CA2088342C - Concentrate for activating and refining bath and bath obtained from this concentrate - Google Patents
Concentrate for activating and refining bath and bath obtained from this concentrate Download PDFInfo
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- CA2088342C CA2088342C CA002088342A CA2088342A CA2088342C CA 2088342 C CA2088342 C CA 2088342C CA 002088342 A CA002088342 A CA 002088342A CA 2088342 A CA2088342 A CA 2088342A CA 2088342 C CA2088342 C CA 2088342C
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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
- C23C22/78—Pretreatment of the material to be coated
- C23C22/80—Pretreatment of the material to be coated with solutions containing titanium or zirconium compounds
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Abstract
Concentrate for activating and refining bath employed in processes of zinc phosphatization, characterized by the fact that it is based on an aqueous dispersion containing from 2 to 20% by weight of Jernstedt salts, the concentration of titanium in the dispersion consequently being from 140 to 10,000 ppm of Ti, this dispersion in addition containing:
- a proportion of from 0.2 to 8% by weight of at least one dispersing or sequestering agent and - a proportion of from 0.05 to 7% by weight of at least one thickener based on polysaccharide.
- a proportion of from 0.2 to 8% by weight of at least one dispersing or sequestering agent and - a proportion of from 0.05 to 7% by weight of at least one thickener based on polysaccharide.
Description
CONCENTRATE FOR ACTIVATING AND REFINING BATH
AND BATH OBTAINED FFtQ~ ~IIS CONCENTRATE
The invention has as its object a liquid concen-trate for providing, by dilution with a suitable quantity of water, an activating and refining bath containing titanium for use in a process of crystalline zinc phospha-tization.
It also relates to the activating and refining bath obtained from the said concentrate.
Processes for crystalline zinc phosphatization ors substrates of steel, aluminium, galvanized steel or galva-nized steel alloyed with nickel, cobalt, aluminium or iron are widely used for protecting the said substrates against corrosion or for lowering the coefficients of friction when these substrates are subjected to cold working.
They generally comprise:
- one ou more stages of alkaline degreasing, - one or more stages of rinsing with runnning tap water, - a stage of activation and refining, - a stage of zinc phosphatization properly speaking, - one or more stages of rinsing with water, - preferably a stage of final passivating rinsing, in particular with salts of hexavalent chromium or of mixtures of hexavalent chromium and trivalent chromium.
Before the phosphatization treatment properly speaking, the stage, of activation is capable of producing chemical heterogeneities on the cleaned metallic surface, thus promoting germination of the layer of crystalline phosphates and enabling a fine and dense coating to be formed. Such a coating is desired - either for improving the adherence of a layer of paint which may subsequently be applied and improving the resistance to corrosion in the event of damage to the layer or skin of paint, - or for depositing firmly adhering crystals on the metal-lic substrate in the context of a cold forming treat-ment.
The stages in particu7Lar of activation and phospha-tization are generally carried out by spraying a suitable bath on the substrate, by steeping the substrate in the bath or by successive spraying and steeping.
The stage of activation may possibly be carried out at the same time as the stage of degreasing by mixing the aqueous degreasing solution with a concentrated activating product or by preparing a degreasing-activating bath from a concentrated degreasing composition containing an acti-vating concentrate. Such simultaneity of the two stages is practised in installations for the treatment of surfaces in which only spraying is carried out at the stage of phosphatization. If, however, the phosphatization stage also includes a phase of immersion, fine and dense phos-phatization can only be achieved by means of an indepen-dent stage of activation.
Titanium, which is employed at the stage of activa tion and refining, constitutes 'the refining agent; the activating and refining baths are generally baths based on titanium salts and contain alkali phosphates.
It is known to prepare them from solid pulverulent concentrates generally consisting of mixtures of alkali phosphates and colloidal titanium salts known under the name of Jernstedt salts which are described, for example, in US Patent 2 456 947.
Such a Jernstedt salt may be obtained by mixing 95 parts of disodium phosphate with 5 parts of potassium fluotitanate in a sufficient quantity of water to dissolve them; polyphosphates of sodium and potassium may also be added to this mixture, in particular in a proportion of 1 to 300 parts by weight Of PZO~'-. The water is then removed from the mixture by evaporation until a pulverulent pro duct is obtained.
The sulphate, oxide or oxysulphate of titanium may be used instead of potassium fluotitanate as source of titanium.
One example of a Jernstedt salt commonly employed and marketed by the Applicant under the trademark FIXODIN~
5 consists of:
- from 0.7 to 5 ~ by weight o~ titanium expressed as titanium (IV) in the form of titanium phosphate, - from 85 to 99.3 by weight of sodium phosphate and - from 0 to 10 ~ by weight of sodium polyphosphate.
As indicated above, the known concentrates used for the preparation of the activating and refining baths are pulverulent products.
They have the following disadvantages:
- they contain water insofar as in the course of their manufacture it is not considered economical to heat them to temperatures above 110°C for complete removal of the water so that part of the water is left in the powder obtained: this frequently leads to the formation of lumps which are difficult to dissolve; the formation of these lumps is also promoted by the humidity in the workshops in which the surface treatment is carried out and by the hygroscopicity of the powder;
- they contain a not negligible proportion of fine parti ales capable of polluting the atmosphere of the place where they are employed;. further, for preparing the activating bath, the user is required to prepare an aqueous mother solution from the concentrate; this mother solution must be prepared with vigorous stirring since the Jernstedt salts are highly insoluble under such conditions of preparation;
- they must be introduced evenly and hence preferably automatically into the water of dilution at the time of preparation of the activating bath since the stage of activation induces nucleation of the subsequent phase of phosphatization; however, the apparatus for automatic introduction of powder are in many cases designed with endless screws placed under feed hoppers for the powder and these screws compress the powder and frequently cause the formation of lumps which block the operation of the said screws.
This presentation in powder form has hitherto been necessary due to the fact that once the Jernstedt salt has been introduced into water, it forms a suspension of insoluble crystals after several hours and these crystals are capable of increasing in size in the course of time, whereas it is known that only fine crystals (< 3 pm) have the desired activating effect.
It has also been proposed to employ liquid concen trates (EP-A-454 212) which are based on Jernstedt salts and which, due to their liquid nature, do not have the disadvantages due to the pulverulent nature of the solid concentrates described above.
However, although these liquid concentrates can be stored without sedimentation for three months due to the addition of thickeners, in particular polysaccharides which are well known for their multiple thickening proper-ties, they have the major disadvantage that they must contain a sufficiently high concentration of titanium so that when diluted with the normal quantity of water they will provide an effective activating bath after several months' storage, that is to say they must have a titanium content, still in a finely crystallized state, capable of conferring on the bath the required activating properties;
such a high titanium content in the concentrate has the result that an activating bath which has been prepared from this concentrate immediately after preparation of the latter or a short time thereafter and therefore before crystal growth has taken place will in turn have such a high titanium concentration that the treatment of a subs-trace with such an activating bath will result in a sur-face which is too highly activated so that at the stage of phosphatization proper the thickness of the layer will be virtually zero; this layer will therefore be a layer of passivation rather than of phosphatization.
It is thus a main object of the present invention to provide a concentrate suitable for the preparation of activating and refining baths of the type in question which do not have the disadvantages of the concentrates of the prior art.
It is to the merit of the Applicant company to have found that this object is achieved if the said concentrate is in the form of an aqueous dispersion containing from 2 to 20% by weight of Jernstedt salt, the concentration of titanium in the dispersion being therefore from 240 to 10,000 ppm of Ti, this dispersion in addition containing:
- a proportion of from 0.2 to 8% by weight of at least one dispersing or sequestering agent to be defined hereinafter and - a proportion of from 0.05 to 7% by weight of at least one thickener based on polysaccharide also defined hereinafter.
The concentrate thus constituted is stable for at least three months both physically and in its activity and can at any time, that is to say immediately after its preparation or equally well after several months' storage, provide, by dilution with the same quantity of water, an activating and refining bath having a titanium content of from 1 to 75 ppm and giving satisfactory results as re-gards activation of the treated substrate.
The invention therefore has as its object, by way of concentrate suitable for the preparation of activating and refining baths employed in zinc phosphatization pro cesses, an aqueous dispersion of Jernstedt salts contain ing from 2 to 20% by weight of these salts, which corres ponds to a concentration of Ti of from 140 to 10,000 ppm, the said dispersion containing, in addition:
- a proportion of from 0.2 to 8% by weight of at least ~~~o one dispersing or sequestering agent selected from the group comprising alkali metals or ammonium phospho-nates, alkali or ammonium salts of sequestering carbo-xylic acids, and any combination of several of these derivatives, it being understood that - the phosphonates are preferably selected from the group comprising those of - hydroxymethyl-phosphonic acid, - hydroxygropyl-phosphonic acid - 1-hydroxyethylidene-1,1-diphosphonic acid, - amino-tri(methylene-phosphonic) acid, - ethylene-diamino-tetra(methylene-phosphonic) acid and - 2-phosphono-butane-1,2,4-tricarboxylic acid and that - among the sequestering carboxylic acids, nitrilotri-acetic or NTA is preferred, - a proportion of from 0.05 to 7% by weight of at least one thickener based on polysaccharide obtained by fermentation of a nutrient medium based on a carbohy drate consisting in particular of a sugar such as glucose, sucrose, fructose, maltose, lactose or galac-tose, and/or on a source of organic and/or inorganic nitrogen consisting in particular of an alkali metal nitrate, an inorganic salt of ammonium, the caseinate of sodium and the soluble extract of corn by the action of a microorganism selected from the class of Xanthomo-nas or Sclerotia, Xanthomonas campestris or Sclerotium rolfsii being preferred.
The proportion of Jernstedt salt is preferably from 4 to 15% by weight of the liquid concentrate.
The proportion of sequestering or dispersing agent is preferably from 4 to 15% by weight of the liquid con-centrate.
The proportion of polysaccharide is preferably from 4 to 15% by weight of the liquid concentrate.
The liquid concentrate according to the invention may contain anti--freeze compounds so that it can be stored at temperatures below 0°C; the anti-freeze compound may be selected from glycol derivatives such as ethyleneglycol, propylene-glycol or high molecular weight glycols or also nitrogen derivatives such as urea.
The pH of the liquid concentrate is preferably adjusted to a value from 7 to 10 and more preferably from 7 to 9; this may be carried out by using an alkaline derivative such as soda, potash, the carbonates of alkali metals or of ammonium hydroxide, phosphates such as triso-dium or tripotassium phosphate, pyro- or tripolyphosphates of sodium or potassium and alkali or ammonium salts of carboxylic acids such as citrates.
The activating and refining bath according to the invention obtained by dilution of the said concentrate to 3-30 g/1 of water contains:
from 60 to 6000 mg/1 of Jernstedt salt, that is to say from 1 to 75 mg/1 of titanium in the form of titanium phosphate in a matrix of alkali phosphates, from 15 to 1500 mg/1 of a derivative of a sequestering carboxylic acid and/or o.f a dispers-ing phosphonic acid, from 3 to 600 mg/1 of a polysaccharide obtained by fer-mentation of a nutrient medium by a microorganism, the volume being made up to 1 litre with water.
To demonstrate the suitability of the concentrates according to the invention for providing, by a constant dilution either just after their preparation or at any time and at least during three months after their prepara tion, activating and refining baths which are entirely satisfactory in processes of zinc phosphatization, tests were carried out comprising a measurement of the efficiency of the baths obtained by dilution of the 2~3~'~~~
concentrates according to the invention in a process of surface treatment comprising phosphatization, on the one hand immediately after dilution and on the other hand after storage at various temperatures.
The surface treatment process, which is the same for all the tests for efficiency, comprises the following stages:
- alkaline degreasing by immersion at 60°C for 3 minutes in a 2~ aqueous solution of an alkali silicate degreas ing agent-,marketed by the Applicant Company under the trademark RIDOLINE 1550 CF/2 with the addition of 0.2g of a surface-active compound also marketed by the Applicant Company under the trademark RIDOSOL 550 CF, - rinsing with running tap water at room temperature, - activation by immersion at room temperature for 1 minute in a dilute bath prepared from water and the liquid concentrate according to the invention, - phosphatization with zinc in an aqueous solution based on acid phosphates of zinc marketed by the Applicant Company under the trademark GRANODINE 958 CF fox 3 minutes at 53°C, - rinsing with running tap water, - drying for 5 minutes in a current of hot air at 80°C.
Since the object here was to study the influence of various activating baths on the morphology and quantity of zinc phosphate crystals deposited during the stags of activation, the subsequent conventional stages of passiva-tion and painting were omitted.
The studies of morphology may be carried out with a scanning electron microscope adjusted for 1500 times enlargement.
The studies of stability may be carried out by weighing the quantity of zinc phosphate deposited after dissolution of the deposit in a scouring medium.
The substrates used for the tests are sheets of cold rolled steel, of electrogalvanized steel or of hot galvanized steel measuring 10 cm x 20 cm x 0.7 mm.
The invention will be better understood with the aid of the non-limiting examples given below in which advantageous embodiments of t:he invention are described.
_EaXAMPLE 1 100 g of Jernstedt salt (marketed by the Applicant Company under -the trademark FIXODINE 5), 4 g of polysac-charide (marketed by KELCO Company under the trademark KELZAN S) and i0 g of the tetrasodium salt of 1-hydroxy-ethylidene-1,1-diphosphonic acid are diluted caith vigorous stirring in 500 g of demineralized water at SO°C.
The composition is made up to 1000 g by the addi-tion of demineralized water.
This preparation is homogenised and is used as liquid concentrate according to the invention.
It is diluted to 10 g per litre of demineralized water to form a dilute aqueous activating solution or activating bath.
The said liquid concentrate is homogeneous and opalescent. It is divided into three equal fractions which are stored for 3 months at 4°C, 20°C and 40°C, respecti-vely.
After this storage and after the fractions stored at 4°C and 40°C, respectively, have been adjusted to 20°C, they are checked to confirm that none of the three frac tions shows any appreciable sign of phase separation, sedimentation, crystallization or thickening.
The activating bath obtained from this concentrate is studied by comparison with a bath prepared from a Jernstedt salt in powder form (marketed by the Applicant Company under the trademark FIXODINE 5).
The surface treatment described above is carried out and the following results are recorded.
TABLE I
Sizes of crystals (in micrometers) ActivatingStorage ConcentrationSize bath of of crystals (in Nm) obtained concentrateof the from bath Substrate (days) (g/I) Steel GalvanizedElectro-galvanized Concentrate according to the invention0 10 1.5 2.0 2.0 90 10 2.0 4.0 2.0 Conventional concentrate (F1XODINE 0 1 2.5 4.0 3.0 5) 90 1 2.5 4.0 3.0 TAPLE II
Weight of layer (g/mZ) ActivatingStorage ConcentrationWeight bath of of layer (g/m2) obtained concentrateof the from bath Substrate (days) (g/I) Steel GalvanizedElectro-galvanized Concentrate according to the invention0 i 0 2.0 1.8 2.2 90 10 2.2 3.1 2.4 Conventional concentrate (FIXODINE 0 1 2.3 2.7 2.7 5) 90 1 2.3 2.7 2.7 Tables I and II show that the liquid concentrate according to the invention is stable after 3 months' storage and provides baths having an activity equivalent to that of baths obtained at the end of three months from solid pulverulent concentrates of the prior art.
Liquid concentrates are prepared for activating baths by the method identical to that described in Example ~~~~i~~
1 but with the polysaccharide replaced by different thickeners conventionally used for stabilizing aqueous concentrates containing dispersions of solids.
The other ingredients are unchanged.
Samples of these concentrates are stored at 4°C, 20°C and 40°C, respectively, and the time taken for sepa-ration of more than 10~ by volume of concentrate to appear is noted, this phenomenon being considered unacceptable for the stability of a liquid concentrate.
The results are summarized in Table III.
TABLE III
SEPARATION
Nature Quantity Time in days required for separation f in 1000 of 10%
g of the in composition o g thickener of concentrateafter storage at None Ammonium alginate (trademark 20 7 3 1 CECALGUM A
500) Cellulose (CMC) (trademark 17 unpumpable BLANOSE 7 ge! in HC) 2 days Aluminosilicate (trademark 30 15 15 8 CLARSOL FB2) Magnesium silicate (trademark 100 0 0 0 BENTONE 38) Mg and AI
silicato (trademark 40 30 30 7 VEEGUM ~
It will have been noted that - CECALGUM A 500 is marketed by the company CECA
- BLANOSE 7 He is marketed by the company HOECHST
- CLARSOL FB2 is marketed by the company CECA
~~~~i~~
- BENTONE 38 is marketed by the company CECA
- VEEGUM F is marketed by the company VAN DER BILT.
Table III clearly shows that none of the thicke-ners, even when based on cellulose such as carboxymethyl cellulose and used at the concentrations conventionally employed for producing a viscosity of from 800 to 2000 cps measured in a Brookfield viscosimeter at 20 rpm/min, provides a stability comparable to that obtained in Example 1.
The nature of the thickener is thus a determining factor.
Liquid concentrates are prepared for activating baths in a manner identical to that described in Example 1 but with 1-hydroxyethylidene-l,l-diphosphonic acid replaced by various other dispersing agents.
The other ingredients are unchanged.
Samples of these concentrates are stored at 4°C, 20°C and 40°C, respectively, and the time taken for the appearance of a persistent crystallization when the tempe rature returns to 20°C is noted, the appearance of this phenomenon being regarded as unacceptable for a liquid concentrate.
The concentrates are then diluted to 10 g/1 in demineralized water to form activating baths and the surface treatment described in Example 1 is carried out on steel sheets.
The product is checked to ascertain whether it is still activating (crystals comparable to those obtained in Example 1).
The results are summarized in Table IV.
TA~hE IV
Storage time (days) at the end Quantity of which Activating coarse crystals appear Nature of ~n g in effect 1000 g after thickener ntrate After dilution f storage conce o None ~ 90 , g0 NEGATIVE
~ g0 Polyacryiic , g0 , g0 NEGATIVE
acid (CORTEX TH 20 > 90 50-50) NTA POSITIVE
' ~0 ~ g0 NTA 10 ~ 90 POSITIVE
ATP 120 4 , ~ ~ 9~ P051TIVE
20 > 90 Tetrapotassium , g0 , 90 NEGATIVE
pyrophosphate100 > 90 Sodium tripoly- NEGATIVE
' 90 > 90 phosphate 100 > gp Sodium hexa- , 90 , gp NEGATIVE
~~, meihaphosphate100 > 90 I
CORTEX TH 50-50 is marketed by CORTEX Company NTA: Sodium salt of nitrilotriacetic acid ATP: Pentasodium salt of amino-tri(methylenephosphonic) acid.
An examination of the results summarized in Table IV clearly shows that only NTA and ATP used in suitable proportions have the advantage not only of rendering the concentrate according to the invention stable as regards 10 crystallization but also of ensuring that after the con-centrate has been stored at different temperatures, it can still provide baths which are usable by virtue of their activating properties.
Such a result was not obvious to the man skilled in 15 the art since he would have expected all dispersing agents and/or sequestering agents to act in the same manner.
The necessity for the simultaneous presence in the )C9~~~s1~
liquid concentrate according to the invention of an effec-tive quantity of a sequestering and/or dispersing agent and of a polysaccharide selected from their respective groups indicated above is thus clearly established.
AND BATH OBTAINED FFtQ~ ~IIS CONCENTRATE
The invention has as its object a liquid concen-trate for providing, by dilution with a suitable quantity of water, an activating and refining bath containing titanium for use in a process of crystalline zinc phospha-tization.
It also relates to the activating and refining bath obtained from the said concentrate.
Processes for crystalline zinc phosphatization ors substrates of steel, aluminium, galvanized steel or galva-nized steel alloyed with nickel, cobalt, aluminium or iron are widely used for protecting the said substrates against corrosion or for lowering the coefficients of friction when these substrates are subjected to cold working.
They generally comprise:
- one ou more stages of alkaline degreasing, - one or more stages of rinsing with runnning tap water, - a stage of activation and refining, - a stage of zinc phosphatization properly speaking, - one or more stages of rinsing with water, - preferably a stage of final passivating rinsing, in particular with salts of hexavalent chromium or of mixtures of hexavalent chromium and trivalent chromium.
Before the phosphatization treatment properly speaking, the stage, of activation is capable of producing chemical heterogeneities on the cleaned metallic surface, thus promoting germination of the layer of crystalline phosphates and enabling a fine and dense coating to be formed. Such a coating is desired - either for improving the adherence of a layer of paint which may subsequently be applied and improving the resistance to corrosion in the event of damage to the layer or skin of paint, - or for depositing firmly adhering crystals on the metal-lic substrate in the context of a cold forming treat-ment.
The stages in particu7Lar of activation and phospha-tization are generally carried out by spraying a suitable bath on the substrate, by steeping the substrate in the bath or by successive spraying and steeping.
The stage of activation may possibly be carried out at the same time as the stage of degreasing by mixing the aqueous degreasing solution with a concentrated activating product or by preparing a degreasing-activating bath from a concentrated degreasing composition containing an acti-vating concentrate. Such simultaneity of the two stages is practised in installations for the treatment of surfaces in which only spraying is carried out at the stage of phosphatization. If, however, the phosphatization stage also includes a phase of immersion, fine and dense phos-phatization can only be achieved by means of an indepen-dent stage of activation.
Titanium, which is employed at the stage of activa tion and refining, constitutes 'the refining agent; the activating and refining baths are generally baths based on titanium salts and contain alkali phosphates.
It is known to prepare them from solid pulverulent concentrates generally consisting of mixtures of alkali phosphates and colloidal titanium salts known under the name of Jernstedt salts which are described, for example, in US Patent 2 456 947.
Such a Jernstedt salt may be obtained by mixing 95 parts of disodium phosphate with 5 parts of potassium fluotitanate in a sufficient quantity of water to dissolve them; polyphosphates of sodium and potassium may also be added to this mixture, in particular in a proportion of 1 to 300 parts by weight Of PZO~'-. The water is then removed from the mixture by evaporation until a pulverulent pro duct is obtained.
The sulphate, oxide or oxysulphate of titanium may be used instead of potassium fluotitanate as source of titanium.
One example of a Jernstedt salt commonly employed and marketed by the Applicant under the trademark FIXODIN~
5 consists of:
- from 0.7 to 5 ~ by weight o~ titanium expressed as titanium (IV) in the form of titanium phosphate, - from 85 to 99.3 by weight of sodium phosphate and - from 0 to 10 ~ by weight of sodium polyphosphate.
As indicated above, the known concentrates used for the preparation of the activating and refining baths are pulverulent products.
They have the following disadvantages:
- they contain water insofar as in the course of their manufacture it is not considered economical to heat them to temperatures above 110°C for complete removal of the water so that part of the water is left in the powder obtained: this frequently leads to the formation of lumps which are difficult to dissolve; the formation of these lumps is also promoted by the humidity in the workshops in which the surface treatment is carried out and by the hygroscopicity of the powder;
- they contain a not negligible proportion of fine parti ales capable of polluting the atmosphere of the place where they are employed;. further, for preparing the activating bath, the user is required to prepare an aqueous mother solution from the concentrate; this mother solution must be prepared with vigorous stirring since the Jernstedt salts are highly insoluble under such conditions of preparation;
- they must be introduced evenly and hence preferably automatically into the water of dilution at the time of preparation of the activating bath since the stage of activation induces nucleation of the subsequent phase of phosphatization; however, the apparatus for automatic introduction of powder are in many cases designed with endless screws placed under feed hoppers for the powder and these screws compress the powder and frequently cause the formation of lumps which block the operation of the said screws.
This presentation in powder form has hitherto been necessary due to the fact that once the Jernstedt salt has been introduced into water, it forms a suspension of insoluble crystals after several hours and these crystals are capable of increasing in size in the course of time, whereas it is known that only fine crystals (< 3 pm) have the desired activating effect.
It has also been proposed to employ liquid concen trates (EP-A-454 212) which are based on Jernstedt salts and which, due to their liquid nature, do not have the disadvantages due to the pulverulent nature of the solid concentrates described above.
However, although these liquid concentrates can be stored without sedimentation for three months due to the addition of thickeners, in particular polysaccharides which are well known for their multiple thickening proper-ties, they have the major disadvantage that they must contain a sufficiently high concentration of titanium so that when diluted with the normal quantity of water they will provide an effective activating bath after several months' storage, that is to say they must have a titanium content, still in a finely crystallized state, capable of conferring on the bath the required activating properties;
such a high titanium content in the concentrate has the result that an activating bath which has been prepared from this concentrate immediately after preparation of the latter or a short time thereafter and therefore before crystal growth has taken place will in turn have such a high titanium concentration that the treatment of a subs-trace with such an activating bath will result in a sur-face which is too highly activated so that at the stage of phosphatization proper the thickness of the layer will be virtually zero; this layer will therefore be a layer of passivation rather than of phosphatization.
It is thus a main object of the present invention to provide a concentrate suitable for the preparation of activating and refining baths of the type in question which do not have the disadvantages of the concentrates of the prior art.
It is to the merit of the Applicant company to have found that this object is achieved if the said concentrate is in the form of an aqueous dispersion containing from 2 to 20% by weight of Jernstedt salt, the concentration of titanium in the dispersion being therefore from 240 to 10,000 ppm of Ti, this dispersion in addition containing:
- a proportion of from 0.2 to 8% by weight of at least one dispersing or sequestering agent to be defined hereinafter and - a proportion of from 0.05 to 7% by weight of at least one thickener based on polysaccharide also defined hereinafter.
The concentrate thus constituted is stable for at least three months both physically and in its activity and can at any time, that is to say immediately after its preparation or equally well after several months' storage, provide, by dilution with the same quantity of water, an activating and refining bath having a titanium content of from 1 to 75 ppm and giving satisfactory results as re-gards activation of the treated substrate.
The invention therefore has as its object, by way of concentrate suitable for the preparation of activating and refining baths employed in zinc phosphatization pro cesses, an aqueous dispersion of Jernstedt salts contain ing from 2 to 20% by weight of these salts, which corres ponds to a concentration of Ti of from 140 to 10,000 ppm, the said dispersion containing, in addition:
- a proportion of from 0.2 to 8% by weight of at least ~~~o one dispersing or sequestering agent selected from the group comprising alkali metals or ammonium phospho-nates, alkali or ammonium salts of sequestering carbo-xylic acids, and any combination of several of these derivatives, it being understood that - the phosphonates are preferably selected from the group comprising those of - hydroxymethyl-phosphonic acid, - hydroxygropyl-phosphonic acid - 1-hydroxyethylidene-1,1-diphosphonic acid, - amino-tri(methylene-phosphonic) acid, - ethylene-diamino-tetra(methylene-phosphonic) acid and - 2-phosphono-butane-1,2,4-tricarboxylic acid and that - among the sequestering carboxylic acids, nitrilotri-acetic or NTA is preferred, - a proportion of from 0.05 to 7% by weight of at least one thickener based on polysaccharide obtained by fermentation of a nutrient medium based on a carbohy drate consisting in particular of a sugar such as glucose, sucrose, fructose, maltose, lactose or galac-tose, and/or on a source of organic and/or inorganic nitrogen consisting in particular of an alkali metal nitrate, an inorganic salt of ammonium, the caseinate of sodium and the soluble extract of corn by the action of a microorganism selected from the class of Xanthomo-nas or Sclerotia, Xanthomonas campestris or Sclerotium rolfsii being preferred.
The proportion of Jernstedt salt is preferably from 4 to 15% by weight of the liquid concentrate.
The proportion of sequestering or dispersing agent is preferably from 4 to 15% by weight of the liquid con-centrate.
The proportion of polysaccharide is preferably from 4 to 15% by weight of the liquid concentrate.
The liquid concentrate according to the invention may contain anti--freeze compounds so that it can be stored at temperatures below 0°C; the anti-freeze compound may be selected from glycol derivatives such as ethyleneglycol, propylene-glycol or high molecular weight glycols or also nitrogen derivatives such as urea.
The pH of the liquid concentrate is preferably adjusted to a value from 7 to 10 and more preferably from 7 to 9; this may be carried out by using an alkaline derivative such as soda, potash, the carbonates of alkali metals or of ammonium hydroxide, phosphates such as triso-dium or tripotassium phosphate, pyro- or tripolyphosphates of sodium or potassium and alkali or ammonium salts of carboxylic acids such as citrates.
The activating and refining bath according to the invention obtained by dilution of the said concentrate to 3-30 g/1 of water contains:
from 60 to 6000 mg/1 of Jernstedt salt, that is to say from 1 to 75 mg/1 of titanium in the form of titanium phosphate in a matrix of alkali phosphates, from 15 to 1500 mg/1 of a derivative of a sequestering carboxylic acid and/or o.f a dispers-ing phosphonic acid, from 3 to 600 mg/1 of a polysaccharide obtained by fer-mentation of a nutrient medium by a microorganism, the volume being made up to 1 litre with water.
To demonstrate the suitability of the concentrates according to the invention for providing, by a constant dilution either just after their preparation or at any time and at least during three months after their prepara tion, activating and refining baths which are entirely satisfactory in processes of zinc phosphatization, tests were carried out comprising a measurement of the efficiency of the baths obtained by dilution of the 2~3~'~~~
concentrates according to the invention in a process of surface treatment comprising phosphatization, on the one hand immediately after dilution and on the other hand after storage at various temperatures.
The surface treatment process, which is the same for all the tests for efficiency, comprises the following stages:
- alkaline degreasing by immersion at 60°C for 3 minutes in a 2~ aqueous solution of an alkali silicate degreas ing agent-,marketed by the Applicant Company under the trademark RIDOLINE 1550 CF/2 with the addition of 0.2g of a surface-active compound also marketed by the Applicant Company under the trademark RIDOSOL 550 CF, - rinsing with running tap water at room temperature, - activation by immersion at room temperature for 1 minute in a dilute bath prepared from water and the liquid concentrate according to the invention, - phosphatization with zinc in an aqueous solution based on acid phosphates of zinc marketed by the Applicant Company under the trademark GRANODINE 958 CF fox 3 minutes at 53°C, - rinsing with running tap water, - drying for 5 minutes in a current of hot air at 80°C.
Since the object here was to study the influence of various activating baths on the morphology and quantity of zinc phosphate crystals deposited during the stags of activation, the subsequent conventional stages of passiva-tion and painting were omitted.
The studies of morphology may be carried out with a scanning electron microscope adjusted for 1500 times enlargement.
The studies of stability may be carried out by weighing the quantity of zinc phosphate deposited after dissolution of the deposit in a scouring medium.
The substrates used for the tests are sheets of cold rolled steel, of electrogalvanized steel or of hot galvanized steel measuring 10 cm x 20 cm x 0.7 mm.
The invention will be better understood with the aid of the non-limiting examples given below in which advantageous embodiments of t:he invention are described.
_EaXAMPLE 1 100 g of Jernstedt salt (marketed by the Applicant Company under -the trademark FIXODINE 5), 4 g of polysac-charide (marketed by KELCO Company under the trademark KELZAN S) and i0 g of the tetrasodium salt of 1-hydroxy-ethylidene-1,1-diphosphonic acid are diluted caith vigorous stirring in 500 g of demineralized water at SO°C.
The composition is made up to 1000 g by the addi-tion of demineralized water.
This preparation is homogenised and is used as liquid concentrate according to the invention.
It is diluted to 10 g per litre of demineralized water to form a dilute aqueous activating solution or activating bath.
The said liquid concentrate is homogeneous and opalescent. It is divided into three equal fractions which are stored for 3 months at 4°C, 20°C and 40°C, respecti-vely.
After this storage and after the fractions stored at 4°C and 40°C, respectively, have been adjusted to 20°C, they are checked to confirm that none of the three frac tions shows any appreciable sign of phase separation, sedimentation, crystallization or thickening.
The activating bath obtained from this concentrate is studied by comparison with a bath prepared from a Jernstedt salt in powder form (marketed by the Applicant Company under the trademark FIXODINE 5).
The surface treatment described above is carried out and the following results are recorded.
TABLE I
Sizes of crystals (in micrometers) ActivatingStorage ConcentrationSize bath of of crystals (in Nm) obtained concentrateof the from bath Substrate (days) (g/I) Steel GalvanizedElectro-galvanized Concentrate according to the invention0 10 1.5 2.0 2.0 90 10 2.0 4.0 2.0 Conventional concentrate (F1XODINE 0 1 2.5 4.0 3.0 5) 90 1 2.5 4.0 3.0 TAPLE II
Weight of layer (g/mZ) ActivatingStorage ConcentrationWeight bath of of layer (g/m2) obtained concentrateof the from bath Substrate (days) (g/I) Steel GalvanizedElectro-galvanized Concentrate according to the invention0 i 0 2.0 1.8 2.2 90 10 2.2 3.1 2.4 Conventional concentrate (FIXODINE 0 1 2.3 2.7 2.7 5) 90 1 2.3 2.7 2.7 Tables I and II show that the liquid concentrate according to the invention is stable after 3 months' storage and provides baths having an activity equivalent to that of baths obtained at the end of three months from solid pulverulent concentrates of the prior art.
Liquid concentrates are prepared for activating baths by the method identical to that described in Example ~~~~i~~
1 but with the polysaccharide replaced by different thickeners conventionally used for stabilizing aqueous concentrates containing dispersions of solids.
The other ingredients are unchanged.
Samples of these concentrates are stored at 4°C, 20°C and 40°C, respectively, and the time taken for sepa-ration of more than 10~ by volume of concentrate to appear is noted, this phenomenon being considered unacceptable for the stability of a liquid concentrate.
The results are summarized in Table III.
TABLE III
SEPARATION
Nature Quantity Time in days required for separation f in 1000 of 10%
g of the in composition o g thickener of concentrateafter storage at None Ammonium alginate (trademark 20 7 3 1 CECALGUM A
500) Cellulose (CMC) (trademark 17 unpumpable BLANOSE 7 ge! in HC) 2 days Aluminosilicate (trademark 30 15 15 8 CLARSOL FB2) Magnesium silicate (trademark 100 0 0 0 BENTONE 38) Mg and AI
silicato (trademark 40 30 30 7 VEEGUM ~
It will have been noted that - CECALGUM A 500 is marketed by the company CECA
- BLANOSE 7 He is marketed by the company HOECHST
- CLARSOL FB2 is marketed by the company CECA
~~~~i~~
- BENTONE 38 is marketed by the company CECA
- VEEGUM F is marketed by the company VAN DER BILT.
Table III clearly shows that none of the thicke-ners, even when based on cellulose such as carboxymethyl cellulose and used at the concentrations conventionally employed for producing a viscosity of from 800 to 2000 cps measured in a Brookfield viscosimeter at 20 rpm/min, provides a stability comparable to that obtained in Example 1.
The nature of the thickener is thus a determining factor.
Liquid concentrates are prepared for activating baths in a manner identical to that described in Example 1 but with 1-hydroxyethylidene-l,l-diphosphonic acid replaced by various other dispersing agents.
The other ingredients are unchanged.
Samples of these concentrates are stored at 4°C, 20°C and 40°C, respectively, and the time taken for the appearance of a persistent crystallization when the tempe rature returns to 20°C is noted, the appearance of this phenomenon being regarded as unacceptable for a liquid concentrate.
The concentrates are then diluted to 10 g/1 in demineralized water to form activating baths and the surface treatment described in Example 1 is carried out on steel sheets.
The product is checked to ascertain whether it is still activating (crystals comparable to those obtained in Example 1).
The results are summarized in Table IV.
TA~hE IV
Storage time (days) at the end Quantity of which Activating coarse crystals appear Nature of ~n g in effect 1000 g after thickener ntrate After dilution f storage conce o None ~ 90 , g0 NEGATIVE
~ g0 Polyacryiic , g0 , g0 NEGATIVE
acid (CORTEX TH 20 > 90 50-50) NTA POSITIVE
' ~0 ~ g0 NTA 10 ~ 90 POSITIVE
ATP 120 4 , ~ ~ 9~ P051TIVE
20 > 90 Tetrapotassium , g0 , 90 NEGATIVE
pyrophosphate100 > 90 Sodium tripoly- NEGATIVE
' 90 > 90 phosphate 100 > gp Sodium hexa- , 90 , gp NEGATIVE
~~, meihaphosphate100 > 90 I
CORTEX TH 50-50 is marketed by CORTEX Company NTA: Sodium salt of nitrilotriacetic acid ATP: Pentasodium salt of amino-tri(methylenephosphonic) acid.
An examination of the results summarized in Table IV clearly shows that only NTA and ATP used in suitable proportions have the advantage not only of rendering the concentrate according to the invention stable as regards 10 crystallization but also of ensuring that after the con-centrate has been stored at different temperatures, it can still provide baths which are usable by virtue of their activating properties.
Such a result was not obvious to the man skilled in 15 the art since he would have expected all dispersing agents and/or sequestering agents to act in the same manner.
The necessity for the simultaneous presence in the )C9~~~s1~
liquid concentrate according to the invention of an effec-tive quantity of a sequestering and/or dispersing agent and of a polysaccharide selected from their respective groups indicated above is thus clearly established.
Claims (6)
1. Aqueous concentrate having a pH from 7 to 10 for preparing an activating and refining bath employed in processes of zinc phosphatization, based on an aqueous dispersion of Jernstedt salts, said concentrate containing from 2 to 20% by weight of said Jernstedt salts, from 0.2 to 8% by weight of at least one dispersing or sequestering agent selected from the group consisting of alkali and ammonium phosphonates of hydroxymethylphosphonic acid, hydroxypropylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, amino-tri(methylene-phosphonic)acid, ethylene-diamino-tetra(methylene-phosphonic) acid, and
2-phosphono-butane-1,2,4-tricarboxylic acid, from 0.05 to 7% by weight of at least one thickener based on a polysaccharide obtained by fermentation, under the action of a microorganism selected from the group consisting of the classes of Xanthomonas and Sclerotia, using a nutrient medium based on at least one constituent selected from the group consisting of glucose, sucrose, fructose, maltose, lactose and galactose, and a member selected from the group consisting of alkali nitrate and inorganic ammonium salt and mixtures thereof, the caseinate of sodium and the soluble extract of corn.
2. Activating and refining bath having a pH from 7 to 10, obtained by dilution of the concentrate according to claim 1, to a concentration corresponding to 3 to 30 g of concentrate/liter of water and containing from 60 to 6000 mg/l of Jernstedt salt, which is 1 to 75 mg/l of titanium in the form of titanium phosphate in a matrix of alkali phosphates, from 15 to 1500 mg/l of a dispersing phosphonic acid compound selected from the group consisting of alkali and ammonium phosphonates of hydroxymethylphosphonic acid, hydroxypropylphosphonic acid, 1-hydroxythylidene-1,1-diphosphonic acid, amino-tri(methylene-phosphonic)acid, ethylene-diamino-tetra (methylene-phosphonic) acid, and 2-phosphono-butane-1,2,4-tricarboxylic acid, from 3 to 600 mg/l of a polysaccharide obtained by fermentation, under the action of microorganism selected from the group consisting of the classes of Xanthomonas and Sclerotia using a nutrient medium based on at least one constituent selected from the group consisting of glucose, sucrose, fructose, maltose, lactose and galactose, and a member selected from the group consisting of an alkali nitrate and inorganic ammonium salt and mixtures thereof, the caseinate of sodium and the soluble extract of corn, the volume being made up to 1 liter with water.
2. Activating and refining bath having a pH from 7 to 10, obtained by dilution of the concentrate according to claim 1, to a concentration corresponding to 3 to 30 g of concentrate/liter of water and containing from 60 to 6000 mg/l of Jernstedt salt, which is 1 to 75 mg/l of titanium in the form of titanium phosphate in a matrix of alkali phosphates, from 15 to 1500 mg/l of a dispersing phosphonic acid compound selected from the group consisting of alkali and ammonium phosphonates of hydroxymethylphosphonic acid, hydroxypropylphosphonic acid, 1-hydroxythylidene-1,1-diphosphonic acid, amino-tri(methylene-phosphonic)acid, ethylene-diamino-tetra (methylene-phosphonic) acid, and 2-phosphono-butane-1,2,4-tricarboxylic acid, from 3 to 600 mg/l of a polysaccharide obtained by fermentation, under the action of microorganism selected from the group consisting of the classes of Xanthomonas and Sclerotia using a nutrient medium based on at least one constituent selected from the group consisting of glucose, sucrose, fructose, maltose, lactose and galactose, and a member selected from the group consisting of an alkali nitrate and inorganic ammonium salt and mixtures thereof, the caseinate of sodium and the soluble extract of corn, the volume being made up to 1 liter with water.
3. Activating and refining bath having a pH from 7 to 10, obtained by dilution of the concentrate according to claim 1, to a concentration corresponding to 3 to 30 g of concentrate/liter of water and containing from 60 to 6000 mg/l of Jernstedt salt, which is 1 to 75 mg/l of titanium in the form of titanium phosphate in a matrix of alkali phosphates, from 15 to 1500 mg/l of a dispersing phosphonic acid compound selected from the group consisting of alkali and ammonium phosphonates of hydroxymethylphosphonic acid, hydroxypropylphosphonic acid, 1-hydroxythylidene-1,1-diphosphonic acid, amino-tri)methylene-phosphonic) acid, ethylene-diamino-tetra (methylene-phosphonic) acid, and 2-phosphono-butane-1,2,4-tricarboxylic acid, from 3 to 600 mg/l of a polysaccharide obtained by fermentation, under the action of microorganism selected from the group consisting of Xanthomonas campestris and Sclerotia rolfsii, using a nutrient medium based on at least one constituent selected from the group consisting of glucose, sucrose, fructose, maltose, lactose and galactose, and a member selected from the group consisting of an alkali nitrate and inorganic ammonium salt and mixtures thereof, the caseinate of sodium and the soluble extract of corn, the volume being made up to 1 liter with water.
4. Concentrate according to claim 1, wherein the concentration of Jernstedt salt is comprised between 4 and 15% by weight of the liquid concentrate.
5. Concentrate according to claim 1, wherein the proportion of sequestering or dispersing agent is comprised between 0.5 and 5% by weight of the liquid concentrate.
6. Concentrate according to claim 1, wherein the proportion of polysaccharide is comprised between 0.1 and 2% by weight of the liquid concentrate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9200945 | 1992-01-29 | ||
| FR9200945A FR2686622B1 (en) | 1992-01-29 | 1992-01-29 | CONCENTRATE FOR ACTIVATION AND REFINING BATH AND BATH OBTAINED FROM THIS CONCENTRATE. |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2088342A1 CA2088342A1 (en) | 1993-07-30 |
| CA2088342C true CA2088342C (en) | 2000-08-15 |
Family
ID=9426097
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002088342A Expired - Fee Related CA2088342C (en) | 1992-01-29 | 1993-01-28 | Concentrate for activating and refining bath and bath obtained from this concentrate |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0554179B1 (en) |
| JP (1) | JP3288782B2 (en) |
| AT (1) | ATE160388T1 (en) |
| CA (1) | CA2088342C (en) |
| DE (1) | DE69315235T2 (en) |
| ES (1) | ES2111139T3 (en) |
| FR (1) | FR2686622B1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5326408A (en) * | 1993-06-15 | 1994-07-05 | Henkel Corporation | Rapidly dissolving and storage stable titanium phosphate containing activating composition |
| US5378292A (en) * | 1993-12-15 | 1995-01-03 | Henkel Corporation | Phosphate conversion coating and compositions and concentrates therefor with stable internal accelerator |
| US5494504A (en) * | 1994-09-12 | 1996-02-27 | Ppg Industries, Inc. | Liquid rinse conditioner for phosphate conversion coatings |
| JP2007204835A (en) | 2006-02-03 | 2007-08-16 | Nippon Paint Co Ltd | Surface conditioning composition and surface conditioning method |
| KR20160149226A (en) | 2014-04-30 | 2016-12-27 | 리오 페어발퉁스 아게 | Treatment device and treatment method for pickling and phosphating metal parts |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3663284A (en) * | 1970-01-09 | 1972-05-16 | Marine Colloids Inc | Titanium dioxide suspensions |
| US3864139A (en) * | 1970-12-04 | 1975-02-04 | Amchem Prod | Pretreatment compositions and use thereof in treating metal surfaces |
| FR2572422B1 (en) * | 1984-10-31 | 1993-03-05 | Produits Ind Cie Fse | IMPROVED ACTIVATION AND REFINING BATH FOR ZINC PHOSPHATATION PROCESS AND CONCENTRATE THEREOF |
| DE4012795A1 (en) * | 1990-04-21 | 1991-10-24 | Metallgesellschaft Ag | ACTIVATING AGENT FOR PHOSPHATING |
| DE4012796A1 (en) * | 1990-04-21 | 1991-10-24 | Metallgesellschaft Ag | PROCESS FOR PREPARING ACTIVATING AGENTS FOR ZINC PHOSPHATING |
-
1992
- 1992-01-29 FR FR9200945A patent/FR2686622B1/en not_active Expired - Fee Related
-
1993
- 1993-01-28 ES ES93400213T patent/ES2111139T3/en not_active Expired - Lifetime
- 1993-01-28 AT AT93400213T patent/ATE160388T1/en active
- 1993-01-28 DE DE69315235T patent/DE69315235T2/en not_active Expired - Fee Related
- 1993-01-28 CA CA002088342A patent/CA2088342C/en not_active Expired - Fee Related
- 1993-01-28 EP EP93400213A patent/EP0554179B1/en not_active Expired - Lifetime
- 1993-01-29 JP JP01414993A patent/JP3288782B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05247664A (en) | 1993-09-24 |
| EP0554179A1 (en) | 1993-08-04 |
| FR2686622A1 (en) | 1993-07-30 |
| CA2088342A1 (en) | 1993-07-30 |
| DE69315235D1 (en) | 1998-01-02 |
| ES2111139T3 (en) | 1998-03-01 |
| FR2686622B1 (en) | 1995-02-24 |
| ATE160388T1 (en) | 1997-12-15 |
| EP0554179B1 (en) | 1997-11-19 |
| DE69315235T2 (en) | 1998-06-18 |
| JP3288782B2 (en) | 2002-06-04 |
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