US3925185A - Prevention of crevice corrosion - Google Patents

Prevention of crevice corrosion Download PDF

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Publication number
US3925185A
US3925185A US457603A US45760374A US3925185A US 3925185 A US3925185 A US 3925185A US 457603 A US457603 A US 457603A US 45760374 A US45760374 A US 45760374A US 3925185 A US3925185 A US 3925185A
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United States
Prior art keywords
cell
nickel
mixture
nickelous oxide
diaphragm
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Expired - Lifetime
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US457603A
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English (en)
Inventor
Joseph J Lint
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Electronor Corp
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Electronor Corp
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Publication date
Application filed by Electronor Corp filed Critical Electronor Corp
Priority to US457603A priority Critical patent/US3925185A/en
Priority to GB476275A priority patent/GB1434185A/en
Priority to CA221,735A priority patent/CA1037902A/en
Priority to FR7510205A priority patent/FR2266754B1/fr
Priority to IT21930/75A priority patent/IT1034789B/it
Application granted granted Critical
Publication of US3925185A publication Critical patent/US3925185A/en
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Expired - Lifetime legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
    • C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/60—Constructional parts of cells
    • C25B9/65—Means for supplying current; Electrode connections; Electric inter-cell connections

Definitions

  • ABSTRACT [52] 204/252; 23/252 204/242; A novel method of preventing damage to the base of Int Cl 2 g ig ggg diaphragm-type cells used for the production of chlorine by electrolysis of brine solutions by incorporating [581 Fleld Search 204/242 279; into the insulating blanket covering the base a mixture 21/2'5 R; 23/252 A of nickel powder and nickelous oxide, the said mixture bein at least in the areas where crevice corrosion is [56] References Cited g to (mun UNITED STATES PATENTS 3,817,704 6/1974 Dearmont et al, 21/25 R 12 Claims, 2 Drawing Figures U.S. Patent Dec.
  • Diaphragm-type cells for the electrolysis of aqueous alkali metal halide brines generally employ a forami lawn or perforated metallic cathode and a fluid-permeable diaphragm overlaying the cathode thereby permitting hydraulic flow of electrolyte from the anode cham- 1 her through the diaphragm and cathode into the cathode chamber.
  • Such cells first made their appearance in the early part of the twentieth century.
  • the fluid permeable diaphragm by separating the anode and cathode chambers, avoids the disturbing effects of convection currents and gas evolution, and generally inhibits migration of hydroxyl ions towards the anode.
  • Those diaphragm-type cells most widely used today are of the circulating electrolyte type, wherein the diaphragms and cathodes may be arranged horizontally or vertically, but in most instances, at least in the United States, the arrangement is vertical.
  • Such cells are in wide-spread use in the industry for the production of chlorine and caustic soda from sodium chloride brines and, through the use of various sophisticated modifications, considerable efficiency has been obtained from the cells which have been operated at current densities approaching l ampere per square inch. However, despite their widespread acceptance, these cells nevertheless have certain drawbacks and disadvantages which limit the further modification and improvement thereof.
  • an electrically insulating coating for example asphalt, which prevents access of the corrosive anolyte to the metal.
  • a layer of concrete is applied over this asphalt layer to complete the base construction.
  • the cell base is made of a conducting material and anodes are positioned thereon by risers passing through the cell base and provided with a flange, preferably made of titanium, on the lower portion thereof and a non-conductive, preferably rubber, sheet on the cell base to act as a compressible seal between the anodes 2 and the cell base and between the cell can and the cell base.
  • crevice corrosion is due to a special type of galvanic cell arising from a difference in the electrolyte composition in the crevice and the electrolyte in contact with the main body of the metal part or 0 flange. The crevice corrosion could cause leaks of electrolyte from the cell and other problems leading to premature shut down of the cell for repairs.
  • the invention relates to an improvement in diaphragm cells wherein the anodes are supported by risers which are secured in the base and the base is insulated from the interior of the cell by a protective sheet, the improvement comprising providing in the area of the cell base where crevice corrosion normally occurs a mixture of metallic powder nickel and nickelous oxide in the protective blanket or gasket sealing means. Usually, it is effected by incorporating into the protective sheet at least in the area thereof through which the risers pass a mixture of metallic nickel powder and nickelous oxide.
  • the said mixture may be incorporated throughout the entire protective sheet or only in the area where the risers pass therethrough.
  • the protective sheets are usually made of chlorinated rubber or neoprene type material and if the said mixture is to be incorporated throughout the sheet, the mixture of metallic nickel powder and nickelous oxide may be substituted for the zinc and magnesium oxide filling and curing agents.
  • the nickel and nickelous oxide provide the needed curing effect during vulcanization of the neoprene blanket and the omission of the zinc and magnesium compounds from the protective blanket avoids their possible chlorination which would aggravate the crevice corrosion problem.
  • the protective sheet is not a neoprene type material but a metal sheet such as a titanium sheet
  • the gaskets used to seal the cell and the area around the anode risers are made of neoprene type material and the nickelnickelous oxide mixture is incorporated in this material to prevent crevice corrosion. It is also possible to merely insert into the neoprene type blanket, small gasket portions which can be inserted into the blanket in those areas wherein the anode risers pass through the protective blanket.
  • Neoprene type material used for the protective blanket or the gasketing material are well known but the most commonly used types are the G and W types.
  • Neoprene is made by polymerizing 2-chlorobutadiene in the presence of suitable catalysts, emulsifying agents,
  • the G-type neoprene differs from the W'types in that G contains a thiuram disulfide stabilizer and are interpolymerized with sulfur.
  • plasticizer and softeners such as naphthenic oils and other petroleum derivatives are used to increase flexibility thereof.
  • Fillers may be carbon black, clays, calcium carbonate, silicon dioxide and other mineral fillers.
  • Antioxidants are added to provide maximum protection from heat, ozone, and/or discoloration.
  • Processing acids may also be incorporated therein which class are included lubricate, tackifiers and agents to control viscosity and nerve.
  • the area of the neoprene in the crevice corrosion problem area should be cut or scraped to remove the fiim inherently formed on the surface of the neoprene during the vulcanization pro cess.
  • the amount of metallic nickel and nickelous oxide to be incorporated into the neoprene may be 25 to 45 preferrably 30 to 40 by weight.
  • the weight ratio of the nickel to nickelous oxide may vary from 3:1 to l:l ,preferably l.5:l to 2:1
  • FIG. 1 is a simplified end view of a typical diaphragm-type electrolytic cell of the invention with the cell can and cathodes removed for clarity.
  • FIG. 2 is a simplified side view of a portion of the diaphragm-type electrolytic cell of FIG. 1 with cell can and cathodes not shown.
  • the cell base 1 is constructed of a material such as aluminum or copper and hence serves as both the supporting means for the cell and the conductor.
  • the power supply is attached directly to this base, for example, by means of a nut 9 and bolt 11.
  • the non-conductive sheet 3 covers essentially all of the cell base 1 and is constructed of an elastic material such as neoprene containing metallic nickel powder and nickelous oxide.
  • the protrusions 5 and 6 on this non-conductive sheet 3 perform separate functions.
  • Protrusion 5 serves as a gasket on which the cell can rests. A small amount of putty 29 lines the inside of the protrusion to insure that no leakage occurs.
  • Protrusion 6 serves as a deflector to prevent brine or water from getting between the non-conductive sheet 3 and the cell base 1.
  • the valve metal anode 19 with the electrocatalytic coating thereon is connected, for example by welding, to the anode riser 13, which riser extends through the nonconductive sheet and cell base and is fastened on the bottom of the cell base by means of a nut 17.
  • suitable electrocatalytic, electrically conductive coatings are described in US. Pat. Nos. 3,632,498 and 3,71 1,385.
  • the preferred coating for chlorine production is TiO RuO This is one of the problem areas in which crevice corrosion generally occurs.
  • the neoprene blanket is scraped in this area to remove the film on the blanket formed during vulcanization.
  • the riser is also provided with a flange which upon tightening the nut 17, forms a hydraulic seal with the non-conduc tive sheet of materiai 3 thereby preventing leakage of anolyte through the cell base. While it is indicated in FIG. 1 that two anodes extend across the width of the cell, this number is not critical and may be changed as conditions warrant.
  • FIG. 2 is a partial side view along the length of a cell, again with the conventional cathodes and cell can removed.
  • This figure shows essentially the same features as in FIG. 1, however, there is also indicated on the anode 19 the electrically conductive surface 21, greatly exaggerated for illustration, in fact being on the order of from 1 to 5 microns in thickness.
  • the resulting neoprene had a durometer hardness rating of 65-70.
  • a 40 mil sheet was cut into circular gaskets 2 inches in diameter, said gaskets being abraded to expose the nickel.
  • a sandwich of alternating discs of titanium and neoprene prepared above were clampedin a press of a titanium frame, nuts and bolts.
  • a second test was run with alternating layers of titanium and conventional neoprene without the metallic nickel-nickelous oxide mixture.
  • the sandwiches were then submerged for 13 days into a refluxing aqueous solution of 25 g/l of sodium chloride with a pH of 1.3 after which the sandwiches were checked for corrosion.
  • the sandwich with conventional neoprene exhibited heavy titanium corrosion and build up of deposits while the sandwich of the invention was free of corrosion.
  • a diaphragm cell comprising a cell base with anodes mounted thereon and covered with a protective blanket and a cell can with cathodes mounted therein, the improvement comprising providing in the area of the cell base where crevice corrosion normally occurs a mixture of metallic powder nickel and nickelous oxide in the protective blanket or gasket sealing means.
  • an improved diaphragm cell comprising a cell base with dimensionally stable metal anodes mounted thereon, a protective rubber blanket covering said cell base and a cell can with cathodes mounted therein resting on the cell base, the improvement comprising a rubber blanket having incorporated therein a mixture of metallic powdered nickel and nickelous oxide, the blanket surface in the areas where crevice corrosion is likely to occur being abraded.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Sealing Material Composition (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
US457603A 1974-04-03 1974-04-03 Prevention of crevice corrosion Expired - Lifetime US3925185A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US457603A US3925185A (en) 1974-04-03 1974-04-03 Prevention of crevice corrosion
GB476275A GB1434185A (en) 1974-04-03 1975-02-04 Electrolytic cells and methods of operating them
CA221,735A CA1037902A (en) 1974-04-03 1975-03-10 Prevention of crevice corrosion
FR7510205A FR2266754B1 (enExample) 1974-04-03 1975-04-02
IT21930/75A IT1034789B (it) 1974-04-03 1975-04-02 Procedimento per impedire la corrosione interstiziale in particolare alla base di celle del ipo a diaframa

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US457603A US3925185A (en) 1974-04-03 1974-04-03 Prevention of crevice corrosion

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US3925185A true US3925185A (en) 1975-12-09

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US457603A Expired - Lifetime US3925185A (en) 1974-04-03 1974-04-03 Prevention of crevice corrosion

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US (1) US3925185A (enExample)
CA (1) CA1037902A (enExample)
FR (1) FR2266754B1 (enExample)
GB (1) GB1434185A (enExample)
IT (1) IT1034789B (enExample)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4098670A (en) * 1975-03-27 1978-07-04 The Goodyear Tire & Rubber Company Sealing member for an electrolytic cell
US4699703A (en) * 1986-05-02 1987-10-13 Lauren Manufacturing Company Anodic boot for steel reinforced concrete structures

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3817704A (en) * 1971-04-15 1974-06-18 Phillips Petroleum Co Sludge- and corrosion-inhibiting compositions
US3857773A (en) * 1973-04-05 1974-12-31 Ppg Industries Inc Suppression of crevice corrosion in gasketed titanium crevices by the use of rubber compound gaskets substantially free of calcium

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3817704A (en) * 1971-04-15 1974-06-18 Phillips Petroleum Co Sludge- and corrosion-inhibiting compositions
US3857773A (en) * 1973-04-05 1974-12-31 Ppg Industries Inc Suppression of crevice corrosion in gasketed titanium crevices by the use of rubber compound gaskets substantially free of calcium

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4098670A (en) * 1975-03-27 1978-07-04 The Goodyear Tire & Rubber Company Sealing member for an electrolytic cell
US4699703A (en) * 1986-05-02 1987-10-13 Lauren Manufacturing Company Anodic boot for steel reinforced concrete structures
WO1987006628A1 (en) * 1986-05-02 1987-11-05 Lauren Manufacturing Company Anodic boot for steel reinforced concrete structures

Also Published As

Publication number Publication date
CA1037902A (en) 1978-09-05
IT1034789B (it) 1979-10-10
FR2266754B1 (enExample) 1979-08-03
FR2266754A1 (enExample) 1975-10-31
GB1434185A (en) 1976-05-05

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AS Assignment

Owner name: ELECTRODE CORPORATION, A DE CORP., OHIO

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:DIAMOND SHAMROCK TECHNOLOGIES, S.A.;REEL/FRAME:005004/0145

Effective date: 19881026