CN101928966B - Method for plating chrome on surface of thin plate - Google Patents

Abstract

The invention discloses a method for plating chrome on a surface of a thin plate. The method comprises the following steps: 1) alkali washing, including alkali liquor leaching, electrolysis washing and alkali washing; 2) pickling, including electrolysis pickling and acid washing; 3) electroplating, including chromeplating and washing; and 4) oiling. The method sufficiently utilizes the performance advantage of CrO3+NH4 plating solution, optimizes the pre-treatment pickling process and electroplating parameters, particularly controls the solution concentration of alkali washing and pickling, strictly controls the current efficiency of an electroplating section and the electroplating concentration, overcomes the defects in the tradition process, generates compact metal chrome and chromic oxide layers on the surface of strip steel, realizes one-step production of an electrolytic chromium steel plate the strip steel surface of which is plated with optimally combined metal chromium and chromic oxide so as to obtain the excellent chromeplated plate with bright and uniform plating layer. Meanwhile, the method saves energy consumption, reduces pressure environment-friendly emission, reduces cost for production and maintenance, and creates a condition for improving the chromeplated plate, thus having excellent popularization and application prospect.

Description

A kind of method of plating chrome on surface of thin plate

Technical field

The present invention relates to the chromed treatment process of a kind of surface of steel plate, relate in particular to a kind of method of plating chrome on surface of thin plate.

Background technology

Over more than 100 year; Tin plate is wrapping material such as main Can container material and shell always, about 2,000 ten thousand tons of the present YO in the whole world, but because tin resource is limited; So people just begin to manufacture experimently thin sheet surface not tinned " tin free steel sheet ", replace tin plate.

In the beginning period of other surface treatment thin plate steel plates of research; Be that " conversion coating " promptly makes iron surface produce chemical conversion layer mostly, manufactured experimently the dipping chromic acid and handled steel plate, electrolytic phosphate processing steel plate etc., also once manufactured experimently Nickeled Steel Plate, vacuum aluminum-coated steel plate etc. that these materials are compared with electrolytic tinplate in the aqueous solution; Solidity to corrosion is good inadequately; Process treatment time is more much longer than the zinc-plated time, and production process equipment is complicated, can not meet the requirement of production of large-scale industry property and use.

Subsequently; Japan at first successfully obtains a kind of special " tin free steel sheet "---electrodeposited chromium s.t. steel plate; Its characteristics for its surface by as thin as a wafer metallic chromium layer with hydrated chromium oxide layer is compound constitutes; This technology receives immediately to be paid attention to widely and adopts, and American and Britain, West Germany, France etc. produce in succession soon and uses very much.

Consult the data of publishing, the chromed technology of belt steel surface has two kinds of methods, i.e. single stage method and two-step approach in the world.The technology of two kinds of methods is fully different with the equipment configuration.The configuration of single stage method equipment is comparatively simple; But can't accurately control the amount of chromium metal and chromic oxide: chromium metal too many (greater than 250mg); The solidity to corrosion of product not necessarily improves; Not only increase cost, and too much coating when machining deformation owing to its fragility is easy to generate tiny crack, impair the solidity to corrosion behind the formed product system jar on the contrary; Chromic oxide is too many, makes being a bit darkish in color of product, influences outward appearance; Chromic oxide very little, the porous bad adhesion.

Show according to data introduction and production use experience; Chromium oxide layer for the solidity to corrosion of product with other can with the metallic chromium layer no less important; The hole of metallic chromium layer can be by amorphous hydrated chromium oxide layer sealing; The solidity to corrosion after thereby raising solidity to corrosion, this composite bed provide good coating tack again jointly and be coated with.So most critical is accurately to control each processing parameter in process of production, keeping the suitable composition of composite bed, the consisting of of this top layer:

Cold rolled sheet factory electrodeposited chromium unit chrome plating unit is to introduce Japanese Nippon Steel Technology, on the basis of band steel pre-treatment, adopts CrO ₃+ NH ₄The F plating bath; Through the good chrome plating of two-step approach obtained performance; Promptly at first in 1 preimpregnation groove 4 plating tank and 2 accumulator tanks, the acquisition metallic chromium layer is set and controlled to parameters such as bath concentration, temperature, current density; Then through second step; In 1 preimpregnation groove and 1 chromic oxide groove (the chromic oxide groove is to be used for electroplating chromic oxide, is adjustment chrome plating surface color), once more the acquisition chromium oxide layer is set and controlled to parameters such as bath concentration, temperature, current density in single stage method in two-step approach.

Though two-step approach can comparatively accurately be controlled the amount of chromium metal and chromic oxide, can not influence chrome plating because of too much chromium metal through the erosion resistance behind the machining deformation, or too much chromic oxide makes the surface color obfuscation, influences outward appearance; But investment, production cost is higher relatively, and environment protection emission pressure is bigger.

Summary of the invention

The method that the purpose of this invention is to provide a kind of plating chrome on surface of thin plate; On two-step approach equipment configure base,, generate chromium metal and chromic oxide synchronously through processing parameter, process optimization; Regulate the chromic oxide total amount through the aqueous solution at last, form the bright chrome plating of performance color and luster.

Technical scheme of the present invention is following: under the condition of existing installation configuration; Through pre-treatment acid cleaning process and electroplating parameter are optimized, particularly alkali cleaning, the control of Acidwash solution concentration, a plating section current efficiency, plating concentration are carried out strictness control, will electroplate the emptying of accumulator tank plating bath simultaneously; The displacement de-salted water; Close and electroplate chromic oxide cell body RF, only rely on 4 plating tanks to generate metallic chromium layer and chromium oxide layer, form qualified electrodeposited chromium steel plate.

The objective of the invention is to realize like this: a kind of method of plating chrome on surface of thin plate, it comprises following steps:

1) alkali cleaning: comprise that a) alkali lye embathes, b) electrolytic cleaning, c) alkaline flushing;

2) pickling: comprise a) electrolytic pickling, b) acid flushing;

3) electroplate: comprise a) chromium plating, b) flushing;

4) oiling.

Preferably, said step 1) a) middle alkali lye is an active alkali, and concentration is 30 ± 5g/l, alkali liquid temperature: 45 ± 5 ℃.

Preferably, said step 1) a) middle alkali lye is also added electrolytic cleaning additive 25 (low-temperature cleaning agent), and the amount of interpolation is every 1m ³Alkali lye adds 3kg electrolytic cleaning additive.

Preferably, said step 1) b) in the electrolytic cleaning, electrolytic solution is active alkali in, and concentration is 30 ± 5g/l, alkali liquid temperature: 45 ± 5 ℃, and current density established standards=20 ± 10A/dm ², the electrode useful length is 1.50～1.70m, pole plate material=SS41, thickness: 15～18mm, interpole gap=top 40 ± 3mm, bottom 40 ± 3mm.

Preferably, alkaline flushing is that concentration is the low chlorine ion water of 60ppm said step 1) c)

Flow: more than the 125l/min

Pressure: 2kg/cm ²More than

Temperature: 40 ℃ ± 5.

The purpose of alkaline flushing is to prevent that alkali lye from getting into pickling tank, mixes with acid solution and takes place to neutralize and pollution.

Preferably, said step 2) a) in electrolytic pickling liquid be sulfuric acid, concentration: 25 ± 3g/l, Fe ⁺⁺Ionic concn: below the 25g/l, the sulfuric acid temperature: 32 ± 5 ℃, the current value of each passage:

I＝QVW/1200A

Wherein, the corresponding electric current A of I:1 passage

Q: energising amount c/dm ²

V: unit speed m/min

W: strip width mm

Battery lead plate material: terne metal

Interpole gap=top: 40mm ± 3mm; Bottom: 40mm ± 3mm.

Preferably, the acid flushing is with the flushing of the water below the cl ions 60ppm said step 2) b):

Flow: more than the 200l/min

Pump flow 1m ³/ min

Pressure: 2kg/cm ²More than

Temperature: 30 ℃ ± 5.

The purpose of acid flushing is after pickling, to pass through dipping and spray the pickling resistates of removing belt steel surface.It is acceptable that a certain amount of sulfate ion is blended in the plating bath, but excessive sneaking into can produce bad influence.

Preferably, 1 the preimpregnation groove that is arranged in order is adopted in said step 3) chromium plating, 4 plating tanks, 2 accumulator tanks, 2 adjustment grooves and 3 flushed channels.

Electroplate unit and adopt special chromium plating pole plate, its useful length is 500mm, and electrolytic solution belongs to strong acid type sexavalent chrome solution, and sexavalent chrome mainly exists with dichromate ion and two kinds of forms of chromate in the aqueous solution.In electrolytic solution (CrO3) concentration is 150g/L, under the condition of HCD, through pole plate useful area zone CrO takes place at the band steel ₄ ^2-+ 8H ⁺+ 6e-=Cr+4H2O reaction is deposited on the steel band metallic chromium layer; And in plating tank, do not taken place by pole plate useful area region covered

Reaction is deposited on the steel band chromium oxide layer, thereby reaches the chromed effect of single stage method.Single stage method is that two different chemical reactions take place in same cell body.Wherein, though the trivalent chromium that cathodic process generates in the plating bath is not participated in electrode reaction directly, their existence and content are most important to the chromium coating quality.Trivalent chromium is the important component of hydrated chromium oxide, if content is low, colloidal film (chromium oxide film) is difficult to be formed or approach and porous, and sulfuric acid is prone to its dissolving; Trivalent chromium concentration is high, colloid thickness and densification, and sulfuric acid is difficult to dissolving, and the chromium layer can only be grown up on former crystal grain, causes crystallization coarse, and coating is dark and matt, so must strict control sulfate ion in the chromium plating and the concentration of trivalent chromic ion.In addition the temperature of plating bath also and important, the too high meeting of temperature causes chromium oxide layer thickness to be difficult to control, temperature is crossed the low chromium metal electroplating efficiency that can cause and is descended.

Actual conditions is:

(1) preimpregnation groove and plating tank strength of solution:

CrO ₃ 150±5g/l；

NH ₄F 3.5±0.2g/l

Cr ³⁺≤5g/l

Fe ³⁺≤5g/l

Cl ^-≤30ppm

H ₂SO ₄≤0.09g/l

(2) temperature: 37～39 ℃

(3) 1# accumulator tank: de-salted water (CrO ₃Trace) temperature is 40～50 ℃

(4) 2# accumulator tank: de-salted water (CrO ₃Trace) temperature is 40～50 ℃

(5) adjustment groove (trough of band dilute solution, the final content of adjustment chromic oxide) solution condition:

CrO ₃ 75±3g/l

NH ₄F 1.5±0.2g/l

H ₂SO ₄≤0.08g/l

(6) electroplating current condition:

Electroplating voltage 30V

Current density 100～120A/dm ²

Current efficiency 20%

Electroplating current

$I=\frac{G\·V\·W}{60\·C\·\mathrm{\η}}\×9.65\×{10}^{-2}$

G(mg/m ²)＝〔C(g/F)/96500(C)〕×I(A)/W(mm)×60/V(mpm)×η×10 ⁶

I(A)＝G(mg/m ²)×W(mm)×V(mpm)/C(g/F)×60×η×96500(C)×10 ^-6

＝G(mg/m ²)×W(mm)×V(mpm)/C(g/F)×60×η×9.65×10 ^-2

Wherein:

I: total current A

G: theoretical chromium plating amount mg/m ²

V: process section speed m/min

W: the wide mm of plate

C: chromium equiv.=52.01/6 g/F

η: cathode efficiency

Suppose that the chromium plating amount is 70mg/m ²,

The wide 800mm of plate, η 0.2, process section speed 400mpm,

Then electroplating total current is:

Current density

Current density range 100～120A/dm ²

$D_K=\frac{I_K}{L\·W}\×{10}^4$

Wherein: D _KThe expression current density; L representes pole plate length; W representes strip width

Suppose I _K=4000A, L=500mm, W=800mm

$D_K=\frac{I_K}{L\·W}\×{10}^4=\frac{4000}{500\×800}\×{10}^4=100.0(A/d{m}^2)$

Preferably, said step 3) a) middle positive plate adopts the edge-masking structure, and useful area is 500mm * 1200mm.

Preferably, with oil misting, spraying gun and high voltage supply link together said step 4) electrostatic oiler through rotary atomizer, make the elaioleucite subband of the atomizing lotus that powers on.Under the effect of rotary atomizer; The oil particulate forms one and disperses smog uniformly; Because the principle that the same sex electrical charge rejection and the charges of different polarity attract, the formation electrostatic attraction in the smog between charged particle and the counterpoise grounding steel, fogging oil are adsorbed on the mobile band steel.The homogeneity of fogging oil has guaranteed the uniform deposition on whole strip width.Being coated with oil mass can set according to user's needs, and setting range is 1.25～12.5mg/m ²

The present invention makes it compared with prior art owing to adopted above technical scheme, has the following advantages and positively effect:

1) the present invention is through technical process and process parameter optimizing; Realize that a step produces the electrodeposited chromium steel plate of belt steel surface metallizing chromium and chromic oxide best of breed, steel plate after the chromium plating is had plating measure little, production cost is low, the coating tack is good, temperature tolerance and the good characteristics of anti-sulphur alkali resistance;

2) the present invention makes full use of the advantage of ammonium fluoride additive, has overcome the weakness of traditional one-step technology, can obtain bright, the uniform chrome plating of coating, further improves the chrome plating surface quality;

3) the present invention can save energy consumption through reducing pickling concentration, close plating chromic oxide unit, substituting technical process and parameter adjustment such as accumulator tank circulating bath with clear water, reduces environment protection emission pressure, reduces and produces and maintenance cost.

Description of drawings

Come the present invention is described further below in conjunction with accompanying drawing and specific embodiment.

The electrodeposited chromium section of steel plate figure that Fig. 1 forms for the method for using plating chrome on surface of thin plate of the present invention;

Fig. 2 is existing alkali washing process layout of equipment;

Fig. 3 is existing acid cleaning process layout of equipment;

Fig. 4 is existing electroplating technology layout of equipment;

Fig. 5 is the positive plate layout n.;

Fig. 6 is anode plate structure figure;

Fig. 7 is the chrome plating cohesiveness comparison diagram of different additive;

Fig. 8 is the chrome plating appearance comparison diagram of different additive.

Among the figure: preimpregnation groove 1, electrolyzer 2, scrub groove 3, flushed channel 4, electrolytic pickling groove 5, flushed channel 6, preimpregnation groove 7, plating tank 8, accumulator tank 9, adjustment groove 10, flushed channel 11, anode 13, band steel 14, anode shutter 15, effective surface 16, busbar (copper) 18, oil film 19, chromium oxide layer 20, metallic chromium layer 21, steel plate 22

Embodiment

The concrete steps and the processing parameter of embodiments of the invention are following:

One, alkali cleaning

As shown in Figure 2, this equipment makes band steel process solution place to go stick to the oil and the dirt of belt steel surface, and it comprises a preimpregnation groove 1, embathes the band steel and carries out preliminary degreasing; 2 electrolyzers 2 carry out degreasing through the electrode effect that is installed in band steel two sides in the electrolytic solution; Scrub groove 3 for 1 and carry out the physics degreasing; 2 flushed channels 4 are through the alkali lye of high-temperature water spray removal belt steel surface.

1, alkali embathes

Alkali concn: active alkali 35g/l

Solution temperature: 45 ℃

Additive: electrolytic cleaning additive 25 (low-temperature cleaning agent);

2, electrolytic cleaning

Liquid: active alkali

Temperature: 45 ℃

Concentration: 35g/L

Power supply: 8.0KA, 30V, 2 covers

Electrode: 1200mm is wide, and 1650mm is long, and 16mm is thick, 8 of quantity

Electrolytic current density established standards 20A/dm ²

3, scrub

Liquid: active alkali

Temperature: 45 ℃

Concentration: 35g/L

4, flushing

Liquid: de-salted water

Temperature: 45 ℃

Concentration: trace

Flow: more than the 130l/min

Two, pickling section

As shown in Figure 3, in order to remove the oxide compound of belt steel surface, the band steel will get in the stream acid solution, carry out electrolytic pickling by the electrode that is contained in band steel both sides in the solution tank simultaneously.It is made up of two electrolytic pickling grooves 5, two flushed channels 6.Spray out high-temperature water in the flushed channel 6 and rinse out sulfate ion.

1, electrolytic pickling

Concentration: 25g/l

Solution: sulfuric acid

Fe ³⁺Ionic concn: below the 25g/l

Temperature: 32 ℃

Anode: 1200mm is wide, and 1650mm is long, and 30mm is thick, 8 of quantity

Basic material, Pb-Sn+SS400

2, pickling flushing

Liquid: de-salted water

Temperature: 32 ℃

Concentration: trace

Flow: 230l/min

Pressure: 2.8kg/cm ²Temperature:

Water quality: cl ions (Cl-) 30ppm

Three, electroplate

As shown in Figure 4, form by 10,3 flushed channels 11 of 8,2 accumulator tanks of 7,4 plating tanks of 1 preimpregnation groove, 9,2 adjustment groove.Through at insoluble anode, be with steel to do to set up Faradaic current in the electroplate liquid of negative electrode, at the belt steel surface electrodeposited chromium.

1, electric chrome solution condition

Preimpregnation groove and plating tank strength of solution:

CrO ₃ 150g/l；

NH ₄F 3.5g/l

Cr ³⁺ 3g/l

Fe ³⁺ 2g/l

Cl ^- 15ppm

H ₂SO ₄ 0.08g/l

Temperature: 39 ℃

1# accumulator tank: de-salted water, 45 ℃ of temperature

2# accumulator tank: de-salted water, 45 ℃ of temperature

Adjustment groove groove solution condition

CrO ₃ 77g/l

NH ₄F 1.5g/l

H ₂SO ₄ 0.06g/l

2, electroplating voltage 30V

Current density 100A/dm ²

Current efficiency 20%

The layout of anode 13 and structure such as Fig. 5, shown in Figure 6, positive plate are provided with anode shutter 15, and effective surface 16 exposes, and band steel 14 passes in the middle of two anodes 13.

Four, oiling

Be coated with oil mass and set 4mg/m ²

The electrodeposited chromium section of steel plate figure that uses the method for plating chrome on surface of thin plate of the present invention to form is as shown in Figure 1: on steel plate 22, be coated with metallic chromium layer 21, chromium oxide layer 20 successively, the top layer is an oil film 19.

Following table is put into practice the embodiment that achieves success, product specification such as embodiment 1,2,3,4 for adopting method of the present invention:

As shown in Figure 7, the chrome plating of the A of chrome plating of the present invention and prior art, B company improves a lot on cohesiveness, and the coating tack is good.As shown in Figure 8, the lightness of coating also is significantly improved, and has improved the surface quality of chrome plating.And, according to the inventive method thin sheet surface is carried out chromium plating, can accurately control the amount of chromium metal and chromic oxide, realize the electroplating steel plate of a step production chromium metal and chromic oxide best of breed.Simultaneously; It can also save energy consumption, reduces environment protection emission pressure, reduces and produces and maintenance cost; Can be widely used in the wrapping material such as shell of lid, beverage/food jar, assorted jar, fine arts jar, electric cooker, thermos flask, family expenses dust scrubber, thereby possess good prospect for promotion and application.

Be noted that above enumerate be merely several specific embodiment of the present invention, obviously the invention is not restricted to above embodiment, many similar variations are arranged thereupon.If those skilled in the art all should belong to protection scope of the present invention from all distortion that content disclosed by the invention directly derives or associates.

Claims (9)

1. the method for a plating chrome on surface of thin plate is characterized in that comprising following steps:

1) alkali cleaning: comprise that a) alkali lye embathes, b) electrolytic cleaning, c) alkaline flushing;

2) pickling: comprise a) electrolytic pickling, b) acid flushing;

3) electroplate: comprise a) chromium plating, b) flushing;

4) oiling;

Wherein, 1 the preimpregnation groove that is arranged in order is adopted in said step a) chromium plating, 4 plating tanks, and 2 accumulator tanks, 2 adjustment grooves and 3 flushed channels, actual conditions is:

(A) preimpregnation groove and plating tank strength of solution:

CrO ₃?150±5g/l；

NH ₄F?3.5±0.2g/l

Cr ³⁺≦5g/l

Fe ³⁺≦5g/l

Cl ^-≦30ppm

H ₂SO ₄≦0.09g/l

(B) temperature: 37～39 ℃

(C) 1# accumulator tank: 40～50 ℃ of de-salted water temperature

(D) 2# accumulator tank: 40～50 ℃ of de-salted water temperature

(E) adjustment groove solution condition:

CrO ₃?75±3g/l

NH ₄F?1.5±0.2g/l

H ₂SO ₄≦0.08g/l

(F) electroplating current condition:

Electroplating voltage 30V

Current density 100～120A/dm ²

Current efficiency 20%

Electroplating current

$I=\frac{G\·V\·W}{60\·C\·\mathrm{\η}}\×9.65\×{10}^{-2}$

G(mg/m ²)=〔C(g/F)/96500(C)〕×I(A)/W?(mm)×60/V(mpm)×η×10 ⁶

I(A)=G(mg/m ²)×W(mm)×V(mpm)/C(g/F)×60×η×96500(C)×10 ^-6

=G(mg/m ²)×W(mm)×V(mpm)/C(g/F)×60×η×9.65×10 ^-2

Wherein:

2. the method for plating chrome on surface of thin plate as claimed in claim 1 is characterized in that: step 1) a) in alkali lye be active alkali, concentration is 30 ± 5g/l, alkali liquid temperature: 45 ± 5 ℃.

3. the method for plating chrome on surface of thin plate as claimed in claim 2 is characterized in that: step 1) a) in alkali lye also add the electrolytic cleaning additive, the amount of interpolation is every 1m ³Alkali lye adds 3kg electrolytic cleaning additive.

4. the method for plating chrome on surface of thin plate as claimed in claim 3 is characterized in that: in the electrolytic cleaning, electrolytic solution is active alkali step 1) b), and concentration is 30 ± 5g/l, alkali liquid temperature: 45 ± 5 ℃, and current density established standards=20 ± 10A/dm ², the electrode useful length is 1.50～1.70m, thickness: 15～18mm, interpole gap=top 40 ± 3mm, bottom 40 ± 3mm.

5. the method for plating chrome on surface of thin plate as claimed in claim 3 is characterized in that: alkaline flushing is to use the low chlorine ion water of concentration as 60ppm step 1) c)

Flow: more than the 125l/min

Pressure: 2kg/cm ²More than

Temperature: 40 ℃ ± 5.

6. like the method for claim 4 or 5 described plating chrome on surface of thin plate, it is characterized in that: step 2) a) in electrolytic pickling liquid be sulfuric acid, concentration: 25 ± 3g/l, Fe ²⁺Ionic concn: below the 25g/l, the sulfuric acid temperature: 32 ± 5 ℃, the current value of each passage: I=QVW/1200A

Wherein, the corresponding electric current A of I:1 passage

Q: energising amount c/dm ²

V: unit speed m/min

W: strip width mm

Battery lead plate material: terne metal

Interpole gap=top: 40mm ± 3mm; Bottom: 40mm ± 3mm.

7. the method for plating chrome on surface of thin plate as claimed in claim 6 is characterized in that: step 2) b) in acid flushing be to wash with the water below the cl ions 60ppm:

Flow: more than the 200l/min

Pump flow 1m ³/ min

Pressure: 2kg/cm ²More than

Temperature: 30 ℃ ± 5.

8. the method for plating chrome on surface of thin plate as claimed in claim 7 is characterized in that: step 3) a) in positive plate adopt the edge-masking structure, useful area is 500mm * 1200mm.

9. the method for plating chrome on surface of thin plate as claimed in claim 8 is characterized in that: adopt in the step 4) electrostatic oiler through rotary atomizer with oil misting, spraying gun and high voltage supply link together, and make the elaioleucite subband of the atomizing lotus that powers on.

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