WO1994002661A1 - Process for treating steel to minimize filiform corrosion - Google Patents

Process for treating steel to minimize filiform corrosion Download PDF

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Publication number
WO1994002661A1
WO1994002661A1 PCT/US1993/006605 US9306605W WO9402661A1 WO 1994002661 A1 WO1994002661 A1 WO 1994002661A1 US 9306605 W US9306605 W US 9306605W WO 9402661 A1 WO9402661 A1 WO 9402661A1
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WIPO (PCT)
Prior art keywords
range
during step
chromium
process according
total
Prior art date
Application number
PCT/US1993/006605
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English (en)
French (fr)
Inventor
Thomas J. Prescott
Ronald J. Munch
Original Assignee
Henkel Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Henkel Corporation filed Critical Henkel Corporation
Priority to AU46769/93A priority Critical patent/AU4676993A/en
Publication of WO1994002661A1 publication Critical patent/WO1994002661A1/en

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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
    • 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
    • C23C22/73—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 characterised by the process
    • C23C22/74—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 characterised by the process for obtaining burned-in conversion coatings

Definitions

  • This invention relates to processes of treating steel surfaces to increase the re ⁇ sistance to corrosion of the treated steel surface, either as thus treated or, most espe- cially, after subsequent overcoating with some conventional, relatively flexible or ⁇ ganic based protective layer.
  • British Patent 1 498 490 published 18 Jan. 1978 teaches a phosphate conver- sion coating process for iron or steel, using a nickel phosphating composition con ⁇ taining hydroxycarboxylic acid.
  • British Patent 1,040,020 published 24 Aug. 1966 teaches phosphating steel with a phosphating solution containing calcium and, optionally, nickel ions, then "sealing" the phosphate conversion coating with a rinse solution containing hexaval ⁇ ent chromium.
  • Nickel coatings can also be applied to steel surfaces by electroless nickel and other plating procedures generally known in the art. These can be used to deposit a relatively thick nickel coating on the steel, and provide substantial protection, but would be uneconomical for use in the described invention.
  • step (B) rinsing the surface as treated in step (A) with water
  • step (C) coating the rinsed surface from the end of step (B) with a substantially uni ⁇ form coating of an aqueous composition containing hexavalent chromium; and (D) drying into place on the surface the coating established in step (C), without intermediate rinsing.
  • step (A) Before performing step (A) according to the present invention, it is normally preferable to clean the steel substrates to be treated by means conventional per se.
  • a wide variety of suitable cleaning methods including but not limited to vapor de- greasing, liquid solvent cleaning, and cleaning with aqueous solutions of surfactants, are known to those skilled in the art and may be suitably used in conjunction with this invention.
  • the aqueous composition with which the steel substrate is treated in step (A) as described above preferably contains cations of nickel in a concentration of from 0.05 to 2.0, more preferably from 0.1 to 1.0, or still more preferably from 0.15 to 0.60, percent by weight (hereinafter often abbreviated as "PBW").
  • PBW percent by weight
  • the aqueous com ⁇ position preferably has a pH in the range from 2 to 5, more preferably from 2.5 to 4.3, or still more preferably from 2.9 to 4.0 and a total acid content in the range from 5 to 100, more preferably from 5 to 50, or still more preferably from 10 to 30, "points" (defined as the milliliters ⁇ "ml" ⁇ of 0.1 N base required to titrate a 10 ml sample of the composition to a phenolphthalein end point).
  • the aqueous composition with which the steel substrate is treated in step (A) as described above need not contain any ingredients other than water, the nickel ions and source of acidity as specified above, and counterions as needed for these essen- tial constituents.
  • this aqueous composition may also contain other constit ⁇ uents, preferably selected from the group consisting of oxidizing agents, fluoride and complex fluoride anions, and phosphate and condensed phosphate anions.
  • the amount of the preferred oxidizing agent, chlorate ions is preferably in the range from 0.25 to 3, more preferably from 0.25 to 1.5, or still more preferably from 0.35 to 1.0, PBW; if other oxidizing agents, or a mixture of oxidizing agents, is used, the amount preferably is chosen to give the same oxidizing potential in the solution as that achieved with the above specified amount of chlorate ions; the oxidizing potential can be measured by the electrical potential developed be ⁇ tween a clean platinum electrode immersed in the solution and some reference elec- trode.
  • the total concentration of fluoride and complex fluoride anions in the aqueous composition used in step (A) is preferably in the range from 0.3 to 3.0, more preferably from 0.4 to 1.5, or still more preferably from 0.50 to 0.80, PBW.
  • Complex fluoride ions are generally preferred over simple fluoride ions, with fluoti- tanate, fluosilicate, fluoborate, and/or fluozirconate ions especially preferred.
  • the total concentration of phosphate and condensed phosphate an- ions in the aqueous composition used in step (A) is preferably in the range from 0.2 to 9, more preferably from 0.4 to 4.5, or still more preferably from 0.60 to 2.0, PBW.
  • the anions derived by any degree of ionization of orthophosphoric acid (H 3 PO 4 ) are preferred, and all these anions, and any free phosphoric acid that may be present, are measured as their stoichiometric equivalent as PO 4 "3 ions for the purpose of calculating these concentrations.
  • aqueous composition used in step (A) may also contain, although it most preferably usually does not contain, other ingredients that do not affect the operation of the process according to this invention.
  • Step (A) of a process according to the present invention in some of its pre ⁇ ferred embodiments, is distinguished from conventional phosphate conversion coating processes with nickel containing phosphating solutions by the relatively small amount of nickel deposited.
  • the amount of deposited nickel is from 3 to 50, preferably from 4 to 30, more preferably from 5.0 to 20, milligrams per square meter (hereinafter often abbreviated as "mg/m 2 ") of nickel on the steel surface.
  • the amount of metal deposited may be conveniently measured by atomic emission spectroscopy, which does not distinguish the oxidation state of the metal, but measures its atomic concentration; for this reason, all descriptions herein of the amounts of metal deposited on the surface refer to amounts of stoichiometrically equivalent free metal, irrespective of the actual chemical nature of the metal present.
  • the time of contact between the aqueous composition and the steel substrates to be treated during step (A) preferably is in the range from 3 to 60, more preferably from 3 to 30, or still more preferably from 5 to 15, seconds, and the temperature of the aqueous composition during the time of contact preferably is maintained within the range from 46 to 93, more preferably from 54 to 82, or still more preferably from 60 to 77, ° C.
  • Contact between the steel to be treated and the various liquid compositions used in the course of a process according to this invention may be accomplished by any convenient method, such as spraying, roll coating (for flat substrates), or immer- sion; many satisfactory methods are known to those skilled in the art and may be ap ⁇ plied to this invention.
  • spraying is generally the preferred method of contact, except possibly for step (C) where a reasonably uniform coating thickness is needed and may be difficult to achieve by a spraying operation.
  • step (B) a single or multiple stage rinse may be used, and conventional domestic/industrial water supplies may often be satisfactorily be used, although use of distilled, deionized, or otherwise purified water may be preferred in some in ⁇ stances for maximum quality.
  • an optional step (B') it is usually preferable to dry the sub ⁇ strates being treated in an optional step (B').
  • drying may be accomplished by any convenient method, of which many are known to those skilled in the art and may be applied to this invention. Some non-limiting examples are forced air drying with or without heating the air, oven drying, drying with infrared or microwave radi ⁇ ation, and the like.
  • residual heat in the metal from some prior step in the process and the removal of any excess solution from prior processing steps, by means of a squeegee or the like will result in satisfactory "flash" drying within a very short time period, without needing any additional external heat source.
  • the metal temperature not exceed 100, more preferably not exceed 80, or still more preferably not exceed 40, ° C.
  • the chromating aqueous composition used in step (C) of a process according to this invention must contain dissolved hexavalent chromium, which preferably is derived from dissolving chromic anhydride (CrO 3 ) in water, although it may also be derived wholly or partially from other sources such as dichromate salts.
  • dissolved hexavalent chromium which preferably is derived from dissolving chromic anhydride (CrO 3 ) in water, although it may also be derived wholly or partially from other sources such as dichromate salts.
  • the concentration of hexavalent chromium in the chromating aqueous compo ⁇ sition used may vary over a wide range.
  • the important characteristic for maximiz- ing the benefit of the invention is the amount of chromium retained on the surface after drying in place, and any particular amount obviously may be obtained by dry ⁇ ing in place either a thick coating of dilute solution or a thin coating of a concentrat ⁇ ed solution.
  • the increase in the total amount of chromium present on the surface af ⁇ ter completing steps (C) and (D) of a process according to this invention is preferab- ly from 28 to 280, more preferably from 56 to 140, still more preferably from 70 to 100, mg/m 2 .
  • the amount of chromium may conveniently be measured by atomic emission spectros- copy, without concern about the actual oxidation state of the metal present.
  • the concentration of total chromium in the chromating composition used in step (C) normally is preferably in the range from 0.3 to 3.5 PBW.
  • the chromating solution used in step (C) of a process according to this invention preferably also contains one or more other ingredients as disclosed in detail in U. S. Patent 4,647,316, the entire disclosure of which, to the extent not inconsistent with any explicit statement herein, is hereby in ⁇ corporated herein by reference.
  • the chromating solution used in step (C) of a process according to this invention preferably also contains dissolved trivalent chromium in a ratio by weight to the total chromium in the range from 0.1:1 to 0.5:1, more preferably from
  • the chromating solution used in step (C) of a process according to this invention preferably also contains dissolved and/or dispersed silica in a ratio by weight to the total chromium in the range from 0.5:1 to 5:1, more preferably from 1:1 to 3:1, or still more preferably from 1.5:1.0 to 2.0:1.0; and, independently, the chromating so ⁇ lution also contains dissolved phosphoric and/or condensed phosphoric acids and an ⁇ ions derived by ionization therefrom (measured as their stoichiometric equivalent of PO 4 "3 ions) in a ratio by weight to the total chromium content in the range from 0.01 to 3:1, more preferably from 0.05:1.0 to 1.0:1.0, or still more preferably from 0.10:1.0 to 0.35:1.0.
  • the trivalent chromium may be incorporated into the chromating so ⁇ lution used in this invention by adding a suitable salt such as chromium nitrate, it is conventional, applicable to this invention, and generally preferred, to derive the tri ⁇ valent chromium content of a chromating solution by initially dissolving in the solu- tion a sufficient amount of hexavalent chromium to include the total amount of chromium in both trivalent and hexavalent oxidation states eventually desired in the final composition and then to reduce some of the hexavalent chromium to trivalent chromium by addition of an organic material such as corn starch, methanol, or the like.
  • a suitable salt such as chromium nitrate
  • the chromating composition to be used in step (C) of this in- vention may contain other ingredients that do not affect the performance or results of the process of this invention, but it is gener ⁇ ally preferred that the amounts of such other ingredients be kept to a minimum.
  • alkali metal ions and other cations capable of forming water soluble chromates and/or dichromates are generally undesirable, as the presence of such ions in the dried coating is likely to diminish the resistance of the treated substrates to wet corrosive processes.
  • the ratio by weight of total alkali metal ions to total chromium in the chromating solution used in step (C) be kept, with increasing preference in the order given, below 1:10, 1:17, 1:34, 1:66, 1:125, 1:271, 1:603, 1:1500, or 1:3350.
  • the temperature during coating of the substrate in step (C) of a process ac ⁇ cording to this invention is generally not at all critical and may be any temperature at which the aqueous composition to be used is liquid. In practice, in order to achieve reasonable economy of operation at a practical processing speed, it is preferred that the temperature during this process be kept within the range from 5 to 65, more preferably from 15 to 50, or still more preferably from 15 to 40, ° C.
  • Drying step (D) may be accomplished by any convenient method, of which many are known to those skilled in the art and may be applied to this invention. Some non-limiting examples are forced air drying with or without heating the air, oven drying, drying with infrared or microwave radiation, and the like. It is pre- ferred that during this drying step, the maximum metal temperature reached should fall within the range from 35 to 150, more preferably from 43 to 120, or still more preferably from 60 to 80, ° C. Although the time of drying is not critical to the ben ⁇ eficial effect of the process, for practical economy in operation it is usually preferred that the time be kept at not more than 20, or more preferably not more than 10, sec ⁇ onds. The practice of this invention may be further appreciated by consideration of the following, non-limiting, working examples, and the benefits of the invention may be further appreciated by reference to the comparison examples.
  • Composition A BONDERITETM 902 (a conventional iron phosphate conversion coating composition, commercially available from Parker +Amchem Div, of Henkel Corp., Madison Heights, Michigan, USA.), diluted with tap water to a concentration of 15 PBW.
  • Composition B An amount of 65 grams (hereinafter often abbreviated "g") of nick ⁇ el carbonate (NiCO 3 ) and 130 g of 60 PBW fluotitanic acid (H 2 TiF 6 ) were dissolved in tap water to make 8 liters of Composition B, containing 0.37 PBW of Ni +2 cat ⁇ ions and 0.98 PBW of H 2 TiF 6 . The pH was 3.65. When contacted with the steel substrates for 7 seconds at 62 - 66 ° C, this composition produced an add-on of 4.0 mg/m 2 of Ni.
  • Composition C A concentrated nickel acid phosphate solution containing 8.3 PBW of nickel and 37.6 PBW of PO 4 "3 ions was prepared from nickel oxide (or alterna ⁇ tively from nickel carbonate) and orthophosphoric acid. An amount of 180 g of this solution, 75 g of sodium chlorate (NaClO 3 ), and 2 g of sodium carbonate (NZJCO J ) were dissolved in tap water to make Composition C, which contained 0.19 PBW of Ni +2 ions, 0.85 PBW of PO 4 "3 ions, and 0.73 PBW of ClO 3 ions and had a pH of 2.6.
  • NaClO 3 sodium chlorate
  • NZJCO J sodium carbonate
  • Composition D An amount of 125.1 g of nickel acetate tetrahydrate and 29.4 g of glacial acetic acid were dissolved in tap water to produce 8 liters of Composition D, which contained 0.37 PBW of Ni +2 ions and 0.74 PBW of acetate ions and had a pH of 4.6. When contacted with the steel substrates for 7 seconds at 62 - 66 ° C, this composition produced an add-on of 7.5 mg/m 2 of Ni.
  • substrates of carbon steel in the form of sheets with dimensions of 10 x 30 centimeters x 0.43 mm thick were used.
  • the substrates were cleaned by wiping with mineral spirits, followed by spray cleaning in a solution of 15 grams per liter of PARCO CLEANERTM 338 in water at 65° C (the cleaner is a product commercially available from the Parker+Amchem Div. of Henkel Corp., Madison Heights, Michigan, USA), then by a tap water rinse for about 10 seconds at 45 - 55 ° C.
  • the cleaned substrates were then treated by immersing them for 7 seconds at 62 - 66 ° C in the nickelizing or comparison com ⁇ position shown in Table 1, followed by spray rinsing with tap water for 5 seconds at 15 - 25 ° C, followed by drying with forced air at room temperature.
  • the dried sub ⁇ strates were then either roll coated with a sufficient amount to contain 70 - 100 Table 1 NICKELIZING AND CHROMATING TREATMENTS AND TEST RESULTS
  • paint creepage was measured in intervals of 1.0 mm.
  • test results are based on two test panels which gave the same results within the limits of experimental error inherent in the tests.
  • Table 1 shows that the substrates processed according to the invention were superior in at least one aspect of corrosion resistance, and not inferior in any aspect of corrosion resistance, to any of the comparison examples.

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  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Treatment Of Metals (AREA)
PCT/US1993/006605 1992-07-20 1993-07-16 Process for treating steel to minimize filiform corrosion WO1994002661A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU46769/93A AU4676993A (en) 1992-07-20 1993-07-16 Process for treating steel to minimize filiform corrosion

Applications Claiming Priority (2)

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US91665692A 1992-07-20 1992-07-20
US07/916,656 1992-07-20

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WO1994002661A1 true WO1994002661A1 (en) 1994-02-03

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CN (1) CN1084905A (enrdf_load_stackoverflow)
AU (1) AU4676993A (enrdf_load_stackoverflow)
MX (1) MX9304352A (enrdf_load_stackoverflow)
TW (1) TW232714B (enrdf_load_stackoverflow)
WO (1) WO1994002661A1 (enrdf_load_stackoverflow)
ZA (1) ZA935175B (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999018257A1 (en) * 1997-10-07 1999-04-15 Henkel Corporation Conversion coating zinciferous surfaces to resist blackening and white rust
US6461449B1 (en) 1997-10-07 2002-10-08 Henkel Corporation Conversion coating zinciferous surfaces to resist blackening and white rust

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3468724A (en) * 1966-03-31 1969-09-23 Amchem Prod Metal coating process
FR2120141A1 (enrdf_load_stackoverflow) * 1971-01-02 1972-08-11 Collardin Gmbh Gerhard
US4647316A (en) * 1984-03-23 1987-03-03 Parker Chemical Company Metal base coating composition comprising chromium, silica and phosphate and process for coating metal therewith
WO1991011542A2 (en) * 1990-01-30 1991-08-08 Henkel Corporation Surface treatment method and composition for zinc coated steel sheet
WO1992007107A1 (en) * 1990-10-15 1992-04-30 Henkel Corporation Preatment for zinc and zinc alloy pior to chromating

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3468724A (en) * 1966-03-31 1969-09-23 Amchem Prod Metal coating process
FR2120141A1 (enrdf_load_stackoverflow) * 1971-01-02 1972-08-11 Collardin Gmbh Gerhard
US4647316A (en) * 1984-03-23 1987-03-03 Parker Chemical Company Metal base coating composition comprising chromium, silica and phosphate and process for coating metal therewith
WO1991011542A2 (en) * 1990-01-30 1991-08-08 Henkel Corporation Surface treatment method and composition for zinc coated steel sheet
WO1992007107A1 (en) * 1990-10-15 1992-04-30 Henkel Corporation Preatment for zinc and zinc alloy pior to chromating

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Patent Abstracts of Japan, Vol 8, No 283, C-258, abstract of JP, 59-153884 (NITSUSHIN SEIKOU K.K.), *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999018257A1 (en) * 1997-10-07 1999-04-15 Henkel Corporation Conversion coating zinciferous surfaces to resist blackening and white rust
US6461449B1 (en) 1997-10-07 2002-10-08 Henkel Corporation Conversion coating zinciferous surfaces to resist blackening and white rust

Also Published As

Publication number Publication date
MX9304352A (es) 1994-04-29
CN1084905A (zh) 1994-04-06
TW232714B (enrdf_load_stackoverflow) 1994-10-21
AU4676993A (en) 1994-02-14
ZA935175B (en) 1994-03-02

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