JPS62180099A - Electrolytic degreasing solution having surface polishing activity - Google Patents

Abstract

PURPOSE:To shorten the time required to treat a metal with an electrolytic degreasing soln. and to improve the luster of the metal by using an alkali metallic chloride at a high concn. in the degreasing soln. contg. the alkali metallic chloride combined with an alkali metallic phosphate or sulfate as a builder for a surfactant. CONSTITUTION:An alkali metallic chloride is used at such a high concn. as >=8g/l in an electrolytic degreasing soln. having surface polishing activity and contg. the alkali metallic chloride combined with an alkali metallic phosphate or sulfate as a builder for a surfactant. The degreasing soln. contains no inorg. or org. complexing agent and keeps the treatability of waste water satisfactory.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface polishing active type electrolytic degreasing liquid.

[Conventional technology]

Generally, when surface treatments such as plating and painting are applied to metal surfaces, dirt such as oil and rust adhering to the surface deteriorates the quality of the surface-treated product, so it is necessary to remove such dirt through pre-treatment. . Pretreatment has a large impact on quality and cost, and it is said that the majority of defects in plating factories are due to incomplete pretreatment.

Dirt such as oil and fat adhering to metal surfaces is usually removed by solvent degreasing, alkaline immersion degreasing, and electrolytic degreasing. Final electrolytic degreasing is used as a final degreasing method to completely remove oils and other stains that cannot be removed by solvent degreasing, which is preliminary degreasing, or alkaline immersion degreasing. Electrolytic degreasing is a method of physically removing metal using hydrogen gas or oxygen gas generated from the metal surface due to electrolysis by passing electricity through an electrode opposite to the metal to be treated in an alkaline solution, and it is highly effective. It has the advantage that it can be degreased in a short time, and that oils and lipids that are difficult to remove using other methods can be removed relatively easily.

However, products that require high levels of smoothness and gloss,
Since machining and polishing are performed strongly, there is no oil etc. on the surface.
．． It penetrates into a single layer of about 1 μm thick rubber and is strongly adsorbed and held. Therefore, it is much more difficult to degrease than ordinary adhering oil. Degreasing products that are difficult to remove,
For example, use stronger and more corrosive degreasers, or
Alternatively, it is carried out by a method such as degreasing over a long period of time. According to these methods, there is a problem in that a highly processed smooth surface becomes a rough surface, making it impossible to obtain the required finished surface.

For this reason, there are surface-dissolved electrolytic degreasing baths that use extremely stable complexing agents such as sodium cyanide, citric acid, ethylenediaminetetraacetate, and diethyldithiocarbamate; Defatted wastewater significantly interferes with the formation of heavy metal precipitates in wastewater treatment, making it difficult to treat.

Furthermore, recently, more and more functional parts have to undergo surface treatment, and the products are required to have high precision and quality, as well as to speed up production in order to reduce costs.

For example, in the plating of electronic components, as plating speeds increase, pretreatment speeds up are required, and what used to take 1 to 10 minutes to perform electrolytic degreasing now has to be done in a few seconds to several tens of seconds. It's disappearing.

[Problem that the invention seeks to solve]

The conventional electrolytic degreasing solutions and metal surface treatment methods described above cannot meet the demands for faster degreasing of functional parts, etc.
A large number of defective products occur due to variations in electrical properties such as magnetic properties, poor plating adhesion, poor appearance, etc., and major problems remain in product reliability, and wastewater treatment has become a problem.

[Means for solving problems]

The purpose of the present invention is to solve these problems.The present invention does not contain inorganic or organic complexing agents, and has a high concentration of alkali metals in the electrolytic degreasing solution while maintaining good wastewater treatment properties. This was obtained based on the knowledge that an electrolytic degreasing solution containing a chloride of 100% can be used as an electrolytic degreasing solution for functional parts, etc.

That is, the present invention provides an electrolytic degreasing solution containing an alkali metal chloride and an alkali metal phosphate as surfactants, in which the alkali metal chloride is added at 8 g/A.
It is a surface polishing active type electrolytic degreasing liquid characterized by containing the above-mentioned high concentration. This is a surface polishing active type electrolytic degreasing liquid characterized by containing an alkali metal chloride at a high concentration of 8 g/l or more.

According to the above configuration, ions such as chlorine ions are concentrated on the surface of the metal to be treated during electrolysis, and the surface is dissolved by these ions, and the reactive oil or adsorbed oil on the surface is reduced in seconds. Since it is quickly removed in a short time and the surface is polished at the same time, the glossiness of the metal to be treated is improved. In this way, degreasing is completed in a short period of time on the order of seconds, polishing is performed, and the gloss rate is improved, so the degreasing process can be shortened and the next process of chemical polishing and electrolytic polishing can be omitted, improving productivity and quality. , rationalization of preprocessing, etc. can be achieved.

The present invention will be further explained in detail below.

The composition of the electrolytic degreasing solution of the present invention includes an alkaline pH buffer,
It consists of an alkali metal chloride, an alkali metal phosphate or an alkali metal sulfate, and a surfactant.

As specific examples of these alkaline pH buffers,
Examples of alkali metal chlorides include sodium chloride and potassium chloride; examples of alkali metal phosphates include sodium phosphate; examples of alkali metal sulfates include sodium sulfate. . Further, as the surfactant, a commercially available surfactant can be used.

Sodium carbonate, which is normally included in a degreasing agent for pH adjustment, is an indispensable constituent of the degreasing solution for purposes such as saponification of oil. However, carbonate is applied to the surface of the metal being treated during electrolysis.
A carbonate film is formed in the same way as a phosphate film, which interferes with the surface treatment in the next step. Although this thickness is up to 0.01 μm, this film is dissolved during electrolytic degreasing due to the alkali metal chloride in the degreasing solution, and no carbonate film is formed.

The electrolytic degreasing solution of the present invention can be applied to known electrolytic degreasing methods such as cathodic electrolysis, anodic electrolysis, PR electrolysis, and high-speed current reversal electrolysis.

Next, the features of the present invention will be explained.

First, the first feature of the present invention is that the electrolytic degreasing solution contains alkali metal chloride at a high concentration. Alkali metal chlorides are usually used as salting-out agents in the production of oil emulsions or surfactants, but when alkali metal chlorides are contained in high concentrations, they have the opposite effect on cleaning and reduce the cleaning effect. It was thought that it would reduce the

Normally, sodium chloride exists in a surfactant as an impurity in trace amounts, with less than 1% of sodium chloride in the surfactant.
In the degreasing solution, the presence of 5Qppm level is said to clearly increase the cleaning effect;
At high concentrations of g/l, it acts as a salting-out agent for surfactants, and is actually used as a salting-out agent during purification during surfactant production. It was believed that the presence of such substances would reduce the cleaning effect.

However, sodium chloride is added to the electrolytic degreasing solution at 88%
Normally, when sodium chloride is contained at a high concentration of C or more, it is expected to have an obvious adverse effect and reduce cleaning efficiency, but actual test results show that during electrolytic degreasing, sodium chloride
I! - and Na'', Na4 shows the effect of dispersing the surfactant in the liquid as an alkaline component, and C1-
It was confirmed that the oxide acts as an acid and can dissolve and remove dirt such as oil that has adsorbed and eaten into the sample surface along with the metal. By containing a high concentration of alkali metal chloride such as sodium chloride in the electrolytic degreasing solution as described above, it is possible to remove oil and other dirt that has adsorbed or eaten into the surface extremely efficiently in a short time. Surface polishing also progresses at the same time, resulting in a clean and shiny metal surface.

This function is exactly the same for potassium chloride, and its effects are also the same.

The second feature of the present invention is that good degreasing can be carried out without using phosphoric acid-based buildup, which is generally considered to be the most excellent surfactant. Phosphate is the best dispersant for surfactants in general cleaning, but when used for degreasing metals, it forms a phosphate film on the surface of the metal being treated, resulting in surface activation. After degreasing, it must be activated by acid treatment, etc. On the other hand, alkali metal sulfates such as sodium sulfate and alkali metal chlorides such as sodium chloride and potassium chloride, which have inferior properties to phosphates but are considered to be relatively good builders, are used. For example, when the electrolytic degreasing solution contains 3 g/l or more and 8 g/l or more, degreasing progresses rapidly while the surface of the metal to be treated is polished well without the formation of a phosphate film. Furthermore, since the dispersing power of the surfactant is not impaired, it has a degreasing power equal to or greater than that of a phosphate bath.

Furthermore, even if it does not contain phosphate, the same or better degreasing effect can be obtained, which is a great advantage in terms of environmental protection.

The third feature is that when performing electrolytic degreasing using the electrolytic degreasing solution of the present invention, the polarity is reversed in extremely short periods during electrolysis, such as the fast current reversal electrolysis method, compared to electrolytic degreasing using normal direct current. The effect will be even more pronounced.

In other words, when the metal to be treated becomes an anode, chlorine ions and sulfate ions promote dissolution and polishing of the surface and degrease adsorbed oil, and when the metal is reversed and becomes a cathode, sodium ions, etc. It is concentrated in the surrounding area and has the effect of saponifying and degreasing oil.

The fourth feature is that the electrolytic degreasing solution of the present invention can perform degreasing and polishing well regardless of the material and type of metal to be treated. General electrolytic degreasing liquids are formulated for each material depending on the alkali resistance of each material. For example, iron alloys have the highest alkali resistance, while aluminum alloys have the lowest alkali resistance due to their poor alkali resistance.

This is because when a highly alkaline degreasing liquid with excellent degreasing power is applied to an aluminum alloy with weak alkali resistance, the surface of the metal to be treated becomes rough due to etching and cannot be used as a pretreatment for degreasing. be.

As a result, there is no choice but to use a low alkaline degreasing solution with weak degreasing power.

Although the electrolytic degreasing solution of the present invention maintains an appropriate alkaline property, the alkali metal chloride blended in the solution at a high concentration dissociates into C1- and Na'' etc. during electrolysis. Since degreasing, dissolution, and polishing are carried out quickly, there is no need to make the liquid extremely high or low alkaline.

Furthermore, since melting, polishing, and degreasing proceed according to electrolytic conditions, the electrolytic degreasing solution of the present invention can be applied to all materials by setting conditions such as voltage, current, time, and bath temperature.

In addition, compared to general electrolytic degreasing liquids for various materials, the electrolytic degreasing liquid of the present invention is extremely superior in improving degreasing speed, activation rate, and surface gloss rate for all metal materials, and is versatile. It is something.

〔Example〕

This will be explained in detail below with reference to examples.

Example 1 As an electrolytic degreasing liquid composition, an alkaline pH* such as sodium carbonate is used! Shock agent 40g//l, sodium chloride 40g//l
β, sodium phosphate 5g/7! , surfactant 1-5g
Electrolytic degreasing liquid (IllkLl) whose main component is sodium chloride such that the composition of 1ml is 1g/l. electrolytic degreasing liquid (N13), commercially available alkaline phosphate electrolytic degreasing liquid (l
k4), phosphorus-free organic complexing agent-added electrolytic degreasing liquid (IIk
Table 1 shows the results of electrolytic degreasing of an iron alloy plate using cathode direct current and 15 A/dmr using L5).

Table 1 As is clear from Table 1, the presence of about 1 g/l of sodium chloride clearly has the opposite effect when viewed from the results using the electrolytic degreasing solution in 3. In the case of the example in which it is blended at a high concentration of 8 g/l or more, the required degreasing time is shortened to less than half, and the degreasing process is accelerated. In addition, not only does the degreasing finish quickly, but the gloss rate of the sample also increases, and the comparison examples I', No. 2, No. 3, No. 4, etc.
The effect is extremely large compared to the case where the electrolytic degreasing solution No. 5 is used.

Example 2 Using the electrolytic degreasing solution shown in Example 1, an iron alloy plate was heated at a frequency of 13.3 Hz and a duty of 95 on a cathode basis.
%, and the results of degreasing by high-speed current reversal electrolysis under the conditions of current density 15 A/drrr are shown in Table 2.

When the electrolytic degreasing solution of the example containing 8 g/l or more of sodium chloride in Table 2, No. 1 was used, the time was 20 seconds, which was 1/3 of that of the case of using the electrolytic degreasing solution of the comparative example. Degreasing is completed in a short time. Furthermore, the gloss rate is also significantly improved.

Note that when electrolytic degreasing was performed under the conditions of Example 2 using potassium chloride instead of the sodium chloride of Example 1, the results were the same.

In this way, with conventional degreasers, the degreasing speed is extremely slow.
In addition, while the gloss rate of the metal to be treated decreases during degreasing, with an electrolytic degreasing solution containing 8 g/14 or more of sodium chloride, the degreasing time is reduced by 1/2 to 1/3.
The electrolytic degreasing solution of the present invention is extremely excellent because it can shorten the process time and improve the gloss rate of the surface, leading to rationalization of pretreatment and improvement of the quality of plating.

According to the composition of the embodiment of the present invention, not only degreasing progresses rapidly, but also the carbonate film and phosphate film are dissolved by the chlorine ions concentrated on the surface of the metal to be treated, resulting in an extremely good surface finish. was activated.

In addition, when an iron alloy plate was cathodic DC electrolytically degreased for 60 seconds with these solutions and then directly plated with bright nickel plating to a thickness of 10 μm without performing strike plating, it was found that it contained more than 8 g/β of sodium chloride. In the electrolytic degreasing treatment using the electrolytic degreasing liquid in Part 1, the adhesion failure was 0% and the adhesion strength was 100%, whereas in the treatment using the electrolytic degreasing liquid in the comparative example, the adhesion failure was approximately 50% and the adhesion strength was 100%. It became 75%. Also, when comparing the gloss rate of plated products, the gloss rate of the plated products is 3 to 5% when treated with other degreasing agents.
The degreasing liquid also improved, demonstrating the superiority of this degreasing solution.

Example 3 40 g/l of alkaline pH buffer such as sodium carbonate,
Sodium chloride 40g/A, sodium sulfate 5g/! !
, an electrolytic degreasing solution (N1) 6) adjusted to a concentration of 1 to 5 g/l of surfactant, and 10 g/l of sodium chloride.
Il, electrolytic degreasing solution (N[17') adjusted to have a concentration of 5 g/l of sodium sulfate, and N1)l of Example 1
Table 3 shows the results of electrolytic degreasing of various materials using the electrolytic degreasing solution of Comparative Example No. 2.

The degreasing conditions were fast current reversal electrolysis at 13.3 Hz, 95% cathode-based duty, and 15 A/d m.

Table 3 As shown in Table 3, in the electrolytic degreasing solution of the present invention, the metal dissolving action of sodium chloride and sodium sulfate and the dispersing action of the surfactant of sodium sulfate work effectively, and the electrolytic degreasing solution of the present invention works effectively for each material in an extremely short time. The degreasing is completed. Since these electrolytic degreasing solutions do not contain phosphoric acid, a phosphate film is not generated during electrolysis, so chlorine ions and sulfate ions are not consumed in dissolving the phosphate film, and work effectively for polishing in a short time. The gloss rate was improved. Further, similar results were obtained when potassium chloride was used in place of sodium chloride in l1h6 and Na7 in Examples.

The test results in Tables 1, 2, and 3 of Examples were obtained as follows.

(1) Time taken to complete degreasing.

The time required to reach a water-wetted area that does not cause plating defects is shown in seconds.

(2) Gloss change rate.

The amount of change with respect to the gloss rate of the metal to be treated is shown in %.

(3) Degreasing rate in 20 seconds.

Judgment was made based on water wet area.

〔Effect of the invention〕

The present invention is an electrolytic degreasing solution containing an alkali metal chloride and an alkali metal phosphate or sulfate as a surfactant, which contains a high concentration of an alkali metal chloride. When this is used as an electrolytic degreasing liquid for degreasing metals to be treated, the following excellent effects can be obtained, making it an industrially useful invention.

+1) Compared to conventional electrolytic degreasing liquid, the processing time is shortened to 1/2 to 1/10, and the surface of the metal to be treated is polished and the gloss rate is improved, so the pre-treatment process for plating is faster. This improves quality and streamlines the plating pre-treatment process.

(2) Since it does not contain organic or inorganic complexing agents that interfere with wastewater treatment, the burden on pollution prevention is reduced.

(3) It is also possible to create a phosphorus-free and nitrogen-free electrolytic degreasing solution, reducing the burden on pollution prevention and the environment, as well as achieving extremely fast degreasing speeds, making this an extremely innovative electrolytic degreasing solution. It is a liquid.

Claims (2)

[Claims] (1) In an electrolytic degreasing solution using an alkali metal chloride and an alkali metal phosphate as surfactant builders,
A surface polishing active type electrolytic degreasing liquid containing an alkali metal chloride at a high concentration of 8 g/l or more. (2) An electrolytic degreasing solution containing alkali metal chloride and alkali metal sulfate as surfactant builders, characterized by containing alkali metal chloride at a high concentration of 8 g/l or more. Surface polishing active type electrolytic degreasing liquid.