JPS633032B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a polymer-coated steel material that is applied to the surface of steel materials such as plates, tubes, rods, wire rods, etc., and which requires heat resistance and corrosion resistance at the same time, especially in a heated atmosphere below about 250 degrees Celsius. It is related to. Conventional heat-resistant and corrosion-resistant polymer-coated steel materials are generally put into practical use by simply forming a normal chromate coating on a zinc plating layer on the steel surface formed by electroplating or dipping, or In connection with the requirement for quality value in terms of appearance, a black chromate film was formed on the zinc plating layer on the surface of the steel surface for practical use. However, in the case of conventional products having the above-mentioned coating structure, which are attached as various parts around the engine, for example, in an internal combustion engine, the chromate coating on the surface is damaged due to the influence of heat from continuous or repeated use from the engine. Alternatively, black chromate coatings generally discolor in a short period of time, causing disappearance, peeling, etc., resulting in a deterioration of heat resistance, and at the same time, this deterioration of heat resistance also impairs corrosion resistance, leading to its decline. Therefore, the current situation is that there is a widespread demand for improvements. The purpose of the present invention is to solve this problem very effectively, especially by improving the adhesion on the surface of the zinc plating layer.
1 is a steel material made of a plate, tube, rod, wire rod, etc., and the steel material 1 has been pretreated in advance by conventional methods such as degreasing and derusting, and the steel surface 1' is prepared by a conventional electroplating method or dipping method. It has a zinc plating layer 2 on it. 3 further includes 30% by weight of zinc deposited and polymerized on the surface 2' of the zinc plating layer 2 by electroplating.
This is a black nickel electroplated layer with a nickel-zinc alloy layer containing 50% by weight. The range of zinc content in the deposited and polymerized black nickel electroplated layer 3 is 30% by weight.
In the following cases, the adhesion with the lower galvanized layer 2 cannot be achieved extremely well, and if it exceeds 50% by weight, the heat resistance on the surface cannot be sufficiently exhibited. . In addition, during the above-mentioned deposition polymerization, the electroplating bath should be
Since it can be used with 5.6 to 5.9,
It is possible to form the film with excellent adhesion and sufficient heat resistance without intentionally restricting intermediate pre-processing or requiring complicated processing. In this way, the zinc plating layer 2 is formed as a lower layer on the steel skin surface 1', and the electrolytic plating layer 3 of black nickel is formed as an upper layer on the surface 2' of the plating layer, which is deposited and polymerized. In relation to excellent adhesion, the upper black nickel electroplated layer 3 provides heat resistance in a heated atmosphere of about 250℃ or less, and the lower zinc plating layer 2 provides corrosion resistance. At the same time, in order to use the plating bath within the range of PH value when depositing and polymerizing the electroplated layer 3 of black nickel, the pretreatment in the middle is extremely simple, and therefore the production is significantly improved. This is an extremely useful heat-resistant and corrosion-resistant polymer coated steel material that has improved properties and can be formed at a low cost. Examples of the present invention are as follows. Example 1 ●Steel material...Material STPG38, outer diameter 10.0m/m,
A pipe material with a wall thickness of 0.7 m/m and a length of 500 m/m is pretreated to degrease and remove rust using conventional methods. ●Zinc plating treatment: Using a plating bath consisting of 30 g of zinc oxide, 50 g of cyanide soda, and 60 g of caustic soda, the tube material is used as a cathode, while the zinc plate is used as an anode, and a cathode current is applied at room temperature. density
After energizing at 3A/ ^dm2 for 15 minutes and washing with water,
A zinc plating layer having a layer thickness of 9 μm was obtained. ●Intermediate pretreatment: Dip in 3% HCl aqueous solution for 10 seconds, then wash with water. ●Black nickel electroplating treatment……Nickel sulfate 75
g/, zinc sulfate 38 g/, nickel ammonium sulfate 45 g/, potassium thiocyanide 15
Using an electroplating bath with a pH of 5.6 and a composition of
Similarly, the tube material was used as a cathode, and the nickel plate was used as an anode, and the bath temperature was 50℃ and the cathode current density was
After applying electricity for 5 minutes at 1A/ ^dm2 , the result was washed with water.
An electrolytic plated layer of black nickel having a thickness of 4 μm was formed on the plated layer by deposition and polymerization. Example 2 ●Steel materials...Same as Example 1 ●Zinc plating treatment...Zinc sulfate 360g/, aluminum chloride 12.5g/, soda sulfate 75g/
A plating bath with a pH of 3 having the composition of
After applying electricity for 3 minutes at 60° C. and a cathode current density of 12 A/dm ² , washing with water resulted in a zinc plating layer having a layer thickness of 9 μm. ●Intermediate pretreatment...Same as Example 1 ●Black nickel electroplating treatment...Same as Example 1,
However, a black nickel electroplated layer having the same layer thickness of 4 μm was deposited and polymerized at a pH of 5.0 and a bath temperature of 60°C. Comparative Example After performing zinc plating treatment under the same conditions as in Example 1 to obtain a zinc plating layer with a thickness of 9μ on the surface of the pipe material, it was immersed in a black chromate bath for 20 seconds at room temperature, and then washed with water. Obtained by drying. The results of the comparative characteristics of the products of the present invention (Examples 1 and 2) and the conventional product (comparative example) in heat resistance and corrosion resistance tests are shown in Tables 1 and 2 below. ●Heat resistance test After continuous heating in a heating atmosphere of 200℃ for 24 hours,
The specimens were left to cool in the atmosphere, and after checking the temperature drop to atmospheric temperature, they were heated again for 24 hours in an atmosphere where the temperature was raised to 250°C, and the external appearance of each specimen was observed.

[Table] ●Corrosion Resistance Test The samples after 24 hours of heat resistance test at 200°C were subjected to the salt spray test method according to JISZ-2371.

[Table] In the table, R indicates red rust spots and RR indicates flowing red rust.The numbers attached to the above-mentioned occurrences indicate the average number of occurrences at the time of recording, and only R is recorded. If RR occurred, only RR was recorded regardless of the occurrence of R.

[Brief explanation of the drawing]

FIG. 1 is an enlarged partially cutaway cross-sectional view of a heat-resistant and corrosion-resistant polymer coated steel material according to an embodiment of the present invention, and FIG. 2 is an enlarged view of the main part A of FIG. 1. 1...Steel material, 1'...Steel skin surface, 2...Plating layer, 2'...Surface, 3...Electroplated layer.

Claims (1)

[Claims] 1. A zinc plating layer 2 is provided as a lower layer on the steel skin surface 1' of the steel material 1, and zinc is further applied to the surface 2' of the plating layer.
A heat-resistant and corrosion-resistant polymer coated steel material characterized in that it is constructed by depositing and polymerizing a black nickel electroplated layer 3 made of nickel-zinc containing 30% to 50% by weight as an upper layer.