Classifications

• • 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
  • C23C22/48—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 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates

Definitions

• the invention relates to a process for depositing conversion layers on a metallic surface chosen from zinc, iron, aluminum, copper, lead, and their alloys as well as galvanized, aluminized, copper-coated steels for producing at high speed, conversion layers formed of very small crystals.
• these metal surface conversion treatments When applied before shaping the sheet, these metal surface conversion treatments generally have at least one of the following effects:
• pre-phosphating treatments which result in the deposition of a layer of metallic phosphate whose grammage is of the order of 1 to 1.5 g / m 2 .
• these conversion treatments can also be carried out after the sheet is shaped, to improve the adhesion of organic coatings deposited subsequently, such as paints.
• the conversion baths essentially contain anions and cations capable of forming insoluble compounds with the metal dissolved on the surface.
• the main conversion treatments are thus chromation treatments on zinc-plated or aluminized steel, phosphating on bare unalloyed steels or on coated steels, or even oxalation on alloy steels such as stainless steels, for example.
• the treated surface After being brought into contact with a conversion bath, the treated surface is generally rinsed to remove the components of the surface and / or of the treatment solution which have not reacted, then this surface is dried in particular to harden the conversion layer. and / or to improve its properties.
• the application conditions, the nature and the concentration of the additives have an important influence on the structure, the morphology and the compactness of the conversion layer obtained, and therefore on its properties.
• the conversion treatment can itself be preceded by a pretreatment, generally consisting of degreasing and rinsing the surface beforehand, followed by a so-called refining operation using a suitable pretreatment solution to create and / or favor germination sites on the surface to be treated.
• a pretreatment generally consisting of degreasing and rinsing the surface beforehand, followed by a so-called refining operation using a suitable pretreatment solution to create and / or favor germination sites on the surface to be treated.
• a polyhydroxyaryl-carboxylic acid for example gallic acid or protocatechuic acid, or a depside of this acid which may result from its reaction with glucose, such as tannic acid, and - an adhesion promoter based on silane.
• accelerating agents are used for galvanized surfaces, such as phosphates, nitrates, fluorides or organic acids.
• the treatment carried out using this composition provides both good protection against corrosion and good adhesion for paints.
• Patent application FR 2 465 008 describes a process for the deposition of conversion layers on zinc-plated surfaces, using a treatment solution which may contain a soluble oxalate, associated with activating agents which are carboxylic acids, especially short diacids.
• the concentration of oxalic acid in the treatment solutions described is less than 7.5 g / l, ie 0.08 mole / liter.
• the layer weight, or grammage, resulting from these different treatments is very variable depending on the main objective pursued and can range from less than 1 g / m 2 to 8 g / m 2 .
• the object of the invention is therefore to offer a treatment for converting metal surfaces before they are shaped, using a bath free of compounds harmful to the environment but also making it possible to deposit layers on these surfaces. more effective conversion to protect against corrosion and / or for pre-lubrication than those obtained by the processes of the prior art.
• Another objective pursued by the invention is also to be able to apply an organic coating with good adhesion, in particular by cataphoresis, on a surface treated according to the invention, after it has been shaped and degreased, which supposes that the applied conversion layer is easily removed during this degreasing.
• the subject of the invention is a method of treatment by carboxylation, before shaping, of a metal surface chosen from zinc, iron, aluminum, copper, lead, and their alloys as well as galvanized, aluminized, copper-coated steels, under oxidizing conditions with respect to the metal, by contacting with an aqueous, organic or hydro-organic bath comprising at least one organic acid in free form or in the form of salt, characterized in that than :
• organic acid is a saturated or unsaturated aliphatic monocarboxylic or dicarboxylic acid
• said organic acid is in solution and / or in emulsion in the bath at a concentration greater than 0.1 mole / liter
• the pH of the bath is acidic.
• the invention also relates to the use of said surface treatment process by carboxylation for the temporary protection against corrosion of said metal surface.
• the subject of the invention is also a method of manufacturing a shaped sheet having a metallic surface chosen from zinc, iron, aluminum, copper, lead, and their alloys as well as galvanized steels, aluminized, coppery, in which a surface treatment of said sheet is carried out according to the invention, said treated sheet is oiled, and it is shaped. It is more particularly preferred to apply this method according to the invention to a steel sheet covered with zinc or zinc alloy which is then shaped by stamping.
• FIG. 1 illustrates the evaluation of the stamping behavior of sheets not treated according to the invention and oiled (symbol 0) and sheets treated according to the invention not oiled (symbol ⁇ ) or oiled (symbol D); it represents the evolution of the maximum drawing force F max as a function of the holding force Fs.
• FIG. 2 shows the evolution of the grammage P of the conversion layer obtained according to the invention, as a function of the duration of immersion Di in a carboxylation solution, using a chemical means of oxidation of zinc and the co - following solvents: "ethanol (symbol +)
• FIG. 4 illustrates a potentiometric evaluation of the resistance to aqueous corrosion, in terms of polarization resistance Rp as a function of the immersion time in the measurement electrolyte, for the following surfaces:
• conversion layers are deposited by carboxylation of metal surfaces by bringing the surface into contact with an organic or hydro-organic aqueous bath comprising at least one organic acid in solution or in emulsion, under oxidizing conditions. metal screw.
• the present invention uses aliphatic monocarboxylic or dicarboxylic acids, optionally comprising one or more unsaturations.
• the acid constants of these acids being of the order of 4.8, the natural pH of the baths according to the invention will generally be less than this value. If you wish to lower the pH, you can acidify the treatment bath, for example using nitric acid. We can also increase the pH of the bath by adding sodium hydroxide, for example.
• the acid bath used in the treatment according to the invention must in all cases have a pH value of between 1 and 7, the upper limit making it possible to avoid the presence of a metal hydroxide in the conversion layer. As for the minimum pH value, it will be adapted according to the metal of the surface in order to ensure satisfactory deposition of the conversion layer.
• the at least one organic acid used according to the invention is dissolved or emulsified in the bath at a concentration greater than 0.1 mol / liter.
• the rate of formation of the conversion layer based on metal carboxylate is no longer sufficient to obtain a conversion layer which is effective over time. outsourced to processing.
• the aliphatic organic acids according to the present invention are chosen from saturated monocarboxylic acids containing from 5 to 16 carbon atoms. Particular preference is given to hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid and decanoic acid.
• the aliphatic organic acids according to the present invention are chosen from unsaturated monocarboxylic acids containing from 10 to 18 carbon atoms. Particular preference is given to undecenoic acid, oleic acid or linoleic acid.
• the aliphatic organic acids according to the present invention are chosen from saturated dicarboxylic acids containing from 4 to 12 carbon atoms. Particular preference is given to sebacic acid or azelaic acid.
• the at least one selected aliphatic monocarboxylic acid is heptanoic acid.
• the bath comprises, in addition to heptanoic acid, decanoic acid or undecenoic acid.
• the oxidizing conditions of the carboxylation bath are obtained by the following means:
• this oxidizing and / or accelerating agent is preferably chosen from the group including sodium perborate, nitrites, hydrogen peroxide, hydroxylamine sulfate and nitro-guanidine.
• the conversion baths can optionally contain:
• additives which facilitate the implementation of the treatment and the distribution of the bath over the surface to be treated, such as surfactants,
• additives making it possible to increase the life of the bath, such as, for example, chelating agents for delaying the precipitation of other compounds than those which it is desired to obtain in the conversion layer, or bactericidal agents, and
• the conversion treatment bath according to the invention can also comprise a co-solvent such as ethanol, n-propanol, butanol, dimethylsulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol, glycol ethers, etc., or other organic or mineral acids. Particular preference is given to diacetone alcohol.
• a co-solvent such as ethanol, n-propanol, butanol, dimethylsulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol, glycol ethers, etc., or other organic or mineral acids. Particular preference is given to diacetone alcohol.
• the carboxylation treatment bath comprises in solution rare earth ions such as gadolinium in the +3 oxidation state at a concentration greater than or equal to 1.10 -3 mole / liter.
• the conversion layer obtained is then composed of two types of crystals of composition and possibly of different shape and it proves to be of an even increased efficiency for resistance to corrosion.
• the concentration of organic acids in the bath, the conditions of use of this bath and the oxidizing conditions with respect to the metal are adapted to obtain on the metal surface a carboxylation layer of grammage between 1 and 6 g / m 2 .
• Sheet steel of quality ES (steel for deep drawing) or HES (steel for deep drawing), micro-alloyed or not, of thickness between 0.7 and 1.2 mm, bare or coated with a layer of zinc about 10 ⁇ m thick, applied by electrodeposition in a chloride-based or sulphate-based bath, or by hot-dip galvanizing. 2) Components of the conversion treatment baths tested
• the treatment solutions tested are generally water-based as the main solvent and ethanol as the co-solvent; propanol, DMSO, NMP or 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol) or other polar solvents at least partially miscible with water, can also be used as co-solvents.
• HC 7 heptanoic acid
• HCin decanoic acid
• Ridoline TM is an aqueous degreaser solution containing alkali metal salts, surfactants and potassium hydroxide.
• Ridosol TM is a wetting base for liquid degreasers comprising a mixture of surfactants.
• Fixodine TM 50CF is an activator (also known as a germinator) comprising compounds based on alkali metal salts such as titanium salts.
• the conversion layer formed on a determined surface is dissolved with a complexing solution, the duration of soaking in this solution being adapted to obtain complete dissolution of the layer (of the order of one minute for one layer made from of HC 7 , at a rate of 0.3 mg / cm 2 ).
• the grammage expressed in mg per cm 2 , is evaluated from the difference in weight between the coated sample and this same sample having undergone the dissolution treatment.
• the composition of this dissolution solution is as follows:
• the pH of this solution is adjusted to a value close to 8 by adding sodium hydroxide, in order to obtain optimal complexation of the metal cation.
• This test consists of a periodic potentiometric measurement of the polarization resistance R p by a voltage sweep with an amplitude of +/- 10 mV around the corrosion potential E cor .
• the device used for this evaluation comprises, in a conventional manner:
• This electrolyte comprises 148 mg / l of sodium sulphate (Na 2 SO), 138 mg / l of sodium bicarbonate (NaHCO), and 165 mg / l of sodium chloride (NaCl) and has a pH close to 8;
• a working electrode constituted by the metal surface coated with the conversion layer to be evaluated obstructing the window at the bottom of the cell, a reference electrode with saturated calomel ("ESC"), and a platinum electrode as auxiliary counter electrode;
• ESC saturated calomel
• first part duration: 8 hours - 40 ° C; 100% relative humidity
• second part duration: 16 hours - ambient temperature and humidity
• the rating then consists of counting the number of cycles at the end of which it is found that at least 10% of the treated surface is covered with white rust.
• This test consists in measuring the coefficient of plane-plane friction by increasing the clamping pressure up to 80 MPa.
• the treated samples are covered with an oil referenced 6130 from the company QUAKER, the quantity of oil deposited being of the order of 1 to 2 g / m 2 for example.
• This test consists of making complete stampings from samples of sheet metal blank having undergone the conversion treatment.
• an initial blank of diameter 64 mm a bucket with a diameter of 32 mm and a depth of 25 mm is produced.
• the maximum drawing force is evaluated beyond which there is a rupture of the blank during drawing, for a clamping force of the clamps. predetermined blanks. This maximum value is identified for a series of clamping force values of the blank clamps, so as to draw, as illustrated in FIG. 1, curves representing the variation of the maximum drawing force Fmax as a function of the force of blank holder.
• Starter 958 / CF aqueous solution containing zinc salts in the presence of a slight excess of nitric acid
• Intensifier N ° 1 aqueous solution of metal salts in the presence of a small amount of phosphoric acid
• Primer M aqueous solution containing sodium hydroxide> 26% to regulate the pH
• Compensator M aqueous solution based on sodium nitrite, accelerator for crystalline phosphating bath
• the analyzes should fall within the following ranges:
• the quality of the phosphate layer obtained is examined using an electron microscope.
• Control bath formula - 43.16% by weight of deionized water (10 ⁇ S max),
• the purpose of this example is to determine the conditions for the treatment of carboxylation according to the invention, making it possible to obtain, on a surface of galvanized sheet, a conversion layer which is both compact and finely crystallized.
• the galvanized surfaces of steel sheets are treated according to the following steps:
• the initial preparation treatment is that mentioned in Table I. in successive references 1 to 4.
• the solvent of the conversion bath is a water-ethanol mixture, the ratio of which is adjusted in order to completely dissolve the added organic acid.
• the temperature of the bath is varied between 20 and 80 ° C. and it is observed that the increase in temperature accelerates the rate of deposition. 1.3. Concentration of organic acid or corresponding salt
• the concentration of the organic acid is varied and it is found that the concentration range must be between 0.1 and 1.5 M. Indeed, as we have seen previously, if the concentration is less than 0.1 M, the rate of formation of the conversion layer based on metal carboxylate is no longer sufficient to obtain an effective conversion layer in the time allowed for the treatment. A concentration greater than 1.5 M is not possible due to the limit of solubility of organic acid close to 1.4 - 1.5 M.
• chlorides, nitrates or sulphates are preferably used at a concentration less than or equal to 3 g / l.
• the weight of the conversion layer is high: about 1.5 times higher for example when n goes from the value 7 to the value 10.
• the compactness of the conversion layer also increases with the length of the aliphatic chain of the carboxylic acid used, as well as the resistance to corrosion brought by this layer.
• oxidants such as dissolved oxygen (O 2 ), nitrites (NO 2 "), hydrogen peroxide (H 2 O 2 ) or perborates (BO 3 -). It is found that the presence of oxidant or accelerating agent has a favorable effect on the compactness of the conversion layer.
• the conventional phosphating treatment is carried out on a degreased surface according to the bath conditions specified in 6) (Suitability for phosphating after degreasing the layer), 2.
• the pre-phosphating treatment is carried out on a degreased surface according to the following conditions:
• Oxalated sheet according to FR 2 465 008 the procedure described in example 4 of this document is carried out using a treatment solution containing a complex fluoride and an oxalate.
• Carboxylated sheet according to WO 95/21177 the procedure described in Example 1 of this document is carried out using a treatment solution containing gallic acid and 3-glycidoxypropyl-trimethoxy-silane .
• the treatment according to the invention provides better resistance to atmospheric corrosion than the treatments of the prior art.
• the treatment according to the invention makes it possible to obtain significantly improved friction coefficients compared to the pre-phosphating treatment.
• the conversion treatment according to the invention can advantageously replace the conventional pre-phosphating treatment, all the more since it avoids the pollution problems posed by the use of phosphates.
• Example 3 Suitability for Painting Metallic surfaces subjected to the conversion treatment according to the invention find their main use in the automotive field. It is therefore important to verify that these surfaces, once coated, are compatible with the processes usually used in the industry for painting metal sheets, in particular zinc-plated sheets.
• Shaping by stamping generally requires that the metal surface be oiled, which means, when it is desired to then carry out other operations such as painting or enamelling, to remove all traces of oil from this surface and, at the same time, to eliminate the possible conversion layer formed before shaping.
• a degreasing treatment is carried out, for the success of which it is important that the conversion layer be easily removed. It is therefore important to verify that the conversion layer according to the invention is easily degreasable.
• an alkaline degreasing of the metal surface carrying a conversion layer is carried out under the conditions specified in Table I - steps 1 and 2 of 3) "Standard operating procedure for treatment with conversion baths "/" MATERIAL part to obtain the conversion layers ".
• the procedure defined in point 6) is carried out according to the methods by treating the two faces of the sample according to the invention, namely the bare steel face and the galvanized face, and it is observed that the conversion layer obtained ' has a covering aspect.
• the grammage of the conversion layer obtained is evaluated as a function of the immersion time of the sheet blank to be treated in the solution according to the invention, for different compositions of solvents (% by volume):
• Case 3 43% water, 57% DMSO (symbol ⁇ ),.
• Case 4 56% water, 44% NMP (symbol D), .
• Case 5 60% water, 40% diacetone alcohol (symbol o).
• the growth rate of the layer is lower in cases 2 and 3 than in cases 1, 4 and 5. From observations using a scanning electron microscope, we notes that the morphologies of the crystals of the layers are identical:
• amide solvents such as N-methylformamide, N-N-dimethylformamide or sulfone solvents such as tetramethylsulfone.
• an emulsion is prepared containing 50 g / l of heptanoic acid and 2 g / l of sodium perborate tetrahydrate.
• the emulsion contains no other solvent than water and, thanks to the surfactant, all of the acid is in emulsion and / or solution in water.
• Two treatment solutions differentiated by pH are prepared: one at natural pH ⁇ 4, the other at pH adjusted to about 4.7 by addition of sodium hydroxide.
• One proceeds according to the operating method of the Methods paragraph by soaking for five minutes samples of sheets identical to those of Example 3 in one or the other treatment solution, then rinsing and dries the treated surface.
• the substrate which is here a galvanized sheet is subjected to a potential and an anode current by immersion of the galvanized sheet in the treatment solution between two titanium plates electrically connected and at the same potential.
• treatment solution a 50% water / 50% ethanol solution containing 0.38 mol / liter of heptanoic acid is used and the pH of which is between 3.2 and 4.7 depending on the amount of sodium hydroxide added.
• the procedure described in point 3) of the paragraph is applied.
• the conversion treatment according to the invention is applied by dipping the sheet sample in the treatment solution and passing an electric current between the submerged sheet and the titanium plates.
• the procedure is carried out under current densities of 10 and 25 mA / cm 2 for treatment times of 1, 3, 5 and 10 seconds.
• FIG. 3 represents the results obtained in terms of grammage, the symbol D representing the curve obtained with a current density of 10 mA / cm 2 and the symbol ⁇ representing the curve obtained with a current density of 25 mA / cm 2 .
• Example 4 The procedure is as in Example 4, replacing the heptanoic acid at 0.38 mol / liter with an 80/20 (case A) or 50/50 (case B) mixture of heptanoic acid (abbreviation: HC 7 ) and decanoic acid (abbreviation: HC-10), the immersion time being 5 minutes.
• the decanoic acid is represented by the symbols x, - a mixture of heptanoic and decanoic acids in an HC7 / HC10 ratio equal to 80/20 by mole is represented by the symbols *.
• the other curves of FIG. 4 will be used later. It can be seen by comparing these three curves that the mixture of heptanoic and decanoic acids exhibits improved resistance to aqueous corrosion compared to the heptanoic or decanoic acids used alone.
• a galvanized sheet is treated by soaking for five minutes in a 50/50 water / ethanol solution containing 0.38 mole / liter of heptanoic acid and
• the post-treatment is then carried out by soaking in a post-treatment solution, the characteristics of which are summarized in Table V for 60 seconds, before the final rinsing of the procedure described in point 3 of the Materials paragraph.
• the treated surface of the samples is observed and / or analyzed and a potentiometric evaluation of the resistance to aqueous corrosion is carried out according to point 2 of the Materials paragraph.
• the post-treatment Ti has no effect but that the post-treatment Si makes it possible to slightly improve the resistance to corrosion, apparently without morphological modification of the conversion layer.
• Example 9 Addition of Gadolinium Ions to the Treatment Solution
• other components or additives can be introduced into the carboxylation solution according to the invention.
• the treatment according to the invention is carried out by soaking for five minutes in a 50/50 water / ethanol solution containing 0.38 mol / liter of heptanoic acid, 2 g / l of hydrated sodium perborate, and one of the additives listed in Table VI, the pH can be adjusted by adding nitric acid.

Landscapes

• 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)
• Chemically Coating (AREA)
• Electroplating Methods And Accessories (AREA)
• ing And Chemical Polishing (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Related Child Applications (1)

Publications (2)

Family

ID=8861553

Family Applications (1)

Country Status (11)

Cited By (3)

Families Citing this family (6)

Citations (6)

Family Cites Families (13)

• 2001
  • 2001-03-27 FR FR0104064A patent/FR2822852B1/fr not_active Expired - Fee Related
• 2002
  • 2002-03-21 JP JP2002575356A patent/JP4242653B2/ja not_active Expired - Fee Related
  • 2002-03-21 BR BRPI0208680-8A patent/BR0208680B1/pt not_active IP Right Cessation
  • 2002-03-21 ES ES02753732T patent/ES2312604T3/es not_active Expired - Lifetime
  • 2002-03-21 WO PCT/FR2002/000988 patent/WO2002077324A2/fr active IP Right Grant
  • 2002-03-21 DE DE60228425T patent/DE60228425D1/de not_active Expired - Lifetime
  • 2002-03-21 KR KR1020037012552A patent/KR100871674B1/ko not_active IP Right Cessation
  • 2002-03-21 EP EP02753732A patent/EP1373597B1/fr not_active Expired - Lifetime
  • 2002-03-21 CA CA002442502A patent/CA2442502C/fr not_active Expired - Fee Related
  • 2002-03-21 AT AT02753732T patent/ATE405690T1/de active
• 2003
  • 2003-09-26 US US10/670,513 patent/US20040118482A1/en not_active Abandoned

Patent Citations (6)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events