CN109267067B

CN109267067B - Environment-friendly chemical polishing solution for high-glossiness polishing of aluminum and aluminum alloy

Info

Publication number: CN109267067B
Application number: CN201811395993.1A
Authority: CN
Inventors: 周虎强
Original assignee: Shanghai Yinmu Electronics Manufacture Co ltd
Current assignee: Shanghai Yinmu Electronics Manufacture Co ltd
Priority date: 2018-11-22
Filing date: 2018-11-22
Publication date: 2021-03-30
Anticipated expiration: 2038-11-22
Also published as: CN109267067A

Abstract

The invention discloses an environment-friendly chemical polishing solution for high-glossiness polishing of aluminum and aluminum alloy, belonging to the technical field of surface treatment industry. The additive comprises a base liquid and an additive, wherein the base liquid is 85% concentrated phosphoric acid: 80-90% (mass fraction), 98% concentrated sulfuric acid: 10-20% (mass fraction); the additive is sulfolane, and the additive is added according to the proportion of 25-100 mL/L. The invention aims to develop the environment-friendly chemical polishing solution for aluminum and aluminum alloy, which can be used for an automatic line, does not use nitric acid, does not generate nitrogen oxide, has simple components, is easy to maintain, has proper price and does not generate air passage corrosion and flow marks after parts with high gloss requirements are polished.

Description

Environment-friendly chemical polishing solution for high-glossiness polishing of aluminum and aluminum alloy

Technical Field

The invention relates to an environment-friendly chemical polishing solution for high-glossiness polishing of aluminum and aluminum alloy, belonging to the technical field of surface treatment industry.

Background

Aluminum and aluminum alloy have the advantages of light weight, easy processing and the like, are one of important metal materials, and are widely applied to various industries such as instruments, machines, traffic, daily hardware and the like. In order to make up for the defects of poor corrosion resistance, low wear resistance, poor decoration and the like of the aluminum alloy, the aluminum alloy needs to be subjected to surface treatment. Polishing of aluminum and aluminum alloys is a crucial step in the surface treatment process thereof. For example, anodic oxidation coloring and chemical polishing of aluminum alloy mobile phone shells and computer shells are indispensable pretreatment processes. There are many common polishing processes for aluminum and aluminum alloys, wherein the chemical polishing process belongs to one of the following processes:

chemical polishing refers to polishing of a part by chemical etching in a suitable solution without using an external power source. Chemical polishing is widely applied to polishing of aluminum and aluminum alloy due to the simple and economical equipment required. At present, the most used polishing solution is a triacid polishing solution prepared by concentrated sulfuric acid, concentrated phosphoric acid and concentrated nitric acid according to a certain proportion, and in addition, the polishing solution is a two-acid polishing solution which is formed by concentrated sulfuric acid-concentrated phosphoric acid and an additive and appears in recent years. The following problems are found in practical use:

(1) pollution to the environment

Nitric acid is present in the triacid polishing solution, and polishing is carried out at relatively high temperatures (generally above 85 ℃), typically by the following chemical reaction:

7Al+7H3PO4+5HNO3→7AlPO4+2N2↑+NO2↑+13H2O

5Al+22HNO3→3N2O3+NO↑+11H2O+5Al(NO3)3

2Al+3H2SO4→Al2(SO4)3+6H2↑

during the polishing process, a large amount of nitrogen oxides NOx are generated, and a large amount of nitric acid steam is released, so that the gases have high toxicity, strongly stimulate respiratory mucosa and cause cough, headache and chest distress. NO is also carcinogenic and affects cell division. NO2 may reach the deep parts of the lungs, causing severe respiratory diseases. Nitrogen oxides also tend to form photochemical smog and are a large cause of acid rain. In addition, the generated wastewater contains a large amount of NO3-, which easily causes the total nitrogen to exceed the standard. NO 3-is difficult to treat chemically and only microbial treatment is applied, which increases the difficulty and cost of wastewater treatment.

(2) High price and difficult maintenance

The existing chemical polishing additive and the commercial two-acid polishing solution are expensive and large in dosage, so that the production cost is increased. Meanwhile, the components are complex, the addition and maintenance are difficult, manufacturers keep the components strictly secret, and the problems in the production process can be solved only by dispatching technicians of manufacturers and the like, so that the time period is long, and the production is seriously delayed.

(3) The parts are easy to generate air flue corrosion

Above three acid polish, two acid polish of commodity discover in the in-service use process, to having the aluminium and the aluminum alloy part of hole, recess, when requiring high glossiness, the polishing time is long, can produce the air flue corrosion in the top of hole, recess after the polishing: that is, a large amount of gas generated in the holes and grooves escapes from the upper part of the polishing pad during polishing, a dent is punched on the upper part, and the brightness of the dent is different from that of other parts. This seriously affects the decorativeness of the finished product and the appearance does not meet the customer's requirements. The applicant tests the chemical polishing solutions of various manufacturers, and the phenomenon exists more or less, which is undoubtedly a great industrial problem.

(4) The parts are easy to generate flow marks

After the part is lifted out of the polishing groove, the chemical reaction is still carried out due to the polishing liquid adhered to the surface, and meanwhile, the adhered polishing liquid is gathered and flows downwards, so that a light and shade alternative stripe is formed on the surface of the part after washing. In the aluminum alloy anodizing coloring process, the common factor causing the appearance of the product to be unqualified is that the aluminum alloy is subjected to the anodizing coloring process.

(5) Is difficult to be applied to an automatic line

An aluminium anodic oxidation longmen transfer machine of Shanghai silver-wood electrical apparatus manufacturing Limited company uses the two acid polish in-process of triacid polish, commodity, and it is higher than the upper end often to appear that rack lower extreme part glossiness is higher than, single part lower extreme glossiness also is higher than the upper end, analyzes its reason and does: the running speed of the vehicle is limited, the lower end of the hanger is firstly immersed in the polishing solution when the vehicle enters the tank, and the polishing solution is finally extracted when the vehicle leaves the tank. The polishing liquid has too high light-emitting speed and short polishing time (generally about 60 seconds). In addition, 10-15s is needed for transferring the hanger from the chemical polishing tank to the rinsing tank, and the polishing solution can gather to the lower end of the part to continue to react.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the environment-friendly chemical polishing solution solves the problems that nitric oxide generated by nitric acid is utilized to cause environmental pollution, components are complex, maintenance is difficult, price is high, parts are easy to generate air passage corrosion, parts are easy to generate flow marks, and the parts are difficult to apply to an automatic line due to the defects of commonly used three-acid polishing solution and commodity two-acid polishing solution in the current market.

The technical problem to be solved by the invention is realized by adopting the following technical scheme:

an environment-friendly chemical polishing solution for polishing high glossiness of aluminum and aluminum alloy, which comprises a base solution and an additive,

the base solution is 85% concentrated phosphoric acid: 80-90% (mass fraction), 98% concentrated sulfuric acid: 10-20% (mass fraction);

the additive is sulfolane, and the additive is added according to the proportion of 25-100 mL/L.

The preparation method of the environment-friendly chemical polishing solution for high-glossiness polishing of aluminum and aluminum alloy comprises the following steps:

1. adding 85% concentrated phosphoric acid in a calculated amount into an acid-resistant heat-resistant chemical polishing tank with air stirring and steam heating, slowly adding 98% concentrated sulfuric acid under air stirring, and mixing the two at a mass ratio of 4:1 to 9:1 to obtain a base solution, wherein the optimal ratio of aluminum materials of different types can be determined through experiments.

2. According to the volume of the basic liquid, 25-100mL/L of sulfolane is added, the stirring is uniform, the preparation of the chemical polishing liquid is completed, the melting point of the sulfolane is 28 ℃, the sulfolane can be solidified when the air temperature is low, a plastic barrel filled with the sulfolane can be placed into a hot water tank to be properly heated and melted, the addition of the sulfolane can improve the viscosity of the basic liquid of the polishing liquid, and the residence time and the uniformity of bubbles in the polishing liquid are improved, so that the air channel corrosion of holes and grooves during the high-gloss polishing of the aluminum alloy parts is prevented, and a small addition amount can be selected when the parts are simple in structure and the holes and the grooves are few; when the part structure is complicated, more addition is needed when holes and grooves are more, and the part structure can be specifically tested and adjusted.

The environment friendly chemical polishing liquid for polishing high glossiness of aluminum and aluminum alloy includes the following steps:

step (A), hanging a part on a hanger, wherein the hanger is arranged on a pole rod of a gantry automatic line;

step (B), pretreatment:

(1) the parts to be processed are chemically degreased,

(2) etching is carried out by using alkaline washing solution containing sodium hydroxide,

(3) washing off surface hanging ash by using a solution containing a neutralization ash remover;

step (C), chemical polishing: heating the chemical polishing solution to 85-95 ℃, putting the chemical polishing solution into the pretreated part, reacting for 90-180s, taking out and washing;

step (D), drying or anodizing treatment is carried out according to the subsequent process flow in the actual production;

step (E), maintaining the polishing solution:

1. in the using process, the proportion of phosphoric acid and sulfuric acid in the polishing solution is analyzed every day, the adjustment is carried out in time when the deviation occurs, and sulfolane is added according to the proportion;

2. when the liquid level is lower, concentrated sulfuric acid and sulfolane can be added according to the proportion during slotting to complement the liquid level;

3. the content of aluminum ions in the polishing solution is measured every two days, when the content of the aluminum ions exceeds 35g/L, the polishing solution is replaced, a part of old solution can be drained, and new solution is prepared to supplement the liquid level.

The invention has the beneficial effects that:

1. the environment is protected and no pollution is caused; the invention does not contain nitric acid, no nitric oxide is generated in the using process, no nitrate which is difficult to treat exists in the wastewater, and the phosphate radical can be removed to reach the standard by adding lime to adjust the pH value to about 7; the contained sulfolane is non-volatile, has good thermal stability, is not decomposed in the polishing solution, and has no toxic or side effect on microorganisms; the sulfolane concentration in the rinsing bath is extremely low, and the COD value in the discharged wastewater is not obviously increased in the actual use process; if necessary, the post-chemical polishing cleaning water may be separately collected and subjected to Fenton oxidation or biological treatment to further reduce the COD value.

2. The aluminum alloy after high-gloss polishing has no air channel corrosion and no flow mark; the sulfolane added in the polishing solution can improve the viscosity of the polishing solution and improve the retention time and uniformity of bubbles in the polishing solution, so that air channel corrosion does not exist at holes and grooves while high glossiness of aluminum alloy parts is obtained, and the bubbles are uniformly covered and no flow mark is generated after the parts are lifted from the polishing groove.

3. The components are simple and stable, and the maintenance is easy; the polishing solution only consists of phosphoric acid, sulfuric acid and sulfolane, and has simple components; phosphoric acid and sulfuric acid can be measured by a double-indicator titration method and are supplemented according to the measurement result; sulfolane is not volatilized, the thermal stability is excellent, even if the material is heated to 220 ℃ and is kept for 5 hours, only 2 percent of the material is decomposed, the loss is basically brought out, and the material can be supplemented according to the supplementing amount of phosphoric acid and sulfuric acid according to the slotting proportion.

4. Can be used for automatic line production; the polishing solution can adjust the polishing time according to the requirement of an automatic line, improve the mass fraction of sulfuric acid, raise the temperature and shorten the polishing time, and conversely, the polishing time can be prolonged, so that the polishing effect with uniform brightness can be obtained; after an aluminum oxidation gantry automatic line of Shanghai silver-wood electrical appliance manufacturing Limited company of the applicant polishes a notebook shell made of 6063 materials by using the polishing solution, the polishing solution is tested by using a glossiness instrument with an incident angle of 60 degrees, and the glossiness difference between the upper end part and the lower end part of the hanger and the glossiness of the upper end and the lower end part of the parts is less than 10 percent, so that the requirements of customers are completely met.

Detailed Description

In order to make the technical means, the original characteristics, the achieved purpose and the efficacy of the invention easily understood, the invention is further described with reference to the following embodiments.

The first embodiment is as follows: an aluminium alloy anodic oxidation transfer machine of Shanghai silver-wood electrical apparatus manufacturing Limited company mainly engages in the anodic oxidation of certain 6063 material aluminium alloy notebook shell and colours, there are more louvre, screw hole in the notebook shell, the customer requires that glossiness is 120 ± 10% (the incident angle is 60 degrees) after the chemical polishing, can not appear the visible flow mark of naked eye, the louvre, the screw hole can not appear the visible air flue of naked eye and corrode, the intercepting notebook shell is tested as the test block, the process specification who reachs the chemical polishing liquid is:

1. base liquid: 85% concentrated phosphoric acid: 80% (mass fraction), 98% concentrated sulfuric acid: 20 percent (mass fraction),

2. additive: sulfolane 75 mL/L;

3. temperature: 95 ℃;

4. time: 150 s;

example two: an aluminium alloy anodic oxidation transfer machine of Shanghai silver-wood electrical apparatus manufacturing Limited company mainly engages in the anodic oxidation of certain 6063 material aluminium alloy notebook shell and colours, there are more louvre, screw hole in the notebook shell, the customer requires that glossiness is 120 ± 10% (the incident angle is 60 degrees) after the chemical polishing, can not appear the visible flow mark of naked eye, the louvre, the screw hole can not appear the visible air flue of naked eye and corrode, the intercepting notebook shell is tested as the test block, the process specification who reachs the chemical polishing liquid is:

1. base liquid: 85% concentrated phosphoric acid: 90% (mass fraction), 98% concentrated sulfuric acid: 10 percent (mass fraction),

2. additive: sulfolane 100 mL/L;

3. temperature: 90 ℃;

4. time: 180 s;

example three: an aluminium alloy anodic oxidation transfer machine of Shanghai silver-wood electrical apparatus manufacturing Limited company mainly engages in the anodic oxidation of certain 6063 material aluminium alloy notebook shell and colours, there are more louvre, screw hole in the notebook shell, the customer requires that glossiness is 120 ± 10% (the incident angle is 60 degrees) after the chemical polishing, can not appear the visible flow mark of naked eye, the louvre, the screw hole can not appear the visible air flue of naked eye and corrode, the intercepting notebook shell is tested as the test block, the process specification who reachs the chemical polishing liquid is:

1. base liquid: 85% concentrated phosphoric acid: 85% (mass fraction), 98% concentrated sulfuric acid: 15 percent (mass fraction),

2. additive: sulfolane 60 mL/L;

3. temperature: 87 ℃;

4. time: 100 s;

the production line is provided with an acid-resistant and heat-resistant stainless steel chemical polishing tank, the bottom of the production line is provided with a steam heating pipe and air stirring, 3000L of chemical polishing solution needs to be prepared, and the preparation method comprises the following steps:

1. 3840kg of 85% concentrated phosphoric acid is added into the polishing tank;

2. starting air to stir, slowly adding 960kg of 98% concentrated sulfuric acid, and finishing the preparation of the base liquid;

3. adding 210L of sulfolane, uniformly stirring, and finishing the preparation of the polishing solution.

The chemical polishing process flow comprises the following steps:

1. hanging: fixing the notebook shell on a hanger, and hanging the hanger on the pole rod;

2. oil removal: sulfuric acid 200-250g/L, temperature 50-60 ℃, time 3-5 min; removing the adhered oil stains;

3. two-way countercurrent water washing;

4. alkali washing: 40-80g/L of sodium hydroxide, 50-60 ℃ and 15-30s of time; washing away oxide skin and a processing layer on the surface;

5. two-way countercurrent water washing;

6. neutralizing: 20-50g/L ferric trichloride, 100 g/L hydrochloric acid and 150g/L hydrochloric acid, and the temperature is normal temperature and the time is 30-60 s; washing off the hanging ash on the surface

7. Two-way countercurrent water washing;

8. chemical polishing: starting air stirring and steam heating of the chemical polishing tank, controlling the temperature to be 95 +/-1 ℃ by using an automatic temperature control device, controlling a travelling crane to be placed into the cleaned notebook shell, reacting for 150 seconds, and taking out;

9. three countercurrent water washes;

10. the anodic oxidation, coloring and hole sealing are carried out according to the prior process.

Randomly extracting three notebook shells which are chemically polished and washed in different batches, drying the notebook shells by cold air, and respectively measuring the glossiness of the upper left corner, the upper right corner, the center, the lower left corner and the lower right corner of each appearance surface by using a glossiness instrument (with an incidence angle of 60 degrees), wherein the measurement results are as follows:

the glossiness completely meets 120 +/-10% of the customer requirements, and meanwhile, no macroscopic airway corrosion and flow marks exist after polishing; the chemical polishing yield is basically kept about 95 percent in normal production.

Maintenance of the polishing solution:

1. in the using process, the proportion of phosphoric acid and sulfuric acid in the polishing solution is analyzed every day, the adjustment is carried out in time when the deviation is 4:1, and the following are added according to the proportion of the polishing solution: namely, 1L of sulfolane is added when 22.5kg of phosphoric acid is added; adding 1L of sulfolane every 24.5kg of sulfuric acid;

3. measuring the content of aluminum ions in the polishing solution every two days, draining a part of old solution when the content of the aluminum ions exceeds 35g/L, and preparing a new solution to supplement the liquid level.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. An environment-friendly chemical polishing solution for polishing high glossiness of aluminum and aluminum alloy, which comprises a base solution and an additive, and is characterized in that:

the base solution is 85% concentrated phosphoric acid: 80-90% mass fraction, 98% concentrated sulfuric acid: 10-20% mass fraction;

2. The use method of the environment-friendly chemical polishing solution for high-gloss polishing of aluminum and aluminum alloys according to claim 1 comprises the following steps:

step (B), pretreatment:

(1) the parts to be processed are chemically degreased,

step (E), maintaining the polishing solution:

2. when the liquid level is lower, concentrated sulfuric acid, concentrated phosphoric acid and sulfolane can be added according to the proportion during slotting to complement the liquid level;