreatment - Same as Example 1.

・Black nickel electroplating treatment: Same as Example 1.

・Chromic acid treatment: The coated and polymerized pipe material was immersed in a water bath containing 50 Vt of chromic acid anhydride for 40 seconds, washed with water, and then dried in an oven at 120°C. This series of treatments was performed twice. A chromic acid film was formed.

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 acid anhydride 500? The coated and polymerized tube material was immersed in an aqueous solution of 200.degree.

Example 4 The steel material, zinc-nickel alloy plating treatment, intermediate pretreatment, and black nickel electroplating treatment were all the same as in Example IK.

・Chromic acid treatment: The adhered and polymerized pipe material was immersed in an aqueous solution of 250 f/l of chromic acid anhydride for 25 seconds, dried at room temperature, and then heated at 230°C for 5 minutes, and this series of treatments was performed twice. A chromic acid film was formed.

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: The coated and polymerized pipe material was immersed in an aqueous solution of chromic anhydride 750 f/l for 30 seconds, washed with water, dried at 60°C, and then treated with chromic anhydride 2501/l again.
After immersing in an aqueous solution of l for 30 seconds and drying at 60°C,
A chromic acid film was formed by heating at 250° C. for 3 minutes.

Comparative Example Using the same steel material as in Example 1, a plating layer consisting of 302/L of zinc oxide, 509/L of soda cyanide, and 60Vt of caustic soda was used, and the tube material was used as a cathode, while the zinc plate was used as an anode at room temperature. After applying current at a cathode current density of 3 Vd- for 15 minutes, the plate was washed with water to obtain a zinc plating layer with a layer thickness of 9μ, and then immersed in a black chromate bath for 20 seconds at room temperature, then washed with water, and dried. A black chromate coating was obtained.

The above-mentioned products of the present invention (Examples 1 to 5) and conventional products (Comparative example)
For comparative characteristics results regarding heat resistance and corrosion resistance tests with
It is described in Table-1 and Table-2 below.

・Heat resistance test results After constant constant heating for 24 hours in a heated atmosphere of 200°C, the temperature was allowed to cool down to the atmospheric temperature f, and then heated again at 200°C.
The specimens were continuously heated at a constant temperature of 50° C. for 24 hours, and the external appearance of each specimen was visually observed.

Table 1 - Corrosion Resistance Test Results The heat resistance test samples after 24 hours at 200°C were tested according to the salt spray test method specified in JIS Z-2371.

In the table, W indicates white rust spots, B indicates red rust spots, WW indicates flowing white rust,
RR indicates flowing red rust, and the numbers attached to the generated items indicate the average number of generated rust at the time of recording and the surface area of the generated part, and if R occurs, Wl
Only R was recorded regardless of whether WW occurred, and if RR occurred, only RR was recorded regardless of whether R occurred.

〔Effect of the invention〕

As described above, the heat-resistant and corrosion-resistant polymer coated steel material and the method for forming the polymer coat according to the present invention include the mutual zinc-nickel alloy plating layer (2) and the black nickel electroplating layer (3), each of which is heated by the heating process. 1. The surface (3') of the black nickel electroplated layer (3) can simultaneously satisfy heat resistance and corrosion resistance under atmospheric conditions, and has extremely good adhesion between these mutually adhered polymerized surfaces. The chromic acid film (4) formed by applying a series of treatments to the chromic acid film (4), which is related to the above-mentioned formation method, suppresses the occurrence of white rust, and prevents the formation of pinholes in the chromium compound caused by the reaction between zinc and chromic acid. This synergistic effect of promoting pore sealing and stabilizing the formation of a passive film on the surface further improves corrosion resistance. At the same time, it also reduces discoloration, disappearance, or peeling of the chromic acid film itself. , can be prevented, and furthermore, during the polymerization coating process, productivity can be improved and the cost can be made relatively low by simplifying the intermediate pretreatment related to the range of use of the pEI value of the electroplating bath. The present invention provides an extremely useful heat-resistant and corrosion-resistant polymer coated steel material and a method for forming the polymer coat, which have many features such as 1.

[Brief explanation of the drawing]

Fig. 1 is an enlarged cross-sectional view with a partial cutout of a main part of a plate material coated with a heat-resistant and corrosion-resistant polymeric coating according to an embodiment of the present invention;
The cocoon was also made on the pipe material! It is an enlarged sectional view with a part notch of the part. (1)...Steel material, (1...Surface, (2)...Zinc-nickel alloy plating layer, (2')...Surface, (3
)...Black nickel electroplating layer, (3')...Surface,
(4)...Chromic acid coating. Patent applicant Usui Kokusai Sangyo Co., Ltd. Agent 1) Ryotooke

Claims (1)

[Claims] 1) The surface of the steel material (1) (1), the lower layer is the plating layer (2) made of zinc-nickel alloy, and the surface of the plating layer (2) is the lower layer.
A black nickel electroplating layer (3) is applied and polymerized as an upper layer, and the surface (3') of the black nickel electroplating layer (3) is then polymerized.
A heat-resistant and corrosion-resistant polymer coated steel material characterized by having a K chromic acid coating (4). 2) The surface of the steel material (1) which has been pre-treated by degreasing, derusting, etc. (one is a zinc-nickel alloy plating layer (2) formed by electroplating method). The surface of the plating layer (2) (29) is coated with the electroplated layer (3) of black nickel by the electroplating method, and then the surface of the electroplated layer (3) of iron black nickel (3) is immersed in a chromic acid aqueous solution and washed with water. A method for forming a polymer coating on a heat-resistant and corrosion-resistant polymer-coated steel material, characterized in that a chromic acid coating (4) is formed by subjecting the steel to a chromic acid treatment consisting of a series of steps of chromic acid treatment and drying at least once. 3) Claim 2 In the method for forming a polymeric coating of heat-resistant and corrosion-resistant polymeric-coated steel material described in Section 1, the chromic acid coating (4) is formed by applying a series of treatments t-1 or more times consisting of immersion in an aqueous chromic acid solution, drying, and heating. A method for forming a polymeric coating on a heat-resistant and corrosion-resistant polymeric-coated steel material, which is characterized by forming a polymeric coating on the surface of the steel material (1) that has been previously subjected to degreasing, derusting, etc. A plating layer (2) of the zinc-nickel alloy is formed, and then the surface of the plating layer (2) of the zinc-nickel alloy (the electroplating layer (3) of black nickel by electroplating method) is completely deposited and polymerized, and then the black nickel The surface of the electroplated layer (3) (39) was subjected to a chromic acid treatment consisting of a series of steps of dipping in an aqueous chromic acid solution, washing with water, and drying.
A heat-resistant and corrosion-resistant polymer-coated steel material characterized by forming a chromic acid coating (4) by applying a series of treatments consisting of immersion in a recondensed chromic acid aqueous solution, drying, and heating one or more times. A method for forming a polymeric coating.