Electrodes for electrolytic cells

Abstract

An electrode for use in an electrolytic cell, and a method for producing same, wherein said electrode comprises an internal copper conductor and an external element of a second metal, at least a portion of each having contact surfaces being held in intimate contact with the other, said conductor and said element each having a conductive coating applied to the contact surface, said conductive coating comprising between about 20 and about 30 percent indium and between about 80 and about 70 percent gallium, whereby the contact resistance between said conductor and said element is reduced.

Description

for four days or even less.

EXAMPLE 1

Two coupons of copper C 110 strip, each being 0.045"×1"×2" were cleaned by degreasing with methanol and acid etching in a 12 weight percent H₂ SO₄ solution for about 10 seconds to produce a material having a front to back resistance of about 0.06 milliohms. At the same time, two coupons of nickel 200 alloy, each being 0.055"×1"2" were cleaned by vapor degreasing in methanol and acid etching in a solution comprising 37.8 milliliters H₂ O+56.8 milliliters H₂ SO₄ +85.2 milliliters HNO₃ for 10 seconds at 35°C to produce material having a front to back resistance of about 0.23 milliohms. After being rinsed with distilled water and dried, an area of about one square inch of a predesignated mating surface of one copper coupon and one nickel coupon was evenly coated with a thin layer of conductive coating 25 having a composition of about 23% indium and 77% gallium, using a cotton swab applicator after which said coated surfaces were pressed together to form a conductive copper-nickel couple. This was placed in an oven set for a nominal temperature of about 90°C For purposes of comparison a cleaned but uncoated copper-nickel couple made from the remaining coupons was also placed in the oven. Both couples were also loaded to 10 psi to simulate both thermal and mechanical levels experienced in a typical chlor-alkali cell electrode installation. When assembled, no bonding was experienced with either couple.

The resistance across the couples was periodically measured with results as follows:

______________________________________
[Cu--Ni Couple Resistance]
(Milliohms)
Aging Time    Coated     Uncoated
______________________________________
0 days                   0.55
1 day    0.21
3 days        0.19
4 days                   2.80
6 days                   63.50
8 days        0.21
10 days       0.07
11 days                  142.5
15 days       0.19
17 days                  135.6
25 days       0.14
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The results of this example show that whereas the contact resistance of the untreated couple increased rapidly, that of the coupled couple remained stable and may have actually decreased slightly after 25 days of testing.

EXAMPLE 2

The procedure of Example 1 was repeated with the nickel coupon being replaced with 0.00385"×1"×2" titanium (Grade 1) coupons having, after etching, a front to back resistance of about 1.75 milliohms.

Results obtained are given below:

______________________________________
[Cu--Ni Couple Resistance]
(Millohms)
Aging Time    Coated     Uncoated
______________________________________
4 days        2.60       170
8 days        0.95       190
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Results comparable to Example 1 were observed. Note, however, how rapidly and to what degree the electroresistant oxide coating builds up on the titanium surface.

EXAMPLE 3

The procedure of Example 2 was followed with the titanium being replaced by titanium coupons containing a 0.1 micron thick layer of copper sputtered onto the mating surface. This was cleaned using the procedure for copper as detailed in Example 1.

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[Cu--Cu Sputtered Ti Couple Resistance]
(Milliohms)
Aging Time Coated        Uncoated
______________________________________
0 days                   0.4
1 day 0.98          4.4
3 days     1.03
4 days     0.63          50.5
6 days                   60.5
8 days     0.63
10 days    0.64
11 days                  70
15 days    0.65
17 days                  70
25 days    0.85
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This shows that sputtering copper on titanium produces a system which while superior to a Cu-Ti couple will still quickly break down on long-term exposure to the temperature and pressure environmental conditions of a cell to achieve uncoated contact resistance values substantially higher than those found with coated couples.

This invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. An electrode for use in an electrolytic cell, said electrode being comprised of an internal copper conductor and an external element, said element being selected from the group consisting of titanium and nickel, at least a portion of said copper conductor having contact surfaces which are held in intimate contact with contact surfaces of said external element, said conductor and said element having at an area of contact a conductive coating between said contact surfaces of said conductor and said element, said conductive coating being comprised of a mixture of between about 20 and about 30 percent indium by weight and about 80 and about 70 percent gallium by weight, whereby the contact resistance between said conductor and said element is reduced.

2. The electrode of claim 1 wherein said conductive compound is comprised of between about 23 and about 26 percent by weight of indium and about 77 and about 74 percent by weight of gallium.

3. An electrolytic cell containing the electrode of claim 1.

4. The electrode of claim 1 wherein the titanium further has a layer of copper on said contact surface.

5. An electrode for use in an electrolytic cell said electrode comprising in combination:

(a) copper means having at least a first mating contact surface for conducting electrical energy;

(b) electrolyte corrosion-resistant means having a second mating contact surface which contacts the conductor means along the first mating surface to prevent corrosion of the conductor means, the corrosion-resistant means being selected from the group consisting of titanium and nickel;

(c) electrode surface means connected to the conductor means; and

(d) an electrically conductive coating in contact with the at least first mating contact surface of the copper conductor means and the second mating contact surface of the corrosion-resistant means, the electrically conductive coating being a liquid-metal mixture comprising between about 20 and about 30 percent indium by weight and between about 80 and 70 percent gallium by weight such that the electrical contact resistance between the conductor means and the corrosion-resistant means is reduced. 6. The electrode according to claim 5 wherein said conductive compound is comprised of between about 23 and about 26 percent by weight of indium and about 77 and about 74 percent by weight of gallium. 7. The electrode according to claim 5 wherein the corrosion-resistant means is made of titanium and has a layer of copper on the mating contact surface. 8. An electrode for use in an electrolytic cell having copper conductor means with at least a first mating contact surface for conducting electrical energy, electrolyte corrosion-resistant means having a second mating contact surface which contacts the conductor means along the first mating contact surface, the corrosion-resistant means being selected from the group consisting of titanium and nickel, and electrode surface means connected to the conductor means, the improvement comprising:

an electrically conductive coating in contact with the at least first mating contact surface of the copper means and the second mating contact surface of the corrosion-resistant means, the electrically conductive coating being a liquid-metal mixture comprising between about 20 and about 30 percent indium by weight and between about 80 and about 70 percent gallium by weight such that the electrical contact resistance between the conductor means and the corrosion-resistant means is reduced. 9. The electrode according to claim 8 wherein said conductive compound is comprised of between about 23 and about 26 percent by weight of indium and about 77 and about 74 percent by weight of gallium. 10. The electrode according to claim 8 wherein the corrosion-resistant means is made of titanium and has a layer of copper on the mating contact surface.