JPH06280066A - Cleaning agent for nickel-plated surface and cleaning method - Google Patents

Abstract

PURPOSE:To obtain a cleaning agent capable of removing scale without dissolving nickel by incorporating formic acid or hydroxycarboxlic acid and araboascorbic acid, ascorbic acid or boron hydride compound. CONSTITUTION:This cleaning agent is a water base cleaning agent for nickel- plated surface containing one or more kind of (a) formic acid, hydroxycarboxylic acid or these mixture and (b) araboascorbic acid, ascorbic acid and boron hydride compound and the scale is removed without dissolving a protective nickel layer by dipping the nickel surface into a solution containing the cleaning agent. In the cleaning agent, the component (b) is preferably incorporated by 5-20wt.% of the component (a). And, if necessary, a metallic chloride such as ferric chloride is incorporated by 1-5% of the component (a). The cleaning solution contains 1-20% the component (a) and is preferably used at ordinary temp. to 90 deg.C for 1-6 hours in dipping time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous cleaning agent and a cleaning method for nickel-plated surfaces. In particular, it relates to a cleaning agent and a cleaning method for a nickel plating surface in a chemical device.

[0002]

2. Description of the Related Art Conventionally, iron or stainless steel has been often used as a material for chemical equipment, but recently, nickel-plated material has been used for chemical equipment, particularly for heat exchangers and reactor jackets. Is becoming. In the heat exchange device, the material is selected from the viewpoint of economy in consideration of heat transfer coefficient, corrosiveness due to cooling or heating medium, resistance to temperature and pressure, etc., and iron has been mainly used. However, on the surface of the heat exchange device that comes into contact with water used as a cooling medium or a heating medium, salts dissolved in water to be used, salts due to an added anticorrosive agent, etc. are precipitated as scales, The overall heat transfer coefficient gradually decreases. Therefore, in order to return the surface to which the scale is attached to the original state, the attached matter is removed by pickling or high pressure jetter. However, iron is a material that is easily oxidized, and once it is oxidized, iron rust is deposited and the overall heat transfer coefficient is extremely lowered, so that the conventional method for removing deposits is not sufficient. Therefore, nickel plating is applied to the surface of iron to prevent rust (iron oxide) from being deposited on the surface of the iron, to reduce the heat transfer coefficient, and to be applied even with a complicated shape.

[0003]

However, even in a nickel-plated heat exchange device, the water used as a cooling medium or a heating medium has water quality and dissolved salts which vary greatly depending on the water source. Due to the salts derived from the added anticorrosives, etc., during the long-term use, these salts are deposited as a scale on the heat transfer surface where they are exchanging heat, so that the overall heat transfer coefficient does not decrease. I can't.
If the structure of the scale adhering surface is simple, the adhering matter can be removed by a high pressure jetter or the like, but if the scale adhering surface has a complicated structure, it is difficult to remove it by a high pressure jetter or the like. On the other hand, pickling with hydrochloric acid etc. causes a large elution amount of plated nickel,
Eventually the surface of the iron is exposed and the meaning of protection disappears. From such a situation, without melting the protective nickel layer,
A cleaning agent and a cleaning method capable of removing scale are desired.

[0004]

Means for Solving the Problems The inventors of the present application have earnestly studied a cleaning agent or a cleaning method that removes scale, slime, etc. that adhere to a nickel-plated surface and does not elute nickel in a protective film as much as possible. The inventors have found that a cleaning agent containing a specific organic acid and a specific reducing substance is effective, and completed the invention of this application. The structural feature of the invention of this application is that nickel containing at least one selected from (a) formic acid, hydroxycarboxylic acid or a mixture thereof and (b) araboascorbic acid, ascorbic acid and a borohydride compound as an active ingredient. An aqueous cleaning agent for a plating surface and a method for cleaning a nickel plating surface using this cleaning agent. The invention of this application will be described in detail below.

The cleaning agent of the invention of this application comprises formic acid, which is the main component,
Hydroxycarboxylic acid or a mixture thereof (hereinafter referred to as (a)
The component) and a small amount of reducing component (hereinafter referred to as the component (b)) are the active components. The hydroxycarboxylic acid as the component (a) of the detergent of the present invention is an aliphatic hydroxycarboxylic acid such as malic acid, lactic acid, citric acid and glycolic acid, and the hydroxycarboxylic acid may be one kind or a mixture of two or more kinds. It may be. Further, it may be a mixture of one or more hydroxycarboxylic acids and formic acid. The component (b), araboascorbic acid, ascorbic acid and a borohydride compound, are mixed and used in a proportion of 5 to 20% by weight based on the total amount of the carboxylic acid as the component (a). In the invention of this application, the ascorbic acid as the component (b) contains its oxidized form ascorbic acid, and the arabo ascorbic acid contains its oxidized form. Further, the borohydride compound is sodium borohydride, potassium borohydride, lithium borohydride, calcium borohydride, aluminum borohydride, borohydride amine, etc., preferably sodium borohydride Used. When the component (a) alone is used, a cleaning effect is recognized, but the amount of nickel eluted is large, which is not suitable for practical use. By coexisting the above-mentioned reducing substance as a minor component in this, the elution amount of nickel can be remarkably suppressed without reducing the cleaning effect. When a metal chloride such as ferric chloride is added as the component (c) to the components (a) and (b), the amount of nickel eluted is further suppressed.

In cleaning the nickel-plated surface, the component (a) in the cleaning liquid is preferably 1 to 20.
%, More preferably 2 to 15% by weight, and the component (b) should be dissolved in an amount of 0.01% by weight or more, preferably 0.1 to 3% by weight. Is preferred. In addition to these components, a metal chloride, such as ferric chloride, is preferably added to the cleaning liquid in an amount of 0.1 to 1
Weight%, more preferably 0.05 to 0.5% by weight is also effective in suppressing the elution of nickel. In addition, each of these detergent components may be prepared by dissolving it in water so as to have the above-mentioned use concentration each time it is used.
It is convenient to prepare a high concentration in advance and dilute it before use.

The washing temperature of the present invention is from room temperature to 90 ° C., preferably 40 to 80 ° C., and 0.5 to 10 ° C.
Immersion treatment is carried out for a time, preferably 1 to 6 hours. At this time, the cleaning liquid may be in a static state, but preferably, it is brought into a flowing state by using a circulation pump or the like. By heating the cleaning liquid and further flowing it, the cleaning effect can be enhanced and the cleaning time can be shortened.

The components of the deposits in the heat exchanger of the chemical device are zinc, phosphorus, which are dissolved in water used as a heating medium or a cooling medium, which are oxides of iron, calcium, silicon compounds and salts and anticorrosive agents. Examples include acid salts and slime generated in an aqueous medium. The composition of these deposits is not the same depending on the water source of the water used and the type of the anticorrosive agent, but the deposits can be sufficiently dissolved and removed by washing as described above. Even when immersed for a long time so that the deposits can be sufficiently dissolved and removed, the elution amount of nickel into the cleaning liquid is extremely small as shown in the examples. The nickel plating method may be either electrolytic plating or electroless plating. Further, if the nickel plating has a film thickness of 10 to 50 μm, the scale removal method according to the invention of the present application will not substantially lose the film. Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

[0009]

【Example】

Example 1 A carbon steel (25 × 50 × 1 mm) surface was plated with nickel to a thickness of 30 to 40 μm by an electroless nickel plating method to prepare a test piece. Each test piece was suspended and immersed in a beaker containing 300 ml of the cleaning liquid having the composition shown in Table 1 and Table 2, and the mixture was stirred with a Magnetus Kustler while maintaining the temperature at 60 ° C. After 3 hours, the test piece was taken out, the nickel concentration in the cleaning liquid was measured by an atomic absorption spectrometer, and the nickel elution amount was measured. Table 1 shows the results of the examples using the cleaning solution of the present invention, and Table 2 shows the results of other cleaning agents as comparative examples.

[0010]

[Table 1]

[0011]

[Table 2]

Example 2 To measure the dissolving power of a scale, 100 ml of a detergent having the composition shown in Table 3 was placed in a 300 ml beaker, and 2 g of a scale containing calcium phosphate as a main component was added to the beaker and maintained at 40 ° C. While stirring, it was stirred with McNetch Kusterer. The amount of calcium dissolved in the washing solution after 1 hour was measured by an atomic absorption spectrometer. The results are shown in Table 3.

[0013]

[Table 3]

[0014]

EFFECT OF THE INVENTION The cleaning agent of the present invention comprises formic acid or a specific hydroxycarboxylic acid as a main component and a small amount of a specific reducing component coexistent. Can be effectively removed by washing while suppressing the elution of

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hirofumi Nakanishi Hirofumi Nakanishi 1082 Shiizu, Ichihara-shi, Chiba Inside Chiba Sales Office, Hakuto Co., Ltd. Yokkaichi Institute

Claims (5)

[Claims] 1. (a) Formic acid, hydroxycarboxylic acid or a mixture thereof and (b) Araboascorbic acid,
An aqueous cleaning agent for a nickel-plated surface, which comprises at least one selected from ascorbic acid and a borohydride compound. 2. The aqueous detergent for a nickel-plated surface according to claim 1, wherein the component (b) is contained in an amount of 5 to 20% by weight of the component (a). 3. The aqueous cleaning agent for a nickel-plated surface according to claim 1, further comprising (c) a metal chloride. 4. The nickel according to claim 3, wherein the component (b) contains 5 to 20% by weight of the component (a) and the component (c) contains 1 to 5% by weight of the component (a). Aqueous cleaning agent for plating surface. 5. A method for cleaning a nickel-plated surface, which comprises immersing the nickel-plated surface in a solution containing the aqueous cleaning agent according to claim 1.