LT4211B - Method for the formation of black phosphatic coating on the surface of steel - Google Patents

Abstract

The black phosphate coating production method may be used for the protection against corrosion and for the appearance (decoration) improvement of various products or elements in a range of industrial branches. Using this method the black phosphate coatings are produced out of a solution containing zinc, nickel, copper, phosphate, nitrate ions, where according to the invention, there are additional selenite and organic amino sulfo acids and it is coated in a period of 7-10 minutes at a temperature of 45-50 degrees Celsius and a solvent of a pH value of 2.0-2.4.

Description

The present invention relates to a process for the preparation of chemical coatings, namely, a process for the preparation of black phosphate coatings on a steel surface and can be used in various industrial applications for protecting products or parts thereof against corrosion and improving their appearance.

There is a known method of obtaining black coatings on a steel surface (ex USSR Standard 9.305-84, Metal-to-Metal Non-Metallic), from a solution containing caustic soda, sodium phosphate and sodium nitrate. The process takes 40-60 minutes and the coating temperature 135-145 ° C.

The coating obtained in this way is relatively soft and has low corrosion resistance. Technologically, the process is very long, with high coating temperatures, and very high concentrations of the materials used.

There is a known process for obtaining black phosphate coatings on a steel surface (English Patent No. 1,156,357, cl. C23F 7/08, 1969) using several solutions. First, the steel parts are corroded in phosphoric acid solution. It is then immersed in SbCle - HCl and then transferred to a standard phosphate solution. Coat the parts for 30 minutes at 90 ° C. Phosphated and dried parts are further immersed in i. Cr03 solution or lubricants such as machine oil.

The method of preparation of these coatings is technologically complex due to the use of several solutions, as well as the long process time and high coating temperature. The phosphate coatings obtained in this way are of relatively low corrosion resistance, uneven and dark gray in color.

Another method of obtaining black phosphate coatings is known (U.S. Patent No. 4,621,424, C 23F 7/07, 1967), wherein the phosphated standard solution additionally designates steel components into a solution containing potassium permanganate, copper sulfate and iron sulfate.

The method of obtaining these coatings is technologically complex because the coatings are obtained from several solutions of different compositions. The coatings obtained in this way are poorly decorative, have a dirty black color and have relatively low corrosion resistance.

The closest technical solution is essentially to obtain black phosphate coatings on a steel surface (Polish Patent No. 139,481, Cl. C 23C 22/12, 1988) from a solution containing zinc, nickel, copper, manganese, phosphate and nitrate ions. . Phosphate for at least 10 minutes at a coating temperature of 60-65 ° C.

The phosphate coatings obtained in this way do not have sufficient decorative properties because they are dark gray in color. In addition, the resulting coatings have relatively low corrosion resistance. The process is technically complex, as additional varnishing or lubrication is required to improve its anticorrosive properties.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for preparing a black phosphate coating on a steel surface from a weakly acidic phosphating solution and to obtain a rich, black, smooth, corrosion-resistant, non-abrasive coating.

Another task is to increase process technology by using easily decontaminated materials, in addition to shortening the deposition time of the coatings and reducing the coating temperature.

The essence of the invention lies in the fact that the steel parts after the degreasing and etching are made into. a weakly acidic phosphating solution containing zinc, nickel, copper, phosphate, nitrate ion, selenic acid or its salts and organic acid of the class of aminosulphonic acid.

Coat the parts for 7-10 minutes at a coating temperature of 45-50 ° C and pH 2.0 - 2.4.

The proposed method is more technological, since black and corrosion-resistant phosphate coatings are obtained without additional operations.

The resulting phosphate coatings on the steel surface are rich black, fine crystals, smooth, with high corrosion resistance. In addition, coatings are formed in a relatively short period of time and at relatively low coating temperatures.

The resultant phosphate coatings on the steel surface, compared to known technical solutions, help to intensify production (shorter coating time), reduce energy consumption (lower coating temperature), extend the life of the coated article (high corrosion resistance of coatings).

The phosphate solution is prepared according to the proposed process in salted water by dissolving the amounts of the substances specified in the recipe.

The source of zinc ions may be zinc oxide, zinc dihydrogen phosphate, zinc nitrate; nickel ion source nickel nitrate; as a source of copper ions - copper nitrate, copper sulfate; phosphate ion source - phosphoric acid, zinc, nickel phosphates; nitrate ion source - nitric acid, sodium, nickel, zinc nitrates.

Further, the parts, which have been chemically or electrochemically degreased and activated in 1: 1 HCl solution, are immersed in steel into a ready-made solution having a pH of 2.0 to 2.4 and applied for 7 to 10 minutes at a coating temperature of 45 to 50 ° C. At the end of the process, the parts are removed from the solution, washed with water and dried in warm air.

The properties of the skies are analyzed after 24 hours. from cover.

The corrosion resistance of coatings is determined by the drop method (USSR standard 9.308 - 85). Apply a solution of 40 ml of 0.5 M CuSO ₄ .5H ₂ O, 20 ml of 10% NaCl and 0.8 ml of 0.1 N HCl on the surface of the phosphated steel in 5 places and observe the change of color from blue to brown:

(up to 15s low, 15-30s down, 30-60s medium, over 60s high).

Color saturation is determined visually: dark gray, black, rich black.

The crystallinity of the coating structure is determined visually with the aid of an x6 magnifier: coarse crystal, medium crystalline, fine crystal. The covered weights (Pf, g / m ² ) are determined by weighing the samples 3 times:

1) before phosphating,

2) after phosphating,

3) after dissolving the phosphatin coating in 25% CrOe solution.

From these weights also calculate the weight of melted steel during coating (Pm®, g / m ² ).

The abrasion resistance of coatings is determined by rubbing with a wet piece of filter paper on a phosphated surface, and is evaluated by the brightness of the imprint on a three-point system:

1) the coating is subject to severe wear,

2) the coating is slightly abrasive,

3) the coating is practically non-abrasive.

The uniformity of the steel surface is evaluated visually: the surface is even, the surface uneven.

For the evaluation of the effectiveness of the proposed method, 8 examples were prepared, one of which being a control and 7 examples according to the invention with different concentrations of the solution:

Control sample

The degreased and activated steel parts are immersed in a solution containing (g / 1):

HsPCU

HNOs

17.9

8.2

ZnO - 5.0

MnCO a - 0.9

Ni (N0 ₃₎ s.6H2O - 7.0

Cu (NO ₃ ) ₂ .3H ₂ 0 - 0.01

The acidity of the solution is pH = 2.2, the application time is 10 minutes and the application temperature is 65 ° C. The coated parts are washed with water and dried in warm air.

example

The prepared steel parts are immersed in solutions containing (g / 1):

Zn (H ₂ P0 _{4) 2} .2HsO - 25.0 NaN0 ₃ to 10.0 Ni (NO _{3) 2} .6H ₂ 0 to 7.0 CuS0 ₄ .5H ₂ 0 to 2.0 H3PO4 - 2.5 HsSeOa - 0.5 sulfamic acid - 1.0

The acidity of the solution is pH 2.2, coating time 7 minutes and coating temperature 45 ° C. The coated parts are washed with water and dried in warm air.

example

Finished parts of steel are made into solutions containing (g / 1):

ZnO - 13.7 NaNO ₃ - 10.0 Ni (NO ₃ ) ₂ 6 H ₂ 0 - 4.0 Cu (NO ₃ ). ₅ H ₂ O - 1.9 H ₃ PO _{4 -} 38.0 H ₂ SeO ₃ - 0.5 Sulphamic acid - 1.0

The acidity of the solution is pH = 2.0, the application time is 50 ° C. Cover the parts with water and dry in warm air.

example

The finished steel parts are immersed in the solution, (g / 1):

Zn (H ₂ P0 ₄ ) ₂ .2H ₂ 0 - 25.0 Zn (N0s) ₂ .6H ₂ 0 - 25.0 Ni (N0 ₃ ) ₂ .6H ₂ 0 - 7.0 CuS0 ₄ .5H ₂ 0 - 2.0 HsPO ₄ - 19.0 H ₂ SeO 3 - 0.25 sulfamic acid - 1.0 Acidity of the solution pH 2.3, coating time

coating temperature - 48 ° C. Cover the parts with water and dry in warm air.

example

Finished steel parts are immersed in solution (g / 1):

Zn (H ₂ PO ₄ ) ₂ .2H ₂ 0 - 50.0 NaNOs - 10.0 Ni (NOs) ₂ .6H ₂ 0 - 7.0 CuSO 4 - 4.5H ₂ 0 - 1.0 H 3 PO 4 - 2.5 Na ₂ SeO3 - 0.5 sulfamic acid - 1.0

The acidity of the solution is pH = 2.4, the application time is 45 ° C. Cover the parts with water and dry in warm air.

- 7 minutes, and wash containing

- 8 minutes while washing contains

- 10 minutes, and wash the sample

The finished steel parts are immersed in a solution containing (g / l):

Zn (H ₂ PO ₄ ) 2.2H ₂ O - 50.0 NaNOs - 10.0 Ni (NO ₂ ) ₂ .6H ₂ O - 7.0 CuSO ₄ .5H ₂ 0 - 2.0 HsPO ₄ - 2.5 H ₂ SeO 3 - 0.5 sulfamic acid - 2.0

The acidity of the solution is pH = 2.2, the application time is 7 minutes and the application temperature is 45 ° C. The coated parts are washed with water and dried in warm air.

example

The finished steel parts are immersed in a solution containing (g / l):

Zn (H ₂ PO ₄ ) ₂ .2H ₅ O - 50.0 NaNOs - 10.0 Ni (NO 3) ₂ .6H ₂ 0 - 7.0 CuSO ₄ .5H ₂ 0 - 2.0 H ₃ PO 4 - 0.5 H ₂ SeO - 0,5 sulphanilic acid - 2,0

The acidity of the solution is pH = 2.2, the application time is 7 minutes and the application temperature is 45 ° C. The coated parts are washed with water and dried in warm air.

example

The finished steel parts are immersed in a solution containing (g / 1):

Ζη (Η ₂ Ρ0 ₄ ) ₂ .2Η ₂ 0 - 50.0

NaNO 10.0

Ni (NO 3) ₂ .6H ₂ O - 7.0

CuSO-4.5H ₂ 0 - 2.0

H3PO4 - 2.5

H ₂ SeO 3 - 0.5

Aminosulfosalicylic acid 2.0

The acidity of the solution is pH = 2.2, the application time is 7 minutes and the application temperature is 45 ° C. The coated parts are washed with water and dried in warm air.

Data on the properties of the coatings are given in the table.

• o i-M {U

-P c

Φ

J i · α>

1 • P ai <· <S C-1-H «S Ai P to o +3 P 1 Z Ό Pm G * - She>, • H 1 T3 0 3p CO 03 co «3 Ό tO 1 o b e l Li 3 >> - i ω -o cn ii C r-1

Checklist! The examples are prepared according to the proposed method

ΙΩ

I -3 ai t — i Ai • h ai P r-f • P {S She + J m O Oh >> • H L T3 P cn o * no Ό you Ό 0 3 -r-i co 03 CO L 3 >> O 3 e l C r — H cn ό cn She 1-3 C rp Ai • h ai p p H CO She p O o Oh >> • H Li Ό p cn o - - ai Ό to Τ3 O 3 -H co CO co L 3 K * » o b ε L C r-H cn -o cn she I-o 3 1-1 • h ai Ai h ai Oh p O ΙΩ P i-l L T3 r — i cn o * * She to » • H Ό 0 3 -H o 03 CO ai Ό to o b £ L L 3 cn -η cn Ai C 1-3 no p • p ai - Oh • H (C Ai P m o P P Li Ό p cn o - * Oh >> • r-l Ό 0 3h CT> 03 00 ali T3 you O 3 ε L L 3 >> cn · ο cn Ai C r-1 1-3 no i — i h ai ΙΩ o Ai • h ai Ai P O * * -P P L Ό P cn cn 03 00 Ai f » • H Ό 0 3 -H ai Ό to O 0 £ L L 3 >> M Ό cn Ai C r— | 1-3 no i — i • h ai m o Ai H Cj Ai P o - * -P P Li T3 r-ι cn σ> 03 co Oh >> • 1 ”1 • a o 3h ai Ό to O 3 £ L L 3 t » cn -o cn Ai C r - l

I

CH

cn 1 P 1 cn T) 1P • P 0 O m 0 N 1 al L £ co - - Oh • H 1p M 3 03 P 1-1 to > 1 cn Ai • Oh t-4 Oh >> > ·. «I 1 £ A 'Ό > Cfi ai Ό 1-1 A 1 alp • P • H L 3 3 1 P A > r — I C C

l CM • H 1 O £ 3 1 P £ 1 al to ♦ H 1 P - r-H 1 al 3 cn • r-l 1> cn £ CM • P T5 1P £ L 1 3 cn - 0 O cn 1 A al al • P • p to > al 1 cn L £ al cn cn £ cn 1 13th 3 3 - 3 cn cn • 3 1 cn P L • P A cn cn L al 0 A 1 0 M al N L • P 0 al £ to t » 1 te 3 A O • H L to A 3 C > 1 C L cn L P 0 c cn to al al 1 al P P O 3 > al P > » O cn 10 CO <C Oh Z cn « < J

Claims (1)

A process for preparing a black phosphate coating on a steel surface, wherein the steel parts are immersed in a weakly acidic phosphate solution containing zinc, nickel, copper, phosphate and nitrate ions, characterized in that the solution is supplemented with selenium acid or its salts and organic of an acid of the class of aminosulfic acid.