Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/003—Alloys based on aluminium containing at least 2.6% of one or more of the elements: tin, lead, antimony, bismuth, cadmium, and titanium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
• • 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
  • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
  • C23F13/06—Constructional parts, or assemblies of cathodic-protection apparatus
  • C23F13/08—Electrodes specially adapted for inhibiting corrosion by cathodic protection; Manufacture thereof; Conducting electric current thereto
  • C23F13/12—Electrodes characterised by the material
  • C23F13/14—Material for sacrificial anodes
• • 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
  • Y10S72/00—Metal deforming
  • Y10S72/70—Deforming specified alloys or uncommon metal or bimetallic work

Definitions

• aluminum should be expected to perform satisfactorily as a sacrificial anode because the element aluminum fulfills the two primary requirements for sacrificial anodes, that is, a high theoretical oxidation potential (1.90 volts v. saturated KCl calomel reference) and a high theoretical electrical output per unit mass of metal consumed (2.98 amp.-hrs. per gram).
• a high theoretical oxidation potential (1.90 volts v. saturated KCl calomel reference
• a high theoretical electrical output per unit mass of metal consumed (2.98 amp.-hrs. per gram).
• unalloyed aluminum has not proven to be satisfactory for use as a sacrificial anode since it does not exhibit these favorable theoretical properties when used as a sacrificial galvanic anode.
• the effective oxidation potential of the aluminum metal in fresh water is about 0.4 volt (as measured in a closed circuit at milliamperes per square foot in water having a resistivity of about 5000 ohm.cm).
• the effective oxidation potential of aluminum in a saturated calcium sulfate (CaSO electrolyte is about 0.4 volt (as measured in a closed circuit at a current density of 50 milliamperes per square foot). At such low operating voltages, no effective cathodic protection is given to, for example, ferrous based structures; therefore, the anode exhibits no useful electrical output.
• a method to produce an aluminum alloy suitable for use as an anode in various environments including water heating systems and underground environments is desired.
• the novel method of the present invention comprises first providing an aluminum alloy consisting essentially of about 0.02 to about 2 weight per cent bismuth, about 0.005 to about 0.05 weight per cent gallium, about 0.005 to about 0.5 weight per cent indium and the balance of the alloy being essentially aluminum.
• the aluminum alloy is then hot worked sufficiently to provide a worked alloy suitable for use as a galvanic anode with an oxidation potential of about 1.0 to about l.3 volts at a current density of 10 ma/ft in a fresh water electrolyte with a resistivity of 5,000 ohm.cin or about 1.3 to 1.6 volts at a current density of about 50 ma/ft in a saturated CaSO electrolyte.
• the sacrificial anode of the present invention is useful in low resistivity aqueous liquids and is especially useful for the galvanic protection of ferrous members in, for example, water heaters or other aqueous environments having a resistivity of at least about 200 ohms centimeter.
• the method of forming the aluminum alloy galvanic anode comprises first hot working a preferred alloy consisting essentially of about 0.03 to about 0.3 weight per cent bismuth. about 0.005 to about 0.04 weight per cent gallium, about 0.02 to about 0.3 weight per cent indium with the balance of the alloy being essentially aluminum.
• This alloy contains the normal impurities present in aluminum.
• the aluminum alloy is worked sufficiently to provide the desired oxidation potential.
• the hot working can be carried out by the known processes of drawing, forging, rolling and the like; however, it is preferred that the work be imparted into the alloy by means of extrusion.
• the hot working is carried out in a manner to provide a reduction in crossectional area from the starting aluminum billet to the final worked anode of at least about 9 to l and more preferably at least about 25 to l.
• the temperature of the solid metal during hot working is at least about 200C. and preferably from about 400 to about 600C.
• the described alloy is preferably prepared by melting aluminum with a purity of at least about 99.5 weight per cent aluminum and then adding a sufficient amount of the elements bismuth, gallium and indium to the molten aluminum to provide an alloy within the above defined composition ranges when the added elements are substantially uniformly dispersed within the aluminum.
• These elements can be readily dispersed in the aluminum by mixing equipment and methods commonly accepted in the art.
• Aluminum, bismuth, gallium, and/or indium alloys in amounts sufficient to form an aluminu m alloyp vvithin the herein described composition ranges is contemplated and included herein.
• the metal melted have an aluminum purity of at least about 99.7 weight per cent and preferably at least about 99.85 weight per cent.
• the molten metal is poured or cast into a suitable form or mold of a predetermined shape.
• the molten alloy is solidified and removed from the mold.
• the as-cast shape such as an ingot, is heated to or maintained at a temperature sufficient for hot working of the metal.
• the temperature is sufficient to afford extrusion into a shape adapted for use as a galvanic anode in, for example, water heaters.
• the described worked alloy can be employed as a sacrificial anode using methods known to those skilled in the art. For example, attaching the anode to a more electropositive metal structure, such as a steel member contained in a water heater, to afford an electrical contact between the anode and the steel causes preferential corrosion of the anode in corrosive environments.
• the sol1d1f1ed mgots were removed (m7 (m4 (m2 L5 625 from the molds and heated to a temperature of 480C. 15 0.10 0.01 0.02 1.55 860 prior to being extruded into /2 inch diameter rod.
• the H extruded rod was cut into about 7 inch long sections. 121 0.23 0.04 0.01 1.55 767
• the individual sections were tested in an electrolyte ⁇ is 2%? comprising a mixture of tap water and deionized water. 15 21 0:51 0:01 0:07 1:37 662
• the water had an electro-resistivity of 5.000 ohmcentimeters and a temperature of 70C.
• Each of the EXAMPLES 22-26 sections was immersed in the aqueous electrolyte to a Aluminum with a purity of 99.9 weight per cent was depth of l /2 inches and electrically attached to the melted and heated to a temperature of 750"C.
• Sufflstainless steel container which acted as the cathode.
• cient amounts of bismuth, gallium. and indium were The anode current density was approximately 10 ma/ft" dissolved in the molten aluminum to provide the alloy during testing.
• the described alloys potassium chloride-calomel half cell.
• the anode current density was approxi- 40 mately 50 malft
• the voltage potential as shown in Table 111 was measured with reference to a standard EXAMPLES 941 saturated KCl calomel half cell. It is readily apparent Specimens obtained substantially as described in Exthat extrusion of the indicated alloys significantly imamples l through 8 were tested in a saturated CaSO proved the anode characteristics of the alloys.
• aqueous electrolyte Each specimen was immersed in EXAMPLES 27-58 the aqueous electrolyte to a depth of 3 inches and elec- Aluminum base alloys with a composition as shown trically connected through an 18,200 ohm resistor to in Table IV were prepared substantially as described in the positive side of a rectifier.
• Stainless steel rods were Examples 22-26.
• the anode current density was about connected to the negative side of the rectifier and im- 36 ma/ft
• the data contained in Table IV represents mersed in the electrolyte to act as cathodes.
• the anode the anode characteristics after about 30 days in the cor-. current density during testing was approximately 50 rosive environment. It is apparent that the anode voltma/ft
• the voltage potentials shown in Table ll were age potential and current capacity of the extruded anmeasured with reference to a standard saturated KC] odes are more uniform than and improved over the ascalomel half cell. cast material.
• An extruded sacrificial aluminum anode consisting essentially of about 0.02 to about 2 weight per cent bismuth. about 0.005 to about 0.05 weight per cent gallium. about 0.005 to about 0.5 weight per cent indium and the balance being essentially aluminum.
• the extruded anode of claim 1 consisting essentially of about 0.03 to about 0.3 weight per cent bismuth, about 0.005 to about 0.04 weight per cent gallium and about 0.02 to about 0.3 weight per cent indium.
• a method to form a sacrificial anode comprising providing an alloy consisting essentially of about 0.02 to about 2 weight per cent bismuth, about 0.005 to about 0.05 weight per cent gallium, about 0.005 to about 0.5 weight per cent indium and the balance being essentially aluminum; and working the alloy sufficiently to provide a reduction ratio of the crosssectional areas of the starting alloy to the extruded anode of at least about 9:1.
• the method of claim 7 including working the alloy sufficiently to provide a sacrificial anode with an oxidation potential of about 1.0 to about 1.3 volts at a current density of about 10 ma/ft in an aqueous electrolyte with a resistivity of about 5,000 ohm.cm.
• the method of claim 7 including working the alloy sufficiently to provide a sacrificial anode with an oxidation potential of about 1.3 to about 1.6 volts at a current density of about 50 ma/ft in a saturated calcium sulfate aqueous electrolyte.
• the method of claim 13 including heating the alloy to provide an extrusion temperature of from about 400C. to about 600C.
• the method of claim 7 including heating the alloy to provide a working temperature of at least about 200C.
• the alloy provided consists essentially of about 0.03 to about 0.3 weight per cent bismuth, about 0.005 to about 0.04 weight per cent gallium and about 0.02 to about 0.3 weight per cent indium.
• the method of claim 19 including heating the alloy to provide an extrusion temperature of from about 400C. to about 600C.
• the method of claim 20 wherein the reduction essentially aluminum. 7 ratio is at least about 25 to 23.
• the alloy of claim 22 consisting essentially of aluminum alloy consisting essentially of about about 0.03 to about 0.3 weight per cent bismuth, about to about 2 Weight per cent i about 0005 0.005 to about 0.04 weight per cent gallium and about to about 0.05 weight per cent gallium, about 0.005 to about 0.5 weight per cent indium and the balance being to about welght per Cent mdlum' UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO. 5,878,081 Dated p il 15, 1975 l t r( John T. Reding; Robert L. Riley, Jr'.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrolytic Production Of Metals (AREA)
• Prevention Of Electric Corrosion (AREA)
• Heat Treatment Of Nonferrous Metals Or Alloys (AREA)
• Extrusion Of Metal (AREA)
• Cell Electrode Carriers And Collectors (AREA)

Priority Applications (12)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

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Cited By (14)

Citations (1)

• 1974
  • 1974-07-15 US US488334A patent/US3878081A/en not_active Expired - Lifetime
• 1975
  • 1975-07-10 NL NL7508258A patent/NL7508258A/xx unknown
  • 1975-07-11 DK DK315975A patent/DK315975A/da not_active Application Discontinuation
  • 1975-07-11 GB GB2928575A patent/GB1449118A/en not_active Expired
  • 1975-07-11 FR FR7521966A patent/FR2278791A1/fr active Granted
  • 1975-07-11 CA CA231,268A patent/CA1066175A/en not_active Expired
  • 1975-07-11 IT IT50472/75A patent/IT1040860B/it active
  • 1975-07-14 BE BE158274A patent/BE831339A/xx unknown
  • 1975-07-14 JP JP8611375A patent/JPS5417566B2/ja not_active Expired
  • 1975-07-14 ZA ZA00754513A patent/ZA754513B/xx unknown
  • 1975-07-14 DE DE19752531423 patent/DE2531423A1/de not_active Withdrawn

Patent Citations (1)

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