RU2350695C1 - Bright zinc plating solution - Google Patents

Abstract

FIELD: chemistry, electrochemistry.

SUBSTANCE: invention refers to electrochemistry, particularly to electroplating and can be used in mechanical engineering to ensure corrosion prevention of fabricated metals. Solution contains, wt %: ZnSO₄·7H₂O 15.0-25.0; Na₂SO₄·10H₂O 10.0-11.0; bone glue 0.20-0.25; dry potato beetle tincture (dry weight equivalent) 0.5-1.0; water the rest.

EFFECT: higher zinc plating brightness and improved current scattering power of solution.

2 tbl, 2 dwg

Description

The invention relates to the field of electrochemistry, in particular to the deposition of galvanic coatings, and can be used in the engineering industry to protect metal structures from corrosion.

Known acidic electrolyte of brilliant galvanizing (patent RU No. 2054835 dated 04/20/1996, Mcl. ⁶ C25D 3/22), which contains zinc sulfate, sodium sulfate, aminoacetic acid, and 1-hydroxyethyl-3,4 as a bright-forming additive , 6-trimethyl-1,2-dihydro-2-oxopyrimidinium iodide in the following ratio of components, g / l:

Zinc Sulfate - 200-250 Sodium Sulfate - 30-40 Aminoacetic acid - 10-20 1-hydroxyethyl-3,4,6-trimethyl- -1,2-dihydro-2-oxopyrimidinium iodide - 0.7-2

The galvanizing process is carried out at a cathodic current density of 10-15 A / DM ² , pH 2.0-4.0. Zinc current output 70-90%. The zinc coatings obtained in this electrolyte have good adhesion to the base metal; gloss level 55-85%.

The disadvantages of electrolyte include the following.

1. A small range of cathodic current density 10-15 A / DM ² .

2. The lack of intensification of the process.

3. Insufficiently high degree of gloss of 55-85%.

4. Higher acidity (pH 2.0-4.0).

5. The synthesis of a bright-forming additive — 1-hydroxyethyl-3,4,6-trimethyl-1,2-dihydro-2-oxopyrimidinium iodide — is associated with economic costs. The fact of the harmful effect of this additive as an iodine preparation on a living organism is not excluded.

The closest in technical essence is an acidic electrolyte of brilliant galvanizing (patent RU No. 2063481 dated 10.07.1996, Ml. ⁶ C25D 3/22), which contains zinc salt, sodium sulfate, glue, and, as a brightening additive, infusion of rhizome ragweed in the following ratio of components, wt.%:

Zinc salt (in terms of metal) - 1.0-1.3 Sodium sulfate - 3.0-3.5 Glue glue - 0.20-0.25 Rhizome infusion leaf ragweed (in terms of dry weight) - 0.5-0.7 Water - the rest

The galvanizing process is carried out at a temperature of 18-35 ° C, cathodic current density of 1-18 A / DM ² , moderate stirring of the electrolyte. The current dissipation capacity of the electrolyte is 72-73%, the current efficiency is 98-99%. During the operation of the known electrolyte, light, uniform, non-porous, finely crystalline coatings with a degree of gloss of 93-95% are obtained.

The disadvantages of the known electrolyte include the following.

1. The known electrolyte is characterized by a lower value of the degree of gloss (93-95% against 96-99% of the proposed electrolyte), which indicates the worst mechanical and protective-decorative properties.

2. The known electrolyte has a lower current dissipation ability (72-73% versus 75-78%), therefore, the known electrolyte can be used for applying zinc coatings to parts of a less complex configuration.

3. The known electrolyte is characterized by a smaller interval of cathodic current density (D _to 1-18 A / dm ² ) compared with the proposed electrolyte (D _to 0.5-18 A / dm ² ).

The present invention is the creation of an electrolyte with higher quality characteristics.

The technical result consists in increasing the degree of gloss of galvanic zinc coatings and increasing the current dissipation of the electrolyte.

The essence of the invention is that in a brilliant galvanizing electrolyte containing heptahydric zinc sulfate crystalline hydrate, decahydrate crystalline sodium sulfate, bone glue, a tincture of dry individuals of the Colorado potato beetle is introduced as a brightening additive in the following ratio of components (wt.%):

ZnSO ₄ · 7H ₂ O - 15.0-25.0;

Na ₂ SO ₄ · 10H ₂ O - 10.0-11.0;

Bone glue - 0.20-0.25;

Infusion of dry individuals of the Colorado potato beetle

(in terms of dry weight) - 0.5-1.0.

The choice of the infusion of dry individuals of the Colorado potato beetle as a brightening additive was justified by the results of preliminary tests for the presence of substances with surface activity in its composition. Under the influence of surfactants, the kinetics of electrodeposition of metals, the structure and properties of precipitation (corrosion resistance, porosity, internal stresses, hardness, gloss) change (Kabanov BN Electrochemistry of metals and adsorption. M .: Nauka. 1996. P.56-61).

Information on the presence of surfactants in the biomass of the Colorado potato beetle in literature was not found. Therefore, the method of volt-ampere curves studied the effect of the infusion of dried and ground individuals of the Colorado potato beetle on the process of deposition of zinc from an electrolyte of the above composition (figure 1). The shift of the current-voltage curve 2 to the region of large voltage values relative to curve 1 clearly indicates the presence of surfactants in the infusion of the additive. The decrease in the polarographic maximum at the polarogram of oxygen recorded against the background of 0.1 M KCl within the potentials of 0.7-1.8 V (Fig.2) also indicates the presence of surfactants in the biomass of the Colorado potato beetle.

A brilliant galvanizing electrolyte is prepared by simple mixing of the initial solutions of zinc and sodium sulfates obtained by complete dissolution of the calculated weights in distilled water. Glue infusion and additives are introduced into the electrolyte immediately before the experiment. Then the total volume of the electrolyte is adjusted to a predetermined volume with distilled water.

The galvanizing process in the proposed electrolyte is carried out at a temperature of 20-35 ° C, a cathode current density of 0.5-19 A / dm ² , moderate stirring of the electrolyte solution. The appearance of the coating was evaluated visually. The reflectivity was determined in comparison with the reflectivity of a silver mirror. The adhesion strength of the coating to the base was carried out by applying a network of scratches. The current dissipating capacity of the electrolyte was determined by the Field method in a 2 L galvanic bath with a ratio of the distance between the anode and the far cathode, the anode and the near cathode equal to 5: 1. The cathode was steel plates with a working surface of 0.04-0.08 dm ² , the anode was a zinc plate with a working surface of 0.80 dm ² .

The porosity of the coating was determined by applying to the experimental surface of filter paper moistened with a solution of red blood salt, followed by counting the number of turnbull blue points per 1 cm ² .

As a result of tests, it was found that:

1) the proposed electrolyte allows you to get bright, uniform, non-porous, fine crystalline coatings with a high degree of gloss (99-96% within the cathode current density of 0.5-19 A / DM ² ) when the zinc output current 99-97%, which says about the intensification of the process. Known electrolyte operates in the range of 1-18 A / DM ² ; in this case, coatings with a degree of gloss of 95-93% are obtained;

2) the proposed electrolyte is characterized by a higher current dissipation capacity (75-78% versus 72-73% of the known electrolyte), which makes it possible to apply high-quality coatings to parts of a more complex profile;

3) the proposed electrolyte is recommended to be operated in a less acidic environment than the known electrolyte (pH 4.5-5.8 versus pH 2.9-3.5 of the known electrolyte), which does not require additional reagent costs and, therefore, economic costs to neutralize acidity of the medium during discharge of spent electrolyte;

4) the bright-forming additive used in the proposed electrolyte is extraordinary, a terrible pest of vegetable crops benefits humanity.

The proposed proposed electrolyte does not require purification by additive.

Table 1 The composition of galvanizing electrolytes Components The content of the components in the composition the proposed electrolyte,% prototype% analog, g / l one 2 3 ZnSO ₄ · 7H ₂ O 15.0 20,0 25.0 1.0-1.3 (in terms of metal) 200-250 Na ₂ S0 ₄ · 10H ₂ O 10.0 10.5 11.0 3.0-3.5 30-40 Aminoacetic acid - - - - 10-20 Bone glue 0.20 0.22 0.25 - - Glue glue - - - 0.20-0.25 - 1-hydroxyethyl-3,4,6-trimethyl-1,2-dihydro-2-oxopyrimidinium iodide - - - - 0.7-2.0 Infusion of rhizomes of ragweed - - - 0.5-0.7 - Infusion of dry individuals of the Colorado potato beetle 0.5 0.7 1,0 - - Water rest rest rest rest rest

table 2 Technological process parameters and results Components The content of the components in the composition the proposed electrolyte,% prototype% analog, g / l one 2 3 pH 4,5 5.1 5.8 2.9-3.5 2.0-4.0 Temperature, ° C twenty thirty 35 18-35 - Cathode current density, A / dm ² 0.5 10 19 1-18 10-15 Electrolyte dissipating current (Field method),% 78 76 75 72-73 - Current output,% 99 98 97 98-99 90-70 Gloss degree,% 99 96 96 93-95 55-85 Visual assessment of coating quality Light, uniform, non-porous, finely crystalline - Adhesion sat. sat. sat. - -

Claims (1)

Brilliant galvanizing electrolyte containing heptahydric zinc sulfate crystalline hydrate ZnSO ₄ · 7H ₂ O, decahydrate crystalline sodium sulfate Na ₂ SO ₄ · 10H ₂ O, bone glue, brightening additive and water, characterized in that it contains tincture of dry individuals as a brightening additive Colorado potato beetle in the following ratio of components, wt.%:
ZnSO ₄ · 7H ₂ O 15.0-25.0 Na ₂ SO ₄ · 10H ₂ O 10.0-11.0 bone glue 0.20-0.25 infusion of dry Colorado potato beetle (in terms of dry weight) 0.5-1.0 water rest

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