CN113774371A

CN113774371A - Method for oxidizing and blackening surface of brass workpiece and workpiece prepared by method

Info

Publication number: CN113774371A
Application number: CN202111175230.8A
Authority: CN
Inventors: 李莹
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-10-09
Filing date: 2021-10-09
Publication date: 2021-12-10
Anticipated expiration: 2041-10-09
Also published as: CN113774371B

Abstract

The invention discloses a method for oxidizing and blackening the surface of a brass workpiece. The blackness and the matte degree of the brass blackened workpiece prepared by the method can be controllably improved, and the reflectivity is greatly reduced and can be reduced to less than 0.5%; after the treatment by the method, the surface of the workpiece is uniform and fine, and the firmness of the blackened film layer is high. Is particularly suitable for being applied to the field of optics.

Description

Method for oxidizing and blackening surface of brass workpiece and workpiece prepared by method

Technical Field

The invention relates to the field of material surface treatment, in particular to a method and a process for oxidizing and blackening the surfaces of copper and brass workpieces, and the method is particularly suitable for oxidizing and blackening the surfaces of brass optical workpieces.

Background

The oxidation blackening of the surface of copper and brass workpieces is a common method used in the chemical conversion coating treatment of copper and brass. There are many kinds of oxidizing agents for blackening copper and brass, and persulfate (CN 109207980A, CN 101497996A) and selenite (CN 110042379A, CN 112111734A) are the oxidizing agents frequently used in the prior art. However, persulfate has poor stability, and a film layer is loose and easy to fall off after blackening; selenite is toxic and causes environmental pollution. Sodium chlorite is also a common oxidant (CN 101747073A, CN 102286739A), but is mainly used for roughening copper to increase adhesion to plastics, paints, ceramics, etc. The sodium chlorite has strong oxidizability, is very stable under alkaline conditions, and the reaction product is sodium chloride, so the method is environment-friendly. It is particularly advantageous in the oxidation blackening of copper and brass workpieces.

In the oxidation blackening application, after a brass optical workpiece is blackened, the requirements of blackness, matte, low reflectivity and the like are often met; meanwhile, the blackening difficulty is increased due to the existence of zinc in the brass. For example: h59 the copper and zinc contents are 59%, therefore, the copper content of the workpiece surface is low, and after blackening, the blackness is obviously less than that of pure copper after blackening. Moreover, after simple oxidation and blackening, the blackening film layer is seriously ash-removed, so that a great quality hidden danger exists, and as shown in fig. 2, black marks are left on the surface of the 3M adhesive tape by unqualified products. Therefore, the development of a new oxidation blackening process improves the blackening effect and has great significance.

Disclosure of Invention

The invention provides a method for oxidizing and blackening the surfaces of copper and brass workpieces. The blackness and the matte degree of the brass blackened workpiece prepared by the method can be controllably improved, and the reflectivity is greatly reduced and can be reduced to less than 0.5%; after the treatment by the method, the surface of the workpiece is uniform and fine, and the firmness of the blackened film layer is high. Is particularly suitable for being applied to the field of optics.

In order to meet the technical requirements, the invention firstly provides a process flow for oxidation blackening of the brass surface, which comprises the following specific steps as shown in fig. 1:

s110, oil removal: soaking an alkalescent degreasing agent for ultrasonic degreasing;

s120, activation: soaking with dilute acid solution at normal temperature;

s130 blackening: sodium chlorite is used as an oxidant, and one or more times of blackening treatment can be carried out according to the requirements of matte, blackness or reflectivity of a final product;

s140, film removing: soaking and membrane removing treatment at normal temperature by using an acid solution, wherein the membrane removing times correspond to the blackening times;

s150, baking: placing the blackened brass workpiece into an oven for baking treatment;

s160, polishing: polishing by using grinding powder;

rinsing: after the steps of oil removal, activation, blackening and film removal are finished, the workpiece is rinsed by pure water so as to clean away the residual treatment liquid on the surface of the workpiece after the last step is finished.

Further, each specific step is explained in detail.

S110, oil removal:

the alkalescent degreasing agent is a phosphorus-free formula and mainly comprises the following components: 0.1-1% of sodium metasilicate pentahydrate, 1-5% of sodium citrate, 1-5% of sodium gluconate, 1-10% of triethanolamine, 10-20% of surfactant and the balance of water;

the types of surfactants employed include, but are not limited to, these types: alkylphenol ethoxylates, fatty alcohol-polyoxyethylene ether, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, fatty alcohol-polyoxyethylene ether sodium sulfate AES, polyethylene glycol and the like; the formula contains one or more of the surface activity;

in the oil removing step, soaking type ultrasonic cleaning is adopted, the grooving concentration of an oil removing agent is 30-100 g/L, and ultrasonic cleaning is carried out for 5-20 minutes at the temperature of 40-60 ℃; the optimal conditions are that the grooving concentration of the degreasing agent is 50 g/L, ultrasonic waves with the frequency of 50KHz are used for cleaning at the temperature of 50 ℃, and the cleaning time is 8 minutes.

S120, activation:

the acids used include, but are not limited to, one or more mixed solutions of these acids: sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, citric acid, oxalic acid; preferably, a mixed solution of sulfuric acid and nitric acid is adopted, or preferably, a nitric acid solution is adopted;

the concentration of dilute acid used for activation is 50-200 g/L; the optimal concentration is 120-180 g/L;

the soaking method is adopted, and the time is 0.5-3 minutes.

S130 blackening:

the blackening solution consists of an oxidant, inorganic alkali and the balance of water; the oxidant is sodium chlorite, and the inorganic alkali is sodium hydroxide or potassium hydroxide;

the content of sodium chlorite is 1-30%, preferably 5-25%, and more preferably 10-20%. The inorganic base is preferably sodium hydroxide; the content of the inorganic base is 1-25%, preferably 5-15%, and more preferably 8-12%;

the blackening temperature is 80-105 ℃, and preferably 90-100 ℃; the blackening time is 1-10 minutes, preferably 2-5 minutes;

the blackening times are one or more times of blackening treatment according to the requirements of matte, blackness or reflectivity of the final product; for an optical workpiece, the reflectivity is generally required to be less than 0.5% within the wavelength range of 380-680 nanometers of incident light, and the blackening times can be controlled to be 2-6 times, preferably 3-5 times.

S140, film removing:

the acid adopted by the film stripping is sulfuric acid or nitric acid or a mixed solution of the sulfuric acid and the nitric acid, preferably the nitric acid, and the concentration of the nitric acid is 2-20%, preferably 5-15%;

soaking the film in an acid solution at normal temperature for 1-3 minutes;

the film stripping times are determined by the blackening times, and if the product subjected to one-time blackening can meet the quality requirement, the film stripping treatment is not needed. For an optical workpiece, under the condition that the blackening times are 2-6 times, the corresponding film stripping times are 1-5 times; preferably, the blackening times are 3-5 times, and the corresponding film stripping times are 2-4 times; namely, the corresponding relation is as follows: the number of times of film removal = the number of times of blackening-1.

S150, baking:

placing the blackened and rinsed brass workpiece into an oven, and baking at the temperature of 80-200 ℃, preferably 100-150 ℃; the baking time is 10-30 minutes.

S160, polishing:

the components of the blackening film layer are copper oxide and needle crystals, the film layer is very loose, and as shown in figure 3, the surface film layer needs to be removed by polishing treatment;

the walnut powder is ground and polished for polishing, the particle size of the walnut powder is 0.1-1 mm, preferably 0.3-0.5 mm, and the time is 2-20 minutes.

Rinsing step

After the steps of deoiling, activating, blackening and stripping, a rinsing step is required to remove the treatment liquid remained on the surface of the workpiece after the steps of deoiling, activating, blackening and stripping;

rinsing with two times of pure water, and adding an overflow device into the rinsing tank; the temperature is 20-50 ℃; in order to control the product cleanliness, the conductivity of the second rinsing bath is controlled to be less than 5 micro Siemens/centimeter (mu S/cm).

The invention also provides a brass blackening workpiece, which is prepared by adopting the brass workpiece surface oxidation blackening method.

Drawings

FIG. 1 is a flow chart of the blackening process of the present invention.

Figure 2 is a photograph of a black mark left on the surface of a 3M tape for a non-conforming sample.

FIG. 3 is an electron micrograph of a blackened film, needle-shaped crystals, loose.

FIG. 4 shows the reflectivity of the workpiece after three blackening processes, wherein the reflectivity is less than 0.5% within the wavelength range of 380-680 nm.

Detailed Description

The following is a specific embodiment, and the specific process is as follows.

S110, oil removal: 70% of pure water is added into the oil removing groove, 5% of oil removing agent is added, and then water is added to 100%. The temperature was set at 50 ℃ and the washing time was 8 minutes. Then the heating rod is opened, and after the set temperature is reached, the ultrasonic wave is started, and the frequency is 50 KHz. And (3) putting the H59 brass workpiece into a porous cleaning frame, putting the porous cleaning frame into the bath solution, shaking up and down, and cleaning for 8 minutes. After oil removal and cleaning, putting the mixture into a pure water tank to shake up and down, and carrying out two times of pure water rinsing treatment;

the oil removing agent adopted in the embodiment comprises the following components: 1% of sodium metasilicate pentahydrate, 5% of sodium citrate, 5% of sodium gluconate, 5% of triethanolamine, 10% of alkylphenol polyoxyethylene ether and the balance of water.

S120, activation: the activation is carried out by soaking in 10% dilute nitric acid solution at normal temperature for 1 minute. During the activation process, the cleaning frame filled with the workpiece is put into a dilute nitric acid solution and shaken up and down; after the activation, two rinsing treatments with pure water were carried out.

S130 blackening: the blackening solution comprises the following components: 10% of sodium chlorite and 10% of sodium hydroxide. When preparing the blackening solution, firstly adding 80% of pure water, then slowly adding 10% of sodium hydroxide solid, and stirring simultaneously; after the solution is cooled, 10% sodium chlorite solid is added and stirred to dissolve. The blackening temperature is 95 ℃, and the cleaning frame filled in the workpiece is put into the blackening solution for 4 minutes. After blackening, two rinsing treatments with pure water were carried out.

S140, film removing: adopting 10% dilute nitric acid solution for 2 minutes; and after the membrane is removed, carrying out two times of pure water rinsing treatment. The film was removed 2 times and blackened 3 times in total. After stripping, the H59 brass turned a yellow-earth color, matte.

S150, baking: and respectively putting the brass workpieces subjected to the primary blackening, the secondary blackening and the tertiary blackening into a tray, putting the tray into an oven, and baking for 20 minutes at the temperature of 120 ℃.

S160, polishing: and (3) polishing the workpiece which is subjected to primary, secondary and tertiary blackening and baking by a polishing machine, wherein the particle size of the walnut powder is 0.5 mm, and the time is 15 minutes.

As a result:

primary blackening of the sample: the color is black brown, and copper leakage occurs;

secondary blackening of the sample: the color is gray;

three blackening samples: the color is darker and the effect is better. The requirement that the reflectivity of the workpiece is less than 0.5% is met within the range of 380-680 nanometers of the wavelength of incident light, as shown in FIG. 4.

Claims

1. The method for oxidizing and blackening the surface of the brass workpiece is mainly suitable for oxidizing and blackening the brass optical workpiece and is characterized by comprising the following steps of:

s120, activation: soaking with dilute acid solution at normal temperature;

s160, polishing: polishing by using grinding powder;

in addition, the method also comprises a rinsing step: after the steps of oil removal, activation, blackening and film removal are finished, the workpiece is rinsed by pure water so as to clean away the residual treatment liquid on the surface of the workpiece after the last step is finished.

2. The method for oxidizing and blackening the surface of a brass workpiece recited in claim 1, wherein the step S110 of removing oil comprises:

the alkalescent degreasing agent is a phosphorus-free formula product, and comprises the following main components: 0.1-1% of sodium metasilicate pentahydrate, 1-5% of sodium citrate, 1-5% of sodium gluconate, 1-10% of triethanolamine and 10-20% of surfactant; the surfactant components employed include, but are not limited to: one or more of alkylphenol polyoxyethylene, fatty alcohol polyoxyethylene ether, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, fatty alcohol polyoxyethylene ether sodium sulfate AES and polyethylene glycol.

3. The method of claim 2, wherein the step S110 of removing oil further comprises:

cleaning by adopting immersion type ultrasonic waves, wherein the slotting concentration of the degreasing agent is 30-100 g/L, and preferably 50 g/L; ultrasonic cleaning is carried out for 5-20 minutes at the temperature of 40-60 ℃; preferably, the washing is performed at a temperature of 50 ℃ by using ultrasonic waves having a frequency of 50KHz for 8 minutes.

4. The method for oxidizing and blackening the surface of a brass workpiece recited in claim 1, wherein the step S120 of activating specifically comprises:

the acids used include, but are not limited to, one or more mixed solutions of these acids: sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, citric acid and oxalic acid, preferably a mixed solution of sulfuric acid and nitric acid, or preferably a nitric acid solution; the concentration of the dilute acid is 50-200 g/L, and the optimal concentration is 120-180 g/L; the soaking time of the workpiece is 0.5-3 minutes.

5. The method for oxidizing and blackening the surface of a brass workpiece recited in claim 1, wherein the step S130 of blackening specifically comprises:

the oxidant in the blackening solution is sodium chlorite, and the inorganic alkali is sodium hydroxide or potassium hydroxide; the content of sodium chlorite is 1-30%, preferably 5-25%, and more preferably 10-20%; the inorganic base is preferably sodium hydroxide; the content of the inorganic base is 1-25%, preferably 5-15%, and more preferably 8-12%; the blackening temperature is 80-105 ℃, and preferably 90-100 ℃; the blackening time is 1 to 10 minutes, preferably 2 to 5 minutes.

6. The method for oxidizing and blackening the surface of a brass workpiece recited in claim 1, wherein the step S130 of blackening specifically comprises:

performing one or more times of blackening treatment according to the matte, blackness or reflectivity requirements of the final product; for an optical workpiece, the reflectivity is generally required to be less than 0.5% within the wavelength range of 380-680 nanometers of incident light, and the corresponding blackening times are 2-6 times; preferably 3 to 5 times.

7. The method of claim 1, wherein the step S140 of stripping the film comprises:

the acid selected for film stripping is sulfuric acid or nitric acid, preferably nitric acid, the concentration is 2-20%, preferably 5-15%, and the soaking time is 1-3 minutes; under the condition that the blackening times are 2-6 times, the corresponding film removing times are 1-5 times; preferably, the blackening is carried out for 3-5 times, and the corresponding film stripping times are 2-4 times.

8. The method for oxidizing and blackening the surface of a brass workpiece recited in claim 1, wherein the step S150 of baking comprises:

putting the blackened brass workpiece into an oven, wherein the temperature of the oven is 80-200 ℃, and preferably 100-150 ℃; baking for 10-30 minutes.

9. The method for oxidizing and blackening the surface of a brass workpiece recited in claim 1, wherein the step S160 of polishing comprises:

the grinding powder used for polishing is specifically walnut powder, and the particle size of the grinding powder is 0.1-1 mm, preferably 0.3-0.5 mm; grinding for 2-20 minutes;

in addition, the rinsing step between the adjacent steps specifically includes:

and (3) cleaning with pure water twice, adding an overflow device into the cleaning tank, and rinsing at the temperature of 20-50 ℃.

10. A brass blackened workpiece is characterized in that the workpiece is prepared by any one method of the steps 1-9; preferably, the brass blackened workpiece is used in the field of optics.