CN113774371B

CN113774371B - Method for blackening brass workpiece surface through oxidation and workpiece prepared by method

Info

Publication number: CN113774371B
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: 2023-09-05
Anticipated expiration: 2041-10-09
Also published as: CN113774371A

Abstract

The invention discloses a method for oxidizing and blackening the surface of a brass workpiece, wherein sodium chlorite is used as an oxidizing agent for the blackening agent in the method, and the oxidation blackening of the brass workpiece is realized through a repeated oxidation blackening process. The blackness and the matte degree of the brass blackened workpiece prepared by the method can be controlled to be improved, the reflectivity is greatly reduced to be less than 0.5%; after the treatment by the method, the surface of the workpiece is uniform and fine, and the blackened film layer has high firmness. Is particularly suitable for being applied to the optical field.

Description

Method for blackening brass workpiece surface through oxidation 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 blackening the surface of copper and brass workpieces by oxidation, and the method is particularly suitable for blackening the surface of brass optical workpieces by oxidation.

Background

The oxidation blackening of copper and brass work piece surfaces is one method commonly used in chemical conversion coating treatment of copper and brass. There are many blackening oxidants concerning copper and brass, persulfates (CN 109207980a, CN101497996 a) and selenites (CN 110042379a, CN 112111734A) being oxidants frequently used in the prior art. However, persulfate has poor stability, and a film layer is loose after blackening and is easy to fall off; selenite is toxic and causes environmental pollution. Sodium chlorite is also a common oxidizer (CN 101747073a, CN102286739 a), but is mainly used for roughening copper to increase adhesion to materials such as plastics, paints, ceramics, and the like. Sodium chlorite has strong oxidizing property, is very stable under alkaline conditions, and the reaction product is sodium chloride, thereby being environment-friendly. In the oxidation blackening of copper and brass workpieces, there is a further advantage.

In the application of oxidation blackening, after the brass optical workpiece is blackened, high requirements such as 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: the content of H59 copper and zinc is 59%, so that the content of copper on the surface of a workpiece is low, and the blackness after blackening is obviously smaller than that after blackening of pure copper. Moreover, after the film layer is simply oxidized and blackened, the blackened film layer is seriously grey, and a great quality hidden trouble exists, as shown in fig. 2, the unqualified product has black marks on the surface of the 3M adhesive tape. Therefore, a new oxidation blackening process is developed, blackening effect is improved, and significance is great.

Disclosure of Invention

The invention provides a method for oxidizing blackening of surfaces of copper and brass workpieces, which adopts sodium chlorite as an oxidant and realizes the oxidizing blackening of the brass workpieces through a repeated oxidizing blackening process. The blackness and the matte degree of the brass blackened workpiece prepared by the method can be controlled to be improved, the reflectivity is greatly reduced to be less than 0.5%; after the treatment by the method, the surface of the workpiece is uniform and fine, and the blackened film layer has high firmness. Is particularly suitable for being applied to the optical field.

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

s110, oil removal: soaking and ultrasonic degreasing treatment is carried out by adopting a weak alkaline degreasing agent;

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

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

s140, film removal: adopting an acidic solution to perform normal-temperature soaking film stripping treatment, wherein the film stripping times correspond to blackening times;

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

s160 polishing: polishing with grinding powder;

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

Further, each specific step is described in detail.

S110, oil removal:

the adopted weakly alkaline degreasing agent is a phosphorus-free formula and comprises the main 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 ethoxylates, sodium dodecylbenzene sulfonate, sodium dodecylsulfonate, sodium fatty alcohol ethoxylate sulfate AES, polyethylene glycol, etc.; the formula contains one or more of the above surface active agents;

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

S120, activation:

the acids employed include, but are not limited to, a mixed solution of one or more 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 used, or preferably, a nitric acid solution is used;

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

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

S130, blackening:

the blackening liquid comprises 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 ℃, preferably 90-100 ℃; the blackening time is 1-10 minutes, preferably 2-5 minutes;

the blackening times are that one or more times of blackening treatment is carried out 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% in the wavelength range of 380-680 nm of incident light, and the blackening times can be controlled to be 2-6 times, preferably 3-5 times.

S140, film removal:

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

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

the film removing times are determined by the blackening times, and if the product subjected to primary blackening can meet the quality requirement, film removing treatment is not needed. For the 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: number of film fading = number of blackening-1.

S150, baking:

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

S160 polishing:

the blackened film layer is made of copper oxide and needle-shaped crystals, is very loose, and needs to be polished to remove the surface film layer as shown in figure 3;

the walnut powder is ground and polished, the grain 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 degreasing, activating, blackening and film removing, a rinsing step is needed to remove the residual treatment liquid on the surface of the workpiece after the steps of degreasing, activating, blackening and film removing;

rinsing adopts two pure water cleaning steps, and a cleaning tank is provided with an overflow device; the temperature is 20-50 ℃; to control product cleanliness, the conductivity of the second wash tank is controlled to be less than 5 microsiemens per centimeter (μS/cm).

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

Drawings

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

FIG. 2 is a photograph of a black print left on the surface of a 3M tape of a failed sample.

FIG. 3 is an electron micrograph of a darkened film, needle-like crystals, fluffy.

FIG. 4 shows the reflectivity of the workpiece after three blackening, 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 procedure is as follows.

S110, oil removal: 70% of pure water is added into the oil removal tank, then 5% of oil removal agent is added, and then water is added to 100%. Setting the temperature at 50 ℃ and cleaning for 8 minutes. Then the heating rod is turned on, and after the set temperature is reached, the ultrasonic wave is turned on with the frequency of 50KHz. And (3) loading the H59 brass workpiece into a porous cleaning frame, putting the porous cleaning frame into a bath solution, shaking up and down, and cleaning for 8 minutes. After the oil removal and cleaning are finished, the oil is put into a pure water tank to shake up and down, and two pure water rinsing treatments are carried out;

the degreasing agent adopted in the embodiment comprises the following components: sodium metasilicate pentahydrate 1%, sodium citrate 5%, sodium gluconate 5%, triethanolamine 5%, alkylphenol ethoxylates 10% and the balance water.

S120, activation: the activation is carried out by adopting 10 percent dilute nitric acid solution for 1 minute at normal temperature. In the activation process, a cleaning frame filled with a workpiece is put into a dilute nitric acid solution and shakes up and down; after the activation is finished, two rinsing treatments with pure water are carried out.

S130, blackening: blackening liquid composition: 10% of sodium chlorite and 10% of sodium hydroxide. When blackening liquid is prepared, 80% of pure water is firstly added, then 10% of sodium hydroxide solid is slowly added, and stirring is carried out simultaneously; after the solution is cooled, adding 10% of sodium chlorite solid, stirring and dissolving, and then using. The blackening temperature was 95℃and the cleaning frame loaded with the workpiece was placed in the blackening liquid for 4 minutes. After blackening, two rinsing treatments with pure water were performed.

S140, film removal: 10% dilute nitric acid solution is adopted for 2 minutes; after film removal, two rinsing treatments with pure water are carried out. The film was removed 2 times and blackened 3 times in total. After film removal, H59 brass changed to a earthy yellow color and matt.

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

S160 polishing: and respectively adding the workpiece subjected to primary, secondary and tertiary blackening and baking into a polishing machine for polishing, wherein the grain size of the walnut powder is 0.5 mm, and the time is 15 minutes.

Results:

primary darkening of the sample: the color is blackish brown, and copper leakage occurs;

secondary darkening samples: color is gray;

three blackening samples: the color is black, and the effect is good. In the range of 380-680 nanometers of the wavelength of the incident light, the requirement that the reflectivity of the workpiece is less than 0.5 percent is met, as shown in fig. 4.

Claims

1. A method for oxidative blackening of a surface of a brass workpiece, the method being suitable for oxidative blackening of a brass optical workpiece, comprising the steps of:

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

s130, blackening: sodium chlorite is used as an oxidant, and blackening treatment is carried out according to the requirements of matte, blackness or reflectivity of a final product, and the method specifically comprises the following steps: for an optical workpiece, in the wavelength range of 380-680 nanometers of incident light, the reflectivity is required to be less than 0.5 percent, and the corresponding blackening times are 2-6 times;

s160 polishing: polishing with grinding powder;

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

2. The method for oxidizing blackening a surface of a brass workpiece as set forth in claim 1, wherein the step S110 of degreasing specifically includes:

the adopted weakly alkaline degreasing agent is a phosphorus-free formula product, and comprises the following main components: sodium metasilicate pentahydrate 0.1-1%, sodium citrate 1-5%, sodium gluconate 1-5%, triethanolamine 1-10% and surfactant 10-20%; the surfactant components used include: one or more of alkylphenol ethoxylates, fatty alcohol ethoxylates, sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate, sodium fatty alcohol ethoxylate sulfate AES and polyethylene glycol.

3. The method of surface oxidative blackening of a brass workpiece as set forth in claim 2, wherein the step S110 of degreasing further includes:

soaking type ultrasonic cleaning is adopted, and the slotting concentration of the degreasing agent is 30-100 g/L; ultrasonic cleaning is carried out for 5 to 20 minutes at the temperature of 40 to 60 ℃.

4. A method of oxidative blackening of a surface of a brass workpiece as claimed in claim 3, wherein the degreasing of step S110 further comprises:

the grooving concentration of the degreasing agent is 50 g/L, and the degreasing agent is cleaned by ultrasonic waves with the frequency of 50kHz at the temperature of 50 ℃ for 8 minutes.

5. The method of oxidizing blackening of a surface of a brass workpiece in accordance with claim 1, wherein the step S120 of activating specifically comprises:

the acids employed include a mixed solution of one or more of these acids: sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, citric acid, oxalic acid; the concentration of the dilute acid is 50-200 g/L; the soaking time of the workpiece is 0.5-3 minutes.

6. A method for oxidation blackening of a surface of a brass workpiece as described in claim 5, wherein the steps of

The S120 activation specifically includes:

a mixed solution of sulfuric acid and nitric acid is adopted, or a nitric acid solution is adopted; the concentration of the dilute acid is 120 to 180

Gram/liter.

7. The method for oxidative blackening of a surface of a brass workpiece as set forth in claim 1, characterized by the steps of

The S130 blackening specifically includes:

the oxidant in the blackening liquid is sodium chlorite, and the inorganic base is sodium hydroxide or potassium hydroxide; the content of sodium chlorite is 1-30%; the content of the inorganic alkali is 1-25%; the blackening temperature is 80-105 ℃; the blackening time is 1-10 minutes.

8. A method for oxidation blackening of a surface of a brass workpiece as described in claim 7, characterized by the steps of

The S130 blackening specifically includes:

the content of sodium chlorite is 5-25%; the content of inorganic alkali is 5-15%; the blackening temperature is 90-100 ℃;

the blackening time is 2-5 minutes.

9. A method for oxidation blackening of a surface of a brass workpiece as described in claim 7, characterized by the steps of

The S130 blackening specifically includes:

the content of sodium chlorite is 10-20%; the content of inorganic alkali is 8-12%.

10. The method for oxidative blackening of a surface of a brass workpiece as set forth in claim 1, characterized by the steps of

The S130 blackening specifically includes:

the blackening times are 3-5 times.

11. The method for oxidative blackening of a surface of a brass workpiece as set forth in claim 1, characterized by the steps of

S140, film removal specifically comprises the following steps:

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

12. The method of oxidizing blackening of a surface of a brass workpiece in accordance with claim 11, wherein step S140 of removing the film specifically comprises:

the acid concentration for film stripping is 5-15%; under the condition that the blackening times are 3-5 times, the corresponding film stripping times are 2-4 times.

13. The method of oxidizing blackening of a surface of a brass workpiece as set forth in claim 1, wherein the baking in step S150 specifically includes:

and placing the blackened brass workpiece into an oven, and baking for 10-30 minutes at the temperature of 80-200 ℃.

14. The method of oxidizing blackening of a surface of a brass workpiece in accordance with claim 13, wherein the baking in step S150 specifically comprises:

the temperature of the oven is 100-150 ℃.

15. The method of oxidizing blackening of a surface of a brass workpiece in accordance with claim 1, wherein the step S160 polishing specifically comprises:

the grinding powder adopted in polishing is specifically walnut powder, the grain diameter of the walnut powder is 0.1-1 mm, and the grinding time is 2-20 minutes;

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

and (3) cleaning by two pure water steps, adding an overflow device into a cleaning tank, and rinsing at 20-50 ℃.

16. The method of oxidizing blackening of a surface of a brass workpiece in accordance with claim 1, wherein the step S160 polishing specifically comprises:

the grain size of the grinding powder used for polishing is 0.3-0.5 mm.

17. A brass blackening workpiece, characterized in that the workpiece is manufactured by the method of any one of claims 1 to 16, and the brass blackening workpiece is applied to the field of optics.