CN104018153A - Multi-step hot-dip galvanizing passivation method - Google Patents
Multi-step hot-dip galvanizing passivation method Download PDFInfo
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- CN104018153A CN104018153A CN201410272477.5A CN201410272477A CN104018153A CN 104018153 A CN104018153 A CN 104018153A CN 201410272477 A CN201410272477 A CN 201410272477A CN 104018153 A CN104018153 A CN 104018153A
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- passivation
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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
The present invention relates to a kind of method of processing passivation galvanizing by multistep, belong to surface treatment technology of material field.
Background technology
Pot galvanize is make molten metal zinc and iron-based precursor reactant and produce alloy layer, thereby make matrix and coating, the two combines.Galvanizing has lot of advantages, for example, dissolves zinc and is all easy to cover uniformly whole steel surface, is included in recess inside pipe fitting, matrix is played to the effect of all-round protection.Zinc attachability is strong simultaneously, long service life.The consumption of zinc layer in atmosphere is very slowly, is about 1/17 to 1/18 of steel corrosion speed, and can estimates.Its life-span far surpasses other any coating.
If do not take effective passivation measure yet be exposed to airborne zinc coating, solidity to corrosion is still undesirable.At present galvanized workpiece passivation means be the most widely that chromating is processed, major cause is that the method technique is simple, cost is low, etch resistant properties is good, and passive film has self-healing ability.After chromic salt is processed, form chromium/matrix metal mixed oxide rete, in rete, chromium mainly exists with sexavalence and trivalent form.Because sexavalent chrome is carcinogenic substance, human body and environment are had to serious harm, along with the enhancing of people's Environmental awareness, must study a kind of method that replaces chromating.
The rare earth passivation of zinc or inhibition research start from early 1980s.Rare earth passivating method is simple, pollution-free, is a kind of eco-friendly conversion film, can be used for substituting the passivation of sexavalence network.Rare-earth conversion coatings solidity to corrosion may be that negative electrode suppresses mechanism, thinks and has hindered the covering of rare-earth conversion coatings anticathode reactive site transfer and the transmission between metallic surface and solution of oxygen and electronics, thereby suppressed rotten candle speed.Molybdenum and chromium belong to group vib element together, and molybdate has many similaritys as the agent of slow candle and complex acid salt, lower than chromic salt toxicity, thereby has more superior environmental compatibility.Oneself is widely used as inhibiter and the passivator of iron and steel and non-ferrous metal molybdate.Research shows that molybdate passivation can significantly improve the resisting salt fog corrosion ability of zinc coating again simultaneously, and anti-corrosion effect and chromating are suitable, are even better than chromating under acidic corrosive media.The method of molybdate passivation mainly contains anodic polarization processing, cathodic polarization processing and chemical immersion processing etc.It is generally acknowledged that molybdate can be compound with different kinds of molecules, borrow intermolecular collaborative slow releasing function to improve anti-corrosion efficiency, molybdate belongs to anode passivation type inhibiter, and molybdate film can hinder the process of zinc corrosion, significantly reduces corrosion electric current density, thereby hinders the corrosion of zinc.In molybdate passivation, conventional is the system that molybdate and phosphoric acid form, and adding of phosphoric acid can significantly improve the bonding force that improves film.
In molybdate passivation, due to thickness, think it is to determine corrosion resisting property and ornamental important factor, therefore on affecting, passive film forms and the control of passivating solution concentration, passivation temperature and the pH value of thickness is very important.Conventionally should make pH<5, so that the zinc dissolving region in pH-Electric Potential Graph just in time.
Yet, owing to adopting the passivation of single rare earth salt, have that passivation film thickness is inadequate, solidity to corrosion not, the shortcoming of passivation salt-stable deficiency.Therefore, current research direction, is to consider to attempt increasing other inorganic salt in rare earth passivation system, meanwhile, adopts multistep Passivation Treatment, to improve thickness, self-healing ability and the solidity to corrosion of passivation film.
Based on this, employing rare earth-molybdate two step Passivation Treatment of novelty of the present invention, solved the thickness low LCL that exists in single rare earth passivation, solidity to corrosion not and the passive film existing in molybdate passivation without the problem of self-healing ability, the solidity to corrosion of passive film is greatly improved.
Summary of the invention
The defect existing for prior art, the object of this invention is to provide a kind of method of processing passivation galvanizing by multistep.
For achieving the above object, the present invention adopts following technical scheme:
A method of processing passivation galvanizing by multistep, has following passivating solution proportioning and treating processes:
A. rare earth passivating solution composition proportion
Ce(NO
3)
3：0.001~2?mol/L；
H
2O
2：0.05~6?vol/L；
Na
2SO
4：0.1~2?mol/L；
B. molybdate passivating liquid composition proportion
Na
2(MoO
4)·2H
2O：4~80g/L；
ZrF
4：4~40g/L；
H
2C
2O
4：0.05wt%~15?wt%；
C. treating processes
1) rare earth passivating solution is coated on to galvanized sheet surface, is then cured processing; Solidification value wherein: 50 ~ 150 ℃
Set time: 30min ~ 5h; Naturally cooling subsequently, the naturally cooling time: 20min ~ 2h;
2) again molybdate passivating liquid is coated on to the galvanized sheet surface after step 1) is processed, is then cured processing; Solidification value wherein: 100 ~ 250 ℃, set time 5min ~ 2h; Naturally cooling subsequently, the naturally cooling time: 3 ~ 24h..
Compared with prior art, the present invention has following outstanding substantive distinguishing features and significant advantage:
The present invention is by rare-earth salts and molybdate substep Passivation Treatment, obtain uniform two-layer passive film, although the more single passivation of technique is complicated, but can effectively solve individual layer rare-earth salt passive film thickness low LCL, problem that solidity to corrosion is strong not containing the multilayer passive film of rare-earth salt passive film, solve the problem that passive film in molybdate passivation does not possess self-healing ability simultaneously, effectively slowed down the erosion rate of galvanized sheet.
Embodiment
Specific embodiment of the invention is described below:
embodiment 1
1) preparation rare earth passivating solution, its composition is Ce (NO
3)
3: 0.001 mol/L; H
2o
2: 0.5 vol/L; Na
2sO
4: 0.5mol/L.By the passivating solution pH regulator to 1 preparing, under constant temperature, passivating solution is evenly coated on galvanized sheet, solidify set time: naturally cooling 2h at 100 ℃.
2) prepare molybdate passivating liquid, its composition is Na again
2(MoO
4) 2H
2o:4 g/L; ZrF
4: 4 g/L; H
2c
2o
4: 15 wt%.Regulate pH to 3, passivating solution is evenly coated on the galvanized sheet of RE-treated, solidify set time: naturally cooling 5h at 150 ℃.
The passive film making is carried out to corrosive nature test.
embodiment 2
1) preparation rare earth passivating solution, its composition is Ce (NO
3)
3: 0.05 mol/L; H
2o
2: 2 vol/L; Na
2sO
4: 0.5 mol/L.By the passivating solution pH regulator to 1 preparing, under constant temperature, passivating solution is evenly coated on galvanized sheet, solidify set time: naturally cooling 30min at 50 ℃.
2) prepare molybdate passivating liquid, its composition is Na again
2(MoO
4) 2H
2o:20g/L; ZrF
4: 8g/L; H
2c
2o
4: 0.2 wt%.Regulate pH to 4, passivating solution is evenly coated on the galvanized sheet of RE-treated, solidify set time: naturally cooling 5h at 150 ℃.
The passive film making is carried out to corrosive nature test.
embodiment 3
1) preparation rare earth passivating solution, its composition is Ce (NO
3)
3: 1 mol/L; H
2o
2: 0.05/L; Na
2sO
4: 1 mol/L.By the passivating solution pH regulator to 1 preparing, under constant temperature, passivating solution is evenly coated on galvanized sheet, solidify set time: naturally cooling 30min at 50 ℃.
2) prepare molybdate passivating liquid, its composition is Na again
2(MoO
4) 2H
2o:20 g/L; ZrF
4: 8g/L; H
2c
2o
4: 0.2 wt%.Regulate pH to 3, passivating solution is evenly coated on the galvanized sheet of RE-treated, solidify set time: naturally cooling 5h at 100 ℃.
The passive film making is carried out to corrosive nature test.
embodiment 4
1) preparation rare earth passivating solution, its composition is Ce (NO
3)
3: 2 mol/L; H
2o
2: 3 vol/L; Na
2sO
4: 1 mol/L.By the passivating solution pH regulator to 2 preparing, under constant temperature, passivating solution is evenly coated on galvanized sheet, solidify set time: naturally cooling 30min at 50 ℃.
2) prepare molybdate passivating liquid, its composition is Na again
2(MoO
4) 2H
2o:30g/L; ZrF
4: 8 g/L; H
2c
2o
4: 10 wt%.Regulate pH to 3, passivating solution is evenly coated on the galvanized sheet of RE-treated, solidify set time: naturally cooling 2h at 100 ℃.
The passive film making is carried out to corrosive nature test.
embodiment 5
1) preparation rare earth passivating solution, its composition is Ce (NO
3)
3: 2 mol/L; H
2o
2: 6vol/L; Na
2sO
4: 2 mol/L.By the passivating solution pH regulator to 1 preparing, under constant temperature, passivating solution is evenly coated on galvanized sheet, solidify set time: naturally cooling 2h at 150 ℃.
2) prepare molybdate passivating liquid, its composition is Na again
2(MoO
4) 2H
2o:15g/L; ZrF
4: 40g/L; H
2c
2o
4: 10 wt%.Regulate pH to 4, passivating solution is evenly coated on the galvanized sheet of RE-treated, solidify set time: naturally cooling 5h at 250 ℃.
The passive film making is carried out to corrosive nature test.
embodiment 6
1) preparation rare earth passivating solution, its composition is Ce (NO
3)
3: 2 mol/L; H
2o
2: 2 vol/L; Na
2sO
4: 0.5 mol/L.By the passivating solution pH regulator to 1 preparing, under constant temperature, passivating solution is evenly coated on galvanized sheet, solidify set time: naturally cooling 1h at 150 ℃.
2) prepare molybdate passivating liquid, its composition is Na again
2(MoO
4) 2H
2o:80g/L; ZrF
4: 6 g/L; H
2c
2o
4: 12 wt%.Regulate pH to 4, passivating solution is evenly coated on the galvanized sheet of RE-treated, solidify set time: naturally cooling 5h at 250 ℃.
The passive film making is carried out to corrosive nature test.
the test result of all case study on implementation is listed in table 1.
The corrosive nature test of rare earth molybdate passive film prepared by table 1 the present invention
| ? | Embodiment 1 | Embodiment 2 | Embodiment 3 | Embodiment 4 | Embodiment 5 | Embodiment 6 |
| Copper sulfate drop time/s | 170 | 178 | 165 | 167 | 172 | 174 |
| 5%NaCl immersion test/h | 96 | 120 | 96 | 96 | 120 | 120 |
Rare earth-molybdate dual layer passivation film prepared by examples prove the present invention, its density corrosion resisting property is greatly improved, and raw materials cost is cheap, is applicable to industrial production and application.
Claims (1)
1. by multistep, process a method for passivation galvanizing, it is characterized in that thering is following passivating solution proportioning and treating processes:
A. rare earth passivating solution composition proportion
Ce(NO
3)
3：0.001~2?mol/L；
H
2O
2：0.05~6?vol/L；
Na
2SO
4：0.1~2?mol/L；
B. molybdate passivating liquid composition proportion
Na
2(MoO
4)·2H
2O：4~80g/L；
ZrF
4：4~40g/L；
H
2C
2O
4：0.05wt%~15?wt%；
C. treating processes
1) rare earth passivating solution is coated on to galvanized sheet surface, is then cured processing; Solidification value wherein: 50 ~ 150 ℃
Set time: 30min ~ 5h; Naturally cooling subsequently, the naturally cooling time: 20min ~ 2h;
2) again molybdate passivating liquid is coated on to the galvanized sheet surface after step 1) is processed, is then cured processing; Solidification value wherein: 100 ~ 250 ℃, set time 5min ~ 2h; Naturally cooling subsequently, the naturally cooling time: 3 ~ 24h.
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|---|---|---|---|
| CN201410272477.5A CN104018153A (en) | 2014-06-18 | 2014-06-18 | Multi-step hot-dip galvanizing passivation method |
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| CN104018153A true CN104018153A (en) | 2014-09-03 |
Family
ID=51435137
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Cited By (3)
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|---|---|---|---|---|
| CN105970208A (en) * | 2016-06-03 | 2016-09-28 | 哈尔滨工业大学 | Method for preparing false boehmite/rare earth conversion coating anti-corrosion composite coating |
| CN109943835A (en) * | 2019-04-30 | 2019-06-28 | 兴化市华成镀锌管件有限公司 | A kind of preparation method of hot galvanized layer rare-earth salt passivation liquid |
| CN111063501A (en) * | 2019-12-26 | 2020-04-24 | 深圳市艺感科技有限公司 | Preparation method of low-loss powder for producing integrally-formed inductor |
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2014
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105970208A (en) * | 2016-06-03 | 2016-09-28 | 哈尔滨工业大学 | Method for preparing false boehmite/rare earth conversion coating anti-corrosion composite coating |
| CN105970208B (en) * | 2016-06-03 | 2018-07-06 | 哈尔滨工业大学 | A kind of preparation method of the anti-corrosion composite coating of pseudo-boehmite alumina/rare-earth conversion coatings |
| CN109943835A (en) * | 2019-04-30 | 2019-06-28 | 兴化市华成镀锌管件有限公司 | A kind of preparation method of hot galvanized layer rare-earth salt passivation liquid |
| CN111063501A (en) * | 2019-12-26 | 2020-04-24 | 深圳市艺感科技有限公司 | Preparation method of low-loss powder for producing integrally-formed inductor |
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Application publication date: 20140903 |