JPS60194296A - Material for heat exchanger, which is prominent in anticorrosion - Google Patents

Abstract

PURPOSE:To improve anticorrosion by a method wherein copper or copper alloy, whose surface is covered by a diffusion layer consisting principally of intermetallic compound of nickel and tin, is employed for the material of a radiator. CONSTITUTION:In order to form the diffusion layer, consisting principally of the intermetallic compound of nickel and tin, on the surface of the copper alloy for the purpose of providing the copper alloy with anticorrosion, a coating layer consisting of two layers of nickel and tin is formed and, thereafter, heat treatment is applied thereto. In order to form two layers of nickel and tin, electroplating, electroless plating, fusion plating, flame spray coating or the like may be employed and the order of forming, however, is nickel first and tin second. At least 0.2mum of thickness of the coating layer is necessary in total of the thicknesses of nickel layer and tin layer and any proportion between the thicknesses of nickel layer and tinlayer, which can form the thickness of intermetallic compound of at least 0.2mum after heating, may be selected arbitrarily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a material having excellent corrosion resistance used in heat exchangers and the like, and particularly to a material for radiators used in automobiles and the like.

Radiators, especially automobile radiators, dissipate heat by circulating liquid between the engine and the radiator as a cooling medium to adjust the temperature of the engine.The radiator fins dissipate heat from the tubes in which the refrigerant circulates to the atmosphere. It has the function of dissipating. Therefore, a 0u-8u alloy with high thermal conductivity has been used as a conventional radiator fin material. In recent years, there has been a strong demand for lighter vehicles as a measure to save energy.

Radiator fins are also becoming thinner. However, while the car is running, the radiator is heated to nearly 100 degrees Celsius, exposed to salty coastal air, and even factory air. Due to exposure to gas and mist containing anti-freezing agents in the winter, corrosion of the fins progresses rapidly and, combined with the thinning of the fins, the heat dissipation of the radiator is affected.

The strength of the radiator is significantly reduced, and the lifespan of the radiator is becoming shorter. Therefore, in order to make the radiator fins thinner and extend the life of the radiator, there has been a desire to develop a heat exchanger material with excellent corrosion resistance.

In response to this demand, many attempts have already been made to add various elements to copper to improve its corrosion resistance. A material that exhibits excellent corrosion resistance has not yet been found.

The present invention has been made based on various studies in view of the above points, and has been developed as a material for heat exchangers, especially radiators, in which the surface of copper or copper alloy is covered with a diffusion layer mainly composed of an intermetallic compound of nickel and tin. We have developed a heat exchanger material with excellent corrosion resistance.

Any copper alloy can be used as the base material used in the present invention, but when used in heat exchangers, especially fins for automobile radiators, it is recommended to use a copper alloy with high strength and high conductivity. can be made thinner.

In order to form a diffusion layer mainly composed of an intermetallic compound of nickel and tin on the surface of the copper alloy in order to impart corrosion resistance to the copper alloy, a coating layer consisting of two layers of nickel and tin is formed and then heated. Apply processing.

The methods for forming two layers of nickel and tin are electroplating, electroless plating, and hot-dip plating.

A thermal spraying method or the like may be used, but the coating is performed in the order of nickel and tin. When the coating order is tin and nickel, the tin is in contact with the copper alloy during the subsequent heat treatment.The nickel and tin metals are necessary to obtain excellent corrosion resistance because of the diffusion of the rounded tin into the steel. This is because sufficient generation of intermediate compounds cannot be obtained. The thickness of the coating layer is 0 including the nickel layer and tin layer.
．． It is necessary to have a thickness of 2 μm or more, and the ratio between the thickness of the nickel layer and the thickness of the tin layer in the coating layer may be such that the thickness of the intermetallic compound layer after heating is Q, 2 μm or more. Furthermore, it is understood that a pure nickel layer and a pure tin layer remain after the heat treatment, so that they do not have any adverse effect on corrosion resistance.

Therefore, the diffusion layer in one aspect of the present invention includes a residual layer of pure nickel or pure tin after heat treatment.

The temperature of the heat treatment may be at least the melting point of tin.

The heat treatment time is determined by the time it takes for tin to diffuse into the nickel layer and form an intermetallic compound.
When each tin layer is 1.0 μm.

It takes about 5 minutes at 350°C.

Next, an example will be described.

Example C After forming a nickel layer and a tin layer with the thickness shown in Table 1 on a 14 m thick tough pitch copper by electroplating,
Heat treatment was performed at 0° C. for 5 minutes. This test piece was heated at 70℃
90 ['LH atmosphere for 30 days, during the test period 1
The artificial seawater shown in Table 2 was sprayed into the test tank once a day. After the test, the test piece was pickled with an aqueous solution of 5-superior sulfuric acid, and the corrosion rate was calculated from the weight loss before and after the test, and the corrosion resistance was evaluated based on this. Table 3 shows the results. As can be seen from Table 3, the materials of the present invention (sample numbers 1 to 15) exhibit excellent corrosion resistance and are most suitable as materials for heat exchangers, particularly as materials for automobile radiators.

Table 1 Table 2 Table 3

Claims (2)

[Claims] (1) A heat exchanger material with excellent corrosion resistance, in which the surface of copper or copper alloy is covered with a diffusion layer mainly composed of an intermetallic compound of nickel and tin. (2) A material for a heat exchanger having excellent corrosion resistance according to claim 1, wherein the thickness of the coating layer is 0.2 μm or more.