Chromium-free passivation method for galvanized steel sheet by using molybdate/polyphosphate composite system

A technology of polyphosphate and chromium-free passivation, which is applied in the coating process of metal materials, etc., can solve problems such as poor corrosion resistance, and achieve the effects of stable process, easy control, and stable solution

Inactive Publication Date: 2012-10-24
NANCHANG HANGKONG UNIVERSITY
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  • Abstract
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Problems solved by technology

Zhou Wanqiu's invention patent (application number 200610047751.4) discloses a process using a molybdate composite passivation system. The formula uses molybdate and phosphate as the main salt. Poor corrosion resistance in alkaline and alkaline environments

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0036] The experimental material is hot-dip galvanized steel plate

[0037] 1. Degreasing: Sodium hydroxide 5g / L, sodium silicate 7g / L, sodium phosphate 3g / L, OP emulsifier 3g / L, temperature 50~60℃, time 1 minute, tap water for 1 minute, deionized water for 0.5 Minutes, wash with alcohol and acetone mixture for 1 minute, dry with cold air, and seal the non-working surface with chemical glue;

[0038] 2. Acid etching: a mixture of 3% nitric acid and 3% hydrochloric acid, the temperature is room temperature, the time is 0.5 minutes, tap water for 1 minute, deionized water for 0.5 minutes;

[0039] 3. Passivation treatment: sodium molybdate 20g / L, sodium polyphosphate 30g / L, nitric acid 2ml / L, sulfuric acid 0.2ml / L, temperature 55°C, pH value 2, treatment time 2 minutes, tap water wash 1 minute , The drying temperature is 55°C.

[0040]4. The galvanized steel sheet obtained by the above method is tested according to GB / T 10125-1997 artificial atmosphere corrosion test salt ...

Embodiment 2

[0042] The experimental material is galvanized steel plate

[0043] 1. Degreasing: sodium hydroxide 5g / L, sodium silicate 7g / L, sodium phosphate 3g / L, OP emulsifier 3g / L, temperature 50-60℃, time 1 minute. Wash with tap water for 1 minute, wash with deionized water for 0.5 minutes, wash with a mixture of alcohol and acetone for 1 minute, dry with cold air, and seal non-working surfaces with chemical glue;

[0044] 2. Acidic etching: a mixture of 3% nitric acid and 3% hydrochloric acid, the temperature is room temperature, the time is 0.5 minutes, tap water for 1 minute, deionized water for 0.5 minutes;

[0045] 3. Passivation treatment: sodium molybdate 30g / L, sodium polyphosphate 40g / L, nitric acid 2ml / L, sulfuric acid 0.2ml / L, temperature 55°C, pH value 2, treatment time 2 minutes, tap water wash 1 minute , The drying temperature is 55°C.

[0046] 4. The galvanized steel sheet obtained by the above method is tested according to GB / T 10125-1997 artificial atmosphere corrosi...

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Abstract

The invention relates to a chromium-free passivation method for a galvanized steel sheet by using a molybdate / polyphosphate composite system. The method overcomes the problems of high cost and insufficient corrosion resistance of a passive film in the prior art and realizes passivation of a galvanized steel sheet through the two steps of acid etching and passivation so as to achieve the purposes of protection and decoration. Molybdate and polyphosphate are utilized as main salts for a passivation solution used in the method and are assisted by other additives, and the passivation solution can form a compact passive film on the galvanized steel sheet so as to realize chromium-free passivation of the galvanized steel sheet. Steps of the method comprise: a degreasing procedure, an acid pickling procedure, a passivation procedure, at least a rinsing procedure and a drying procedure. According to the invention, a novel composite passivation system is used, an obtained passivation layer has better corrosion resistance and can provide good protection for the galvanized steel sheet, and the advantages of reduction in production cost, decrease in environmental pollution and easiness in realization of industrialization are obtained.

Description

technical field [0001] The invention relates to a chromium-free passivation method for a galvanized steel sheet, in particular to a chromium-free passivation method for a galvanized steel sheet molybdate / polyphosphate composite system. Background technique [0002] Galvanized steel sheets are widely used in fields such as automobiles, construction and electrical appliances. Theoretically, since zinc has a low electrode potential compared to steel, zinc acts as an anode to electrochemically protect the steel substrate when corrosion occurs in a humid environment. However, in fact, the metal galvanized layer can only provide reliable protection to the steel substrate in a dry and non-corrosive atmosphere. Under actual use conditions, the surface of the galvanized layer often becomes dark gray due to corrosion, or appears The deposition of white corrosion products reduces the corrosion resistance of galvanized steel sheets. Therefore, it is particularly important to passivate...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23C22/73C23C22/42
Inventor 刘光明刘斌于斐
Owner NANCHANG HANGKONG UNIVERSITY
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