EP0797691A1 - Procede de traitement a base d'elements terres rares pour ameliorer la resistance a la corrosion des metaux et alliages - Google Patents

Procede de traitement a base d'elements terres rares pour ameliorer la resistance a la corrosion des metaux et alliages

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Publication number
EP0797691A1
EP0797691A1 EP95933276A EP95933276A EP0797691A1 EP 0797691 A1 EP0797691 A1 EP 0797691A1 EP 95933276 A EP95933276 A EP 95933276A EP 95933276 A EP95933276 A EP 95933276A EP 0797691 A1 EP0797691 A1 EP 0797691A1
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Prior art keywords
rare earth
nitrate
composition
cerium
alloys
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EP95933276A
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German (de)
English (en)
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EP0797691B1 (fr
Inventor
Yucheng Lu
Michael Brian Ives
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McMaster University
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McMaster University
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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
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
    • C23F11/04—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in markedly acid liquids
    • 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
    • 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
    • C23C22/50—Treatment of iron or alloys based thereon
    • 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
    • C23C22/52—Treatment of copper or alloys based thereon
    • 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
    • C23C22/56—Treatment of aluminium or alloys based thereon
    • 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
    • C23C22/68—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 solutions with pH between 6 and 8
    • 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

Definitions

  • the present invention relates to a process of increasing corrosion resistance of metals and alloys by surface treatment with one or more elements from the rare earth group of elements. More particularly, the present invention provides a method of increasing corrosion resistance of metals such as stainless steels, nickel based alloys, aluminum alloys and copper alloys in aqueous solutions by treatment in a solution of rare earth salts.
  • crevice corrosion in aerated solutions involves an oxygen concentration cell.
  • cathodic reduction of the depolarizers on the large areas surrounding the attacked site is necessary to support the high rate of anodic dissolution. It has been disclosed by Y.C. Lu, J.L. Luo and M.B. Ives, ISIJ International, Vol. 31 , 210 (1991 ), that the enhanced cathodic reduction of oxidant adjacent to a localized attack site produces an increase of localized corrosion.
  • a powerful means of preventing crevice corrosion would be to constrain or significantly inhibit the cathodic reactions such as oxygen reduction, hydrogen evolution and the like.
  • Aluminum alloys are of commercial and industrial significance comparable or greater than that of stainless steels. Corrosion and corrosion induced failure is a major problem associated with aluminum alloys. Aluminum alloys are widely used in very corrosive environments, for example in automotive applications such as brazed aluminum heat exchangers, coolers, evaporators, radiators and the like. Known methods of corrosion protection of aluminum and aluminum alloys involve the use of chromate ions to form conversion coatings on the alloys. Environmental concerns associated with chromate ions are a drawback to widespread use of this technique. Other strategies for increasing corrosion resistance of aluminum based alloys based on physical deposition methods such as sputtering are inherently limited since the area being coated is by line-of-sight from the source.
  • Cerium containing solution treatment has been effective in improving the localized corrosion resistance of aluminum alloys.
  • chemical passivation of aluminum alloys immersed in cerium chloride solutions for 7 days or longer produces a conversion coating on the aluminum alloy exhibiting increased corrosion resistance, see F. Mansfield, S.Lin, S. Kim and H. Shih, J. Electrochem. Soc, Vol. 137, 78 (1990).
  • the aluminum alloys have dipped into hot cerium salt solutions followed by direct current (DC) anodic polarization in a molybdate solution to produce an anodized passive layer containing Ce and Mo as disclosed in F. Mansfield, V. Wang and H. Shih, J. Electrochem. Soc, Vol. 138, L74 (1991 ).
  • Alternating current (AC) passivation of aluminum alloys in the same types of cerium salt solutions has also been used to form conversion coatings exhibiting corrosion resistance as disclosed in H. Shih,
  • the present invention provides compositions and a method for increasing the corrosion resistance of metals and alloys by exposing the surface of the metals to the compositions.
  • the compositions may be used to treat chromium, molybdenum, nickel, copper, a range of austenitic and ferritic stainless steels, nickel based alloys, aluminum and aluminum alloys, copper and copper alloys, chromium, molybdenum, nickel and the like to improve the localized corrosion resistance of the alloys.
  • the corrosion behaviour of treated and untreated samples has been compared using a combination of electrochemical measurement techniques in an aerated 0.6M NaCI + 0.1 M Na 2 SO 4 solution, corrosion tests and field tests in natural seawater.
  • the present invention provides a method of treating metals and alloys to increase corrosion resistance.
  • the method comprises exposing a surface of a metal or alloy to an aqueous composition at an effective temperature.
  • the aqueous composition comprises a salt of at least one rare earth element.
  • the composition comprises a pH-modifying agent present in an amount effective to adjust the pH to from about 0.5 to about 6.5 to condition the surface to enhance deposition of the rare earth element thereon.
  • the at least one rare earth salt is selected from the group of salts consisting of yttrium, gadolinium, cerium, europium, terbium, samarium, neodymium, praseodymium, lanthanum, holmium, ytterbium, dysprosium and erbium and substantially excluding rare earth salts containing halides.
  • the at least one rare earth salt being present in an amount of from about 2% by weight to saturation.
  • the surface may be abraded prior to or during exposure to the aqueous composition.
  • the invention is directed to a method of treating metals or alloys to increase their corrosion resistance.
  • the method comprises conditioning a surface of the metal or alloy to substantially remove metal oxide present on the surface and exposing the surface to an effective amount of at least one of the rare earths under conditions sufficiently energetic to incorporate some of the rare earths into the surface.
  • the step of conditioning the surface and exposing the surface includes immersing the metal or alloy in a composition comprising a rare earth salt, but not rare earth halides, in the range from about 2% by weight to saturation, and a pH modifying substance in an amount sufficient to adjust the pH to an effective value in the range from about 0.5 to about 6.5 to facilitate deposition of the rare earth thereon.
  • the step of conditioning may include abrasion of the surface before or during immersing the metal or alloy in the aqueous composition.
  • the present invention provides a method for treating the surface of ferritic stainless steels, austenitic stainless steels, chromium, molybdenum, copper, copper alloys, aluminum and aluminum alloys to increase their corrosion resistance.
  • the method comprises exposing the surface of the metal to a heated composition comprising an aqueous solution of a salt of at least one rare earth element selected from the group consisting of salts of yttrium, gadolinium, cerium, europium, terbium, samarium, neodymium, praseodymium, lanthanum, holmium, ytterbium, dysprosium and erbium.
  • the composition comprises a pH-modifying agent in an amount sufficient to adjust the pH from about 0.5 to about 6.5.
  • the rare earth salt is present in the amount of from about 2% by weight to saturation.
  • the metal is a ferritic stainless steel
  • the pH is adjusted to a value from about 2 to about 4.5, for treating austenitic stainless steels and nickel based alloys, the pH is adjusted to between about 0.5 to about 3.5, for treating aluminum alloys the pH is adjusted to between about 4.5 to about 6.5, and the temperature of the aqueous solution is maintained in the range from about 60°C to about 95°C.
  • a composition for treating metals and alloys to increase their corrosion resistance comprises an aqueous solution of a salt of at least one rare earth element, the rare earth element being selected from the group consisting of salts of gadolinium, yttrium, cerium, europium, terbium, samarium, neodymium, praseodymium, lanthanum, holmium, ytterbium, dysprosium and erbium.
  • the rare earth salt is present in an amount of from about 2% by weight to saturation and the composition includes a pH-modifying agent in an amount effective to adjust the pH from about 0.5 to about 6.5.
  • the composition is preferably substantially exclusive of rare earth salts containing halides.
  • Figure 1 is a plot of disc current vs. potential for both treated (0.05M Ce(NO 3 ) 3 .6H 2 O at 90-95°C for 1 hour) and untreated UNS N08904 stainless steel discs in aerated 0.1 M Na 2 SO 4 + 0.6 M NaCI solution at pH 8.26;
  • Figure 2 displays disc current measured from Figure 1 at -950 mV vs. the square root of the angular velocity of the rotating discs;
  • Figure 3 displays the potentiodynamic polarization curves of treated and untreated UNS S31603 steel in aerated solution at pH 8.26;
  • Figure 4 shows SIMS profiles from UNS S31603 stainless steel samples treated at 95 ⁇ 2°C for 1 hour in distilled water;
  • Figure 5 shows SIMS profiles from UNS S31603 stainless steel samples treated at 95 ⁇ 2°C for 1 hour in 0.05 M cerium nitrate
  • Figure 6 shows galvanostatic polarization curves of UNS S40900 samples before and after treatment in 0.1 M gadolinium nitrate, neodymium nitrate and praseodymium nitrate at 85°C for 20 minutes;
  • Figure 7 shows galvanostatic polarization curves of UNS S40900 samples before and after treatment in 0.1 M cerium, europium, samarium, terbium and ytterbium nitrate at 85°C for 20 minutes;
  • Figure 8 shows galvanostatic polarization curves of UNS S40900 samples before and after treatment in 0.1 M erbium, yttrium, lanthanum, dysprosium and holmium nitrate at 85°C for 20 minutes;
  • Figure 9 shows potentiodynamic polarization plots of UNS S40900 stainless steel samples before and after treating in 0.4M cerium nitrate, gadolinium nitrate, and a mixture of 0.1 M gadolinium nitrate and 0.3 M cerium nitrate at 85°C for 20 minutes;
  • Figure 10 is a flow chart summarizing the weight loss results of UNS S31603 alloy samples after 24 hours of ASTM G48 B testing at 22°C after treatment in each of the indicated rare earth salt containing solutions;
  • Figure 11 illustrates the weight loss after 24 hours ASTM G48 B testing at 22°C for UNS S31603 stainless steel samples treated in solutions of 0.3 M cerium nitrate plus an additional 0.1 M of the different indicated rare earth nitrates including cerium nitrate;
  • Figure 12 illustrates the weight loss after 24 hours ASTM G48 B test at 22°C for UNS S31603 stainless steel samples treated in solutions listed in Table II at 22°C for 20 minutes;
  • Figure 13 shows the galvanostatic polarization plots of the UNS S40900 stainless steel samples before and after being treated in formulation A described hereinafter, formulation B described hereinafter, formulation A with 30% nitric acid, formulation B with 30% nitric acid, and 30% nitric acid alone;
  • Figure 14 shows potentiodynamic polarization plots of UNS S40900 stainless steel samples before and after treating in formulation A alone and in formulation A with 10 ppm and 100 ppm of Fe +3 contamination
  • Figure 15 shows the galvanostatic polarization plots of UNS S40900 stainless steel samples before and after treating in formulation A alone and in formulation A with 10 ppm and 100 ppm of Fe +3 contamination;
  • Figure 16 displays galvanostatic polarization curves for UNS S40900 samples treated in formulation A with 100 ppm of Fe +3 contamination before and after recovery of the solution, compared with a control sample untreated;
  • Figure 17 shows potentiodynamic polarization plots of a brazing aluminum alloy sample treated using a rare earth salt solution according to the present invention and the same alloy treated using a commercial chromate treatment;
  • Figure 18 shows potentiodynamic polarization plots of copper alloy samples treated with rare earth salt solutions discussed hereinafter.
  • rare earth element refers to the lanthanide series of elements in the periodic table with proton numbers ranging from cerium (58) to lutetium (71) inclusive.
  • rare earths specifically refers to the oxides of the rare earth elements, it is used more generally to refer to this particular group of elements both in chemical practise and hereinafter.
  • the data indicates that for the untreated UNS N08904 disc the cathodic current is rotation-speed dependent.
  • the cathodic reaction rates, i.e. cathodic currents on the cerium-treated electrodes are shifted to more negative potentials and are greatly restrained.
  • the current for oxygen reduction does not apparently depend on rotation speed.
  • Figure 2 shows the disc current, measured from UNS N08904 discs at -950mV, as a function of the square root of disc angular velocity.
  • the straight line fit of the data indicates the reduction of oxygen on the untreated stainless steel is mass transport limited.
  • the current measured on the cerium- treated UNS N08904 steel was greatly reduced and did not depend significantly on rotation speed.
  • the data show clearly that the cathodic electrode reaction is inhibited by the cerium nitrate treatment.
  • the electrode process is controlled predominantly by charge transfer processes at the electrode surface.
  • the cerium pretreatment was also found to influence the anodic characteristics of these stainless steels.
  • Figure 3 the anodic polarization of untreated and treated UNS S31603 steel are compared.
  • X-ray photoelectron spectroscopy has previously been used to help identify the chemical state of the cerium present on treated surfaces.
  • the position of the 3d 52 peak was determined to be «888 eV, which compares with values for a Ce(NO 3 ) 3 standard of «889 eV, and a CeO 2 standard of *882 eV (data not shown).
  • Clearly the cerium was present in a trivalent form.
  • a very small amount of nitrogen was also detected by XPS analysis on cerium treated steel, and its peak position ( «401 eV) may suggest the presence of NO " rather than nitrate (408 eV) or nitride (397 eV).
  • the oxygen spectrum showed both O "2 and OH ' signals of about equal intensity.
  • cerium may form Ce 3+ complexes or oxy-hydroxide in the surface of the treated steels.
  • Cerium treatment of iron did not result in an observable improvement in corrosion resistance of the iron, based upon comparison of galvanostatic and potentiodynamic scans on treated and untreated samples (data not shown).
  • Treatment of pure nickel did result in an increase in corrosion resistance determined from a comparison of galvanostatic and potentiodynamic scans on treated and untreated samples (data not shown).
  • Treatment of molybdenum and chromium samples in cerium nitrate containing compositions resulted in a significant increase in corrosion resistance for both metals (data not shown) with molybdenum exhibiting a greater degree of corrosion resistance than molybdenum.
  • the E Final for samples treated in 0.1 M gadolinium nitrate, neodymium nitrate and praseodymium nitrate are each about
  • Figure 9 displays four potentiodynamic polarization plots for an untreated UNS S40900 sample, a sample treated in 0.4M gadolinium nitrate, a sample treated in 0.4M cerium nitrate and a sample treated in a composition containing 0.1 M gadolinium nitrate and 0.3M cerium nitrate solution, all treated samples being exposed to the compositions for 20 minutes at 85°C.
  • the formulation containing the combination of gadolinium nitrate and cerium nitrate showed significant improvement in cathodic inhibition of UNS S40900 samples as compared to samples treated in the compositions containing the individual rare earth nitrates.
  • Figure 10 is a flow chart ' showing the effect of different binary and ternary combinations of lanthanides on weight loss resulting from crevice corrosion tests for UNS S31603 stainless steel samples.
  • UNS S31603 stainless steel samples were treated in solutions containing 0.3M cerium nitrate in combination with 0.1 M concentrations of other different lanthanum nitrates.
  • samples treated in 0.4M cerium nitrate and control samples were tested in parallel. The pH of all solutions was adjusted to 1.32 ⁇ 0.01 except for the solution using cerium nitrate alone. After the treatment, the samples were tested by the ASTM G48 B standard method at 22°C for 24 hours.
  • Ce3La1 0.3M cerium nitrate + 0.1 M lanthanum nitrate
  • Ce3Gd1 0.3M cerium nitrate + 0.1 M gadolinium nitrate
  • Ce2La1Gd1 0.2M cerium nitrate + 0.1 M lanthanum nitrate + 0.1 M gadolinium nitrate
  • Gd3Nd1 0.3M gadolinium nitrate + 0.1 M neodymium nitrate
  • Gd3Pr1 0.3M gadolinium nitrate + praseodymium 0.1 M nitrate
  • Gd3Pr1Nd1 0.3M gadolinium nitrate + praseodymium 0.1 M nitrate + 0.1 M neodymium nitrate
  • the major parameters of the compositions produced in accordance with the present invention are the use of one or more rare earth salt(s), pH range of the composition, temperature of the composition to which the surface of the metal is being exposed, and residence time of the metal therein
  • the residence time may be limited to from about 15 minutes to about an hour at elevated temperatures (about 60°C to 95°C) Lower temperatures of the compositions necessitate longer exposure times.
  • exposure times of the order of several days are required to achieve the corrosion resistance effect obtained for 15 minutes exposure at elevated temperatures
  • Surface conditioning methods other than by exposure to acid solutions, such as mechanical or other chemical processes may also be variables to consider
  • the pH value of the aqueous composition should be adjusted in an appropriate range depending on the metal or alloy being treated Increase in the acidity of the solution to a certain level enhances the surface enrichment of beneficial alloy elements for passivity. However, if the solution pH drop beyond certain values, the effect on cathodic inhibition will be weakened.
  • the galvanostatic polarization plots of Figure 13 illustrates the effect of 30% nitric acid addition can diminish the cathodic inhibition. It also causes attack to the substrate and results in rapid degradation of the treatment solution when treating ferritic stainless steels.
  • the pH should be adjusted in the range of about 0.5 to about 3.5 for austenitic stainless steels and nickel based alloys and in the range from about 2 to about 4.5 for ferritic stainless steel.
  • the pH of the solution may be adjusted by adding nitric acid to the solution.
  • the optimum treatment parameters can be adjusted according to the metals to be treated. Formulations A and B given above are nonlimiting examples. While treatment in these formulations produce significant corrosion inhibition on stainless steels, it will be appreciated that many other compositions of varying rare earth salt components and concentrations produced in accordance with the present invention will provide improvement in corrosion resistance of alloys.
  • Detergents or surfactants may be added to the compositions for cleaning the metal surfaces.
  • a commercial surfactant such as ARMAK 1997( Akzo Chemicals Inc) may be added to the treatment solution at 0.5- 1.0% for samples having surfaces contaminated with for example processing lubricating oils and finger prints which may obstruct effective chemical treatment.
  • the choice of surfactant will be determined in part by the solubility of the surfactant in the composition for the particular pH value.
  • the metal to be cleaned and conditioned may initially be immersed in a preconditioning bath including an acid in addition to a surfactant.
  • Mechanical abrasion of the surface of the metal prior to exposure to the lanthanides has been observed to be beneficial increase the efficacy of the corrosion inhibition effect. This effect is possibly due to the breaking up of an existing oxide layer on the metal surface which may impede the surface reactions leading to the corrosion inhibition effect.
  • Using abrasion in combination with the aggressive aqueous compositions are expected to reduce the residence time of the metal or alloy workpiece in the compositions.
  • mechanical abrasion of metals and alloys being treated by the method disclosed herein is advantageous where native oxide layers are expected to be present and the lanthanide is being integrated into the surface in a method different than using the aqueous compositions of low pH.
  • compositions disclosed herein for economically treating large quantities of metals or alloys depends on long term stability of the compositions.
  • the present compositions were found to be very stable with no observable precipitation or degradation over a period of three years.
  • certain materials will accumulate in the treatment bath over time.
  • Ferric ions will build up in solution which changes the acidity of the bath.
  • Addition of sodium hydroxide may be used to control the change in acidity. Therefore, studies were conducted to determine the effect of ferric ion concentration and sodium concentration on the efficacy of the compositions.
  • ferric ions Due to selected dissolution of iron during exposure of iron based alloys to the compositions, ferric ions will accumulate in the solution resulting in a more aggressive solution.
  • the effect of ferric ion on the performance of the compositions was studied by adding Fe(NO 3 ) 3 to formulation A containing 0.3 M cerium nitrate and 0.1 M gadolinium nitrate.
  • the addition of 10 ppm and 100 ppm of Fe 3+ into formulation A resulted in a reduction in the pH of the formulations from 2.53 to 2.47 and 2.13 respectively.
  • Sodium nitrate will also accumulate in the treatment compositions as a result of bath maintenance.
  • the effect of sodium content in the treatment formulations was studied by adding sodium nitrate to formulation A at three levels, 0.1 M, 0.5M, and 1 M. Potentiodynamic polarization plots on UNS S40900 samples in formulation A with the above levels of sodium nitrate showed the presence of sodium had no discernable adverse affects on the corrosion inhibition behaviour (data not shown).
  • Figure 17 is a potentiostatic polarization plot for a brazing aluminum alloy before and after treatment in a solution comprising formulation A diluted by a factor of 7 using water.
  • the alloy was a two-sided clad brazing sheet comprising a core material consistent with AA4045 aluminum alloy and a lowere melting Al-Si clad layer on both sides of the core.
  • the composition of the double clad aluminum material was: Element Core Clad
  • brazing sheet samples were subjected to a typical brazing cycle (heating to 1100°F for 1-3 minutes in dry nitrogen atmosphere) prior to testing so that the samples were tested in the as brazed condition.
  • the samples were rinsed in acetone and then immersed in diluted formulation A as previously described.
  • the formulation was "aged” by immersing an aluminum sample therein for 8 hours at 85°C after the samples were immersed in the formulation for 1 hour at 85°C.
  • aluminum alloy samples were subjected to a chromate treatment in a 4% by volume chromate solution at 35 to 40°C for 2.7 minutes.
  • the samples were tested for corrosion resistance in a 5% solution of auto coolant, "ZEREX”, BASF 340-2 which also contained 150 ppm salts as follows: 0.2077 g/liter
  • compositions for treating aluminum preferably include aluminum salts in order to reduce the corrosive attack on the alloy by the composition.
  • the salts can be added directly to the compositions, for example aluminum nitrate was added directly and was found to be effective in the range of about 5 to 10 grams of the nitrate per liter of the composition.
  • the salt can be generated in the composition by aging, that is, by placing a piece of aluminum into the freshly prepared composition.
  • Figure 18 is a potentiostatic polarization plot of a C 12200 phosphorous deoxidized copper sample before and after treatment in a composition containing 130.3 g/l of cerium nitrate, and 45.0 g/l gadolinium nitrate and 10 g/l AI(NO 3 ) 3 .9H 2 O.
  • the pH was adjusted to 1 with HNO 3 and the solution heated to 350C.
  • the copper samples were first cleaned in 10% H 2 SO 4 and then rinsed in acetone prior to treatment in the rare earth salt solutions.
  • the samples were tested for corrosion resistance in a 5% solution of auto coolant, "ZEREX", BASF 340-2 which also contained 150 ppm salts as follows: 0.2077 g/liter
  • the corrosion studies comprised free corrosion potential monitoring and cyclic polarization scans. Several samples were tested in the same composition but for different periods of time with the cyclic potentiodynamic scans for a control sample not exposed to the formulation and samples exposed for 1 ,
  • compositions for treatment of copper and its alloys preferably contains aluminum salts to reduce corrosive attack on the copper. Copper salts may also be used alternative to aluminum salts.
  • the pH of the compositions is preferably adjusted in the range of 1 to 6.5.
  • the data of Figure 18 shows that the method of the present invention may be advantageously used to increase the corrosion resistance of copper and its alloys.
  • VDM Cronifer 2803Mo also comprises 0.43% Nb, 0.03% Co and 0.002% B.
  • the composition used for the treatment of the samples comprised 0.05M cerium nitrate and the samples were treated at 90 to 95°C for 1 hour at a pH between 2.5 to 2.9.
  • Samples for seawater field tests were mounted in treated and untreated pairs for visual comparison.
  • a "TEFLON" crevice washer provided twelve crevice sites on each side of the sample. The sea water tests were performed both in brackish water in a channel and in chlorinated brackish water in an outlet trough of a testing rig. Parallel tests for treated and untreated tubes were also conducted in a simulated heat exchanger rig.
  • Table IV summarizes the effect of cerium treatment in improving the crevice corrosion resistance of stainless steels in brackish water and chlorinated seawater.
  • Table IV shows that the treatment of UNS S30403, S31603 and
  • N08904 significantly reduced or eliminated crevice corrosion in brackish water chlorinated with 2 ppm free chlorine for 24 days. Most of the untreated control samples of the same material exhibited significant crevice corrosion. Samples of untreated 6 Mo super stainless steels exhibited significant crevice corrosion after immersion in 2ppm chlorinated brackish water for 60 days. Table V below illustrates that cerium treatment resulted in crevice corrosion resistance of stainless steels immersed in chlorinated seawater.
  • Table VI summarizes the results of steel samples after 100 days of testing in brackish seawater. The effect of the treatment in improving the crevice corrosion resistance in the harsh seawater environment is quite significant.
  • Aqueous compositions using gadolinium nitrate alone give the most improvement in corrosion resistance compared to compositions using the other rare earth nitrates alone. There is a significant synergism among lanthanides in inhibiting the electrode kinetics, especially cathodic kinetics.
  • the pH of the compositions for each the ferritic and austenitic stainless steels is preferably adjusted to assist in the surface enrichment of beneficial alloy elements such as chromium and molybdenum. At pH values too low the metal or alloy will undergo dissolution at rates too high to have a beneficial effect on cathodic inhibition.
  • the surface of the metal or alloy is activated by the pH of the composition.
  • mechanical abrasion may be used as an alternative or in combination with chemical activation. Using mechanical abrasion initially to condition the surface followed by immersion in the composition would facilitate use of higher pH values since a primary effect of the pH is to condition the surface.
  • surface activation may be achieved using mechanical abrasion, sputter etching, particle bombardment and the like.
  • the metal or alloy being treated could be subject to a pretreatment by immersion in an acid bath absent the rare earth salts in order to condition the surface after which the workpiece would be immersed into the particular composition containing the rare earth salt(s).
  • the preferred method disclosed herein of increasing the corrosion resistance of metals comprises exposing the surface of the metal to an aqueous composition containing one or a combination of lanthanides.
  • a liquid solution allows full access to the surface area of any shape of workpiece.
  • other methods of treating the surface of a metal may be used, including sputtering, plasma spraying and the like, wherein rare earths are deposited on the alloy surface. Those skilled in the art would be able to determine the operative processing conditions for each deposition procedure.
  • the method disclosed herein is useful for treating products fabricated from commercial alloys which are used in environments prone to aqueous corrosion.
  • the treatment may be carried out after production of the metal or alloy itself or after the product has been produced from the alloy.
  • After a product has been produced from the alloy it can be treated in a composition specifically optimized for the particular material and corrosive environment in which the product will be used. While the compositions and method of treating metals and alloys for increasing corrosion resistance has been described and illustrated with respect to certain combinations of lanthanides, it will be readily apparent to those skilled in the art that numerous variations of these combinations may be made without departing from the scope of the invention described herein.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Chemical Treatment Of Metals (AREA)

Abstract

La présente invention concerne un procédé de traitement de surface des métaux tels que les aciers ferritiques, les aciers inoxydables austénitiques et les alliages de cuivre et d'aluminium, lequel traitement a pour but d'accroître la résistance à la corrosion. Le procédé consiste à plonger ces métaux dans une composition aqueuse chauffée contenant un sel de terre rare. On obtient la meilleure résistance à la corrosion en utilisant comme sels les nitrates d'yttrium, de gadolinium, de cérium, d'europium, de terbium, de samarium, de néodyme, de praséodyme, de lanthane, de holmium, d'ytterbium, de dysprosium et d'erbium. Le sel de terre rare est présent à raison d'environ 2 % de la masse de saturation de la solution. Pour l'attaque de la surface permettant d'en éliminer les oxydes et d'y faciliter le dépôt de terre rare, la composition contient un modificateur du pH, l'acide nitrique par exemple, qui permet de maintenir le pH entre 0,5 et environ 6,5. Pour les alliages d'aluminium, on maintient le pH entre 4,5 et 6,5. Pour les alliages à base de nickel et pour les aciers inoxydables austénitiques, on maintient le pH entre 0,5 et 3,5. Pour les aciers inoxydables ferritiques, on maintient le pH entre 2,0 et 4,5. On peut également traiter la surface par abrasion avant ou pendant l'immersion dans la composition. La meilleure résistance à la corrosion s'obtient après une immersion de 15 à 20 minutes dans la composition maintenue à une température entre 60 °C et 95 °C. Parmi tous les nitrates simples de terres rares, ce sont les nitrates de gadolinium, de néodyme et de praséodyme qui procurent la meilleure résistance à la corrosion. Des effets de synergie importants sont constatés avec les compositions combinant deux ou plusieurs nitrates de terres rares. Les compositions à base de nitrate de cérium, de nitrate de gadolinium et de nitrate de lanthane se sont avérées très efficaces contre la corrosion fissurante.
EP95933276A 1994-10-07 1995-10-10 Procede de traitement a base d'elements terres rares pour ameliorer la resistance a la corrosion des metaux et alliages Expired - Lifetime EP0797691B1 (fr)

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GB9420295 1994-10-07
GB9420295A GB9420295D0 (en) 1994-10-07 1994-10-07 Method of increasing corrosion resistance of steels by treatment with cerium
PCT/CA1995/000565 WO1996011290A1 (fr) 1994-10-07 1995-10-10 Procede de traitement a base d'elements terres rares pourameliorer la resistance a la corrosion des metaux et alliages

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JP (1) JPH10506959A (fr)
KR (1) KR970706422A (fr)
AU (1) AU3602095A (fr)
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DE (1) DE69522709T2 (fr)
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WO2022197358A1 (fr) * 2021-03-19 2022-09-22 Ppg Industries Ohio, Inc. Systèmes et procédés de traitement d'un substrat

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AUPM621194A0 (en) * 1994-06-10 1994-07-07 Commonwealth Scientific And Industrial Research Organisation Conversion coating and process for its formation
WO1996015292A1 (fr) 1994-11-11 1996-05-23 Commonwealth Scientific And Industrial Research Organisation Procede et solution destines a la formation d'une couche de conversion sur une surface metallique
GB2328447A (en) * 1997-08-16 1999-02-24 British Aerospace A desmutting solution for use prior to anodising
ES2151405B1 (es) * 1998-07-20 2001-07-01 Univ Sevilla Procedimiento para mejorar el comportamiento refractario de aceros inoxidables.
WO2001029285A2 (fr) 1999-10-19 2001-04-26 Advanced Mechanical Technology, Inc. Protection contre la corrosion d'acier de pompes a chaleur fonctionnant a l'ammoniac et a l'eau
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AUPQ633200A0 (en) 2000-03-20 2000-04-15 Commonwealth Scientific And Industrial Research Organisation Process and solution for providing a conversion coating on a metallic surface I
AU774225B2 (en) * 2000-03-20 2004-06-17 Commonwealth Scientific And Industrial Research Organisation Process and solution for providing a conversion coating on metallic surface II
AUPQ633300A0 (en) 2000-03-20 2000-04-15 Commonwealth Scientific And Industrial Research Organisation Process and solution for providing a conversion coating on a metallic surface ii
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US10041176B2 (en) 2005-04-07 2018-08-07 Momentive Performance Materials Inc. No-rinse pretreatment methods and compositions
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WO2022197358A1 (fr) * 2021-03-19 2022-09-22 Ppg Industries Ohio, Inc. Systèmes et procédés de traitement d'un substrat

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GB9420295D0 (en) 1994-11-23
CA2201619A1 (fr) 1996-04-18
WO1996011290A1 (fr) 1996-04-18
KR970706422A (ko) 1997-11-03
JPH10506959A (ja) 1998-07-07
AU3602095A (en) 1996-05-02
EP0797691B1 (fr) 2001-09-12
DE69522709T2 (de) 2002-07-04
DE69522709D1 (de) 2001-10-18

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