CA2558572C

CA2558572C - Method for lowering the coefficient of friction of the surface of metal bands with a coating and device for applying a metallic coating onto a steel band

Info

Publication number: CA2558572C
Application number: CA2558572A
Authority: CA
Inventors: Theodor Florian
Original assignee: ThyssenKrupp Rasselstein GmbH
Current assignee: ThyssenKrupp Rasselstein GmbH
Priority date: 2005-09-21
Filing date: 2006-09-01
Publication date: 2013-11-12
Anticipated expiration: 2026-09-01
Also published as: KR20070033282A; JP2007113113A; KR101260735B1; CN1935391A; CA2558572A1; JP4921903B2; ES2348802T3; EP1767673B1; US20070062617A1; BRPI0603946A; EP1767673A2; AU2006203319A1; ATE478981T1; CN1935391B; DE502006007718D1; DE102005045033B3; EP1767673A3

Abstract

The invention provides a method for lowering the coefficient of friction of the surface of metal bands with a coating, especially of tin-plated or chromium-plated steel bands (S), which are passed through a coating installation at a band speed (v). To be able to lower the coefficient of friction of the surface of the coating even at high band speeds through the coating installation, according to the invention, an aqueous solution of a tenside is sprayed onto the coated metal band passed at the band speed (v) after the coating process. The invention further provides a device for applying a metallic coating onto a steel band, especially in a band tin-plating installation or band chromium-plating installation.

Description

METHOD FOR LOWERING THE COEFFICIENT OF FRICTION OF THE SURFACE
OF METAL BANDS WITH A COATING AND DEVICE FOR APPLYING A
METALLIC COATING ONTO A STEEL BAND
FIELD OF THE INVENTION
The invention relates to a method for lowering the coefficient of friction of the surface of metal bands with a coating, especially of tin-plated or chromium-plated steel bands, which arc moved with a band speed through a coating installation, as well as to a device for applying a metallic coating onto a steel band, especially a bond tin-plating installation or band chromium-plating installation.
BACKGROUND OF THE INVENTION
In the production of tinplate, especially in electrolytically operating band tin-plating installations, and in the production of black plate with electrolytic chromium (EC:CS), the metal-coated and chemically or electrochemically passivated steel plate (tinplate with tin metal and chromium metal + chromium III hydroxide or ECCS = electrolytic chromium coated steel with chromium metal + chromium III hydroxide) is greased after the coating process in order to lower the coefficient of friction of the coated steel plate, in order to make it able to be better processed during subsequent processing. For this purpose, for example, in the production of tinplate in band tin-plating installations, the tin-plated and passivated steel sheet metal band is greased electrostatically after a drying process with dioctyl sebacate (DOS), acetyl tributyl citrate (ATBC) or butyl stearate (BSO), typically with a deposition of 2-6 mg/m2.
Methods for lubricating the surface of coated metals, e.g., tinplate, are described in US 2,579,778 and US 3,826,675, with an aqueous lubricant emulsion with a pH
value between 2 and 6 produced from a weakly ionizable organic acid being used in US

2,579,778, and citric acid ester being used in US 3,826,675.
In band tin-plating installations in which the steel sheet-metal band passes through with a band speed of less than 150 m/min, DOS can be deposited as an emulsion in a mixture of, e.g., 0.8 g/L DOS with 0.08 g/L lauryl ethoxylate in an immersion process after passivation and after rinsing the tin-plated steel sheet-metal band in an immersion tank. The DOS
emulsion that adheres to the sheet-metal band surface due to the passage of the tin-plated steel sheet-metal band through the immersion tank is then pinched off and dried with a band drier. However, in fast-running band tin-plating installations, in which the steel sheet-metal band passes through the installation at band speeds of 300 to 600 m/min, the aforementioned DOS
emulsion has proven to be disadvantageous because of problems occurring with the distribution of the height of the DOS deposition over the band width, when the pinching rollers, with which the emulsion captured in the immersion tank was pinched, had been in use for a long time and exhibited wear, especially erosion at their edges.
Therefore, an objective of the invention is to provide a method for lowering the coefficient of friction of the surface of metal bands with a coating, especially of a tin-plated or chromium-plated steel sheet-metal band, in which the metal band passes through a coating installation at a high speed and is coated there with the metal coating, with the method being able to be performed with the highest possible throughput and. especially at a high band speed.
SUMMARY OF THE INVENTION
The objectives of the invention are obtained by a method for lowering the coefficient of friction of the surface of metal bands with a coating, especially of tin-plated or chromium-plated steel bands, which are moved with a band speed through a coating installation characterized in that after the coating process, an aqueous solution of a tenside is sprayed onto the coated metal band moved at the band speed. The objectives of the invention are also achieved with a device for applying a metallic coating onto a steel band, especially a band tin-plating installation or band chromium-plating installation, with a deposition device for electrolytic deposition of a thin metal layer on the steel band passing through the deposition device at a band speed, a passivation device for passivation of the deposited metal layer, a rinsing bath for rinsing the coated and passivated steel band, and a processing device for reducing the coefficient of friction of the surface of the coated steel band, through which the steel band coated with the metal layer passes at the band speed, characterized in that the greasing device comprises at least one tube arranged at a distance from the coated steel band, with the tube having a plurality of boreholes in the tube jacket, through which an aqueous solution of a tenside is sprayed onto the coated steel band passed through the greasing device According to the method of the invention, an aqueous solution of a tenside is sprayed onto the moving metal band, especially a steel band, after the coating process, for example, after the electrolytic tin-plating in a band tin-plating installation or the electrolytic chromium-plating in the production of ECCS. Here, the tenside solution is sprayed onto the metal band surface in amounts that are so small that only a thin tenside layer composed of a few molecular layers is adsorbed onto the metal band surface. Here, the sprayed tenside solution is then preferably pinched by means of pinching rollers and then dried. After the pinching of the tenside solution and the drying, a tenside film with a coating of, e.g., ca. 0.1-10 mg/m2 remains on the surface of the metal band.
The tcnside preferably involves a non-ionogenic tenside, which is sprayed onto the surface of the coated metal band in an aqueous solution with a concentration of 0.01-20 g/L.
However, other tensides, especially anionic-active or cat-ionic-active and also amphoteric tensides, can also be used.
For spraying the aqueous tenside solution onto the metal band surface, an arrangement with a tube with a plurality of boreholes in the tube jacket has proven to be advantageous. Here, the tube with the boreholes is arranged at a distance from the metal band surface and charged with the aqueous tenside solution. This solution emerges through the boreholes and is led in the form of spraying streams onto the moving metal band. Preferably, on each side of the metal band, at least one such tube with boreholes is arranged, through which the tenside solution is sprayed onto the metal band surface opposite the boreholes. The tubes arranged on both sides of the metal band preferably are at a distance of 5-15 cm from the metal band surface. The fluid streams emerging from the boreholes of the tube intersect the surface of the coated metal band preferably at a right angle or especially at an angle in the range from -15 to +15 with respect to the normal, and are pinched by one or more pinching rollers arranged behind the intersection point in the advancing direction of the band.
In one preferred embodiment of the method according to the invention, the spraying of the tenside solution is performed within a vertical tank, which has an open outlet. In the vertical tank, the excess tenside solution, especially the solution pinched off by the pinching rollers, is collected and can flow via the outlet into a storage tank underneath the vertical tank and from there can be supplied for reuse.
With the method according to the invention, the coefficients of sliding friction of tinplate and ECCS are reduced to values required by the specific application.

In one aspect, the present invention provides a method for reducing the coefficient of friction of a surface of a coated metal strip which is moved through a coating installation at a strip speed, the method comprising after the coating operation spraying an aqueous solution of a surfactant on to the surface of the coated metal strip moved at the strip speed, wherein the aqueous solution consists of water and a surfactant, and wherein after the aqueous solution is squeezed off and dried a film of surfactant with a coverage of 0.1 to 10 mg/m2 is present on the surface of the coated metal strip.
In a further aspect, the present invention provides a device for applying a metal coating to a steel strip, comprising: an application device for electrolytic application of a thin metal coating on the steel strip running through the application device at a strip speed, a passivating device for passivating the applied metal coating, a rinsing bath for rinsing the coated and passivated steel strip and a treatment device for reducing the coefficient of friction of a surface of the coated steel strip, through which the steel strip coated with the metal coating runs at the strip speed, wherein the treatment device comprises at least one pipe arranged a distance from the coated steel strip and having a plurality of boreholes in the pipe surface, through which an aqueous solution consisting of water and a surfactant is sprayed on to the coated steel strip moved through the treatment device, and at least one pair of squeezing rollers for squeezing the sprayed aqueous solution off the surface of the coated metal strip and a drying device for drying a film of surfactant remaining on the surface after squeezing off.
BRIEF DESCRIPTION OF THE DRAWINGS
Below, the invention is explained in more detail with reference to an embodiment, with reference being made to the enclosed drawings. These show:
Figure 1, schematic view of the quenching and post-treatment of a band tin-plating installation for manufacturing tinplate; and Figure 2, perspective view of a processing device of the band tin-plating installation from Figure 1.
DETAILED DESCRIPTION OF THE DRAWINGS
The section of a band tin-plating installation shown schematically in Figure 1 for manufacturing tinplate includes a deposition device not illustrated here. The steel band S
moved by a tin-plating bath is provided electrolytically with a tin coating.
The steel band S is degreased electrolytically before the tin-plating process, rinsed with deionized water, and then coated with deionized water in a pickling and rinsing process. The steel band S cleaned in this way and connected as a cathode is then led into a tin-plating bath, which contains the electrolytes and the tin anodes. Under continuous monitoring and regulation of the tin-plating conditions for high current density, a fixed, dense, and uniform tin deposit is formed on the steel band. Then during electrolysis after a rinsing process, the tin surface is fluxed, i.e., wetted, pinched, dried, and briefly melted inductively or through resistance heating in a melting tower in a 20-70 C warm solution of 1 g/L HCI or 3 g/L zinc chloride/ammonium chloride solution, in order to achieve visual improvement of the surface quality of the tinplate.
Then the tin-plated steel band S is led through a quenching tank 1 via a deflection roller U. In the quenching tank 1, there is deionized water (VE water) with a temperature of 70-95 C. Then the steel band S is led through the passivation device 2 via deflection rollers U
at the band speed v, which typically equals between 200 and 600 m/min. The passivation device 2 comprises one to two passivation tanks 2a and optionally 2b, in which is located a passivation fluid, for example, a 10-25 g/L sodium dichromate solution with 50-70 C bath temperature. The passivation can be performed electrolytically or without current. For the electrolytic passivation, the tin-plated steel band S is polarized as a cathode in the passivation device via a current roller SR and in this way is electrolytically passivated.
For the most part, steel plates are used as anodes in the passivation bath.
4a Then the tin-plated and passivated steel band S is led into a rinsing bath 3 via deflection rollers U. The rinsing bath 3 comprises, in the example in Figure 1, two counter flow rinsing tanks 3a and 3b, in which spraying tubes 3c, 3e are arranged in each tank in the top region. The deionized rinsing water is sprayed through the spraying tubes 3e onto the steel band and then It is also possible to use the rinsing tank 3a and 3b without spraying tubes as opposite current sinks, with the deionized rinsing water being filled into the rinsing tank 3b and being led from there into the rinsing tank 3a via an overflow. However, the amount of rinsing water necessary for this rinsing arrangement is greater than for the (additional) use of spraying tubes After the rinsing, the steel band S is led through a processing device 4 at band speed v via deflection rollers U for reducing the coefficient of friction of the surface of the coated steel band S. In the processing device 4, the coefficient of sliding friction of the tin-plated, passivatcd, and rinsed steel band S is reduced to the values required for later use and processing. The processing This arrangement is shown in detail in Figure 2. In Figure 2, the vertical tank 5 is shown with the outlet 6. In the vicinity of the base, there is a deflection roller U, by means of which the pump 14 with an aqueous solution of a tenside. For each tube 11, a flowmeter 15 is arranged between the pump 14 and the tube inlet.
Behind the tubes 11 in the advancing direction v of the band (thus, above the tubes 11 in Figure 2), there are two pinching roller pairs I2a, 12b. The spacing of the first pinching roller pair 12a to the tubes 13 in the advancing direction of the band equals approximately 20-100 cm.
The spacing between the tubes 11 and the tin-plated steel band S equals between 1 and 50 cm and lies preferably at 5 to 15 cm. Each tube 11 has at least one borehole or opening, but preferably, as shown in Figure 2, there is a plurality of boreholes in the tube jacket arranged at a distance relative to each other in the longitudinal direction of the tube. Preferably, each tube has two to five boreholes with a diameter of 1 to 4 mm, preferably between 2 and 3 mm.
However, tubes with only one borehole or also with more boreholes, for example, up to fifty boreholes, can also be used.
The tubes 11 are charged with an aqueous solution of a tenside. The aqueous tenside solution emerges through the boreholes into the tubes 11 and strikes the moving, tin-plated steel band S in fluid streams. According to the distance of the tubes 11 from the steel band S and the position of the boreholcs relative to the movement direction of the steel band S, the fluid streams strike the steel band surface either at a right angle or at a falling or rising angle. Preferably, the distance between the tubes 11 and the steel band S is set and the position of the boreholes relative to the movement direction of the steel band is selected so that the fluid streams intersect at a right angle onto the steel band surface or at least within an angular range of 45 , preferably within an angular range of 15 , with respect to the normal (perpendicular) band surface.
With the pinching roller pairs 12a, 12b arranged approximately 50 to 100 cm behind the tubes 11 in the advancing direction, the tenside solution sprayed onto the steel band surface is pinched off, so that a tenside layer with only a few molecular layers, possibly only a one-molecule tenside layer, remains on the tin-plated steel band surface.
The excess tenside solution and especially the solution pinched by the pinching rollers 12 from the tin-plated steel band S collects in the vertical tank 5 and flows via the outlet 6 into a storage tank 4 under the vertical tank 5, from where the tenside solution can be supplied for reuse via a pump 8, in that the tenside solution collected in the storage tank 4 is transferred to a tenside application tank 9 and finally pumped back into the tubes 11.

After passing through the processing device 4, the tin-plated steel band S
finally passes into a drying device 10, which is formed by, for example, a hot-air drier, via deflection rollers U.
With the previously described processing device 4, tin-plated steel bands were treated with various tenside solutions in different concentrations and tested in terms of their coefficients of sliding friction.
For greasing the tinplate surface, a plurality of surface-active substances are suitable, especially cationic, anionic, non-ionogenic, and amphoteric tensides.
Preferably, tensides arc used that have meet legal requirements for food use according to FDA
178.9310, FDA
178.3400, and the EG guidelines 2002/72/EG and 1935//2004/EG. For non-approved tensides, an expensive toxicological test and approval is necessary if the steel sheets processed according to the invention are to be used for creating food packages. In addition to the legal approval for food use, also required are good wettability and adhesion of the paint used for coating with the tinplate surface post-treated with tenside, i.e., the tenside used must be tailored to the paints used.
Due to the described application via spray tubes 11, the formation of foam by the tensides that are used does not cause interference in the post-processing of the coated steel band.
Comparison tests with the tenside lauryl ethoxylate with 3 EO were performed in a band tin-plating installation that showed the suitability of the described method for large-scale application. This tenside is legally approved for food use according to FDA
178.9310.
It was sprayed in an aqueous solution in concentrations of 1-8 g/L after the passivation and rinsing in the described band tin-plating installation made from two tubes 11 on each band side onto the tin-plated steel band S, with the two tubes 11 each having five boreholes with a 2.5 mm diameter at a distance of 25 cm from each other in the direction horizontal to the band surface. The two tubes 11 were arranged ca. 80 cm in front of a pinching roll pair 12a in the advancing direction of the band at a distance of 10 cm from the steel band surface. The fluid streams extended approximately horizontally from the boreholes in the tubes 11 onto the galvanized steel surface. The fluid streams striking the band surface were visible in the light of a lamp and one could see that the fluid pinched off by the pinching rollers 12 was distributed uniformly over the width of the pinching rollers 12, detached in the form of droplets, and finally fell into the vertical tank 5. The tin-plated steel band samples treated in this way were then analyzed with a Leco C-analyzer at a maximum oven temperature of 400 C. Here, in the scope of the analysis variation, tenside deposits with equal height over the width of the steel band were measured, which corresponded to 3 1.5 nig/1112 lauryl ethoxylate.
In further tests, by varying the band speeds v, the tenside used, and its concentration and various surface roughness values of the tinplate band surfaces treated in this way, tenside film deposits of 3 1.5 mg/m2 were detected. From this it results that the tenside-containing solution was pinched up to a no longer detectable fluid film of less than 0.5 niL/m2 of the tinplate surface.
In contrast, for tenside-free rinsing water, the fluid film on the tinplate surface is pinched off only up to a residue of 5-10 mL/m2 on the band surface.
The tenside coating remaining on the tin-plated steel band surface after use of the method according to the invention is composed of the tenside deposit adsorbed onto the band surface, and the coating, which is produced from the thickness of the pinched fluid film and its tenside concentration. In comparison to tinplate rinsed conventionally (that is, with tenside-free rinsing water), the tinplate treated according to the method of the invention has significantly lower energy needs for drying in the drying device connected after the processing device. The energy expense for drying the tinplate band can be reduced even more if the passivation fluid is heated in the passivation tanks 2a, 2b and/or the rinsing water is heated in the rinsing tanks 3a, 3b (for example, to temperatures of 50-70 C, the rinsing water also to temperatures up to 80 C).
The adsorption time of the tenside solution sprayed onto the band surface according to the method of the invention is sufficiently short to guarantee a uniform adsorption of the tenside film onto the tinplate surface before the pinching rollers 12 pinch the excess tenside solution.
Due to the short adsorption time, it is presumably not necessary to spray the fluid onto the tinplate surface as uniformly as possible via fine spray nozzles. Instead, it is sufficient-as provided according to the invention-to spray the tenside solution relatively coarsely onto the wet tinplate surface. The advantage of spraying the tenside solution in the form of thin fluid streams distributed over the width of the steel band is that the risk of forming foam in the tank, in which the excess, especially the pinched tenside solution, collects is significantly lower than that when using spray tubes with nozzles, which would spray the tenside solution in a fine mist onto the tinplate surface. The larger borehole diameters of the spray tubes tend to accumulate less foreign matter than do the smaller diameters of the spray nozzles required for the same application.
The tinplate bands examined in the comparison tests were examined with a three-ball tribometer in terms of their coefficient of sliding friction before and after the treatment according to the invention. Here, the following coefficients of sliding friction were determined for electrochemically passivated tinplate with 2.8 g/m2 tin deposit and stone-finish surface:
without slip additive: = 0.40 with 2 mg/m2 lauryl ethoxylate: p. = 0.24 with 4 mg/n12 dioctyl sebacate (DOS): p. = 0.20 The tenside deposit does not reduce the sliding friction of the tin surface as much as does the DOS deposit. However, the sliding friction is good so that scratches and scrapes are not created on the tinplate surface when the tinplate rings break apart and the tables in the next post-processing stage can be cleared of packages without a problem.
However, in contrast to conventional electrostatic greasing of the tinplate surfaces with esters such as DOS, in the tinplate bands treated according to the invention, no tin dust caused by production has been observed. In contrast, especially for tinplate greased with DOS, a dust layer due to production is often observed, which is problematic, because it can be removed only through suitable, complicated, and careful measures during the installation.
The reason for the freedom from dust in the method according to the invention can be traced possibly to the rinsing effect of the tenside solution in the application after the passivation and rinsing, as well as to the better adhesion of the tinplate to the surfaces of the non-driven deflection rollers in the second loop tower of the band tin-plating installation. Due to the low slippage of the tinplate with the deflection rollers in the loop tower, in contrast to greasing with conventional substances such as DOS, obviously no tin particles are rubbed off.
Another advantage over greasing tinplate conventionally, for example, with DOS, ATBC
(acetyl tributyl citrate) or BSO (butyl stearate oil), is the ability for perfect (pore-free) painting of the tinplate surfaces treated according to the invention after typical storage times (for example, more than 12 months). This advantage can be explained presumably in that the adsorbed tenside molecules do not coagulate into droplets, as is often the case for DOS
greasing with >4 mg/m2 in the edge region of the tinplate tables. Paint, which cannot completely dissolve these droplets in the wet film on the tinplate surface, then tends toward formation of pores in the paint layer.
The method according to the invention can also be applied in band tin-plating installations with horizontal rinsing cascades. In these horizontal rinsing cascades, rinsing water is sprayed through spray registers with nozzles onto both band surfaces for each rinsing stage up to 40 m3/h. The rinsing water is then pinched off and flows back into a storage tank under the corresponding rinsing stage, from where it is pumped back into the horizontal rinsing stage. In these horizontal rinsing cascades, the method according to the invention can be used when the spray registers before the last pinching roller pair is replaced by the aforementioned tubes with boreholes, with which the aqueous tenside solution according to the invention is sprayed onto one or both band surfaces. For two-sided spraying of the tin-plated steel band, the tenside solution is sprayed first through a tube arranged above the top side of the band. Second, the aqueous tenside solution is sprayed onto the bottom side of the band, by spraying the tenside solution through a tube with boreholes on the pinching roller adjacent to the bottom side of the band. In this way, the aqueous tenside solution is transported through the gap between the steel band and the pinching roller adjacent to the bottom side of the band, where the fluid mixes with the water film on the bottom side of the band and the band surface is "greased" in this way with the tenside film. Here, the pinched off tenside solution also flows back into a storage tank-as in the described embodiment of the band tin-plating installation with a vertical tank - and can then be reused.
The method according to the invention applied in the processing device 4 of the described band tin-plating installation can be used very generally for reducing the coefficient of friction of metal bands with a metallic coating, e.g., also special chromium-plated steel bands (ECCS).
Examples:
In the laboratory, black plate sheets with a stone finish surface with 17 x 20 cm area were - degreased electrolytically in an alkaline solution - rinsed with deionized water - pickled in 100 g/L sulfuric acid solution - rinsed again with deionized water and - electrolytically tin-plated in a tin methane sulfonate bath with commercially available bath additives (replenisher and stanguardTM by Rohm & Haas) with 2 A/dm2 current density (tin deposit 2.8 g/m2).
The tin-plated sample was - rinsed with deionized water and - electrolytically passivatcd in a 25 g/L sodium dichromate solution (T = 60 C; i =
1.5 Adm-2, t = I sec). The total chromium deposit of the passivation layer equaled 5 mg/m2. The sample was again thoroughly - rinsed with deionized water - fixed in a paint centrifuge (Erichsen) and spun for 5 seconds at 1000 rpm the tin surfaces were covered with aqueous solutions of 1 g/L of the following tcnsides, and the tenside solution was spun for 5 seconds at 1000 rpm:
(designated below as post-processing product X (with X = A, B, C, D) lauryl ethoxylate with 3 EO
B: C12-14 carboxylic acid ethoxylate with 9 EO
C: C10-12 alkane sulfonic acid, Na salt, D: polyethylene oxide (average molecular weight 6000 Dalton) The samples were removed from the paint centrifuge and dried with hot air.
On the samples with the various tenside coatings, the following tests were performed:
- tin deposit - total chromium deposit in the passivation layer - tenside deposit (C contents of the tenside with the Leco carbon measurement device RD 412) - sliding friction - painting with 5 g/m2 epoxide resin paint PPG 3907-301/A
- sterilization in the following solutions:
- 3% ethanoic acid 30 min at 100 C
- 1% hydroxypropionic acid + 2% NaCl 30 min at 121 C
- 0.5 g/L cysteine 90 mm at 121 C
- 1.0 g/L cysteine 90 min at 121 C
The painting adhesion was tested after the steriliz:ation test through a cross-cut adhesion test and tesa test according to EN ISO 2409.
The tinplate samples greased with the various non-ionogenic tensides also had low organic deposits with 55 mg/m2 like tinplate samples greased electrostatically with dioctyl sebacate in a band tin-plating installation (desired deposit in the tinplate production at industrial scale: 4 2 mg/m2 DOS).

The tin oxide deposits and the chromium deposits of the tinplate samples passivated in sodium chromate solution were within the desired range of commercial tinplate production.
With lu = 0.13-0.24, the sliding friction of the tinplate samples greased with tcnside or DOS lay significantly under the sliding friction of ungreased tinplate with pt = 0.4. The tinplate samples with sliding friction in the range of p. = 0.13-0.24 have the same good sliding ability in further processing through painting and shaping in production.
The paint adhesion of the tinplate sample painted with 5 g/m2 paint PPG 3907-301/A and sterilized in various solutions was just as good for the greasing with tenside as for the greasing with DOS.
[Note: commas should be read as decimal points.]
Running Product for treatment tin coating passivation tin-oxide tenside Sliding No. after coating (g/m2) (mg/m2/Cr) coating coating friction (C/m2) (mg/m2 C) coefficient 1 A 2,8 5,0 15 2,3 0,24 1 2 B 2,9 4,8 20 2,7 0,24 __________________________________________________________________________ ¨I
, 3 C 2,8 5,8 15 3,8 0,18 I
__________________________________________________________________________ 1 4 D 2,7 4,5 18 3,5 0,13 Reference sample, tinplate, electrostatically greased with DOS (mg/m2) 5 Dioetylsebacat (DOS) , 2,8 5,4 18 3,5 0,22 No.. Product for treatment- Sterilization resistance after varnishing with after coating 5 g/m2 varnish PPG 3907-301/A; result of the cross-cut adhesion test*
3% ethanoic 1% lactic acid 0,5 g/lCystein 1,0 gil Cystein acid + 2% NaC1 30 min/121 C 90 min/121 C 90 min/121 C
30 min/100 C

3 C GT 0 GT 0 G'1' 0 GT 0 4 D GT 0 GT 0 GT 0 (3T 0 Reference sample, tinplate, electrostatically greased with DOS
5 Dioctylsebacat (DOS) GT 0 GT 0 GT 0 GT 0 * cross-cut adhesion test according to DIN EN 2409.

Claims

1. Method for reducing the coefficient of friction of a surface of a coated metal strip which is moved through a coating installation at a strip speed (v), the method comprising after the coating operation spraying an aqueous solution of a surfactant on to the surface of the coated metal strip moved at the strip speed (v), wherein the aqueous solution consists of water and a surfactant, and wherein after the aqueous solution is squeezed off and dried a film of surfactant with a coverage of 0.1 to 10 mg/m2 is present on the surface of the coated metal strip.

2 The method according to claim 1, wherein the coated metal strip comprises one of a tinned steel strip and a chromed steel strip.

3. The method according to claim 1 or claim 2, wherein the aqueous solution is squeezed off by means of squeezing rollers (12).

4. The method according to claim 3, wherein the coated metal strip is dried after the aqueous solution has been squeezed off.

5. The method according to claim 4, wherein the film of surfactant comprises a coverage of 0.1 to 5 mg/m2 on the surface of the coated metal strip.

6. The method according to claim 5, wherein the film of surfactant comprises a coverage of between 2 and 5 mg/m2 on the surface of the coated metal strip.

7. The method according to any one of the claims 1 to 6, wherein the surfactant is one of an anionic, cationic, non-ionic and an amphoteric surfactant.

8. The method according to any one of claims 1 to 6, wherein the surfactant is a non-ionic block polymer.

9. The method according to any one of claims 1 to 6, wherein the surfactant is a non-ionic block polymer with a concentration of 0.01 to 20 g/l.

10. The method according to any one of claims 1 to 6, wherein the aqueous solution is an aqueous solution of one of a non-ionic and an anionic surfactant.

11. The method according to any one of claims 1 to 10, wherein the aqueous solution is sprayed on through at least one pipe (11) which is arranged a distance from the surface of the coated metal strip and exhibits at least one borehole through which the aqueous solution passes on to the surface of the coated metal strip.

12. The method according to claim 11, wherein the or each pipe (11) exhibits between 1 and 50 boreholes each with a diameter of 0.1 to 5 mm, wherein the borehole diameters are selected so that jets of liquid impinge on the surface of the coated metal strip.

13. The method according to claim 11 or 12, wherein arranged on each side of the metal strip there is at least one of said pipes (11) with boreholes through which the aqueous solution is sprayed on to respective surfaces of the coated metal strip lying opposite the boreholes in the pipe (11).

14. The method according to any one of claims 11 to 13, wherein the or each pipe (11) is arranged horizontally and at a distance of 1 to 50 cm from the surface of the coated metal strip.

15. The method according to claim 14, wherein the or each pipe (11) is arranged at a distance of 5 to 15 cm from the surface of the coated metal strip.

16. The method according to any one of claims 1 to 15, wherein the aqueous solution is sprayed on to the surface(s) of the coated metal strip in the form of jets of liquid, wherein the jets of liquid impinge on the surface of the coated metal strip at an angle range of between +45°
and -45° with respect to a normal direction of the surface.

17. The method according to claim 16, wherein the jets of liquid impinge on the surface of the coated metal strip at an angle range of between +15° and -15°.

18. The method according to claim 16, wherein the jets of liquid impinge on the surface of the coated metal strip at an angle perpendicular to the surface.

19. The method according to any one of the claims 1 to 18, wherein the aqueous solution is sprayed on to the coated metal strip inside a vertical tank (5) with a discharge outlet (6) for the surplus surfactant solution collecting in it.

20. The method according to any one of claims 16 to 19, wherein the jets of liquid impinge on at least one of the two surfaces of the coated metal strip in an area or in a vicinity of the area in which the squeezing rollers (12) contact the surface of the coated metal strip.

21. The method according to any one of the claims 1 to 20, wherein before the aqueous solution is sprayed on, the coating of the coated metal strip is passivated.

22. The method according to claim 21, wherein the coated metal strip is passivated by passing the coated metal strip through a passivating bath.

23. The method according to claim 21 or claim 22, wherein after passivation, the coated metal strip is rinsed with rinsing water by being passed through at least one rinsing tank (3a, 3b).

24. The method according to any one of claims 21 to 23, wherein the passivating bath (2a, 2b) and/or the rinsing water is warmed to temperatures between 50°C and 80°C.

25. The method according to any one of claims 1 to 24, wherein the strip speed (v) is higher than 100 m/min.

26. The method according to any one of claims 1 to 24, wherein the strip speed (v) is higher than 300 m/min.

27. The method according to any one of claims 1 to 24, wherein the strip speed (v) is between 400 and 600 m/min.

28. Device for applying a metal coating to a steel strip, comprising:
- an application device for electrolytic application of a thin metal coating on the steel strip (S) running through the application device at a strip speed, - a passivating device (2) for passivating the applied metal coating, - a rinsing bath (3) for rinsing the coated and passivated steel strip (S) - and a treatment device (4) for reducing the coefficient of friction of a surface of the coated steel strip (S), through which the steel strip (S) coated with the metal coating runs at the strip speed (v), wherein the treatment device (4) comprises at least one pipe (11) arranged a distance from the coated steel strip (S) and having a plurality of boreholes in the pipe surface, through which an aqueous solution consisting of water and a surfactant is sprayed on to the coated steel strip (S) moved through the treatment device (4), and at least one pair of squeezing rollers (12) for squeezing the sprayed aqueous solution off the surface of the coated metal strip and a drying device for drying a film of surfactant remaining on the surface after squeezing off.

29. The device according to claim 28, wherein the device is a strip tinning installation or a strip chroming installation.

30. The device according to claim 28 or 29, wherein first and second ones of the at least one pipe (11) are arranged on each side of the steel strip (S) running through the treatment device (4) for spraying the aqueous solution on to both sides of the steel strip (S).

31. The device according to any one of claims 28 to 30, wherein the treatment device (4) comprises a vertical tank (5) with a discharge outlet (6) in which the surplus aqueous solution collects and flows through the discharge outlet into a supply tank (7) arranged underneath the vertical tank (5).

32. The device according to any one of claims 28 to 31, wherein the at least one pair of squeezing rollers (12) is arranged behind the or each pipe (11) in the running direction of the steel strip to squeeze off the sprayed on solution.

33. The device according to any one of claims 28 to 32, wherein the bores are arranged along the pipe (11) equidistant from one another on a line which runs transversely to the strip running direction of the steel strip (S).