US2499807A - Process for electroplating molybdenum and its alloys - Google Patents

Description

Patented Mar. 7, 1950 PROCESS FOR ELECTROPLATINGr-.MQLYB- DENUM ANDITS ALLOYS Leonard F. Yntema, Webster Groves, and Mary Joecile, Ksycki. St. Louis, Mo., assignors to president and board of trustees of St. Louis University, St. Louis, M0.

N Drawing. Application August 31, 1942, Serial No. 456,820

- solai s. ((1204-43) A The invention relates to the electrodeDQSifion of molybdenum.

We have discovered that molybdenum maybe efficiently.electrodeposited from aqueous electrolytes containingmolybdic acid, its anhydride or itssalts. in the presence of aliphatic acids and highconcentrations of salts of aliphatic acids.

Among .the additional salts which may advantageouslybeused in our process are the sodium, potassium or,.ammonium formate, acetate, and propionate or. combinations of the same. It is of advantage to employ such concentrations of these saltsthat the mol ratio of added anion to water is from 1 to 2 up to 1 to 4, preferably between 1 1302.2 and 1 to 3.

The work on which the electrodeposition of molybdenum is desired is placed in the electrolyte vto form the cathode and the anode. is a conducting material which will notbe attacked by the reaction products at the anode, such as platinum or carbon. A cathode of copper, iron, or nickel has been found to be satisfactory.

The electrolytic bath is preferably maintained slightly acid. the optimum conditions being a pH between 5.5 to 6.8 as measured with a lass electrode. Under some conditions however the pH maybe varied from this range and, in particular, a potassium-ammonium propionate bath will givegood deposits at a pH of 7.4.

The current density may be varied quite widely but the optimum conditions arev between 0.1 to

0.8 ampere per square centimeter of cathode surljace. 1he temperature of the bath is. preferablvv maintained between 30 C. and 50? C.

,Wi h ur processes above des b we. ave been able to. obtain. smooth, bright, adherent deposits of molybdenum in two minutes. The deposited metal is resistant to acids such as 0 1d hydrochloric and sulfuric and is resistant to stron uallialies but is soluble in nitricacid.

Our process is adapted for the electrcplating of articles. to render them corrosionresistant as well as to obtain a bright decorative effect. It is usefulfor preparing: molybdenum sheet byobtaining a thi k deposit i -th m ta on ui abl ca a d'subsequ n i solv n o f. e cathode ea ins-the l e m n. she .io

Our process isadapted for theelectrodeposition of molybdenum alloys or mixtures with other metals Iron may be codeposited with molybdenum by adding to the bath a solution of a ferrous salt, such as ferrous ,i lfate (F8804). Cobalt m e, cod p sit d wi h ely d m, y adding tothe th a solution of acobalt salt, such as coj iidsel. be Qdee s t 2 with molybdenum by adding to the bath asolutime of. n kel-sa s has nicke1...su1. .(N'iSOi).

The. anions of. .thealiphaticacids, ,,such,, as formate, acetate, and propionate. which are pres:- ent in. high concentration increase the solubility f e he t mo1ybden compounds in the acid olutionsand. with the, acid, increa hQSQ ubility of reduction products of -the hexavalent o bd um compo nds .forme ur the P cessor electrolysis therebypreventing the precipitation. Oi, molybdenum hydroxide orf of basic salts.

One of the chief advantages of our process is that the molybdenum ..Gp,n,1pounds used are the most readily available compounds of the element. Molybdic anhydride, M003; and ammonium paramolybdate, (NH4)5M07O24.4H2O are both-,commercially available and are both operative in our process.

To illustrate our invention, the following-1e):- amples are given:

Example I An electrolyte is made up of the following vcomposition: 5 g. molybdicanhydride so g. KOH 55 co. NH'iQ 1 8% N s 75 cc. HCOzH' (8'7 cc, H V Preferablythe bath is subjected. to apreli ninary electrolysis at a current density of 0.53ampere per square centimeter until the bath becomes red in color. The optimum conditions for ob- .t ni amowbde m .fr m th s: ba h are. PH,

to 5.9; current density 0.5 ampere per squarecentimeter; temperature C. to C. Bright metallic deposits of molybdenum are. obtained in -five minutes. The weight of anaveragez-deposit is 0.5 mg. on an area of 8 square centimeters of cathode surface. The current densitynan cfor bright metal plating from this bath.is .,0.35 to 0.6 ampere per square centimeter.

. mlllc II nnelectrolyte made up of the, followingcomposition:

5 g. molybdic anhydride g NH4C2H302 50 g-rKt'JzHsOa l0 col-ICnI-lcOc- (glacial) cc. -;H2Q

No preliminary electrolysisis---needed. '-1 he optimum conditions for obtaining deposition of molybdenum from this bath are pH 5.7 to 6.0; current density 0.5 ampere per square centimeter; temperature 30 C. to 40 C. Bright metallic deposits of molybdenum are obtained in two minutes. The weight of an average deposit is 1.0 mg. on 8 square centimeters of cathode surface. The current density range for bright metal plating is from 0.2 to 0.6 ampere per square centimeter.

Example III An electrolyte is made up of the following composition:

g. molybdic anhydride 74 cc. prooionic acid (HC3H5O2) 32 gm. (NH4) zCOs 19 gm. X011 28 cc. H2O

Example IV An electrolyte is made up of the following com- "position:

5 g. mol bdic anhydride 60 g. KOH

55 cc. N -T4OH (28% NH3) '75 cc. HCOzH (87%) 15 cc. H20

30 cc. FeSO4 (0.1 M)

The optimum conditions for the codeposition of molybdenum and iron from this bath are a current density of 0.2 ampere per square centimeter: temperature 30 C. to 40 C. Bright metallic plates are obtained in two minutes. The current density range for bright metal plating from this bath is 0.15 to 0.5 ampere per square centimeter.

Example V An electrolyte is made up of the following composition:

5 g. molybdic anhydride 50 g. NH4C2H302 cc. HCaHsOz (glacial) 65 cc. H20

3 cc. NiSO4 (0.1 M)

The optimum conditions for obtaining codeposition of molybdenum and nickel from this bath are current density 0.25 ampere per square centimeter; temperature 30 C. to 40 C. Bright metallic plates are obtained in one minute. The weight of an average deposit is 1 mg. on 16 square centimeters of cathode surface. The current density range for bright metal plating from this bath is 0.07 to 1.0 ampere per square Centimeter.

Example VI An electrolyte is made up of the following composition: 5 g. molybdic anhydride 50 g. NH4C2H3O2 50 g. KC2H3O2 10 cc. HC2H302 (glacial) 65 cc. H20 1 cc. 005304 (0.1 M)

The optimum conditions for the codeposition of molybdenum and cobalt from this bath are current density 0.25 ampere per square centimeter; temperature 30 C. to 50 C. Bright metallic plates are obtained in one minute. The weight of an average deposit is 0.5 mg. on 16 square centimeters of cathode surface. The current density range for bright metal plating from this bath is 0.09 to 0.8 ampere per square centimeter.

The above examples are given by way of illustration only.

What we claim as our invention is:

1. The process of plating metallic molybdenum which comprises passing a current between an anode and the work to be plated as a cathode in an electrolyte comprising an aqueous solution or a compound of the class consisting of molybdic acid, its anhydride and its salts and a high concentration of an anion of an aliphatic acid of the class consisting of formate, acetate and propionate, the ratio of said anion to water being between 1 to 2 and 1 to 4 and the pH being between 5.5 and 6.8.

2. The process of plating metallic molybdenum which comprises passing a current between an anode and the work to be plated as a cathode in an electrolyte comprising an aqueous solution of a compound of the class consisting of molybdic acid, its anhydride and its salts and a high con centration of an anion of acetic acid, the ratio of said anion to water being ofthe order of 1 to 2% and the pH being between 5.5 and 6.8.

3. An electrolyte for the electrodeposition of metallic molybdenum comprising an aqueous solution of a compound of the class consisting of molybdic acid, its anhydride and its salts and a high concentration of an anion of an aliphatic acid of the class consisting of formate, acetate and propionate, the ratioof said anion to water being between 1 to 2 and 1 to 4 and the pH being between 5.5 and 6.8.

4. An electrolyte for the electrodeposition of metallic molybdenum comprising an aqueous solution of a compound of the class consisting of molybdic acid, its anhydride and its salts and a high concentration of an anion of an aliphatic acid of the class consisting of formate, acetate and propionate, the ratio of said anion to water being between 1 to 2.2 and 1 to 3 and the pH being between 5.5 and 6.8.

5. An electrolyte for the electrodeposition of metallic molybdenum alloys comprising an aqueous solution of a compound of the class consisting of molybdic acid, its anhydride and its salts, a high concentration of an anion of an aliphatic acid of the class consisting of formate, acetate and propionate and a soluble salt of a metal of the class consisting of iron, nickel and cobalt the ratio of said anion to water being between 1 to 2 and 1 to 4 and the pH being between 5.5 and 6.8.

6. The process of electroplating metallicmolybdenum which comprises passing a current between an anode and the.;work to be plated asf'a cathode in an electrolyte comprising an aqueous solution of a molybdate compound, an aliphatic acid of the class consisting of formic, acetic, and propionic acids and an alkali salt of an aliphatic acid of the class consisting of formate, acetate and propionate, in which the ratio of the anion of said aliphatic acid and salt of said aliphatic acid to water is between 1 to 2 and 1 to 4, the pH being between 5.5 and 6.8, the temperature being between 30 and 50 C. and maintaining the current density between 0.07 and 1.0 ampere per square centimeter.

7. The process according to claim 6 in which the ratio of the anion of said aliphatic acid and salt of said aliphatic acid to water is maintained between 1 to 2.2 and 1 to 3.

8. The process according to claim 1 in which the anode is a conducting material of the class consisting of platinum and carbon.

9. The process of electroplating metallic molybdenum alloys which comprises passing a current between an anode and the work to be plated as a cathode in an electrolyte comprising an aqueous solution of a molybdate compound, an aliphatic acid of the class consisting of formic, acetic, and

propionic acids and an alkali salt of an aliphatic acid of the class consisting of formate, acetate and propionate, and a soluble salt of a metal to be codeposited with molybdenum of the class consisting of iron, nickel, and cobalt, in which the ratio of the anion of said aliphatic acid and salt of said aliphatic acid to water is between 1 to 2 and 1 to 4, the pH being between 5.5 and 6.8, the temperature being between and C. and maintaining the current density between 0.07 and 1.0 ampere per square centimeter.

LEONARD F. YNTEMA.

MARY JOECILE KSYCKI.

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

Quantitative Analysis by Electrolysis," by Classen and Hall, published in 1913 by John Wiley & Sons, Inc., page 146.

Transactions of the Electrochemical Society," vol. (1936) pages 423, 424.

Claims (1)

1. THE PROCESS OF PLATING METALLIC MOLYBDENUM WHICH COMPRISES PASSING A CURRENT BETWEEN AN ANODE AND THE WORK TO BE PLATED AS A CATHODE IN AN ELECTROLYTE COMPRISING AN AQUEOUS SOLUTION OF A COMPOUND OF THE CLASS CONSISTING OF MOLYBDIC ACID, ITS ANHYDRIDE AND ITS SALTS AND A HIGH CONCENTRATION OF AN ANION OF AN ALIPHATIC ACID OF THE CLASS CONSISTING OF FORMATE, ACETATE AND PROPIONATE, THE RATIO OF SAID ANION TO WATER BEING BETWEEN 1 TO 2 AND 1 TO 4 AND THE PH BEING BETWEEN 5.5 AND 6.8.