SU1678900A1 - Solution for chemical oxidation of aluminum and its alloys - Google Patents

Abstract

The invention relates to the chemical treatment of metals, in particular to the chemical oxidation of products from aluminum and its alloys, and can be used in the manufacture of electronic equipment. The goal is to reduce the electrical transient resistance of coatings while simultaneously increasing their protective properties. The solution contains, g / l. ammonium or alkali metal phosphate 15-30, ammonium or alkali metal chloride 20-50, ammonium or alkali citrate 10-25, ammonium molybdate or alkali metal 4-12 and N, N1-diphenylguanidine 0.2-0.6. A decrease in the electrical transient resistance of the coatings while enhancing their protective properties is achieved by introducing ammonium or alkali metal, ammonium molybdate or alkali metal and N, Nl-diphenylguanidine into the composition of the solution of ammonium citrate or alkali metal. 1 tab. cl

Description

The invention relates to the chemical processing of metals, in particular to the chemical oxidation of products from aluminum and its alloys, and can be used in the manufacture of electronic equipment in the electronic and other engineering industries.

The purpose of the invention is to reduce the electrical transient resistance of coatings while simultaneously increasing their protective properties.

The proposed solution contains, g / l: Phosphate of ammonium or alkali metal15 - 30 Chloride of ammonium or alkali metal20 - 50 Ammonium citrate or alkali metal10-25

Ammonium or Alkali Molybdate

,one

4-12

N, N1 -diphenylguanidine 0.2 - 0.6

Preparation of the solution is carried out as follows.

First, the calculated quantities of all components are weighed out and in separate containers they are dissolved (except for molybdate) in warm (60 - 70 ° C) water. N, N1-diphenylguanidine is dissolved in slightly acidified water. Then the solutions of phosphate, chloride and citrate are sequentially poured together. The mixture of solutions is stirred, adjusted with acid (e.g., phosphoric or hydrochloric) to a pH of 1 - 3 and the molybdate salt is poured. After dissolution, the molybdate is introduced.

N, N-diphenylguanidine. adjust to pH 1 - 3 and bring the total volume of the solution to water to the desired value.

The coating process includes the following steps.

First, flat plates 50 x 20 x 2 mm in size made of aluminum of the AO brand and its alloys AMg-6 and D16 AT (surface roughness R 1.25 microns) are degreased in the usual way in an organic solvent (for example, gasoline) and in a solution containing two-substituted sodium phosphate (10-15 g / l) and soda ash (5-7 g / l). Then, the defatted samples are etched in a solution of sodium hydroxide (100-120 g / l) at 50-60 ° C for 0.5-1.5 minutes and, after washing in hot and cold water, are clarified at room temperature in a nitrogen acids (1: 1) for 1 - 5 minutes. After thorough washing, chemical oxidation of the samples is carried out. The oxidation time at room temperature is 20–60 min, depending on the composition of the solution, and at higher temperatures (for example, 80–90 ° C), 3–5 min. The oxidation process is stopped when the yellow or light green color of the samples is reached. The coated samples are washed in hot water and dried in a drying oven.

The density of a single solution loading is not more than 2.0 dm / l. During operation, the pH value of the solution changes upwards, which leads to a significant slowdown in the rate of chemical oxidation before the solution is produced. To prevent a decrease in the rate of formation of the coatings, it is necessary to periodically adjust the pH to the initial value.

The transient electrical resistance of oxide coatings is measured with a millimeter E6-18 / 1 by a four-wire circuit using current and potential conductors. For this purpose, two plates with the test coating are placed in a special device made of dielectric material, in which reliable contact between the plates with a strictly defined area (5 cm2) is provided by a load of 100 g on the entire contacting surface. To insert the plates into the electrical circuit, knife electrodes are used which lead to the surface of the plates that are not in contact with each other.

The protective properties of the coatings are determined by the method of accelerated testing by holding the samples in a 5% NaCl solution. Samples were examined with a BMS-1 microscope (4x magnification) once a day. If corrosion points are detected on the surface of the samples as white bloom, the tests are stopped and the last day does not count as the test result.

The compositions of the tested solutions and

test results of oxide chemical coatings are presented in the table.

As shown by the test results, the proposed solution provides

Coatings with lower transition resistances (0.070 - 0.105 mΩ / cm2) compared with the known (0.310 mΩ / cm), which improves their functional characteristics and allows use in low-current cable connectors.

Higher protective properties of the proposed coatings allow operation of the products to be covered in a marine atmosphere containing chlorides. An important advantage of the proposed solution is that it can operate at room temperature, thereby simplifying the process.

The technical and economic advantage of the proposed solution is to reduce the electrical transient resistance of the coatings while simultaneously increasing their protective properties.

Claims (1)

Invention Formula A solution for the chemical oxidation of aluminum and its alloys, containing ammonium or alkali metal phosphate and ammonium or alkali metal chloride, characterized in that, in order to reduce the electrical transient resistance of coatings while simultaneously increasing their protective properties, it also contains ammonium citrate nor alkali metal, ammonium molybdate or alkali metal and N, N-diphenylguanidine at the following ratio of components, g / l: Ammonium or alkali metal phosphate15-30 Ammonium or alkali metal chloride 20 - 50 Ammonium or alkali metal citrate 10-25 Ammonium or alkali metal molybdate4-12 . eleven . P i l. , v ..- i.rit ... n.j..Л О - О fi N, N -Difenilguanidin Solution components and coating properties cl - 3-5 30-40 90 3 2O 40 8 0.1 90 3 0.310 0.260 Samples of aluminum grade AO. Samples from alloy D16 AT. 2O 40 8 0.1 90 3 0,260 15 30 10 0.2 80 five 20 30 15 6 0.3 20 60 20 35 15 6 0.3 20 60 20 35 15 6 0.4 20 60 20 35 20 8 0.5 20 40 25 40 20 -eight 0.5 90 3 25 40 20 eight 0.6 20 30 30 40 20 10 0.6 20 thirty thirty 50 25 12 0.6 20 20 30 50 25 12 25 50 30 13 0,60,7 2020 2020 j 20 40 20 ten 20 40 0.105 0.095 0.090 0.075 0.070 0.070 0.070 0.085 0.090 0.090 0.045 0.330 677899988865 20 40 20 0.5 20 40 0,290 3 ABOUT) -J 00 (o oh oh