RU2604162C2 - Method of cleaning surfaces of copper and its alloys from corrosion and oxidation by copper compounds (ii) - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to cleaning elements of process and household equipment from copper and its alloys from corrosion products and products of oxidation of copper compounds (II) and can be used in various branches of practical activity, in scientific research and in analytical control. Method involves treatment of copper and its alloys surface with aqueous acid solution in the presence of oxidant, in form of air oxygen, and as acid is water solution of 0.033 n., 0.053 n., 0.06 n., 0.07 n, n 0.237 or 0.47 n. of nitric acid. Cleaned surface is fully submerged into said aqueous solution of acid, in which intensive mixing is conducted, stirring and air barbotage or air barbotage, wherein acid flow rate and accumulation of copper (II) compounds are controlled, and after treatment waste reaction mixture is carefully drained, metal or alloy are washed once or twice with distilled water and dried.

EFFECT: method enables effective and fast cleaning of copper and its alloys surface from corrosion and oxidation products, which include copper oxides (I) and (II) and copper (II) hydroxide, wherein providing removal of deposits only located on surface of copper and its alloys without affecting the metal and without changing relief and structure of its surface.

1 cl, 1 tbl, 13 ex

Description

The invention relates to the cleaning of elements of technological and household equipment from copper and its alloys from corrosion products and oxidation products of copper (II) compounds and can be used in various fields of practical activity, in scientific research and in analytical control.

It is known to clean the surfaces of objects from virtually all water-insoluble corrosion products such as oxides, hydroxides, carbonate, sulfates, Cu ₂ O (cuprite) by treating the item with a hot 10% solution of Trilon B (Kazanskaya KP, Trofimov N.I. On the possibility of using sodium hexametaphosphate and Trilon B for cleaning corrosion products from archaeological bronze objects / Messages of the All-Russian Central Scientific and Medical Class, 1964, No. 13. - P. 118-120). After such cleaning, the product only needs to be washed thoroughly. It does not make sense to carry out additional neutralization.

The disadvantages of this method are:

1. It is impossible to leave the cleaned object in such a solution for a long time and without observation, since it is possible to etch the metal and its weakening.

2. Do not use the same solution for a long time. If a lot of salts have accumulated in the working solution and it has turned blue, it must be replaced with a new one. Otherwise, there may be a copper-plating of the surface of the object.

3. In the described method there are no specific proposals and limitations on its technological implementation.

A method for cleaning products from corrosion products using an aqueous solution of sulfamic acid saturated at room temperature is described (Trofimov N.I., Tkachukova G.V. Application of sulfamic acid

acids for removing corrosion products from objects of applied art // Restoration, research and storage of museum art values / GBL, Informkultura. - M .: 1978. Issue. 3 - S. 3). The cleaning rate from corrosion products is highly dependent on temperature: at 75-80 ° C it is 10 times higher than room temperature. It is noted that if it is necessary to remove uneven thickness of corrosion deposits or individual corrosion spots, sulfamic acid can be used in the form of slurry applied to individual local areas. Attention is drawn to the fact that sulfamic acid is well washed with water from the surface of a metal object until the washings are neutral.

The disadvantages of this method are:

1. The use of systems with a high content of sulfamic acid (10% or more concentrated systems).

2. Use of elevated temperatures in relation to surrounding systems.

3. The lack of specific operational characteristics and recommendations on the hardware design of the most common options.

A method for cleaning from surface deposits using 5-10% sulfuric acid is described (Scott A. Cleaning and restoration of museum exhibits / Izvestia GAIMK, 1935, issue 114). In accordance with it, a cleaned object is placed in a glass vessel with the indicated acid and incubated for 2-3 hours. Then the object is removed from the solution, washed with a soft brush under running water, after which it is again placed in a vessel with the same solution of sulfuric acid and some amount of fresh sulfuric acid is added. Stand for 2-3 hours. Then the object is taken out again, washed again and returned to the sulfuric acid solution. This alternation continues until all layers are completely dissolved. Duration approximately 2 days. Under certain conditions, at some stage, an intermediate placement of an object in a solution of concentrated caustic potassium is possible.

The disadvantages of this method are:

1. Quite high concentrations and, consequently, the cost of sulfuric acid, suggesting the necessary methods of disposal of waste solutions.

2. The need, in addition to acidic, to use alkaline systems, also concentrated.

3. The process is quite lengthy and not fully defined by the performance characteristics and hardware design.

Closest to the claimed is a method of freeing the surface of copper from deposits of copper oxidation products of copper sulfate (II) in the presence of sulfuric acid (S.D. Pozhidaeva, D.A. Sotnikova, A.Yu. Eliseeva, T.A. Mayakova, AM Ivanov . "Copper (II) compounds in the corrosion damage of a metal when it is in contact with solutions of acidic reagents." Collection of scientific articles on the materials of the international scientific-practical conference "Application of innovative technologies in scientific research. Kursk: 2010. P. 379-382) . The method involves the oxidation of copper (I) compounds to more soluble copper (II) compounds and the conversion of the latter from the metal surface into a solution. Hydrogen peroxide is used as an oxidizing agent in the form of a solution in an aqueous solution of acetic or sulfuric acid. It is noted that the purification under certain conditions is quantitative, and the copper purified in this way can be returned as a reagent to the basic redox process.

The disadvantages of this method are:

1. There is no information whether this method will be effective in cleaning the surface of copper from corrosion products, which, unlike the salts of products of redox processes, include copper (I) and (II) oxides and copper (II) hydroxide reacting much slower with both acids and oxidizing agents (copper oxide (I)).

2. The cited method is not well defined either in the ranges of concentrations of hydrogen peroxide and acid, or in terms of temporal characteristics, depending on the equipment used in the process.

3. There is no clear information about how many surface deposits make up the upper limit of the working range and how to control the course of the cleaning process, as well as the moment of its completion.

The objective of the proposed solution is to develop a method that allows you to reliably and quickly clean the surface of copper and its alloys from corrosion products and metal oxidation by copper (II) compounds without significant consumption of metal (alloy) in this operation and changing the surface configuration for this reason, without the use of excessively strong mechanical efforts, as well as without the use of elevated temperatures and relatively concentrated solutions of chemical reagents.

This object is achieved by a method of cleaning the surfaces of copper and its alloys from the products of corrosion and oxidation by copper (II) compounds, including treating the surface of copper and its alloys with an aqueous acid solution in the presence of an oxidizing agent, in which oxygen is used as an oxidizing agent, and 0.033 as an acid N, 0.053 N, 0.06 N, 0.07 N, 0.237 N or 0.47 n. an aqueous solution of nitric acid in an amount sufficient to completely immerse the surface to be cleaned in a solution in which intensive mixing, stirring and bubbling of air or air bubbling are carried out, while the flow of acid and the accumulation of copper (II) compounds are controlled, and after processing the spent reaction mixture is carefully drained, the metal or alloy is washed once or twice with distilled water and dried. In this case, the treatment is carried out in a vessel, the material and dimensions of which, as well as the materials from which the elements for organizing mechanical stirring, mixing and bubbling or one air bubbling are made, are selected taking into account the size and configuration of the surface to be cleaned, whether this surface is represented by one or more objects either in the form crushed to the level of chips and sawdust, as well as the mass of the metal or alloy being cleaned and the relative amount of corrosion products or other copper compounds on it.

The method allows you to efficiently and quickly clean the surface of copper and its alloys from corrosion and oxidation products, which include copper (I) and (II) oxides and copper (II) hydroxide, while only removing copper and its alloys on the surface deposits, without affecting the metal itself and without changing the relief and structure of its surface.

Characteristics of the raw materials used:

Nitric acid according to GOST 4461-77.

Sulfuric acid according to GOST 4204-77.

Distilled water according to GOST 6709-72.

Surface deposits of corrosion products on copper and alloys were obtained naturally by using products from them that were stored for a long time under conditions of free contact with air and atmospheric moisture at ambient temperatures.

Surface deposits of the products of oxidation of the metal and its alloys with copper (II) compounds were obtained during redox processes with the indicated reagents in acidic, mostly aqueous, media in the temperature range of 20-70 ° C in the absence of any restrictions on the contact of the reaction mixtures in the process with air.

The process of cleaning the surfaces of copper and its alloys from the products of corrosion and (or) oxidation of the metal (alloy) with copper (II) compounds of the claimed method is as follows. The metal or alloy to be cleaned is placed in a vessel of an appropriate configuration and with the required volume. The material of the vessel is thick-walled glass or plastic resistant to acidic media. The shape and dimensions of the reactor are determined by the configuration and dimensions of the surface being cleaned. In cases where the metal (or alloy) is taken in finely divided form, chemical glassware in the form of glasses and flat-bottomed flasks, as well as a bead mill or its body with a stirrer, are suitable for use.

A calculated amount of an aqueous acid solution is introduced into a vessel selected as a reactor in such a way that a layer of liquid 30–50 mm thick appears above the top of the surface to be cleaned. They include mechanical stirring (a mechanical shaker with reciprocating or ellipsoidal movement of the platform; a paddle mixer made of durable plastic that can be easily moved along the vertical; a bead mill mixer; other options), supply air to the bubbler (if provided for in the design of the reactor) and begin processing. In its course, without stopping mechanical mixing and air bubbling, samples of the reaction mixture are taken, which are analyzed for the content of acid and copper (II) compounds in them. At the same time, they conduct visual observations of changes in the surface being cleaned. As soon as the accumulation of copper (II) compounds and acid consumption in the reaction mixture are stopped, air bubbling and mechanical stirring are stopped, the spent reaction mixture is carefully drained, distilled water is poured into the reactor and mechanical stirring is turned on for 5-10 minutes, after which the washing solution is analyzed for its content of acid and copper (II) compounds. The washing is repeated again, after which the metal or alloy with a cleaned surface is removed, dried and used for its intended purpose.

The spent reaction mixture can be used to prepare bulk phases of the oxidation of a metal or its alloy as a secondary raw material with copper (II) compounds.

Example No. 1.

In a thick-walled glass cup with an inner diameter of 54 mm and a height of 117 mm with a lid with holes for air circulation, with an stuffing box for a paddle mechanical stirrer (1560 rpm; dimensions of a blade made of PCB 51 × 23 × 2.5 mm), 37 g are placed strongly corroded copper filings (the mass of corrosion products approaches 15% of the mass of the loaded metal), pour 160 ml of 0.47 N. HNO ₃ , include mechanical stirring, serves a stream of air through the gas space of the reactor and begin the cleaning process. After 8 min, a brightening of the metal surface occurred. In the sample taken at this moment, the copper (II) content is 0.337 mol / kg, and the residual acid is 0.141 mol / kg. After 19 minutes, the content of Cu (II) in the reaction mixture reached 0.390 mol / kg, and the acid was 0.091 mol / kg. Over the next 25 minutes, these values remained virtually unchanged. Mechanical stirring is stopped, the spent reaction mixture is carefully poured into a container designed for this purpose, and the remaining purified copper filings remaining in the reactor are washed twice with distilled water. Then they are removed from the reactor, dried, weighed and sent to the loading of the redox process. The mass of purified copper was 31.56 g. The degree of purification achieved was 98%.

Example No. 2.

The reactor vessel, the lid, the width and height of the agitator blades and the speed of its rotation are similar to Example 1. The agitator material is a copper plate 1.73 mm thick coated with surface deposits of products in an amount of 104 g / kg Cu. A submersible elastic air bubbler is inserted into one of the openings of the lid for air circulation with an outlet above the upper edge of the blade mechanical mixer. Contribute 120 ml of 0.06 N. HNO ₃ solution, include mechanical stirring and monitor the progress of the process. Every 5 minutes, a sample of the reaction mixture is taken, in which the content of copper (II) compounds and residual acid are determined. The following values are obtained:

Moreover, after 5 minutes, the reaction mixture is a solution-suspension of products transferred from the surface of the copper blade into the bulk phase. After processing, washing the removable blade of the mechanical stirrer with distilled water and drying, its mass turned out to be 18.12 g, which suggests a degree of purification from surface deposits of more than 98%.

Example No. 3.

Into a thick-walled cup with an inner diameter of 116 mm and a height of 230 mm with a massive textolite cover with a diameter of 140 mm and a thickness of 21 mm with an annular gap of 15 mm depth to fit onto the walls of the cup, the guide for the shaft of the mechanical stirrer in the center and a number of holes at various distances from the center ( to enter the bubbler, the outlet of the flowing air, additional loading of the necessary components and sampling for analysis), a bronze bell with a mass of 117.76, a height of 73 mm and a diameter of 110 mm at the base is placed on a small base made of PCB to ensure fluid circulation between spaces inside and outside the bell. A paddle mixer with a blade size of 36 × 38 × 3 mm is placed so that the lower edge of the blade is higher than the top of the bell with a gap of 1.0-1.5 mm. Inject 800 ml of 0.1 N. sulfuric acid. Turn on the mechanical stirring and set the speed of the mixer so that the liquid layer above the bell turns into foam. At the same time, air is supplied for sparging with exits at the bottom of the glass located at an angle of 120 °. An additional output is introduced into the inside of the bell. Air consumption per bubbler 0.2 l / min for each bubbler outlet.

During the process, samples of the reaction mixture are taken, in which the content of copper (II) compounds and residual acid are analyzed. The following dynamics of changes in these characteristics is obtained:

After 105 minutes, the cleaning process is stopped, the bell is removed from the glass, washed with running water, allowed to air dry and weighed. During the processing, the mass of the bell decreased by 3.28 g, which corresponds to a degree of purification of 96%.

Example 4

In a cylinder with an inner diameter of 25 mm and a height of 600 mm, a dirty-brown-brown copper tube corroded during long-term storage in air is placed with an inner diameter of 6 mm, an external diameter of 8 mm, and a length of 370 mm containing 10.1 g of corrosion products according to the analysis results kg Previously, a submersible elastic bubbler is tied to the tube with an outlet of 5 mm located at a distance of 8 mm from the bottom of the vessel. Pour 230 ml of 0.07 mol / kg of an aqueous solution of nitric acid and apply a stream of air with a flow rate of 0.43 l / (min · (kg of the reaction mixture)), providing stable bubbling and fairly effective pneumatic mixing of the reaction mixture. During the process, samples of the reaction mixture are taken from a central height zone, which are analyzed for the content of copper (II) compounds and residual acid.

These data are given in the table:

At the same time, they observe the color change of the tube being cleaned; it varies unevenly. First, the color of "pure copper" acquired the upper part of the outer surface of the tube. The longest corrosion products lingered below the inside of the tube. For 130 minutes the process is stopped, the tube is washed with running water, dried and weighed. 71.890 g is obtained. A mass loss of 0.726 g, which corresponds to a purity of 98%.

Example 5

In a conical flask with a capacity of 500 ml, equipped with a bubbler with several outlets directly at the bottom, put a piece of 104.52 g of copper wire with a content of corrosion products 11.38% of the mass of crude wire, cleaned from easily braided from aging braid, pour 200 g of 0 5 mol / kg of sulfuric acid solution. This reactor is securely fixed on the table of the mechanical shaker, on the tripod rack of the platform, the air supply to the bubbling is fixed, mechanical shaking is turned on and the air flow is supplied to the bubbling with a flow rate of 0.32 l / min. This moment is taken as the start of processing. During the process, bulk phase samples are taken in which the content of copper (II) compounds and the remaining acid are determined. The data obtained are summarized in the table:

In parallel, observe the state of the metal surface. After 20 minutes, its main part acquired the color of "pure copper". But the remnants of corrosion products are clearly visible in places of denser twisting of the veins. After 10 minutes, these residues disappear from the field of view, which correlates well with the data of the above control. At the 110th minute, the process is stopped. The copper wire is thoroughly washed with running distilled water and dried. The mass of purified copper is 93.11 g. The degree of purification is 96%.

Example 6-13

Other options for the processing that characterize the claimed method, containing various combinations of the types of reactor and the object being cleaned, their material and sizes, as well as the characteristics of loading and holding are summarized in table. Designations: WB - shaft of a mechanical stirrer made of bronze; PB - cup holder made of bronze; KB - bronze shut-off valve body and its elements; LOT - a blade made of copper-plated on one side of the PCB; LM - a blade of a copper plate; LL - a blade from a brass plate; OB - bronze filings; OL - brass filings; St - glass; Pl - plastic; PC - products of corrosion and POC - products of the oxidation process.

The positive effect of the proposed solution is:

1. The method is simple to implement and also diverse in hardware. For him, there is no need to strictly specify the shape and dimensions of both the reactor and the materials being cleaned. In this case, intensive mixing of the liquid phase can be realized mechanically or pneumatically, or both simultaneously.

2. As an oxidizing agent, atmospheric oxygen is used; a natural compound present in sufficient quantity at any place of the cleaning process and not requiring special isolation and transportation.

3. The proposed method uses dilute aqueous solutions of available acids, which may well be obtained from substandard products and industrial wastes.

4. With its help, not only many corrosion products of various origins are removed, but also surface deposits of the oxidation of the metal and its alloys with copper (II) compounds as part of the recycling of copper secondary materials.

5. The solutions obtained during cleaning can well be used to prepare bulk liquid phases of utilization processes involving copper as a secondary raw material, ie to be disposed of and not to turn into regular wastewater.

6. In the proposed method, metal is practically not consumed, and therefore, its surface does not change, which can be used to obtain additional characteristics of the corrosion that has occurred previously.

Claims (2)

1. A method of cleaning the surfaces of copper and its alloys from the products of corrosion and oxidation by copper (II) compounds, comprising treating the surface of copper and its alloys with an aqueous acid solution in the presence of an oxidizing agent, characterized in that atmospheric oxygen is used as an oxidizing agent, and as an acid, 0.033 n, 0.053 n, 0.06 n, 0.07 n, 0.237 n or 0.47 n aqueous nitric acid solution in an amount sufficient to clean the surfaces of corrosion and oxidation products and completely immerse the surface to be cleaned in the solution in which intense mixing, stirring and bubbling of air or bubbling of air, while controlling the flow of acid and the accumulation of copper (II) compounds, and after processing the spent reaction mixture is carefully drained, the metal or alloy is washed once or twice with distilled water and dried. 2. The method according to p. 1, characterized in that the surface treatment is carried out in a vessel, the size and material of which is selected taking into account the size and configuration of the surface being cleaned.