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Multi-step hot-dip galvanizing passivation method

A hot-dip galvanizing and passivation solution technology, which is applied in the coating process of metal materials, can solve the problems of insufficient corrosion resistance, insufficient passivation film thickness, and insufficient passivation salt stability, and achieve the goal of slowing down the corrosion rate. Effect

Inactive Publication Date: 2014-09-03
SHANGHAI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] However, due to the use of a single rare earth salt for passivation, there are disadvantages of insufficient passivation film thickness, insufficient corrosion resistance, and insufficient stability of passivation salts.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] 1) Prepare a rare earth passivation solution whose composition is Ce(NO 3 ) 3 : 0.001 mol / L; H 2 o 2 : 0.5 vol / L; Na 2 SO 4 : 0.5mol / L. Adjust the pH of the prepared passivation solution to 1, apply the passivation solution evenly on the galvanized sheet under constant temperature conditions, and cure at 100°C. Curing time: natural cooling for 2 hours.

[0028] 2) Reconstitute the molybdate passivation solution, the composition of which is Na 2 (MoO 4 )·2H 2 O: 4 g / L; ZrF 4 : 4 g / L; H 2 C 2 o 4 : 15 wt%. Adjust the pH to 3, apply the passivation solution evenly on the rare earth-treated galvanized panel, and cure at 150°C, curing time: natural cooling for 5 hours.

[0029] The prepared passivation film was tested for corrosion performance.

Embodiment 2

[0031] 1) Prepare a rare earth passivation solution whose composition is Ce(NO 3 ) 3 : 0.05 mol / L; H 2 o 2 : 2 vol / L; Na 2 SO 4 : 0.5 mol / L. Adjust the pH of the prepared passivation solution to 1, apply the passivation solution evenly on the galvanized panel under constant temperature conditions, and cure at 50°C. Curing time: natural cooling for 30 minutes.

[0032] 2) Reconstitute the molybdate passivation solution, the composition of which is Na 2 (MoO 4 )·2H 2 O: 20g / L; ZrF 4 : 8g / L; H 2 C 2 o 4 : 0.2 wt%. Adjust the pH to 4, apply the passivation solution evenly on the rare earth-treated galvanized plate, and cure at 150°C, curing time: natural cooling for 5 hours.

[0033] The prepared passivation film was tested for corrosion performance.

Embodiment 3

[0035] 1) Prepare a rare earth passivation solution whose composition is Ce(NO 3 ) 3 : 1 mol / L; H 2 o 2 : 0.05 / L; Na 2 SO 4 : 1 mol / L. Adjust the pH of the prepared passivation solution to 1, apply the passivation solution evenly on the galvanized panel under constant temperature conditions, and cure at 50°C. Curing time: natural cooling for 30 minutes.

[0036] 2) Reconstitute the molybdate passivation solution, the composition of which is Na 2 (MoO 4 )·2H 2 O: 20 g / L; ZrF 4 : 8g / L; H 2 C 2 o 4 : 0.2 wt%. Adjust the pH to 3, apply the passivation solution evenly on the rare earth-treated galvanized sheet, and cure at 100°C, curing time: natural cooling for 5 hours.

[0037] The prepared passivation film was tested for corrosion performance.

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Abstract

The invention relates to a multi-step hot-dip galvanizing passivation method. By virtue of a multi-step process, A double passivation film structure with a rare-earth passivation film and a molybdate passivation film is obtained on the surface of a hot-dip galvanized sheet so as to solve various problems, such as too thin passive film, compactness insufficiency, insufficient self-healing capability and corrosion resistance caused by single rare earth salt passivation and molybdate passivation. Since the active sites of the cathode reaction are covered by a rare earth conversion coating, the transfer and delivery of oxygen and electrons between the surface of the metal and the solution are hindered and thus the corrosion rate is inhibited. The corrosion process of zinc can be prevented by the molybdate film, the corrosion current density is significantly reduced and thus the corrosion of zinc is prevented. By means of molybdate passivation, the resistance to salt spray corrosion of the zinc coating can be significantly improved, the corrosion resistance effect is equivalent to that of the chromate salt passivation and is even superior to that of the chromate salt passivation under the condition of an acidic medium.

Description

technical field [0001] The invention relates to a multi-step passivation hot-dip galvanizing method, which belongs to the technical field of material surface treatment. Background technique [0002] Hot-dip galvanizing is to make the molten metal zinc react with the iron substrate to produce an alloy layer, so that the substrate and the coating are combined. Hot-dip galvanizing has many advantages. For example, molten zinc can easily and evenly cover the entire steel surface, including the inside of the pipe fitting in the depression, which can fully protect the substrate. At the same time, the zinc layer has strong adhesion and long service life. The consumption of zinc layer in the atmosphere is very slow, about 1 / 17 to 1 / 18 of the corrosion rate of steel, and is predictable. Its lifespan far exceeds that of any other coating. [0003] However, if the galvanized layer exposed to the air does not take effective passivation measures, the corrosion resistance is still not ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23C22/53C23C22/44C23C22/73
Inventor 肖轶钟庆东张俊良周代义赵启亮周琼宇
Owner SHANGHAI UNIV
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