US3574081A - Corrosion resistant metallic articles - Google Patents

Corrosion resistant metallic articles Download PDF

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Publication number
US3574081A
US3574081A US697479A US3574081DA US3574081A US 3574081 A US3574081 A US 3574081A US 697479 A US697479 A US 697479A US 3574081D A US3574081D A US 3574081DA US 3574081 A US3574081 A US 3574081A
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Prior art keywords
corrosion
copper
matrix
hydrous
elemental
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US697479A
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Michael J Pryor
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Olin Corp
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Olin Corp
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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
    • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
    • C23F13/005—Anodic protection
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/922—Static electricity metal bleed-off metallic stock
    • Y10S428/9265—Special properties
    • Y10S428/933—Sacrificial component

Definitions

  • the most widely used means of allowing to improve corrosion resistance involves the addition of solid solution elements which have a high afiinity for oxygen.
  • solid solution elements which have a high afiinity for oxygen.
  • addition of such elements as nickel and aluminum, with or without zinc, result in the formation of quite protective oxide films upon the copper alloy.
  • the protective film forming additions are chromium, with or without nickel, which similarly forms highly protective films primarily composed of chromic oxides.
  • Such alloys possessing high intrinsic corrosion resistance due to the presence of a protective oxide film will, characteristically, show low total weight losses in corrosive environments, together with excellent resistance to concentration cell corrosion. They will, however, invariably, and under the appropriate conditions, be subject to quite intense local attack, maifesting itself as pitting, or, in the presence of solid obstructions, as crevice corrosion.
  • the method comprises providing at least one of a series of elemental additions to the metal to be protected. These elemental additions are selected from a group of pure metals or alloys whose corrosion potential in the particular environment is at least 10 millivolts more active than that of the matrix metal.
  • the quantity of elemental anode material to be provided should be between .005 and 25% by weight. More optimally, the
  • United States Patent ice amount of second phase elemental anode should lie between 0.1 and 5% by weight.
  • the resulting product is a mixture of the matrix metal or alloy interspersed with anode material.
  • the hydrous oxide must initially be formed either in colloidal or very finely dispersed form and must be able to pick up a positive charge from solution. The positively charged colloid or fine precipitation will then migrate electrophoretically as a large cation of low transference number. The flow of corrosion current on the corroding specimen will drive the positively charged particles to the cathodic matrix material upon which deposition of a film of hydrous oxide will be obtained.
  • the hydrous oxide may, however, contain anions from the particular electrolyte in which it is formed.
  • Such deposited films of hydrous oxide will provide substantial protection against pitting, crevice corrosion, erosion-corrosion, stress corrosion, and intergranular corrosion.
  • hydrous oxide films by electrophoresis is a self-limiting process. A certain amount of initial corrosion is required to form the film.
  • Such hydrous oxide films appear to exhibit little or no resistance to the outward migration of cations but exhibit high resistance to the passage of electrons and, therefore, polarize the cathodic portion of the overall corrosion reaction most strongly. This has the advantage that once such a film is ruptured locally the remaining specimen does not become an effective cathode thereby leading to pitting. Accordingly, corrosion is limited to the area of the specimen which has been exposed to action of the electrolyte and a new and similar film reforms rapidly. This is the basic reason why such films are most advantageous in protecting against pitting.
  • a matrix 10 is provided having interspersed therein a plurality of elemental anode particles 11. At certain points indicated at 13a and 13b on the surface 12 of the matrix, anode particles 11 will be exposed to electrolyte 14.
  • the anodic members at 13a and 1312 will react with the electrolyte according to the reaction
  • the metal hydroxide formed is highly dispersed and is insoluble. Furthermore, the metal hydroxide, shown in exaggerated form at 15, picks up a positive charge from the solution.
  • the positively charged, dispersed metal hydroxide will migrate to the cathodic matrix 16 and will deposit thereon. Thus, a hydroxide film 17 is formed. The deposition just described will continue until the anodic particles 11 at the surfae 12 are exhausted or until the electronic resistance of the hydroxide film is high enough to stifle further corrosion.
  • the foregoing mechanism is also effective in providing substantial protection against atmospheric corrosion and tarnishing.
  • immersion corrosion it appears that relatively low potential diiferences between matrix and anode from 50-250 millivolts are desirable. How- 3 ever, in the case of protection against atmospheric corrosion, higher potential differences of the order of 400- 600 millivolts appear more advantageous.
  • this application has referred to the use of elemental matrices such as copper and iron. It is, of course, not necessary that the matrix he of pure metals only, since hydrous oxide formation produces films that will not protect against concentration cell corrosion. Accordingly, it is most desirable to provide a matrix of substantial resistance to concentration cell corrosion such as would be provided by the addition of strong film formers and to provide improved protection against the obvious disadvantages of film formers such as pitting corrosion by the mechanism described above.
  • These film formers include, for example, Al: 0.5l%, Si: 0.2%, Cr: 0.5 20%, Mn: 02-10%, Ni: 0.5-40%, Zn: -35%, Be: ODS-4%, Mg: 0.012%, Ti: 0.0l5%, Zr: 0.012%, and Co: .0l-4% by weight or combinations of these elements.
  • anode material there is no reason for the anode material to be an element. Alloys can be used for the anode material if they are specifically desirable.
  • the method of making such two phase metallic mixtures is not critical. Where the two phases show little or no tendency to interact, such as in the case of copper and iron, the mixtures may be made by conventional wrought metallurgy techniques.
  • solutions containing 20 milligrams of the following elements were made up in acid solution: nickel, cadmium, zinc, titanium, indium, niobium, vanadium, molybdenum, thallium, iron, aluminum, cobalt and magnesium.
  • the solutions were then neutralized to pH 7 either with caustic soda or ammonia and the solutions examined for evidence of visible precipitation.
  • Such elements are therefore suitable for inclusion as elemental anodes, provided that they fulfill the corrosion potential requirements outlined above and provided that they fulfill the electrophoretic requirements described in the following section.
  • the shape of the cathodic polarization curve on copper is essentially flat; at currents in excess of 1 microamp per sq. cm., polarization of less than 1 microvolt per microamp is observed for pure copper. By contrast, much higher slopes of the order of 200 millivolts per microamp were obtained for the cathodes carrying the hydrous oxides of zinc, iron, aluminum, nickel, cobalt and cadmium.
  • the high slopes of the cathodic polarization curves imply ohmic interefrence with the half cell cathodic corrosion reaction, i.e., the reduction of oxygen dissolved in the electrolyte or the evolution of gaseous hydrogen.
  • the mixtures were prepared from 300 mesh powders of pure iron, copper and aluminum.
  • the copper and aluminum, and iron and aluminum powders were blended completely and compacted into a green compact at a pressure of 150 tons/sq. in.
  • the green compacts were heated to 650 F. in the case of copper and 800 F. in the case of iron and rolled 65% in one pass into the form of strip.
  • the preheating temperatures were insuflicient to cause detectable reaction between the metallic components of the mixtures.
  • the resulting strip had a densification of in excess of 95% and was structurally sound.
  • the two mixtures were then subjected to corrosion tests for a period of 32 days in .5 M sodium chloride solution.
  • the sodium chloride solution was held at 25 C. with the exception of 1 hour in each day when it was heated and maintained at the boiling point.
  • Control specimens of pure copper and copper-aluminum were also tested as controls.
  • EXAMPLE II In order to test whether a protective film of hydrous alumina had formed on both samples of Example I, they were subjected to cathodic polarization tests in /2 M sodium chloride solution.
  • this curve had a slope of 300 millivolts per microamp compared with less than 1 millivolt per microamp in the case of essentially pure copper.
  • the slope of the cathodic polarization curve was approximately 75 millivolts per microamp, as opposed to approximately 35 millivolts per microamp for unfilmed iron.
  • a corrosion resistant article having at least one surface in aqueous solution, said article having a cathodic metallic matrix which has structural integrity interspersed with an anodic material, said anodic material having a corrosion potential in said solution of at least 10 millivolts more active than the matrix material, said anodic material being present within the range of 0.005% to 25% by weight, an insoluble hydroxide coating of said anodic material formed by exposure to said solution, said coating being deposited on at least a portion of said surface and having a high resistance to the flow of electrons therethrough.
US697479A 1968-01-12 1968-01-12 Corrosion resistant metallic articles Expired - Lifetime US3574081A (en)

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US69747968A 1968-01-12 1968-01-12

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US (1) US3574081A (xx)
BE (1) BE726743A (xx)
CH (1) CH520786A (xx)
DE (1) DE1900982A1 (xx)
FR (1) FR1600605A (xx)
GB (2) GB1252274A (xx)
NL (1) NL6818650A (xx)
SE (1) SE363856B (xx)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10921064B2 (en) * 2014-04-02 2021-02-16 Panasonic Intellectual Property Management Co., Ltd. Heat storage apparatus, method for storing heat, and method for producing heat storage apparatus

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102007015442B4 (de) * 2007-03-30 2012-05-10 Wieland-Werke Ag Verwendung einer korrosionsbeständigen Kupferlegierung

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10921064B2 (en) * 2014-04-02 2021-02-16 Panasonic Intellectual Property Management Co., Ltd. Heat storage apparatus, method for storing heat, and method for producing heat storage apparatus

Also Published As

Publication number Publication date
NL6818650A (xx) 1969-07-15
SE363856B (xx) 1974-02-04
CH520786A (de) 1972-03-31
BE726743A (xx) 1969-07-10
GB1252274A (xx) 1971-11-03
DE1900982A1 (de) 1969-09-11
GB1261330A (en) 1972-01-26
FR1600605A (xx) 1970-07-27

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