SU975832A1 - Solution for preparing steel surface for electroplating - Google Patents

Description

The invention relates to the protection of metals from corrosion, in particular to the chemical treatment of metals, and can be used in the engineering, metallurgical, radio engineering industries when processing the surface of steel by reprecipitation of electroplated coatings.

Known surface preparation of steel before coating, including the sequential execution of operations: etching in sulfuric acid solution, mechanical cleaning of sludge, pickling in weak acid solution and interoperational washing in water [Ts.

However, this process is laborious as it requires mechanical removal of pickling sludge. In addition, the treatment in sulfuric acid is long (60-90 min), and the implementation of interoperational washes require a large consumption of water.

Also known is a solution for preparing a metal surface before electroplating, containing sulfuric acid (18–20 wt. ° / o) and organic matter. After treatment with this solution, mechanical purification is carried out.

surface from sludge and interoperative flushing with water [2].

The closest to the technical essence of the invention is a solution containing sulfuric acid, sodium chloride, surfactant. Substance (surfactant of the type OP-7 or OP-10), thiourea and water [3].

Processing the known solution is time consuming, as it requires removal of pickling sludge by mechanical means; long ⁰ due to multi-operability and duration of etching, amounting to 60-90 minutes; does not provide high quality surface preparation and, as a result, there is not enough strong 15 adhesion of the electroplated coating to the base metal.

The aim of the invention is process intensification, £ Reductions its complexity, improve the quality of the surface preparation for coating and as a consequence, increase the coating ²⁰ adhesion to the metal substrate, the reduction of wash water.

This goal is achieved by the fact that

steel surface preparation solution

before electroplating,

3

four

containing sulfuric acid, sodium chloride, surfactant, thiourea and water, additionally contains sodium salt << - sulfo carboxylic acid fraction C ₁₇ —C ₂₀ , and as a surfactant - sulfonate in the following ratio of components, May. %:

Sulfuric acid 15-20

Sodium chloride 5-7

Sulfonate 0.01—0.1

Thiourea 0.1 —1.0

Sodium salt

σί-sulfocarboxylic acid fraction

ten

C ₁₇ -C ₂₀ 0.05-0.1

Water Rest

The removal of sludge is carried out simultaneously when treated in solution for 6–10 minutes.

As the sodium salts of sulfo carboxylic acid fraction C | ₇ —C ₂₀ can be used, for example, monosodium-<X-sulfononedecanate

15

20

:) ₈ n ₃₇ -sn- _x

HE

di sodium yo-sulfoicosanate

25

C _{) 9} N

39

-С-С

; 0

as well as technical mono- and disodium salts of <3 £ -sulfonic acid fraction C | ₇ —Sgo ·

Keeping the processing in this solution for 6-10 minutes produces besshlamnoy surface as thiourea, facilitating the selective etching of the steel surface reduces the formation of etch products, and salt'sulfokarbonovyh οί-acids fraction C ₍₇ -C ₂ o, ^on particles ^of sludge adsorbing cause their flotation and accelerate the etching process.

The sulfonate ensures the hydrophobization of the treated surface, which allows the subsequent coating process to be carried out without washing with water.

The combined presence of organic additives causes the identification of the crystal structure of the metal and increases the adhesion of the coating to the base metal.

Acceleration of the etching process, elimination of the operations of mechanical removal of sludge and washing with water makes it possible to intensify the process of preparing the surface of the steel before electroplating.

The absence of washing after etching improves the adhesion of the electroplated coating to the base metal, aided by adsorbed on the surfactant surface.

In laboratory conditions prepared solutions presented in table. one.

thirty

35

40

An etching solution was prepared by adjusting the calculated amount of acid to water, followed by dissolving the remaining components in an acidic solution.

The order of introduction of the latter does not affect the properties of the pickling solution.

The tests were carried out on samples of size 50 x 50x1 mm from st. RFP with process scale after heat treatment, which were first degreased, for example, with acetone, then treated in solutions I — VI until scale was completely removed.

In the case of processing samples with scale in solutions I – V, the coating (zinc, copper, nickel) was applied to the samples without subsequent washing. When processing the samples in the solution indicated by examination (variant VI), after etching, the samples were washed with water, then the slurry was removed with a brush, washed with water and decapitated. Metallic coatings of sulfuric electrolytes of the following compositions were applied to the prepared samples, g / l:

I. Zinc

Ζη5Ο ₄ · 7Η ₂ Ο 200

KA1 (5O ₄ ) ₂ -12N _and O 40

Tsa ₂ 5O ₄ -UN ₂ O 40

Water

Up to 1 l

The mode of deposition of the coating: solution temperature 45 ° C; current density 5 A / dm ² ; process time 10 min.

Ii. Nickel

Ν18Ο ₄ · 7Η ₂ Ο

Νί01 ₂ · 6Η ₂ 0

H ₃ IN ₃

Water

The mode of deposition tour solution 40 ° C; current density 3 A / dm ² · process time 10 min.

Iii. Copper

Si5O ₄ 5H ₂ O 180

H ₂ 80 ₄ 75

45

250 60 40

Up to 1 l

Coatings: temperaWater Up to 1 l

The mode of deposition of the coating: solution temperature 25 ° C; current density 2 A / dm ² ; process time 10 min.

The efficiency of the proposed solution was evaluated by the duration of etching, min; the cleanliness of the treated steel surface; coating quality; the quality of adhesion of the coating to the metal base.

The duration of etching was determined by the time of complete removal of scale in min.

The purity of the surface treatment was judged by the results of visual inspection of the surface and the change in weight of the treated sample after wiping it with clean filter paper (g / m ² ).

The quality of the coating was determined by visual inspection for the absence of pitting, color, for the absence of flaking and adhesion of the coating to the substrate in accordance with GOST 3002-70.

975832

five

The test results are shown in Table. 2, from which it follows: the duration of treatment in solutions according to variants II – IV is 6–10 min, which

3-5 times lower than in said expert solution (variant VI), quality of the formed ₅ Botko good slurry on the treated surface is absent, the surface light, the coating adhesion to the substrate a solid; a decrease in the concentration of components in the treatment solution (option I) leads to an increase in the processing time to 10 25 minutes and becomes equal to the processing time in the pickling solution indicated by the expertise (option VI); surface after treatment (option I) dark gray, good adhesion to the base.

The increase in the concentration of components (option V) is technologically feasible, since the processing time is not reduced compared with

6

IV, the quality of surface preparation and the quality of adhesion of the coating to the substrate are not improved.

The use of the proposed solution allows to intensify the process of steel surface preparation before deposition of electroplated coatings by reducing the treatment time in the pickling solution by 2.5—5 times (from 25—30 min to 6—10 min), excluding operations of intermediate water washes, mechanical removal and pickling the surface before deposition of the coating; reduce the complexity of the process by eliminating the operation of mechanical removal of sludge from the surface and the operation of water washing; improve the quality of adhesion of the coating to the base; reduce the cost of treatment by 20-30% by reducing water consumption and reducing acid consumption.

Table 1

Components According to the proposed way In the solution indicated tizoy (U1 g / l pickling grow thief Options solutions, the concentration of components, May. % * expert option) ’! III [.7 ..... 1. Have Sulphuric acid ten 15 17 ²⁰ 25 170 Sodium chloride five 6 7 3 75 Thiourea 0.05 oh 1 0.5 ten 1.5 one) Sodium salt of “Ζ -sulfocarbo • new acids (c-c) 0.01) 0.05 0.075 oh 1 0, 12 Sulfonate 0,005 0.01 0.06 0.1 0.12 - 0P — 10 or 0P-7 - - - - - 17 Water Up to 100 Up to 100 Up to 100 Up to 100 Up to 100 Up I l

table 2

Criteria for evaluating the effectiveness of the method Processing by the proposed method Processing in the specified examination solution (. Option V1) Variants of the composition of the solution for processing ¹ 1 "  one ^{| at} 1 Have The processing time to complete scale removal, min 25 ten eight 6 6 25-30 Appearance of the treated surface Dark gray Light Light Light Light Gray Dark The amount of sludge on the surface after treatment, g / m ² The absence of The absence of The absence of The absence of The absence of 2.0-2.2 Coupling coatings with a metal base Detachment missing Detachment missing Detachment missing Detachment missing Detachment detachment by missing edges Appearance of the deposited plating Matt Light Shining Shining Shining Matt

975832

Claims (1)

A solution for preparing the surface of steel before electroplating, containing sulfuric acid, sodium chloride, surfactant, thiourea and water, characterized in that, in order to intensify the process, increase the adhesion of the coating, the solution additionally contains sodium salt οί- sulfo carboxylic acids fraction С17 — С ^. and as a surfactant sulfonate in the following ratio, wt. ° / ₀ : Sulfuric acid 15-20 Sodium chloride 5-7 Sulfonate 0.01—0.1 Thiourea 0.1 —1.0 Sodium salt of ί-sulfo carboxylic acids ₅ fractions C) 7 — C ₂ about 0.05–0.1 Water Rest