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
  • C22C21/006—Alloys based on aluminium containing Hg
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
  • H01M4/46—Alloys based on magnesium or aluminium
• • 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
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• This invention relates to sacrificial galvanic anodes and more particularly is concerned with a novel aluminum based alloy exhibiting a high electrical output per unit mass of metal, i.e. a high current efiiciency and an oxidation potential in the range particularly suitable for use as a sacrificial anode in sea water applications and to anodes prepared therefrom.
• Zinc is extensively used as a galvanic sacrificial anode in the cathodic protection of installations operated in or in contact with sea water.
• Zinc which has a potential of about 1 volt (measured versus calomel reference), is satisfactory for this use and possesses the advantage that its working potential provides less possibility of damage to protective surface films such as protective coatings and paints than anode materials having ing higher working potentials, such as magnesium (-l.5 volts).
• Zinc however, suffers from the disadvantage that it has a relatively low ampere-hour capacity of about 370 ampere-hours per pound.
• Aluminum which has a high theoretical electrical output per unit mass of metal consumed (about 1350 ampere-hours per pound), in actual practice has not proved to be useful as a sacrificial galvanic anode in that the presence of the normally passive oxide surface film on aluminum apparently presents a barrier to the oxidation of the metal thereby reducing the effective oxidation potential to about 0.7 volt (as measured in closed circuit at either about 250 or about 1000 milliamperes per square foot in a synthetic sea water electrolyte with a standard saturated KCl calomel cell as reference). At such a low operating voltage, no cathodic protection is given to ferrous based structures, for example; therefore, the anode exhibits no useful electrical output.
• Aluminum alloys containing zinc and mercury have been found which provide oxidation potentials of from about 0.9 to about 1.2 volts and a high electrical output per pound. However, in general, these show a marked decrease in current efiiciency (ampere-hours per pound of anode consumed) as the purity of the base aluminum metal is lowered. This particularly is noted with respect to iron inclusion, a common impurity in primary aluminum.
• the present invention comprises a novel aluminum based alloy having from about 0.1 to about 20 weight percent zinc, from about 0.01 to about 0.1 weight percent mercury, a maximum of about 0.5 weight percent iron, a maximum of about 0.6 weight percent silicon and further characterized that the SiiFe ratio ranges from about 0.5 to about 5.
• the alloy comprises aluminum having alloyed therewith from about 0.1 to about 15 weight percent Zinc, from about 0.02 to about 0.1 weight percent mercury, from about 0.08 to about 0.5 weight percent iron, and silicon in an amount to provide a Si:Fe ratio of from about 1 to about 3, the maximum silicon concentration being about 0.6 weight percent. All weight percents are based on total composition weight.
• the present novel alloy composition when employed as sacrificial galvanic anodes exhibits a satisfactory, relatively smooth corrosion pattern throughout the life of the anode, an operating oxidation potential of from about 0.9 to about 1.2 volts depending upon the current density of operation and electrical output in ampere-hour per pound of metal consumed which can closely approach theoretical.
• Galvanic anodes can be prepared from the novel compositions by use of alloying and casting or fabricating techniques ordinarily employed in the aluminum art.
• Aluminum for use in preparing the present novel alloy composition can be a low commercial grade (e.g. 99.5% or lower Al) metal having normal production introduced impurities associated therewith.
• the alloying metals also can be of commercial grade.
• EXAMPLE A number of anodes of the present invention were prepared by melting iron contaminated aluminum ingot in a graphite crucible positioned within an electric furnace. Predetermined amounts of mercury, zinc and silicon alloying ingredients were introduced into the molten aluminum and the resulting mixture stirred to effect dispersion and solution of the alloying ingredients throughout the melt. The resulting alloy was cast in a graphite mold into cylindrical specimens about 5 /2 inches long and either about /8 inch or 1 inch in diameter. The cooling and solidification rate of the castings were controlled such that these simulated the cooling rate experienced in production of commercial, field-sized cast anodes.
• the performance of the alloys was evaluated by positioning a specimen of the cast cylinder (as anode) in a one-half gallon glass jar. A steel wire mesh cloth was placed adjacent to the inner Wall of the jar as a cathode. Synthetic sea water was used as an electrolyte with about 3 inches of each anode specimen being immersed. The cells were completed with respect to electrical circuitry, a rectifier being employed to maintain a constant direct current through a group of cells connected in series.
• Table I show the performance at a current density of about 1000 milliamperes per square foot over a 47 day test period for a number of the novel aluminum alloy anodes of the composition of the present invention. These results present data showing both the solution potential (vs. saturated calomel) and electrical output per unit mass of metal consumed for the anodes tested. The current efficiency was determined by weighing the test anodes before and after testing and comparing the actual weight loss with the theoretical calculated Weight loss.
• An aluminum based sacrificial galvanic anode composition consisting essentially of: from about 0.1 to 20 weight percent zinc; from about 0.01 to about 0.2 weight percent mercury; iron in an amount up to 0.5 Weight percent; and silicon present in an amount in excess of normal impurity level, the silicon:iron ratio in the anode composition being within the range of from about 0.5 to about 5 and the maximum total silicon concentration being about 0.6 weight percent; the balance of the composition being aluminum.
• composition of claim 1 wherein the zinc is present in an amount of from about 0.1 to about percent, mercury from about 0.02 to about 0.1, iron from about 0.08 to about 0.5 percent and silicon in an amount to provide a silicontiron ratio within the range of from about 1 to about 3.
• composition of claim 1 in the form of a cast anode structure.
• S1m1lar galvanic protection to ferrous-based substrates silicon 1n sald anode, and controlling said silicon content is realized by flame spraying the alloy of the present 1nto provide a srliconzrron rat1o 1n said anode within the vention onto the substrate, applying paint or binder sysrange of from about 0.5 to about 5 to enhance current tems thereto wherein the present alloy in powdered form is in high ratio to the carrying vehicle or binder, by spraying the alloy onto a heated ferrous surface, the temperature of the ferrous material being sufficient to melt the aluminum alloy and assure adherence between the alloy and substrate, and the like methods of application.
• novel alloy composition also is suitable for use as sacrificial anodes for applications such as galvanic pigments in paint films, galvanic anode materials for primary batteries and, as shown hereinbefore as sacrificial galvanic coatings for sheet steel and other metals cathodic to aluminum. Additionally this composition finds utility as an active ingredient in flares, for use in chemical reductions and in the preparation of aluminum alkyls.
• said anode also containing zinc in an amount from about 0.1 to about 20 weight percent and mercury in an amount from about 0.01 to about 0.2 weight percent.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Prevention Of Electric Corrosion (AREA)
• Electrolytic Production Of Metals (AREA)
• Meat, Egg Or Seafood Products (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=24165039

Family Applications (1)

Country Status (10)

Cited By (1)

Families Citing this family (2)

Citations (6)

• 1966
  • 1966-04-15 US US542727A patent/US3496085A/en not_active Expired - Lifetime
• 1967
  • 1967-03-28 DE DE19671558478 patent/DE1558478B1/de active Pending
  • 1967-03-30 DK DK171167A patent/DK128909C/da not_active IP Right Cessation
  • 1967-04-07 ES ES339053A patent/ES339053A1/es not_active Expired
  • 1967-04-10 FR FR102170A patent/FR1518355A/fr not_active Expired
  • 1967-04-11 GB GB06604/67A patent/GB1182814A/en not_active Expired
  • 1967-04-13 NO NO167724A patent/NO117336C/no unknown
  • 1967-04-14 NL NL676705305A patent/NL152934B/xx unknown
  • 1967-04-14 BE BE697041D patent/BE697041A/xx not_active IP Right Cessation
  • 1967-04-15 JP JP42023893A patent/JPS493889B1/ja active Pending

Patent Citations (6)

Also Published As

Similar Documents

Legal Events