Classifications

• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/002—Castings of light metals
  • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
• • 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
• • 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 aluminum alloy fabrications and more particularly is concerned with an improved process for preparing aluminum alloy casting exhibiting a high electrochemical efficiency and an oxidation potential in the range particularly suitable for use as sacrificial anodes with ferrous structures in saline water applications.
• Aluminum which has alloyed therewith small amounts of mercury for example, from about 0.001 to about 0.2 weight percent and usually from about 0.005 to about 0.08 weight percent, as well as up to about 35 weight percent zinc and/ or from less than 1 percent up to 20 weight percent of one or more certain other alloying components such as for example magnesium, calcium, manganese, copper, silver, cadmium, tin, gold, antimony, beryllium, silicon, barium, strontium, gallium, bismuth, indium and lead has been found unexpectedly to be cathodic protection of ferrous based installations and objects operated in or in contact with sea water and other saline or brackish waters.
• certain other alloying components such as for example magnesium, calcium, manganese, copper, silver, cadmium, tin, gold, antimony, beryllium, silicon, barium, strontium, gallium, bismuth, indium and lead has been found unexpectedly to be cathodic protection of ferrous based installations and objects operated in or in contact
• mercury containing alloys when cast or otherwise fabricated into anode structures and employed as sacrificial galvanic anodes as set forth hereinbefore exhibit an operating oxidation potential of from about 0.9 to about 1.2 volts (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). Additionally, anodes prepared from the majority of these compositions exhibit a satisfactory, relatively smooth corrosion pattern throughout the operating life of the anode and a high efficiency (actual electrical output in ampere-hours per pound of metal consumed as compared to theoretical) ranging from 70 percent to 98 percent or higher.
• Anodes from these mercury containing aluminum alloy compositions usually are prepared by alloying and castting following conventional aluminum metal handling procedures.
• aluminum alloys are cast while employing melt temperatures between about 1220 F. and 1350 F. Within this range, good melt fluidity and castability results.
• melt temperatures between about 1220 F. and 1350 F. Within this range, good melt fluidity and castability results.
• Those skilled in the aluminum casting art normally do not employ higher casting temperatures because it is universally understood that nothing is gained by casting at higher temperatures.
• a mercury containing aluminum alloy composition which exhibits an electrochemical potential of from about 0.9 to about 1.2 volts and a high efliciency when utilized as a sacrificial anode with a ferrous structure in saline water applications is melted at a temperature of at least about 1400 F. and generally at from about 1400 to about 1800 F., preferably at from about 1500 to about 1800 F. and cast while at this melt temperature.
• Cast anodes prepared by this treatment exhibit markedly reduced surface oxidation during storage as compared to those anodes cast using conventional aluminum melting and casting temperatures.
• the melt and casting temperature is predetermined with respect to the mercury content of the alloy.
• the molds can be preheated to a temperature of from several hundred degrees Fahrenheit up to 1000 F. or more prior to casting the high temperature melt therein. In actual foundry operations, it has been found that the initial casting heats the mold sufficiently such that the mold is still at an elevated temperature of several hundred degrees Fahrenheit or more when subsequent castings are made therein.
• iron molds ordinarily are used in casting aluminum, if desired these can be coated with a thin film of mold wash (a thin graphite suspension in water) or can be coated with acetylene black from an acetylene flame prior to casting the aluminum melt therein. This coating although very thin prevents iron contaminant from the mold wall from being absorbed into the casting as it solidifies.
• the preparation of the alloy itself is carried out in a conventional manner. Since mercury has a low solubility in aluminum and because of its physical state, it is harder to alloy with other higher melting metals. Conveniently the mercury can be prealloyed with other of the other alloying ingredients, for example zinc, and the prealloy be submerged into the molten aluminum at a temperature slightly above the melting point of the aluminum. The prealloy is then dispersed in the melt and the melt heated and cast in accordance with the practice of the present invention.
• the melting of the alloy can be carried out using induction furnaces, gas fired furnaces and the like heating apparatus. Ordinarily, some type of agitation is employed to assure that the alloying component are substantially homogenously blended throughout the melt. With induction type furnaces, no external agitation is needed while with gas fired furnaces generally these are stirred to mix the alloying components throughout the melt.
• Example 1 Aluminum alloy melts having zinc and mercury as the alloying components were prepared in an induction furnace. In this study, a number of alloys were prepared wherein mercury was first prealloyed with zinc in predetermined quantities and the prealloy then added to the molten aluminum. Total melt weights ran from about 10 to about 16 pounds.
• the base aluminum metal employed was a commercially available aluminum of about 99.85 percent purity, the main impurities being iron and silicon.
• the melts were heated to either 1400 or 1800 F. and then each melt was cast into a mold which was at a temperature of about 55-0 F. The cast ingots after solidifying and cooling were removed from the mold and placed in an environment of 100 percent relative humidity at room temperature (i.e., about 80 F.) for two hours.
• Example 2 the ingots were examined to determine the extent of surface oxidation. Prior to placing the ingots in the high humidity test chamber, they were sampled and elemental chemical analysis run to determine the alloy composition. The data and results for these Example 2.
• 99.9 percent purity aluminum as a base metal and following the procedure described in Example 1 a number of mer-cury-zinc-aluminum alloys were melted and cast at a predetermined melt temperature.
• the amount of surface oxidation was determined quantitatively.
• Table II For purposes of comparison, a number of controls wherein the melt temperature was below that employed in the practice of the present invention also are included in Table II.
• Example 3 TABLE II Analysis Temperature Percent of Run No of melt, F. surface Percent Hg Percent Zn oxidation
• Example 3 A series of 249 field size anodes ranging from about 10 to about 75 pounds each were melted and cast using commercial foundry equipment. For these anodes the aluminum base base metal was from about 99.85 to about 99.9 percent pure. Mercury and zinc were prealloyed for addition to the molten aluminum and alloyed with molten aluminum as described in Example 1. Analyses of the cast anodes indicated a mercury concentration of from about 0.0480.05 percent and a zinc concentration from about 0.50.75 percent. The ingots were melted and cast at controlled temperatures ranging from 1300 to about 1800 F.
• Example 4 A series of anodes such as in Example 3 were were cast having mercury concentrations of from about 0.02 to 0.025 weight percent and a zinc concentration of from about 0.2 to 0.37 weight percent. These melts were heated over a temperature range of from 1400 to 1500 F. and cast into ingots at this temperature. After storage for a period of 1 year at ambient temperature in the open atmosphere (Texas Gulf Coast, i.e. -10O percent relative humidity), visual examination showed virtually no surface oxidation on these cast ingots.
• Example 5 A series of about 250 pound castings were prepared from an aluminum-mercury-zinc alloy employing aluminum of about 99.90 percent purity. A prealloy of mercury and zinc was added to the melt and each melt heated to within the temperature range of from about 1400 to 1 600 F. The concentration of mercury and zinc in the castings as determined from chemical analysis of samples taken from 100 of such castings was about 0.045 percent mercury and 0.45 percent zinc there being very little variation from these figures from ingot to ingot. The entire batch of 1 00 castings was exposed for about 2 weeks to ambient outdoor atmosphere on the Texas Gulf Coast (i.e. humidity of about 100* percent). Examination of the cast ingots after this period showed that none of them exhibited any visible surface oxidation.
• I novel process for preparing aluminum alloy castings exhibiting a high electrochemical efficiency and an oxidation potential in the range partcularly suitable for use as sacrificial anodes with ferrous based structures in saline water applications which comprises;

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Prevention Of Electric Corrosion (AREA)
• Sliding-Contact Bearings (AREA)

Priority Applications (8)

Applications Claiming Priority (1)

Publications (1)

Family

ID=24223190

Family Applications (1)

Country Status (7)

Cited By (2)

Citations (3)

• 1966
  • 1966-06-13 US US556877A patent/US3415305A/en not_active Expired - Lifetime
• 1967
  • 1967-05-26 SE SE7422/67A patent/SE301032B/xx unknown
  • 1967-06-07 GB GB26293/67A patent/GB1195552A/en not_active Expired
  • 1967-06-12 NO NO168555A patent/NO117382B/no unknown
  • 1967-06-13 BE BE699831D patent/BE699831A/xx not_active IP Right Cessation
  • 1967-06-13 DK DK306967AA patent/DK113535B/da not_active IP Right Cessation
  • 1967-06-13 NL NL6708179A patent/NL6708179A/xx unknown

Patent Citations (3)

Also Published As

Similar Documents

Legal Events