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

• a galvanic or a consumable anode which has less noble electrode potential than metals to be protected, is electrically connected to the metal structure to be protected. Accordingly, a galvanic anode is consumed and the current for the cathodic protection flows into the metal to be protected.
• aluminum base alloy galvanic anodes which are known at present, there are an alloy comprising 3-6% by weight of zinc; an alloy comprising a total of 01-10% by weight of tin and/ or indium, an alloy obtained by adding 110% by weight of zinc to said alloy; and an alloy prepared by adding zinc or magnesium to an aluminummercury alloy.
• the aluminum-zinc alloy has an anode potential of 0.9 to 1.0 v. (vs. Standard Calomel Electrode) and an anodic current efficiency of about 50%.
• the aluminum-indium alloy has an anode potential of 1.0 to --1.10 v. and an anodic current efficiency of not more than 80%.
• an aluminum alloy containing zinc, indium and cadmium which is considered to be the best commercial aluminum alloy galvanic anode known at present, has an anode potential of about 1.1 v. and an anodic current efficiency of 80-85%.
• the aluminum-mercury alloy shows an anode potential of about -1.3 v., but its anodic current efiiciency is less than 60%, and it is said that an alloy obtained by adding magnesium to said alloy can be improved in anodic current efliciency to about 90%.
• a magnesium containing alloy has a danger of ignition of a fire due to impact with other metallic materials and hence is not desirable as an alloy for the cathodic protection of constructions for handling inflammable materials.
• said alloy shows unnecessary degradation of anode, when used for a long period of time, thereby shortening the life of anode.
• the present inventors made various investigations by adding a variety of elements to said alloy, in order to discover aluminum alloys acceptable as galvanic anodes. As the result, the inventors have found an aluminum alloy galvanic anode which is free from the above drawbacks.
• One object of the present invention is to provide an aluminum alloy galvanic anode which has a lower electrode potential and a higher current efiiciency than prior commercial aluminum base alloys and shows no pitting or selective corrosion.
• the present inven tion provides an aluminum base alloy containing 0.01- 0.2% by weight of mercury, 0.01-10% by weight of zinc and 0.01-2% by weight of lead based on the weight of the alloy, which is an excellent aluminum alloy galvanic anode having an anode potential of about 1.11 v. and an anodic current efiiciency of -95%, showing an uniform corrosion and maintaining a lower electrode potential for along period of time.
• the mercury content of the alloy is desirably 0.01-0.2% by weight based on the weight of the alloy.
• the alloy In case the mercury content is more than 0.2%, the alloy is quite active and starts reaction with moisture in air immediately after preparation.
• the content of Zinc is preferably 0.01-10% by weight based on the weight of the alloy. In case zinc content is more than 10% no difference is observed in effect, but the quantity of generated electricity is reduced.
• the alloy shows a lower anodic current efficiency.
• Preferable amount of lead to be added is 0.01-2% by weight based on the weight of the alloy.
• the dissolution of the alloy becomes uniform, without apparent pitting or selective corrosion.
• the aluminum alloy of the present invention may be heat treated.
• EXAMPLE 1 An alloy prepared by adding to aluminum, 0.05% by weight of mercury, 0.1% by weight of zinc and 0.2%
• test sample was cast in a metal mold into the form of a rod, was shaved so as to have a diameter of 20 mm. and a length of 100 mm., was degreased and was then weighed, and the exposed area of the sample was maintained constant. Subsequently, the test sample was immersed in artificial sea water having the composition shown below, and the iron plate was used as the cathode.
• Table 1 shows the results of tests effected in the same manner as in Examples 1 and 2.
• the anodic current density was maintained at 1 ma./cm. by an external battery.
• the test period was 168 hours.
• the amount of electricity passed was measured by use of the copper coulometer.
• the sample was washed with water, was immersed for 23 minutes in concentrated nitric acid to remove corrosion product from the surface and was weighed to calculate the corrosion loss:
• the current efficiency of the galvanic anode was calculated from the theoretical amount of corrosion obtained from the total amount of electricity passed and from the corrosion loss, and was 94.9%.
• the anode potential was about 1.11 v. throughout the test period.
• the corrosion of the galvanic anode was quite uniform compared with the case of the conventional alloy.
• EXAMPLE 2 An aluminum alloy containing 0.05% by weight of mercury, 0.1% by weight of zinc and 0.01% by weight the lead content is 0.2%.
• An anode as set forth in claim 2 in which the mercury content is 0.05%, the zinc content is 3.0%, and the lead content is 0.2%.

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• 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)

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Citations (2)

• 0
  • NL NL131860D patent/NL131860C/xx active
• 1967
  • 1967-05-19 NL NL6706945A patent/NL6706945A/xx unknown
  • 1967-05-19 US US639605A patent/US3464909A/en not_active Expired - Lifetime
  • 1967-05-19 NO NO168222A patent/NO117567B/no unknown
  • 1967-05-19 GB GB23440/67A patent/GB1128138A/en not_active Expired
  • 1967-05-19 DE DE19671558640 patent/DE1558640B2/de not_active Withdrawn

Patent Citations (2)

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