CA2315778A1 - Phosphatization of a single-face galvanized steel strip - Google Patents
Phosphatization of a single-face galvanized steel strip Download PDFInfo
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- CA2315778A1 CA2315778A1 CA002315778A CA2315778A CA2315778A1 CA 2315778 A1 CA2315778 A1 CA 2315778A1 CA 002315778 A CA002315778 A CA 002315778A CA 2315778 A CA2315778 A CA 2315778A CA 2315778 A1 CA2315778 A1 CA 2315778A1
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- phosphatising
- ions
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- solution
- galvanised
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
- C23C22/08—Orthophosphates
- C23C22/18—Orthophosphates containing manganese cations
- C23C22/182—Orthophosphates containing manganese cations containing also zinc cations
- C23C22/184—Orthophosphates containing manganese cations containing also zinc cations containing also nickel cations
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
- C23C22/08—Orthophosphates
- C23C22/12—Orthophosphates containing zinc cations
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
- C23C22/08—Orthophosphates
- C23C22/12—Orthophosphates containing zinc cations
- C23C22/13—Orthophosphates containing zinc cations containing also nitrate or nitrite anions
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- Chemical & Material Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Chemical Treatment Of Metals (AREA)
Abstract
The invention relates to the phosphatization of the galvanized side of a single-face galvanized steel strip using a phosphatizing solution containing 16 g/l zinc ions and 10-30 g/l phosphate ions. The invention is characterized in that the phosphatizing solution contains one or several constituents a) to c): a) 60-1000 mg/l of one or several monovalent or multivalent alchohols with at least a triple bond between two carbon atoms, b) 10-160 mg/l of one or several alkyl or alkenyl nitrogen compounds with at least 5 C atoms and c) 10250 mg/l alkali metal iodide. Preferably, the phosphatizing solution contains at least 2 and especially all 3 constituents a), b) and c).
Description
p~P~g srteel s~P which has been galvaxtised on one face This invenrion relates to a process for phosphatising the galvanised face of steel strip which has been galvanised on one face, the non-galvanused face not being phosphatised. Selective phosphatisiuag of the galvanised face is achieved by adding to the phosphatising solution s components which are appropriate for inhibiting phosphatising of the non-galvanised steel face but which do not impair phosphatising of the galvanitsed face. The use of physical methods to cover the steel face ding the required phosphatising of only the galva,ttised face are, therefore, unnecessary.
In the context of the present invention, all references to steel strip which has been galvanised on one face are to be understood to be to elearolytically galvanised or alloy galvanised steel strip. rf the latter, then the zinc layer also contains alloying constitiuents, such as iron, nickel az~cUor aluxninuzzt.
i ~ Processes for phosphatising surfaces of iron, steel, zinc and alloys thereof and of aluminum and alloys thereof have long been known in the prior art. Phosphatising of the surfaces mentioned is used to increase the strength of adhesion of lacquers and to improve the corrosion protective properties. Phosphatising is performed by immersion of the metal surfaces in phosphatising solutions or by spraying the metal surfaces with phosphatising 2 o solutions. Combined processes have also been disclosed, Either shaped metal parts, such as car bodies, or metal strips in high-speed conveyer belt systems may be phosphatised. The present invention is concerned with strip phosphatising of the latter type. Strip phosphatising differs from part phosphatising in that, due to the high Zs conveyer belt spends, the phosphatisz~g process, i.e. the deposition of a sealed metal phosphate layer, has to take place within a short time-span of, for example, about 2 to about 20 seconds.
Processes for phosphatising metal strips, in particular electrolytically or hot dip galvanised a o steel strips have been disclosed in the prior art. For example, WO
91/02829 describes a process for phosphatisxz~g electxolytically and/or hot dip galvanised steel strip by short-term 6I /Z 39t1d W I L'IfItiN321 RA'I I ~O A3Z3tfMS ° LI02I3 0E ° 0 i 00-6Z-~fltf ,2_ treatment using acid phosphatising solutions which contain, iu addition to zinc and phosphate ions, manganese and nickel rations and anions of oxygen.~ontaining acids having an.
accelerator effect- The last mentioned component is understood to be, in particular, nitrate ions. Db~-.A,-35 37 108 also describes a process for phosphatising electrolytically galvanised s steel strips by treamnent using acid phosphadsiu~g solutions which contain, in addition to z~c, manganese and phosphate ions, other metal rations, such as nickel ions az~dlor anions of o~cygen~ontaining acids having an accelerator effort, in particular zutrate ions. The conccntration of zinc rations is then within the relatively Iow range of 0.1 to 0.8 gll.
~o ~7~A-197 40 953 describes a process for phosphatising steel strip, or steel stxip which has been galvanised or alloy galvanised on oz~e face or on both faces, by spraying with or imumersiuc~g iux, for a period in the range from 2 to 20 seconds, an acid phosphatsing solution which contains zinc, magnesium and manganese at a temperature in the range 50 to 70°C, characterised in that the phosphatising solution contains no nitrate ions and that it contains:
is 1 to 4 g/1 of zinc ions, 1.2 to 4 gll of manganese ions, 1 ro 4 gll of magnesium ions, to 30 gll of phosphate ions, 0.1 to 3 g/1 of hydroxylamine in the free, ionic or bound form, 2 o with a concentration of free acid in the range from 0.4 to 4 points and a concentration of total acid in the range from 15 to 45 points.
If nickel ions are also added to zino- and manganese~ontaining phosphatising solutions, then so-called "trication" phosphatising solutions arc obtained.
When phosphatising steel strip which has been galvanised on one face, it is generally desired tb~at only the galvanised face be phosphatised, while the non-galvanised face is intended to remain uncaaxed_ The steps taken to achieve this objective, however, should not passivate the non-galvanised face so complctely that, after shaping and joining together componenxs from 3 o the steel strip and cleansing the assembled part, subsequent part phosplaatising is prevented.
6 i /~ 3~'dd ' 4 I .L 'IfltiN32i Jil1'I I ~O 7C3AtfMS ° W02t3 0~
° 0 L 00-6Z-~Ittt _3_ The prior art discloses, for example, adding organic acids (acetic or tartaric acid) or amines (urea) to the phosphatisittg solution for this purpose. However, such use of an additive is associated with the disadvantage that the weight per anal area of the phosphatising layer on the zinc face, in particular during prolonged production, drops below the required value.
s Furthermore, it is known that the phosphatising solution should have a comparatively low pH, and thus a comparatively high free acid value, in order to avoid phosphatising the steel face of steel strip which has been galvanised on one face. However, this type of phosphatising solution exerts a high pickling effect on the zinc face, so the phosphatising solution becomes io greatly enriched with zinc ions. There is then the risk that the zinc concentration reaches the solubility limit for zinc phosphate and zinc phosphate is deposited on the steel face.
This disadvantage has resulted iua large producers of phosphatised steel strip which is galvanised on one face changing over to physical methods for preventing the non-galvanised 1 s steel face coming into contact at all with the phosphatisiug solution. The mechanical covering procedures required for this are complicated and make the produaron moot much more costly.
Attempts to inhibit phosphatising of the non-galvanised steel face by adding pickling inhibitors have hitherto been unsuccessful. These types of additives have hitherto led to the a a phosphatising reaction on the galvanised face, which is very sensitive to changes in operating pax~ete~rs, tal~al~g place either unsatisfactorily or not at all.
Therefore, there is a need for a process for phosphatising only the galvanised face of steel strip which has been galvanised on one face; which does not require mechanical covering 2 s procedures, bus which, nevertheless, does not have the disadvantages mentioned above.
The present invention relates to a process for phosphatising steel strip which has been galvanised on one face using a phosphatising solution which contains 1 to 6 gll of zinc ions and 10 to 3Q gll of phosphate io:as, characterised in that the phosphatising solution also 3 o contains one or more of the components (a) to (c):
(a) 60 to 1000 zngll of one or more mono- or poly-hydric alcohols having at least one 6I /b 30'dd ' Q I 3. 'If1'dN32i 7~A'I I 00 A3HttMS ° W02i3 0~ °
0I 00-6Z-9(1tf carbon-carbon triple bond, (b) 10 to 160 mgJl of one or more alkyl or allcenyl niuogen compounds having at least 5 carbon atoms, {c) 10 to 250 mgll of an alkali metal iodide.
In a preferred embodiment, the process is characterised in that the phosphatising solution contains one or more of coaznponents (a) to (c) in the following concentrations:
(a) 200 to 400 mgll of one or more mono- or poly-ltydric alcohols having at least one carbo~a-carbon triple bond, (b) 30 to 60 mgll of one or more alkyl or alkenyl nitrogen compounds having at least 5 carbon atotxts, (c) 40 to 100 mgll of an alkali metal iodide.
The individual components (a), (b) and (c) hinder or inhibit the pickling rcaction of the s s phospha~isiuag solution with the non-galvanised steel surface so that this is not phosphatised, or is phosphatised only very slightly. The picltling reaction at the galvanised surface, howevez, is not hindered so that the desired, sealed, crystalline, zinc phosphate layer is built up to the desired weight per unit area on this face_ 2 o The expression wcight per unit area is frequently used in the field of phosphatising metal surfaces. The expressions "weight deposited per unit area" or "arearspecific weight" axe also used instead of "weight per unit area", or more specifically "weight of phosphate layer per unit area" . These expressions are to be understood to mean the weight of metal phosphate layer produced on the metal surface by the phosphatising process with reference to one unit of 2s axea. It is generally given in glm~. It may be determined by weighing a phosphatised metal sheet having a known surface area, dissolving the metal phosphate layer and weighing the metal sheet agaiti_ The weight of metal phosphate layer with reference to one m~2 may be calculated from the weight difference determined, by taking account of the sL>rface area of the metal sheet. A 0.5 wt. k strength chromic acid solution, for example, may be used to dissolve 3 o the metal phosphate layer. The procedure for determining the weight per unit area is described in more detail in Cue. standard DIN 50942.
6 L /S 3J'dd ° O I .L 'IfltiN321 JCA'I I JO A3AttMS ~ WO?.13 L E
° 0 L 00-6Z-Ofl'd -S-The weighs per unit area is an essential paramecez for checking phosphatising results. Weights per unit axes within a variety of ranges may be required, depending on the intextded use for the phosphatised metal parts. The present invention is preferentially concerned with metal s sheeting which is to be used in the car manufacturing industry. In this case, weights per unit area of more than 0.8 glm2, but at most about 4 g/m2, are required _ The weight per unit area should preferably be below 3 g/m2 and in particular about 1 to about 2 g/mT.
Each of the components (a), (b) and (c) boosts the effect of the others as an inhibitor of the to pickling reaction at the non-galvanised steel face. Thus, phosphatisiutg of the ttonBgalvanised steel faoe is inhibited more effectively and more reliably if the phosphatising solution contains at least two of components (a), (b) and (c). The phosphatising solution preferably contains all three co~onents (a), (b) and (c).
Co~oo~ponent (a) may be selected, for example, from the a,cetylenically unsaturated diols. A
preferred example such is but-2-yne-1,4-dxol.
Alkyl or alkenyi amines, for example, are suitable for use as component (b).
Furthermore, alkyl- or alkenyl-substituted l~itrogen-containing heterocyclic compounds, in particular Zo unsaxurated heterocyclic compounds are especially suitable. These may have, for example, 1, 2 or 3 nitrogen atoms in the heterocyclic rind. One alkyl group is preferably in a position which is located as far as possible from the nitrogen atom(s). Particularly preferred examples are mono- and di-alkylpyridines having 1 to 22, preferably 1 to 12, carbon atoms in each alkyl group, wherein one alkyl group is preferably in the 4-position with respect to the 2 s nitrogen atom. These alkylated pyridines are generally available as a technical grade mixture.
Due to the fact that it is industrially readily available, potassium iodide is preferably used as component (c).
s o rn addition to components (a), (b) andlor (c), the phosphatising solution may contain up to 250 mg/1, preferably about 40 to 80 mgll, of a non ionic surfactant. In combination with at 6I /9 3~'dd ' 4 I .L 'Ifl'dN321 ~A'I I ~O ~i36'dMS ° Id02i3 L E
° 0I 00-6Z-~f1'd least one of co~oaponents (a), (b) andlor (c), this surfactant supports the inhibiting effect on the non-galvanised steel face. Ethoxylated, propoxylated amilor ethoxylated/propoxylated alcohols having 10 ro 18 carbon atoms in the alkyl chain are preferably used as non-ionic surfactants_ In addition to the ~o~on-ionic surfactant, the phosphatising solution may contain a s solubility promoter for the surfactant. This may be present at a concentration of up to 750 mgll, preferably about 150 to about 300 mgll. Cumene sulfonate, for example, is suitable for use as a solubility promoter.
Apart from the components (a), (b) and/or (c) required for the inhibiting effect on the non-~ o galvanised steel fact, the phosphatising solution may contain other components commonly used in the prior art which either become incorporated into the phosphate layer or, due to the accelerator effect thereof, promote formation of the layer. Accordingly, the phosphatising solutioa preferably also contains one or more of the following canons:
1 to 5 gll of manganese ions, i s 1 to 4 gll of magnesium ions, 0.8 to 4.5 gIl of nickel ions, 0.01 to 0.2 g/1 of copper ions.
In addition to the layer-forming rations mentioned, the phosphansing solutions contazn alkali a o metal andlor ammonium canons in order to adjust the free acid value to withixt the required range.
Conventionally, phosphatising baths also contain so-called accelerators. These are substances which react with the hydrogen being produced during the pickling reaction at the metal 2 5 SUrfaCE. They therefore inhibit so-called polarisation of the metal surface caused by a coating of hydrogen. The accelerators thus improve uniform coating of the metal surface with finely divided phosphate crystals, which generally have a size between about l and about 10 ?m.
Phosphatising solutions which contain the accelerator are also preferably used in the process according to the present invention. Accordingly, the phosphatising solutions used for the 3o present process also contain, as accelerator, once ox more of the following components:
0_5 to 30 gll of nitrate ions, 6I /G 30tfd W I .L'IflttN32i JCA'I I 00 JC3A'dMS ° W02I3 i E = 0 i 00-6Z-Ofltt y o.os to 0.2 g!1 of niuite ions, 0.03 to 0_2 gll of hydrogen peroxide in the fret or bound form, 0.05 to O.b gll of permanganate ions.
Alternatively, or in the event thaw odtrate ions are used, in addition to these, a phosphatising solution which also conrai~ns, as accelerator, about 0.1 to about 3 gll of hydroxylamine in the ft~ee, ionic or bound form is preferably used for the process according to the presem invention.
so Hydroxylamine may be used as the free base, as a compound which releases hydroxylamine, such as hydroxylamine complexes or ketoximes or aldoximes, ox in the form of hydroxylaminonium~ salts_ If free hydroxylamine is added to the phosphatising bath or a phosphatising bath concentrate, then this is largely present as the hydroxylammonium carton due to the acidic character of these solutions. If it is used in the form of a hydroxylaztrtnonium is salt, rhea sulfates and phosphates ace particularly suitable. In the case of phosphates, acid salts are preferred due to the higher solubility thereof. In order, on the one hand, to take account of economic aspects and, on the other hand, not to contami~oate the phosphatising baths too much with sulfate ions, it znay be advantageous to use a combination of free hydroxylamine and hydroxylammonium sulfate. T~ydroxylamine or compounds thereof are 2 o added to the phosphatasiuag solution in an amount such that the calculated ooticentration of free hydroxylamine is betwoen about 0.1 and about 3 gll, prcferably between about 0. is and about 1 gll.
When quotiztg dara relating to the concentration of phosphate, the entire amount of a s phosphorus in the phosphatising bath is regarded as being present in the form of phosphate ions, PO,~_ Therefore, when calculat~g or determining the concentration, the known fact that, at the acidic pHs prevailing in phosphatising baths, in the range from about 2.0 to about 3.b, only a very small proportion of the phosphate is actually in the form of triply chargcd anions, is ignored. ~tather, it would be expected, at these pHs, that the phosphate is probably 3 o present as a singly chaxged dihydrogen phosphate anion, together with undissociated phosphoric acid and small amounts of doubly charged hydrogen phosphate anions.
6 L /8 3Jtfd ' Q I .L 'IfltlN32l xl1'I I ~O ~39tfMS = W0213 ZE = 0 L 00-6Z-9(ltf _$_ The presence of fluoride ions may be advantageous for uniform production of the layer.
Accordingly, there is a further embodiment of the present invention comprising using phosphatising solutions which contain up to about 0.8 gll of fluoride in the free or cort>plexed s form. The preferred fluoride concentrations for phosphatising electrolytically galvanised steel strip, for example, is in the range from 0.0 to about 0.5 g/l, in parnicular in the range from about 0.1 to about 0.2 gll.
The phosphatising solutions are generally prepared in the way which is familiar to a person io skilled in the art. Phosphate is introduced to the phosphaiising solutions, for example, in the form of phosphoric acid. The canons are added to the phosphoric acid in the form o~ acid-soluble compounds, such as carbonates, oxides or hydro~cides, so that the acid is partly neutralised. Further neutralisation to reach the desired ply range is preferably performed by adding sodium hydroxide ox sodium carbonate. Sod~imm or potassium fluoride, for example, is are suitable as sources of free fluoride anions. Tetrafluoroborate or hexafluorosilicate, for example, may be used as complex fluoz~des_ Its, order to produce phosphate layers having a weight per unit area in the desired range, phosphatising solutions which have a concentration of free acid in the range from about 0.4 to s o about 4 points and a concernb~atxolt of total acid iun the range from about 15 to about 45 points are preferably used. The expressions "free acid" and "total acid" and methods for determining them are explained below. The values for fine acid are preferably between about 1.5 and about 3.5 and in particular between about 2.0 and about 3.0 points. The concentration of total acid is preferably in the range from about 25 to about 35 points.
The expressions "free acid" and "total acid" are generally known in the phosphansing field.
They are deternlinod by titrating the acid bath sample with 0 _ 1 normal caustic soda solution and det~xmaning how much is consumed. The amount consumed in ml is quoted as the numerical points value. 1-Ierein, the points value for free acid is tb~e number of ml of O.1N
3o caustic soda solution consumed in order to achieve pH 4_0 in 10 ml of bath solution which has been diluted to 50 ml using fully deionised water. rn the same way, the points value fox total 6 t /6 3Jtfd = D I .L 'IfltIN3M JCA'I I 00 A3SttMS - W0213 ZE ° 0 I 00-6Z-Jfltt _._.,, _ 9 _ acid is the number of mI consumed in order to achieve pH 8.2.
The temperature of the phosphatising solution in the present process is preferably in the range from about 50 to about 70°C and in particular is between 53 aztd 65°C.
s In the process according to the present invention, the steel strip which has been galvanised on one face is contacted with the phosphatising solution for a period in the range hco~txt about 2 to about 30 seconds by spraying the phosphatising solution onto the galvanised steel ship or by immersing the galvanised steel strip in the phosphatising solution. Spray treatment is a io simpler procedure and is thus preferred. 'Treatment times between 3 and 15 seconds axe particularly preferred. After the desired treatment tiucne, the phosphatising solution is rinsed off the galvanised steel strip using water.
The process according to the present invention is preferably adjusted so that crystalline zinc is phosphate layers having weights per unit area in the zange 1 to 2 g/m2 are produced on the galvanised face of the steel strip which has been galvanised on one face.
Before applying the phosphatising solution, the metal surface must be fully water-wettable.
This is generally the case with a continuously operating conveyer belt system.
However, if a o the surface of the strip has been oiled, this oil must be removed using an appxopxi4ate cleanser prior to phosphatising. Processes for this axe laaown in the industry.
Activation using activating agents lmown from the prior art is generally performed before phosphatising.
Solutions or suspensions which contain titanium phosphate and sodium phosphate are generally used. Use of the present phosphatising process follows activation, alxl phosphatising a s may advantageously be followed by a passivating post-rinsing procedure.
Intermediate water rinsing is generally performed between the phosphatising and passivatiztg post-rinsing procedures. Chromac acid-~ontain~ing treamnent baths are widely used for passivating post-rinsiuag. However, for reasons of occupational health and safety and in order to protect the environment, and also for waste disposal reasons, there is the tendency to replace these a o chromium-containing passivating baths with chromium-free ueatment baths.
Purely inorganic bath solutions, in particular those based on hexafluorozirconates, or organic-reactive bath 6I /0I 30ttd ° O I .L'IIlttN3'~.l JCA'I I 00 7~39ttMS ° W02i3 ZE
° 0 L 00-6Z-Ofltf solutions, for example those based on substituted poly(vinylphenols), have been disclosed for this purpose. Furthermore, post-rinsing solutions which contain 0.001 to 10 gll of one or more of th;c following canons may be used: lithium ions, copper ions, silver ions andlor bismuth io~as.
Metal strip which has beta phosphatised according to the prcsent invention may be directly provided with an organic surface coating. However, they may also be assembled, in the initially imlacquerod state, to makc structural components such as car body pants or domestic applia3aces, by cutting, shaping and joiz~g together. The forming processes associated with zo this procedure are facilitated by the phosphate layer. If exposure of the final structural component to corrosive effects is low, for example as in the case of domestic appliances, the appliances asscrnbled from pre~hosphatised metal. zany be directly lacquezed.
If exposure to corrosive effects is more severe, as is the case, for example, in the car industry, it may be advantageous to follow assembly of the body with another phosphadsing treatment. When s s performing this subsequent phosphatising treatment, or during the cleansing procedure preceding this, inhibiting compounds (a), (b) ~ andlor (c) must be sufficiently well removed from the non-galvanised stoel face for the subsequcnt phosphatising process not to be impaired.
s o The present iutvention also relates to use of an aqueous sohltion which contains water and, with reference to the total composition, (a) 10 to 30 wt_ ~, of one or more mono- or poly-hydric alcohols having at least one carbon-carbon triple bond, (b) l .b to 4.8 wt. gfo of one or more alkyl or allcenyl nitrogen compounds having at least 5 2 s carbon atoms, and (c) 2_4 to 7_2 wt_ Wo of alkali metal iodide, as an additive to a phosphatising solution for phosphatising the galvanised face of steel which has been galvanised on one face.
Preferred examples of components (a) (b) and (c) are given above.
so The aqueous solution for use according to the present invention preferably also contains 2 to 8 6I / I I 39'a'd ° 4I .I'tf7tfN32I JiA'I I 00 JL3H'dMS = WOZi3 E~
° 0I 00-6Z-OfltY
/1.
wt_ % of one or more non-ionic surfactants, which have also been chaxacterxsed iota more detail above. The surfactant additive improves the intended object of the present invention, that is to protect from phosphatising the non-galvanised steel face on steel strip which has beezt galvanised on one face. An aqueous solution which contains, in addition to tire nozt-ionic s surfactant, a solubility promoter for this surfactant a preferably used for this purpose.
C~meue sulfonate, for example, is suitable here_ Sufficient solubility promoter is used to produce a clear surfactant solution.
'1'lte use accordiuag to the present invention proceeds in such a way that the aqueous solution zo of components (a), (b) and (c) is added in an amount between 0_ 15 and 1 vol_ 96 of the phosphatising solution. The amount added is selected so that the phosphatising solution contains components (a), (b) and (c) in the following concentration ranges:
(a) 60 io 1040 mgll of one or more mono- or poly-hydric alcohols having at least one carbon-carbon t~itple bond, is (b) 10 to 160 mgll of one or more alkyl or alkenyl nitrogen compounds having at least 5 carbon atoms, and (c) 10 to 250 mgll of an alkali metal iodide.
6I /Z I 3~tfd ' Q I .L 'I fltiN321 AA'I I ~O li3A'dMS ° W02I3 EE
° 0I 00-6Z-9(ttt E
The process according to the present invention was tested in a laboratory phosphatising unit.
Sample sheets which had been elecrrolytically galvanised on one face were activated using a s titanium phosphate-containing activating solution {Fixodine~ 950, Henkel KGa.A, batch concentration; 0.5 wt. °6) and phosphatised under the conditions given in the Table. In addition to the values given in the Table, the phosphatising bath h,ad. the following composition:
l 0 3.5 glI of zinc, 3.0 gll of manganese, 3.0 g/1 of nickel, ~7 gll of phosphate ions, 15 g/1 of nitrate ions, 15 Free acid, 2 - 2.S points Total acid, 30 - 35 points Temperantre, 58?C
Treatment time, 10 seconds (spraying).
z o These values correspond to the commercialljr used phosphatising proo~
~~,p~,Np~~
5854 (Henkel Surface Technologies).
The Table contains the following observations relating to the efficiency of the phosphatisiag process according to the present invention:
zs Z_ The e~ctent of crystal formation on the no~galvanised face II. The concentration of divalent imn ions in the phosp~si~qg solution after phosphaxising an area of 5 m2 per 1 of phosphatising solution. The lower the concentration of divalent iron ions accumulating in the bath, the more effective is inhibition of the pickling reaction on the non-galvanised face.
3 0 11~. The weight per unit area in glm2 on the non-galvanised steel face du~ri~qg subsequent phosphatisatyng using a phosphatising bath corresponding to the prior art for 6I /~ I 3JHd ° 4I .L'IflttN32t AA'I I ~O R39tfMS ° W02I3 ~~
° 0I 00-6Z-~fltf r-, _ z~ _ phosphatising car bodies (GRANODZNE~ SP 2500, Henkel Surface Technologies).
This subsequcnt phosphatisia~g process was performed at a temperature of SS°C fox a pexiod of 120 seconds.
s During this test of the phosphatasi~g process according to the present invention, indcpe~deotly of adding componenLS (a), (b) and (c), a sealed Layer of zinc phosphate crystals having a size in the range from 3 to Spm and a weight per unit area of 1.3 to 1.4 g/xn2 was obtained.
Phosphatising the galvanised face is thus not. affected by adding the components acting as inhibitors for the steel face.
6I /6I 3~'dd ' ~ I .L 'IflttN32t ~iA'I I ~O 1S39t(MS ° W02I3 EE
° 0I 00-6Z-~f1'd 'O
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6 L /S L 30'dd ° Q I .L 'I f1'a'Lt32I JCA'I I 00 ~i3AtYMS °
W02t3 b~ ° 0 L 00-6Z-Oflti
In the context of the present invention, all references to steel strip which has been galvanised on one face are to be understood to be to elearolytically galvanised or alloy galvanised steel strip. rf the latter, then the zinc layer also contains alloying constitiuents, such as iron, nickel az~cUor aluxninuzzt.
i ~ Processes for phosphatising surfaces of iron, steel, zinc and alloys thereof and of aluminum and alloys thereof have long been known in the prior art. Phosphatising of the surfaces mentioned is used to increase the strength of adhesion of lacquers and to improve the corrosion protective properties. Phosphatising is performed by immersion of the metal surfaces in phosphatising solutions or by spraying the metal surfaces with phosphatising 2 o solutions. Combined processes have also been disclosed, Either shaped metal parts, such as car bodies, or metal strips in high-speed conveyer belt systems may be phosphatised. The present invention is concerned with strip phosphatising of the latter type. Strip phosphatising differs from part phosphatising in that, due to the high Zs conveyer belt spends, the phosphatisz~g process, i.e. the deposition of a sealed metal phosphate layer, has to take place within a short time-span of, for example, about 2 to about 20 seconds.
Processes for phosphatising metal strips, in particular electrolytically or hot dip galvanised a o steel strips have been disclosed in the prior art. For example, WO
91/02829 describes a process for phosphatisxz~g electxolytically and/or hot dip galvanised steel strip by short-term 6I /Z 39t1d W I L'IfItiN321 RA'I I ~O A3Z3tfMS ° LI02I3 0E ° 0 i 00-6Z-~fltf ,2_ treatment using acid phosphatising solutions which contain, iu addition to zinc and phosphate ions, manganese and nickel rations and anions of oxygen.~ontaining acids having an.
accelerator effect- The last mentioned component is understood to be, in particular, nitrate ions. Db~-.A,-35 37 108 also describes a process for phosphatising electrolytically galvanised s steel strips by treamnent using acid phosphadsiu~g solutions which contain, in addition to z~c, manganese and phosphate ions, other metal rations, such as nickel ions az~dlor anions of o~cygen~ontaining acids having an accelerator effort, in particular zutrate ions. The conccntration of zinc rations is then within the relatively Iow range of 0.1 to 0.8 gll.
~o ~7~A-197 40 953 describes a process for phosphatising steel strip, or steel stxip which has been galvanised or alloy galvanised on oz~e face or on both faces, by spraying with or imumersiuc~g iux, for a period in the range from 2 to 20 seconds, an acid phosphatsing solution which contains zinc, magnesium and manganese at a temperature in the range 50 to 70°C, characterised in that the phosphatising solution contains no nitrate ions and that it contains:
is 1 to 4 g/1 of zinc ions, 1.2 to 4 gll of manganese ions, 1 ro 4 gll of magnesium ions, to 30 gll of phosphate ions, 0.1 to 3 g/1 of hydroxylamine in the free, ionic or bound form, 2 o with a concentration of free acid in the range from 0.4 to 4 points and a concentration of total acid in the range from 15 to 45 points.
If nickel ions are also added to zino- and manganese~ontaining phosphatising solutions, then so-called "trication" phosphatising solutions arc obtained.
When phosphatising steel strip which has been galvanised on one face, it is generally desired tb~at only the galvanised face be phosphatised, while the non-galvanised face is intended to remain uncaaxed_ The steps taken to achieve this objective, however, should not passivate the non-galvanised face so complctely that, after shaping and joining together componenxs from 3 o the steel strip and cleansing the assembled part, subsequent part phosplaatising is prevented.
6 i /~ 3~'dd ' 4 I .L 'IfltiN32i Jil1'I I ~O 7C3AtfMS ° W02t3 0~
° 0 L 00-6Z-~Ittt _3_ The prior art discloses, for example, adding organic acids (acetic or tartaric acid) or amines (urea) to the phosphatisittg solution for this purpose. However, such use of an additive is associated with the disadvantage that the weight per anal area of the phosphatising layer on the zinc face, in particular during prolonged production, drops below the required value.
s Furthermore, it is known that the phosphatising solution should have a comparatively low pH, and thus a comparatively high free acid value, in order to avoid phosphatising the steel face of steel strip which has been galvanised on one face. However, this type of phosphatising solution exerts a high pickling effect on the zinc face, so the phosphatising solution becomes io greatly enriched with zinc ions. There is then the risk that the zinc concentration reaches the solubility limit for zinc phosphate and zinc phosphate is deposited on the steel face.
This disadvantage has resulted iua large producers of phosphatised steel strip which is galvanised on one face changing over to physical methods for preventing the non-galvanised 1 s steel face coming into contact at all with the phosphatisiug solution. The mechanical covering procedures required for this are complicated and make the produaron moot much more costly.
Attempts to inhibit phosphatising of the non-galvanised steel face by adding pickling inhibitors have hitherto been unsuccessful. These types of additives have hitherto led to the a a phosphatising reaction on the galvanised face, which is very sensitive to changes in operating pax~ete~rs, tal~al~g place either unsatisfactorily or not at all.
Therefore, there is a need for a process for phosphatising only the galvanised face of steel strip which has been galvanised on one face; which does not require mechanical covering 2 s procedures, bus which, nevertheless, does not have the disadvantages mentioned above.
The present invention relates to a process for phosphatising steel strip which has been galvanised on one face using a phosphatising solution which contains 1 to 6 gll of zinc ions and 10 to 3Q gll of phosphate io:as, characterised in that the phosphatising solution also 3 o contains one or more of the components (a) to (c):
(a) 60 to 1000 zngll of one or more mono- or poly-hydric alcohols having at least one 6I /b 30'dd ' Q I 3. 'If1'dN32i 7~A'I I 00 A3HttMS ° W02i3 0~ °
0I 00-6Z-9(1tf carbon-carbon triple bond, (b) 10 to 160 mgJl of one or more alkyl or allcenyl niuogen compounds having at least 5 carbon atoms, {c) 10 to 250 mgll of an alkali metal iodide.
In a preferred embodiment, the process is characterised in that the phosphatising solution contains one or more of coaznponents (a) to (c) in the following concentrations:
(a) 200 to 400 mgll of one or more mono- or poly-ltydric alcohols having at least one carbo~a-carbon triple bond, (b) 30 to 60 mgll of one or more alkyl or alkenyl nitrogen compounds having at least 5 carbon atotxts, (c) 40 to 100 mgll of an alkali metal iodide.
The individual components (a), (b) and (c) hinder or inhibit the pickling rcaction of the s s phospha~isiuag solution with the non-galvanised steel surface so that this is not phosphatised, or is phosphatised only very slightly. The picltling reaction at the galvanised surface, howevez, is not hindered so that the desired, sealed, crystalline, zinc phosphate layer is built up to the desired weight per unit area on this face_ 2 o The expression wcight per unit area is frequently used in the field of phosphatising metal surfaces. The expressions "weight deposited per unit area" or "arearspecific weight" axe also used instead of "weight per unit area", or more specifically "weight of phosphate layer per unit area" . These expressions are to be understood to mean the weight of metal phosphate layer produced on the metal surface by the phosphatising process with reference to one unit of 2s axea. It is generally given in glm~. It may be determined by weighing a phosphatised metal sheet having a known surface area, dissolving the metal phosphate layer and weighing the metal sheet agaiti_ The weight of metal phosphate layer with reference to one m~2 may be calculated from the weight difference determined, by taking account of the sL>rface area of the metal sheet. A 0.5 wt. k strength chromic acid solution, for example, may be used to dissolve 3 o the metal phosphate layer. The procedure for determining the weight per unit area is described in more detail in Cue. standard DIN 50942.
6 L /S 3J'dd ° O I .L 'IfltiN321 JCA'I I JO A3AttMS ~ WO?.13 L E
° 0 L 00-6Z-Ofl'd -S-The weighs per unit area is an essential paramecez for checking phosphatising results. Weights per unit axes within a variety of ranges may be required, depending on the intextded use for the phosphatised metal parts. The present invention is preferentially concerned with metal s sheeting which is to be used in the car manufacturing industry. In this case, weights per unit area of more than 0.8 glm2, but at most about 4 g/m2, are required _ The weight per unit area should preferably be below 3 g/m2 and in particular about 1 to about 2 g/mT.
Each of the components (a), (b) and (c) boosts the effect of the others as an inhibitor of the to pickling reaction at the non-galvanised steel face. Thus, phosphatisiutg of the ttonBgalvanised steel faoe is inhibited more effectively and more reliably if the phosphatising solution contains at least two of components (a), (b) and (c). The phosphatising solution preferably contains all three co~onents (a), (b) and (c).
Co~oo~ponent (a) may be selected, for example, from the a,cetylenically unsaturated diols. A
preferred example such is but-2-yne-1,4-dxol.
Alkyl or alkenyi amines, for example, are suitable for use as component (b).
Furthermore, alkyl- or alkenyl-substituted l~itrogen-containing heterocyclic compounds, in particular Zo unsaxurated heterocyclic compounds are especially suitable. These may have, for example, 1, 2 or 3 nitrogen atoms in the heterocyclic rind. One alkyl group is preferably in a position which is located as far as possible from the nitrogen atom(s). Particularly preferred examples are mono- and di-alkylpyridines having 1 to 22, preferably 1 to 12, carbon atoms in each alkyl group, wherein one alkyl group is preferably in the 4-position with respect to the 2 s nitrogen atom. These alkylated pyridines are generally available as a technical grade mixture.
Due to the fact that it is industrially readily available, potassium iodide is preferably used as component (c).
s o rn addition to components (a), (b) andlor (c), the phosphatising solution may contain up to 250 mg/1, preferably about 40 to 80 mgll, of a non ionic surfactant. In combination with at 6I /9 3~'dd ' 4 I .L 'Ifl'dN321 ~A'I I ~O ~i36'dMS ° Id02i3 L E
° 0I 00-6Z-~f1'd least one of co~oaponents (a), (b) andlor (c), this surfactant supports the inhibiting effect on the non-galvanised steel face. Ethoxylated, propoxylated amilor ethoxylated/propoxylated alcohols having 10 ro 18 carbon atoms in the alkyl chain are preferably used as non-ionic surfactants_ In addition to the ~o~on-ionic surfactant, the phosphatising solution may contain a s solubility promoter for the surfactant. This may be present at a concentration of up to 750 mgll, preferably about 150 to about 300 mgll. Cumene sulfonate, for example, is suitable for use as a solubility promoter.
Apart from the components (a), (b) and/or (c) required for the inhibiting effect on the non-~ o galvanised steel fact, the phosphatising solution may contain other components commonly used in the prior art which either become incorporated into the phosphate layer or, due to the accelerator effect thereof, promote formation of the layer. Accordingly, the phosphatising solutioa preferably also contains one or more of the following canons:
1 to 5 gll of manganese ions, i s 1 to 4 gll of magnesium ions, 0.8 to 4.5 gIl of nickel ions, 0.01 to 0.2 g/1 of copper ions.
In addition to the layer-forming rations mentioned, the phosphansing solutions contazn alkali a o metal andlor ammonium canons in order to adjust the free acid value to withixt the required range.
Conventionally, phosphatising baths also contain so-called accelerators. These are substances which react with the hydrogen being produced during the pickling reaction at the metal 2 5 SUrfaCE. They therefore inhibit so-called polarisation of the metal surface caused by a coating of hydrogen. The accelerators thus improve uniform coating of the metal surface with finely divided phosphate crystals, which generally have a size between about l and about 10 ?m.
Phosphatising solutions which contain the accelerator are also preferably used in the process according to the present invention. Accordingly, the phosphatising solutions used for the 3o present process also contain, as accelerator, once ox more of the following components:
0_5 to 30 gll of nitrate ions, 6I /G 30tfd W I .L'IflttN32i JCA'I I 00 JC3A'dMS ° W02I3 i E = 0 i 00-6Z-Ofltt y o.os to 0.2 g!1 of niuite ions, 0.03 to 0_2 gll of hydrogen peroxide in the fret or bound form, 0.05 to O.b gll of permanganate ions.
Alternatively, or in the event thaw odtrate ions are used, in addition to these, a phosphatising solution which also conrai~ns, as accelerator, about 0.1 to about 3 gll of hydroxylamine in the ft~ee, ionic or bound form is preferably used for the process according to the presem invention.
so Hydroxylamine may be used as the free base, as a compound which releases hydroxylamine, such as hydroxylamine complexes or ketoximes or aldoximes, ox in the form of hydroxylaminonium~ salts_ If free hydroxylamine is added to the phosphatising bath or a phosphatising bath concentrate, then this is largely present as the hydroxylammonium carton due to the acidic character of these solutions. If it is used in the form of a hydroxylaztrtnonium is salt, rhea sulfates and phosphates ace particularly suitable. In the case of phosphates, acid salts are preferred due to the higher solubility thereof. In order, on the one hand, to take account of economic aspects and, on the other hand, not to contami~oate the phosphatising baths too much with sulfate ions, it znay be advantageous to use a combination of free hydroxylamine and hydroxylammonium sulfate. T~ydroxylamine or compounds thereof are 2 o added to the phosphatasiuag solution in an amount such that the calculated ooticentration of free hydroxylamine is betwoen about 0.1 and about 3 gll, prcferably between about 0. is and about 1 gll.
When quotiztg dara relating to the concentration of phosphate, the entire amount of a s phosphorus in the phosphatising bath is regarded as being present in the form of phosphate ions, PO,~_ Therefore, when calculat~g or determining the concentration, the known fact that, at the acidic pHs prevailing in phosphatising baths, in the range from about 2.0 to about 3.b, only a very small proportion of the phosphate is actually in the form of triply chargcd anions, is ignored. ~tather, it would be expected, at these pHs, that the phosphate is probably 3 o present as a singly chaxged dihydrogen phosphate anion, together with undissociated phosphoric acid and small amounts of doubly charged hydrogen phosphate anions.
6 L /8 3Jtfd ' Q I .L 'IfltlN32l xl1'I I ~O ~39tfMS = W0213 ZE = 0 L 00-6Z-9(ltf _$_ The presence of fluoride ions may be advantageous for uniform production of the layer.
Accordingly, there is a further embodiment of the present invention comprising using phosphatising solutions which contain up to about 0.8 gll of fluoride in the free or cort>plexed s form. The preferred fluoride concentrations for phosphatising electrolytically galvanised steel strip, for example, is in the range from 0.0 to about 0.5 g/l, in parnicular in the range from about 0.1 to about 0.2 gll.
The phosphatising solutions are generally prepared in the way which is familiar to a person io skilled in the art. Phosphate is introduced to the phosphaiising solutions, for example, in the form of phosphoric acid. The canons are added to the phosphoric acid in the form o~ acid-soluble compounds, such as carbonates, oxides or hydro~cides, so that the acid is partly neutralised. Further neutralisation to reach the desired ply range is preferably performed by adding sodium hydroxide ox sodium carbonate. Sod~imm or potassium fluoride, for example, is are suitable as sources of free fluoride anions. Tetrafluoroborate or hexafluorosilicate, for example, may be used as complex fluoz~des_ Its, order to produce phosphate layers having a weight per unit area in the desired range, phosphatising solutions which have a concentration of free acid in the range from about 0.4 to s o about 4 points and a concernb~atxolt of total acid iun the range from about 15 to about 45 points are preferably used. The expressions "free acid" and "total acid" and methods for determining them are explained below. The values for fine acid are preferably between about 1.5 and about 3.5 and in particular between about 2.0 and about 3.0 points. The concentration of total acid is preferably in the range from about 25 to about 35 points.
The expressions "free acid" and "total acid" are generally known in the phosphansing field.
They are deternlinod by titrating the acid bath sample with 0 _ 1 normal caustic soda solution and det~xmaning how much is consumed. The amount consumed in ml is quoted as the numerical points value. 1-Ierein, the points value for free acid is tb~e number of ml of O.1N
3o caustic soda solution consumed in order to achieve pH 4_0 in 10 ml of bath solution which has been diluted to 50 ml using fully deionised water. rn the same way, the points value fox total 6 t /6 3Jtfd = D I .L 'IfltIN3M JCA'I I 00 A3SttMS - W0213 ZE ° 0 I 00-6Z-Jfltt _._.,, _ 9 _ acid is the number of mI consumed in order to achieve pH 8.2.
The temperature of the phosphatising solution in the present process is preferably in the range from about 50 to about 70°C and in particular is between 53 aztd 65°C.
s In the process according to the present invention, the steel strip which has been galvanised on one face is contacted with the phosphatising solution for a period in the range hco~txt about 2 to about 30 seconds by spraying the phosphatising solution onto the galvanised steel ship or by immersing the galvanised steel strip in the phosphatising solution. Spray treatment is a io simpler procedure and is thus preferred. 'Treatment times between 3 and 15 seconds axe particularly preferred. After the desired treatment tiucne, the phosphatising solution is rinsed off the galvanised steel strip using water.
The process according to the present invention is preferably adjusted so that crystalline zinc is phosphate layers having weights per unit area in the zange 1 to 2 g/m2 are produced on the galvanised face of the steel strip which has been galvanised on one face.
Before applying the phosphatising solution, the metal surface must be fully water-wettable.
This is generally the case with a continuously operating conveyer belt system.
However, if a o the surface of the strip has been oiled, this oil must be removed using an appxopxi4ate cleanser prior to phosphatising. Processes for this axe laaown in the industry.
Activation using activating agents lmown from the prior art is generally performed before phosphatising.
Solutions or suspensions which contain titanium phosphate and sodium phosphate are generally used. Use of the present phosphatising process follows activation, alxl phosphatising a s may advantageously be followed by a passivating post-rinsing procedure.
Intermediate water rinsing is generally performed between the phosphatising and passivatiztg post-rinsing procedures. Chromac acid-~ontain~ing treamnent baths are widely used for passivating post-rinsiuag. However, for reasons of occupational health and safety and in order to protect the environment, and also for waste disposal reasons, there is the tendency to replace these a o chromium-containing passivating baths with chromium-free ueatment baths.
Purely inorganic bath solutions, in particular those based on hexafluorozirconates, or organic-reactive bath 6I /0I 30ttd ° O I .L'IIlttN3'~.l JCA'I I 00 7~39ttMS ° W02i3 ZE
° 0 L 00-6Z-Ofltf solutions, for example those based on substituted poly(vinylphenols), have been disclosed for this purpose. Furthermore, post-rinsing solutions which contain 0.001 to 10 gll of one or more of th;c following canons may be used: lithium ions, copper ions, silver ions andlor bismuth io~as.
Metal strip which has beta phosphatised according to the prcsent invention may be directly provided with an organic surface coating. However, they may also be assembled, in the initially imlacquerod state, to makc structural components such as car body pants or domestic applia3aces, by cutting, shaping and joiz~g together. The forming processes associated with zo this procedure are facilitated by the phosphate layer. If exposure of the final structural component to corrosive effects is low, for example as in the case of domestic appliances, the appliances asscrnbled from pre~hosphatised metal. zany be directly lacquezed.
If exposure to corrosive effects is more severe, as is the case, for example, in the car industry, it may be advantageous to follow assembly of the body with another phosphadsing treatment. When s s performing this subsequent phosphatising treatment, or during the cleansing procedure preceding this, inhibiting compounds (a), (b) ~ andlor (c) must be sufficiently well removed from the non-galvanised stoel face for the subsequcnt phosphatising process not to be impaired.
s o The present iutvention also relates to use of an aqueous sohltion which contains water and, with reference to the total composition, (a) 10 to 30 wt_ ~, of one or more mono- or poly-hydric alcohols having at least one carbon-carbon triple bond, (b) l .b to 4.8 wt. gfo of one or more alkyl or allcenyl nitrogen compounds having at least 5 2 s carbon atoms, and (c) 2_4 to 7_2 wt_ Wo of alkali metal iodide, as an additive to a phosphatising solution for phosphatising the galvanised face of steel which has been galvanised on one face.
Preferred examples of components (a) (b) and (c) are given above.
so The aqueous solution for use according to the present invention preferably also contains 2 to 8 6I / I I 39'a'd ° 4I .I'tf7tfN32I JiA'I I 00 JL3H'dMS = WOZi3 E~
° 0I 00-6Z-OfltY
/1.
wt_ % of one or more non-ionic surfactants, which have also been chaxacterxsed iota more detail above. The surfactant additive improves the intended object of the present invention, that is to protect from phosphatising the non-galvanised steel face on steel strip which has beezt galvanised on one face. An aqueous solution which contains, in addition to tire nozt-ionic s surfactant, a solubility promoter for this surfactant a preferably used for this purpose.
C~meue sulfonate, for example, is suitable here_ Sufficient solubility promoter is used to produce a clear surfactant solution.
'1'lte use accordiuag to the present invention proceeds in such a way that the aqueous solution zo of components (a), (b) and (c) is added in an amount between 0_ 15 and 1 vol_ 96 of the phosphatising solution. The amount added is selected so that the phosphatising solution contains components (a), (b) and (c) in the following concentration ranges:
(a) 60 io 1040 mgll of one or more mono- or poly-hydric alcohols having at least one carbon-carbon t~itple bond, is (b) 10 to 160 mgll of one or more alkyl or alkenyl nitrogen compounds having at least 5 carbon atoms, and (c) 10 to 250 mgll of an alkali metal iodide.
6I /Z I 3~tfd ' Q I .L 'I fltiN321 AA'I I ~O li3A'dMS ° W02I3 EE
° 0I 00-6Z-9(ttt E
The process according to the present invention was tested in a laboratory phosphatising unit.
Sample sheets which had been elecrrolytically galvanised on one face were activated using a s titanium phosphate-containing activating solution {Fixodine~ 950, Henkel KGa.A, batch concentration; 0.5 wt. °6) and phosphatised under the conditions given in the Table. In addition to the values given in the Table, the phosphatising bath h,ad. the following composition:
l 0 3.5 glI of zinc, 3.0 gll of manganese, 3.0 g/1 of nickel, ~7 gll of phosphate ions, 15 g/1 of nitrate ions, 15 Free acid, 2 - 2.S points Total acid, 30 - 35 points Temperantre, 58?C
Treatment time, 10 seconds (spraying).
z o These values correspond to the commercialljr used phosphatising proo~
~~,p~,Np~~
5854 (Henkel Surface Technologies).
The Table contains the following observations relating to the efficiency of the phosphatisiag process according to the present invention:
zs Z_ The e~ctent of crystal formation on the no~galvanised face II. The concentration of divalent imn ions in the phosp~si~qg solution after phosphaxising an area of 5 m2 per 1 of phosphatising solution. The lower the concentration of divalent iron ions accumulating in the bath, the more effective is inhibition of the pickling reaction on the non-galvanised face.
3 0 11~. The weight per unit area in glm2 on the non-galvanised steel face du~ri~qg subsequent phosphatisatyng using a phosphatising bath corresponding to the prior art for 6I /~ I 3JHd ° 4I .L'IflttN32t AA'I I ~O R39tfMS ° W02I3 ~~
° 0I 00-6Z-~fltf r-, _ z~ _ phosphatising car bodies (GRANODZNE~ SP 2500, Henkel Surface Technologies).
This subsequcnt phosphatisia~g process was performed at a temperature of SS°C fox a pexiod of 120 seconds.
s During this test of the phosphatasi~g process according to the present invention, indcpe~deotly of adding componenLS (a), (b) and (c), a sealed Layer of zinc phosphate crystals having a size in the range from 3 to Spm and a weight per unit area of 1.3 to 1.4 g/xn2 was obtained.
Phosphatising the galvanised face is thus not. affected by adding the components acting as inhibitors for the steel face.
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W02t3 b~ ° 0 L 00-6Z-Oflti
Claims (14)
1. A process for phosphatising the galvanised face of steel strip which has beta galvanised on one face using a phosphatising solution which contains 1 to 6 g/l of zinc ions and 10 to 30 g/l of phosphate ions, characterised in that the phosphatising solution also contains one or more of the components (a) to (c):
(a) 60 to 1000 mg/l of one or more mono- or poly-hydric alcohols having at least one carbon-carbon triple bond, (b) 10 to 160 mg/l of one or more alkyl or alkenyl nitrogen compounds having at least 5 carbon atoms, (c) 10 to 250 mg/l of an alkali metal iodide.
(a) 60 to 1000 mg/l of one or more mono- or poly-hydric alcohols having at least one carbon-carbon triple bond, (b) 10 to 160 mg/l of one or more alkyl or alkenyl nitrogen compounds having at least 5 carbon atoms, (c) 10 to 250 mg/l of an alkali metal iodide.
2. A process as claimed in claim 1 wherein the phosphatising solution contains one or more of components (a) to (c):
(a) 200 to 400 mg/1 of one or more mono- or poly-hydric alcohols having at least one carbon-carbon triple bond, (b) 30 to 60 mg/l of one or more alkyl or alkenyl nitrogen compounds having at least 5 carbon atoms, (c) 40 to 100 mg/l of an alkali metal iodide.
(a) 200 to 400 mg/1 of one or more mono- or poly-hydric alcohols having at least one carbon-carbon triple bond, (b) 30 to 60 mg/l of one or more alkyl or alkenyl nitrogen compounds having at least 5 carbon atoms, (c) 40 to 100 mg/l of an alkali metal iodide.
3. A process as claimed in one or both of claims 1 and 2 wherein the phosphatising solution contains at least two of components (a), (b) and (c).
4. A process as claimed in claim 3 wherein the phosphatising solution contains all three components (a), (b) and (c).
5. A process as claimed in one or more of claims 1 to 4 wherein the phosphatising solution also contains one or more of the following canons:
1 to 5 g/l of manganese ions, 1 to 4 g/l of magnesium ions, 0. 8 to 4.5 g/1 of nickel ions, 0.01 to 0.2 g/l of copper ions.
1 to 5 g/l of manganese ions, 1 to 4 g/l of magnesium ions, 0. 8 to 4.5 g/1 of nickel ions, 0.01 to 0.2 g/l of copper ions.
6. A process as claimed in one or more of claims 1 to 5 wherein the phosphatising solution also contains one or more of the following components as an accelerator:
0.5 to 30 g/l of nitrate ions, 0.05 to 0.2 g/l of nitrite ions, 0.03 to 0.2 g/l of hydrogen peroxide in the free or bound form, 0.05 to 0.6 g/l of permanganate ions.
0.5 to 30 g/l of nitrate ions, 0.05 to 0.2 g/l of nitrite ions, 0.03 to 0.2 g/l of hydrogen peroxide in the free or bound form, 0.05 to 0.6 g/l of permanganate ions.
7. A process as claimed in one or more of claims 1 to 5 whereon the phosphatising solution also contains 0.1 to 3 g/l of hydroxylamine, in free, ionic or bound foam, as an accelerator.
8. A process as claimed in one or more of claims 1 to 7 wherein the phosphatising solution has a concentration of free acid in the range 0.4 to 4 points and a concentration of total acid in the range 15 to 45 points.
9. A process as claimed in one or more of claims 1 to 8 wherein the phosphatising solution has a temperature in the range 50 to 70°C.
10. A process as claimed in ooze or more of claims 1 to 9 wherein the phosphatising solution is contacted, by spraying or by immersion, with the steel strip which has been galvanised on one face for a period of 2 to 30 seconds.
11. A process as claimed in one or more of claims 1 to 10 wherein the phosphate layer on the galvanised face of the steel strip which has been galvanised on one face is produced having a weight per unit area in the range 1 to 2 g/m2.
12. The use of an aqueous solution which contains water and, with reference to the total composition, (a) 10 to 30 wt. % of one or more mono- or poly-hydric alcohols having at least one carbon-carbon triple bond, (b) 1.6 to 4.8 wt. % of one or more alkyl or alkenyl nitrogen compounds having at least 5 carbon atoms, and (c) 2.4 to 7.2 wt. % of an alkali metal iodide,as an additive to a phosphatising solution for phosphatising the galvanised face of steel which has been galvanised on one face and which contains 1 to 6 g/l of zinc ions and 10 to 30 g/l of phosphate ions.
13. A use as claimed in claim 12 wherein the aqueous solution also contains 2 to 8 wt. %
of one or more non-ionic surfactants.
of one or more non-ionic surfactants.
14. A use as claimed in one or both of claims 12 and 13 wherein the aqueous solution is added to the phosphatising solution in an amount between 0.15 and 1 vol. %.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19756735.5 | 1997-12-19 | ||
| DE1997156735 DE19756735A1 (en) | 1997-12-19 | 1997-12-19 | Phosphating one-side galvanized steel strip on the galvanized side only |
| PCT/EP1998/008047 WO1999032687A1 (en) | 1997-12-19 | 1998-12-10 | Phosphatization of a single-face galvanized steel strip |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2315778A1 true CA2315778A1 (en) | 1999-07-01 |
Family
ID=7852655
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002315778A Abandoned CA2315778A1 (en) | 1997-12-19 | 1998-12-10 | Phosphatization of a single-face galvanized steel strip |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP1042533A1 (en) |
| AU (1) | AU2269999A (en) |
| CA (1) | CA2315778A1 (en) |
| DE (1) | DE19756735A1 (en) |
| WO (1) | WO1999032687A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000008224A2 (en) * | 1998-07-21 | 2000-02-17 | Brent International Plc | Nickel-zinc phosphate conversion coatings and process for making the same |
| DE10127513A1 (en) * | 2001-06-06 | 2002-12-12 | Creavis Tech & Innovation Gmbh | Antimicrobial non-woven fabric containing antimicrobial polymer, used e.g. in filters |
| DE102008004728A1 (en) | 2008-01-16 | 2009-07-23 | Henkel Ag & Co. Kgaa | Phosphated steel sheet and method for producing such a sheet |
| WO2017202891A1 (en) * | 2016-05-25 | 2017-11-30 | Chemetall Gmbh | Process for corrosion-protecting phosphatization of a metallic surface with reduced pickling erosion |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3773465A (en) * | 1970-10-28 | 1973-11-20 | Halliburton Co | Inhibited treating acid |
| US4233088A (en) * | 1979-03-29 | 1980-11-11 | International Lead Zinc Research Organization, Inc. | Phosphatization of steel surfaces and metal-coated surfaces |
| JPS6220879A (en) * | 1985-07-18 | 1987-01-29 | Nippon Kokan Kk <Nkk> | One-face chemical conversion treatment of steel plate by galvanizing device |
| DE4228470A1 (en) * | 1992-08-27 | 1994-03-03 | Henkel Kgaa | Process for phosphating steel strips galvanized on one side |
| DE4241134A1 (en) * | 1992-12-07 | 1994-06-09 | Henkel Kgaa | Process for phosphating metal surfaces |
| DE4326388A1 (en) * | 1993-08-06 | 1995-02-09 | Metallgesellschaft Ag | Process for the phosphating treatment of one-sided galvanized steel strip |
| DE4341041A1 (en) * | 1993-12-02 | 1995-06-08 | Henkel Kgaa | Phosphating solns contg hydroxylamine and/or nitrobenzene sulphonate |
| JP3348856B2 (en) * | 1993-09-06 | 2002-11-20 | 日本パーカライジング株式会社 | Nickel free phosphating method |
-
1997
- 1997-12-19 DE DE1997156735 patent/DE19756735A1/en not_active Withdrawn
-
1998
- 1998-12-10 WO PCT/EP1998/008047 patent/WO1999032687A1/en not_active Application Discontinuation
- 1998-12-10 CA CA002315778A patent/CA2315778A1/en not_active Abandoned
- 1998-12-10 AU AU22699/99A patent/AU2269999A/en not_active Abandoned
- 1998-12-10 EP EP98966286A patent/EP1042533A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| AU2269999A (en) | 1999-07-12 |
| EP1042533A1 (en) | 2000-10-11 |
| DE19756735A1 (en) | 1999-06-24 |
| WO1999032687A1 (en) | 1999-07-01 |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Discontinued |