US2599178A - Electrodeposition of alloys of molybdenum with cobalt, nickel, and iron - Google Patents

Description

Patented June 3, 1952 ELEo'raon rosITloN F ALLOYS MOLYBDENUM WITH COBALT, NICKEL,

AND IRON Matthew L. Holt, Madison, Wis., andHenry J. assignors to Wisconsin Alumni Research Foundation, Madison, Wis., a corporation of Wisconsin No Drawing. Application March 10, 1950, Serial No. 149,022

Seim, Reno, N ev.,

This invention relates, generally, to the electrodeposition of molybdenum alloys and it has particular relation to the electrodeposition of alloys of molybdenum with cobalt, nickel or iron.

Among the objects of this invention are: To provide for the electrodeposition of alloys of molybdenum with cobalt, nickel and iron; to improve the current efficiency in the electrodeposition process; to increase the molybdenum content of the alloy deposited on the cathode; and to provide a new bath for use in accomplishing these iron), such as the sulfate, ammonium hydroxide and Water. Electrolysis of this plating bath using soluble anodes, such as cobalt, nickel, iron, or molybdenum anodes, or an insoluble anode, such as platinum, effects the deposition of an .alloy 14 Claims. (01. 2o4 43) of molybdenum with the alloying metal (cobalt;

nickel or iron) on the cathode. The cathode may be formed of any suitable material such as 'plati-' num, gold, copper, iron, nickel, cobalt, brass, or other metals or alloys. While the temperature of the plating bath may vary from room tempera-j ture to the boiling point of the solution, best re suits are obtained when it is kept at a temperatureof from 20 to 30 C. There appears to be no critical cathode current density for the plating bath. The optimum current density is dependent on other electrolysis conditions and the composition of the bath. Cathode current densities that have been found to be satisfactory vary from about 1 ampere per square decimeter to 22.2 amperes per square decimeter. Experimental work in connection with this invention shows that the concentration of the alloying metal compound in the plating bath is not critical. However, it was found that the amount of complexing agent, citric acid in accordance with this invention, which is required depends upon the amount of alloying metal compound which is present. While the amount of the complexing agent is not critical, it appears that, when citric acid is employed, arslight excess of it over the amount of alloying metal compound is required. Preferably a ratio of about 1.5 moles of citric acid to one mole of the alloying metal is employed.

The amount of the soluble molybdate compound which is used to provide a good alloy deposit on the cathode varies according to the electrolysis conditions. In accordance with this invention sodium molybdate is employed. Satis factory alloy deposits have been obtained from baths of the present invention containing less than two grams per liter and as much as forty grams per liter of sodium molybdate. The use of four grams of sodium molybdate per liter gives excellent results.

In order to obtain satisfactory alloy deposits on the cathode it is necessary to control the pH of the plating bath. While alloy deposits of molybdenum can be obtained from plating baths of the present invention with a range of pH from three to nine, it appears, in general, when the bath is neutral or basic (pH '7 to 9), higher cathode current densities are required. For the cobalt-molybdenum bath, a pH of 4 appears to be most satisfactory. For the nickel-molybdenum bath, a pH of either four or eight is satisfactory. For the iron-molybdenum bath, a pH of six was found to give optimum results. In accordance 1 with this invention ammonium hydroxide is employed foradjusting the pH of the bath.

. Cobalt-molybdenum plating bath.

Cobalt sulfate heptahydrate I -grams- 60 Citric acid do 66 Sodium molybdate do 4 Ammonium hydroxide sufiicient to provide a pH of 4 Water to give a total volume of 1 liter Temperature of 25 C.

With the cobalt-molybdenum bath adjusted to a pH of 4, electrolysis at ten amperes per square decimeter deposited a cobalt-molybdenum alloy on the cathode containing 6.9 per cent molybdenum with a cathode current efilciency of 36 per cent. When the pH of the bath was increased to six, electrolysis at the same current density deposited an alloy on the cathode containing 27.2

per cent molybdenum at a cathode current efficiency of 4.0;per :cent.

Nickel-molybdenum plating bath Nickel sulfate hexahydrate grams 6.0 Citric acid ...do 66 Sodium molybdate. ;do .4

Ammonium hydroxide sufflcient'to provide the required pH- Water to give a total volumeiof l' liter Temperature of 25 C.

With a bath pH of 4 and a current densityci ten amperes per square decimeter, the nickel molybdenum alloy deposit on the cathode-contained 13 per cent molybdenum and the cathode current efficiency was 24 per cent. when thegpH of the bath was increased to 8, electrolysis at this same current density deposited an alloy .onthe cathode containing I 518,per cent molybdenum with a cathode current eficiency of 62 per cent.

I ron-molyb'denum platinghain Ferrous suliatemeptahydrate grams -60 Citric acid ..'.do 166 Sodium 'inolybdate do ,4

I Ammonium hydroxide sufficient to provide .the

required pH Waterto give atetal volume of 1 liter. Temperature of 25 C.

When the pH ofthe bath was" adjusted tofi, electrolysis at 10 amperes per-sq-uare decimeter deposited an alloy'on' the cathode containing'48.6 per .cent molybdenum"-at a cathode current erficiency of 17 per cent. On increasing the pH of thebath to '7,'electrolysis' at the same current density deposited an alloy'containing 62'per cent molybdenum with a currenvefficiency or 13 .per

cent.

'Whatis claimed-asnew is:

1. Method of 'ele'ctrodepositing "an alloy :of

molybdenum and a metal of the 'classconsijsting of" cob alt, nickel and iron which comprises "passing current between an-anode and *a cathode on which the alloy is to-bedeposited in-an' aqueous electrolyte consisting essentially of "60 grams per liter ofa sulfate selecte'cl'irom the'class cons-isting ofcobalt, nickel and iron,-citrie acid in an ing current between an anodeand alcalthodeon which the alloy is to be depositedjinan aqueous electrolyte consistingressentiallylOFSDgramsper liter of a sulfate selectedfrom the class .cons'isting of cobalt, nickelandliron, .66 grams per'liter of citric acid, 4 grams per liter.oflsodiummoldybe 4 date, and suflicient ammonium hydroxide to provide a pH ranging from 4 to 8.

5. The invention, as set forth in claim 4, wherein the cathode current density ranges from 1 to 22.2 amperes per square decimeter.

6. A bath for electrodepositing an alloy of molybdenum and a metal of the class consistin of cobalt, nickel and iron consisting essentially of an aqueous electrolyte containing grams per 'liter "of *azisulfate selectedifrom theiclass consist- *ing"of'cobalt, nickel and iron, citric 'acid in an amount in excess of the sulfate, 2 to40 grams per "liter of sodium molybdate, and sumcient amwmoniumhydroxide to provide a pH of from 4 to 8.

':'7. .Theinvention, as set forth in claim 6, wherein 1.5 molesmf citric acid are used to one mole of sulfate.

"8, A bath for ;electrodepositing an alloy of fmolybdenumand a metal of the class consistin ..,ofco.ba1t,...mcke1 and iron consisting essentially of an aqueous electrolyte containing 60 grams per "liter of rasuliateselected from the class consisting of cobalt, nickel and iron, 66 grams per liter oicitrio-acid, 4 grams per liter of sodium molybdate, and sufiicient ammonium hydroxide to pro vide apHof from 4 to 8. 1

"9. A .hath for electrodepositing an alloy .of molybdenum anda metal of. the class consisting of cobalt, nickel and iron consistingessentially or:

"Sulfate selectedfrom theclass consisting- 01' cobalt, nickel and' iron grams -60 'Citric acid ;do '66 Sodium molybdate do 4 Ammonium hydroxide suflicient to 'pr'ovide a pHrangin'g from 4 to 8. "Waterto'give avolume of Iliter.

.10. A bath for :electrodepositing :ran szalloy of molybdenum and cobalt' consisting :essentially of Water :togivea volume of 1. liter.

11. A bath :for electro'depositing an ;,alloy "of molybdenum and cobalt consisting essentially of Cobalt V sulfate heptahydrate .grams- 6O Citric racid do 66 "Sodiummolybdate' do 4 -Ammonium""hydroxide sufiic'ient to provide s.

pI-I of G. I Water'togivea volume of 1 liter.

12. A bath for electrodepositing arr-"alloy 10f molybdenum and nickel consisting essentially ;of

Nickel sulfate hexahydrate. "grams" '6 Citric. acid do.. 66 Sodium-,mo1ybdate. do 1-4 Ammonium. hydroxide sufiicientto providea pH of 4. Water to ggive a volume of 'lyliter.

13. A bath for .electrodepositing ,an alloy ..of molybdenum. and nickel consistingressentiallyrof2 l lick'el sulfate hexahydrate "grams" 60 "Citric --acid -do 66 *Sodiumrmol'ybdate do '4 Ammonium hydroxide sufficient to providea pH1of8. "Water. to give a volume .of I. 1' liter.

14. A bath for electrodepositing an alloy of molybdenum and iron consisting essentially of:

Ferrous sulfate heptahydrate "grams" 60 Citric acid do 66 r Sodium molybdate do 4 Ammonium hydroxide sufficient to. provide a,

pH of '6. Water to give a volume of 1 liter.

MATTHEW L. HOLT. HENRY J. SEIM.

6 REFERENCES CITED 7 The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,160,322 Armstrong et a1. May 30, 1939 2,428,404 Yntema, Oct. 7, 1947 OTHER REFERENCES Metal Industry, Nov. 22, 1946, pp. 434, 435, 436 (an article by L. E. Valler and M. L. Holt).

Claims (1)

1. METHOD OF ELECTRODEPOSITING AN ALLOY OF MOLYBDENUM AND A METAL OF THE CLASS CONSISTING OF COBALT, NICKEL AND IRON WHICH COMPRISES: PASSING CURRENT BETWEEN AN ANODE AND A CATHODE ON WHICH THE ALLOY IS TO BE DEPOSITED IN AN AQUEOUS ELECTROLYTE CONSISTING ESSENTIALLY OF 60 GRAMS PERLITER OF A SULFATE SELECTED FROM THE CLASS CONSISTING OF COBALT, NICKEL AND IRON, CITRIC ACID IN AN AMOUNT IN EXCESS OF THE SULFATE, 2 TO 40 GRAMS PER LITER OF SODIUM MOLYBDATE, AND SUFFICIENT AMMONIUM HYDROXIDE TO PROVIDE A PH OF FROM 4 TO 8.