Zinc-chromate coating on the steels (versions)

FIELD: chemical industry; metal-working industry; other industries; methods of the corrosion protection of the steels by application of the zinc-chromate coatings.

SUBSTANCE: the invention is pertaining to the field of the corrosion protection of the metals and may be used for the protection of the steel articles against corrosion by means of the multilayer coatings. The zinc-chromate coating on the steel contains the zinc layer produced out of the sulfate electrolyte, and the external chromate layer. At that the coating in addition contains the inner electric current- conductive chromate layer produced out of the solution, (g/dm3): CrO3 - 8, HNO3 - 4, Na2SO4 - 12, Cr2(SO4)18H2O - 5, Na2SnO3H2O - 8. The zinc-chromate coating on the steel contains the zinc layer produced out of the sulfate electrolyte, and the outer chromate layer. At that the zinc-chromate coating additionally contains the inner electric current conductive chromate layer produced out of the solution, (g/dm3): CrO3 - 8, Na2SO4 - 12, Cr2(SO4)3 ·18 H2O - 5, In(NO3)3 - 6. The technical result of the invention is the raise of the protective capability of the zinc-chromate coating on the steel on the average in 2 times.

EFFECT: the invention ensures the increased protective capability of the zinc-chromate coating on the steel on the average in 2 times.

1 dwg, 4 ex

 

The invention relates to the field of protecting metals from corrosion and can be used for protection of steel products from corrosion by using multilayer coatings.

Protective ability synchromatic coatings if successful, the combination of zinc and external chromate coating is determined mainly by the resistance of the latter, see the Abstracts of the zonal conference on advanced technology and environmental issues in the electroplating", Penza, 1990, p.7.

Known widely used in industry synchromat coatings on steel, see RU Patent 2223478, IPC G01N 17/00, 2004.

The lack of them is not very high protective ability. The values (twithfor the most successful coatings differ by no more than 1.2 times, see ibid., table 4, the values of twithfor coatings "2-1", "1-1", "3-3".

The closest in technical essence is synchromat coating on steel containing zinc layer, obtained from a sulfate electrolyte, and external chromate layer, see RU Patent 2223478, IPC G01N 17/00, 2004, table 4, covering "2-1".

The disadvantage of this coating is not high enough protective capacity.

The objective of the invention is the creation of synchrometer coating on steel with enhanced protective properties.

The technical problem is solved by the fact that synchromat the coating on the steel, containing zinc layer, obtained from a sulfate electrolyte, and external chromate layer, the zinc layer further comprises an internal conductive chromate layer, obtained from the solution (g/DM3): CrO3- 8, HNO3- 4, Na2SO4- 12, Cr2(SO4)3·N2O - 5, Na2SnO3·3H2O - 8.

The technical problem is solved by the fact that synchromat coating on steel containing zinc layer, obtained from a sulfate electrolyte, and external chromate layer, the zinc layer further comprises an internal conductive chromate layer, obtained from the solution (g/DM3): CrO3- 8, Na2SO4- 12, Cr2(SO4)3·18H2O - 5, In(NO3)3- 6.

Technical solution allows to increase the protective ability synchrometer coatings on steel in average 2 times.

The invention is illustrated by the following examples of specific performance.

An example of the prototype.

Synchromat coating thickness of 20 μm, the zinc layer which is produced from sulfate electrolyte (g/DM3): ZnSO4·7H2O - 215, Na2SO4·10H2AU - 50, Al2(SO4)3·N2O - 30 at pH 3.8, the temperature of 20°C, current density of 1.5 a/DM2(see GOST 9.305-84. Coating of metal and nonmetal instruments is a mini-inorganic. Operation of the technological processes of obtaining coatings. Map 30, part 2), and external chromate layer is obtained from the solution (g/DM3): Likonde 1B - 0.1, Likonde 2A - 70, H2SO4- 3 at a temperature of 20°C for 21 (see, GOST 9.305-84, Map 81), subjected to corrosion testing method of alternating immersion in artificial sea water, simulating seaside atmosphere subtropics (, Batumi), see "Journal of Corrosion: materials, protection, 2005, No. 9, p.27.

The protective ability of the coating, which is expressed by the value of the time of occurrence of the first hearth steel corrosion (t3), is 7 nights.

Examples of the claimed object.

Example 1 on the first option.

Synchromat floor C. XP. C. XP. a total thickness of 20 μm: zinc layers 10 μm produced from sulfate electrolyte (g/DM3): ZnSO4·7H2O - 215, Na2SO4·10H2O - 50, Al2(SO4)3·N2O - 30 at pH 3.8, the temperature of 20°C, current density of 1.5 a/DM2(see GOST 9.305-84, Map 30, part 2), external chromate layer is obtained from the solution (g/DM3): Likonde 1B - 0.1, Likonde 2A - 70, H2SO4- 3 at a temperature of 20°C for 21 s, and the internal chromate layer between the zinc layer is obtained from the solution (g/DM3): CrO3- 8, HNO3- 4, Na2SO4- 12, Cr2(SO4)3·18 the 2O - 5, Na2SnO3·3H2O - 8 at a temperature of 20°C for 1 minute. Synchromat floor C. XP. C. XP. a total thickness of 20 μm is subjected to corrosion testing method of alternating immersion in artificial sea water, simulating seaside atmosphere subtropics (, Batumi).

The protective ability of the coating is 12 days, which is 1.7 times more than in the known coatings, when the same total thickness.

Example 2 under the first option.

Synchromat floor C. XP. C. XP. a total thickness of 20 μm: zinc layers 10 μm produced from sulfate electrolyte (g/DM3): ZnSO4·7H2O - 190, NVO3- 22, (NH4)2SO4- 25, DHTI-102A - 90, DHTI-B - 5 at pH 4,8 temperature of 20°working current density of 1.5 a/DM2(see GOST 9.305-84, Map 30, part 7), external chromate layer is obtained from the solution (g/DM3): Likonde 1B - 0.1, Likonde 2A - 70, H2SO4- 3 at a temperature of 20°C for 21 s, and the internal chromate layer between the zinc layer is obtained from the solution (g/DM3): CrO3- 8, HNO3- 4, Na2SO4- 12, Cr2(SO4)3·18H2O - 5, Na2SnO3·3H2O - 8 at a temperature of 20°C for 1 minute. Synchromat floor C. XP. C. XP. a total thickness of 20 μm is subjected to corrosion testing method changes the CSOs immersion in artificial sea water, simulating seaside atmosphere subtropics (, Batumi).

The protective ability of the coating is 11 hours, which is 1.6 times more than in the known coatings, when the same total thickness.

Example 3 according to the second option.

Synchromat floor C. XP. C. XP. a total thickness of 20 μm: zinc layers 10 μm produced from sulfate electrolyte (g/DM3): ZnSO4·7H2O - 215, Na2SO4·10H2O - 50, Al2(SO4)3·18H2O - 30 at pH 3.8, the temperature of 20°C, current density of 1.5 a/DM2external chromate layer is obtained from the solution (g/DM3): Likonde 1B - 0.1, Likonde 2A - 70, H2SO4- 3 at a temperature of 20°C for 21 s, and the internal chromate layer between the zinc layer is obtained from the solution (g/DM3): CrO3- 8, Na2SO4- 12, Cr2(SO4)3- 18, H2O - 5, In(NO3)3- 6 at a temperature of 20°C for 1 minute. Synchromat floor C. XP. C. XP. a total thickness of 20 μm is subjected to corrosion testing method of alternating immersion in artificial sea water, simulating seaside atmosphere subtropics (, Batumi).

The protective ability of the coating is 16 days, which is 2.3 times more than in the known coatings, when the same total thickness.

Example 4 according to the second option.

Synchromat on the freight C. XP. C. XP. a total thickness of 20 μm: zinc layers 10 μm produced from sulfate electrolyte (g/DM3): ZnSO4·7H2O - 190, NVO3- 22, (NH4)2SO4- 25, DHTI-102A - 90, DHTI-B - 5 at pH 4,8 temperature of 20°working current density of 1.5 a/DM2external chromate layer is obtained from the solution (g/DM3): Likonde 1B - 0.1, Likonde 2A - 70, H2SO4- 3 at a temperature of 20°C for 21 s, and the internal chromate layer between the zinc layer is obtained from the solution (g/DM3): CrO3- 8, Na2SO4- 12, Cr2(SO4)3·N2O - 5, In(NO3)3- 6 at a temperature of 20°C for 1 minute. Synchromat floor C. XP. C. XP. a total thickness of 20 μm is subjected to corrosion testing method of alternating immersion in artificial sea water, simulating seaside atmosphere subtropics (, Batumi).

The protective ability of the coating is 14 days, which is 2 times higher than in the known coatings, when the same total thickness.

The drawing shows the values of the protective ability (t3) synchromatic coatings on prototype and declare the object for the coatings described in examples 1 and 3.

Synchromat coating on steel by the present object and the prototype with the same thickness of 20 μm are tested for adhesion by the method of bending,see GOST 9.302-79. Coating of metallic and non-metallic inorganic. Technical requirements, acceptance rules and methods of control. With 3-fold bending steel samples coated at an angle of 90° cracks to the base metal have smooth walls, peeling and flaking of the coating is not observed, which is consistent with the requirements of the standard. The same coating applied on steel plates, experiencing the fragility of the method of bending with the use of device Ndemera, see the Book Vahramyan A.T., Solovieva Z.A. Methods to study the processes of deposition of the metal, M, Of the Academy of Sciences of the USSR, 1955, s-172. The closeness of the values of the angles of the bend (about 39°) if cracks in the coatings indicates that the presence of internal chromate layer does not reduce the elastic properties of synchrometer coverage.

Thus, as can be seen from the examples of embodiment, the claimed synchromat coating on steel in comparison with the prototype has on average 2 times more protective ability and preserves the most important for electroplating physico-mechanical properties.

1. Synchromat coating on steel containing zinc layer, obtained from a sulfate electrolyte, and external chromate layer, characterized in that it further comprises an internal conductive chromatiaceae, obtained from the solution, g/DM3:

CrO28
HNO34
Na2SO412
Cr2(SO4)3·N2O5
Na2SnO3·3H2O8

2. Synchromat coating on steel containing zinc layer, obtained from a sulfate electrolyte, and external chromate layer, characterized in that it further comprises an internal conductive chromate layer, obtained from the solution, g/DM3:

CrO38
Na2SO412
Cr2(SO4)3·N2O5
In(NO3)36



 

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