US2338529A - Electrodeposition of nickel - Google Patents

Description

j sibly deleterious substances.

'lenious'oxide, 8e01, which is Patented Jan. 4, 1944 troit, Mich, assignors to General Motors Corporation,- Detroit, Mich a corporation of Delaware No Drawing. Amfl cation June 8, 1936,

Serial No. 84,166

29 Claims.

The invention relates to "the electrodeposition of nickel and is more particularly concerned with the production of lustrous or mirror=like deposits. That such deposits could he obtained under certain conditions and in'the presence of certain addition agents has been known for years.

The processes hitherto used, however, have been subject to objectionable features, especially .with reference to the character of the deposit and the cost of materials. Coatings applied in accordance with prior processes genorally-have a tendency to brittleness particu- ..larly upon increase of thickness of the deposit.

As an example of a nickel sulphate electrolyte the following may be given:

' Grams. Nickel sulphate, NiSO4.6H2O Y 240 Nickel chloride, NiCL'lHzO 30 Boric acid, H1303 30 Selenious oxide, SeOz 0.2-0.3

Furthermore, some at least of the addition agents used are expensive and, since they are destroyed or dissipated in the operation of the bath, render the maintenance of the bath costly.

-We have found that improved operation can be obtained from the standpoint of first cost and v maintenance as well as satisfactory character of deposit by the use of a novel addition agent containing selenium. It is necessary that-the selenium be present in some form or compound from which it may be depositedalong with the nickel, at least in very-small amounts, and for this purpose it is, of course, essential that such compound be dispersed or dissolved in the electrolyte. It is also desirable to maintain the electrolyte free of non-essential foreign and pos- Cost or commercial availability is also naturally animportant factor.

' As meeting most fully the above conditions we have preferred .to employ the acids or acid anhydrides of selenium of which two are commercially available,'namely, the selenic andselenious. Selenic acid-is marked in the form of an aqueous solution of HzSeOs while the selenious compound is obtainable as selenious acid or sereadily soluble in water to form Ha8e0:.

- Amounts up to 0.5 gram of SeO: per liter are sat- The selenium. compound is eflectlve to cause deposition of bright coatings in nickel electrolytes of the usual compositions some of which may be mentioned as examples. -In the acetate bath the following solution has given satisfactory results: I Nickel acetate, Ni(CzH:Oz)'a..- i. grams. 100 Nickel chloride, NiClsJHaO do' 100 Acetic acid, HCzHaO: cc

- ;Selenic acid (approximately solution) 7 3 Water to make up '1 'liter and suillcient'HCl to adjust thepH to the desired acidity, for example, 3-3.5. 4

Instead of selenic acid solution in the above bath we may use selenious oxide, the amount required being in the neighborhood of (Ll-03 gram per liter.

Water to make up one liter,sulphuric acid being added in quantity sufllcient to adjust the acidity as desired, for example to a pH of 1.5-5.5. Selenic acid may alsoreplace the selenious oxide in this formula.. As an example of a high sulphate bath, such as may be used for nickel plating-zinc-base die castings, the following may be given:

Nickel sulphate...... 10-12 Sodium sulphate 9 -l1 Ammonium chloride 2 Boric acid 3 Selenious oxide .0.025-0.05 Water sufllcient to make up one gallon, the pH Ounces being adjusted as desired, for example to approximately 5.8.

' It will be understood that the formulas given are merely illustrative and that variations thereof or different types of electrolytes are not excluded. Ineach example given, bright deposits ,are obtainable at current densities of 24-48 am-- varied overa rather 'wide'ranse and increases with concentration of nickel salts, more of the addition agent being used in heavier'solutions.

isfacto'ry in an ordinary commercial bath, such as the examples above. In general, the amount required may be given as from 0.05 to 0.5 gram per liter of bath. The amount added should generally be restricted, however, to that necessary to produce the desired mirror-like tbposlt as ex--v cessive amounts tend to increase brittleness of V the deposit.- The selenious acid has been found more effective per unit of weight than the selenic.

For this reason as well as the lower cost of the selenious acid, the latter is at present preferred. The production of a bright or mirror-like deposit is aflected by a number of factors, particularly concentration of electrolyte, character and amount of addition agent, temperature, current density and acidity at the cathode or pH. bviously, there will'be a range for each of these factors within which most desirable results are secured, which range is dependent also to some extent upon the quantum relations of the other factors, and suitable control of these factors is necessary. Therefore, while we have given specific examples'by way of illustration, it will be understood that variation of the specific condi-.

-cases the effect of destroying the effectiveness of the selenium addition agent, thus rendering it necessary to make new additions of the latter after treatment with H202. We have found, however, that soaps of sulphated higher alcohols such as those sold under the trade name Gardinol,

are effective to reduce pitting in our bright nickel baths and appear to have no deleterious effect.

One of the commercial preparations of these alcohol soaps that is satisfactory for the purpose contains sodium alkyl sulphates which may have 10-14 carbon atoms, the principal constituent of which may be sodium lauryl sulphate,

CH3 (CH2) roCHzOSOsNfi.

The amount to be used depends upon the extent of the tendency to pit. As little as 0.01 gram per liter has an appreciable effect and 0.1 gram is usually sufficient even for baths that tend to pit badly. Amounts larger than one gram have not been found necessary although the larger amounts have not been found detrimental,

In some cases, particularly with bright deposits produced with our process from the nickel sulphate bath, difiiculty may be found in depositing bright chromium over the'nickel. The chromium may tend to deposit only in spots or streaks or with a milky film. We are not at present able to give a definite explanation of this phenomenon but it seems to be due to passivity of the nickelselenium surface induced by some peculiar condition or conditions in the bath or procedure, or to the effect of selenium in the plated surface. The difficulty is readily overcome by lightly bufing or scouring the plated surface before placing it in the chromium plating bath.

We have also found that treatment of the electrodeposited nickel in an electrolytic alkaline cleaner followed by treatment with hydrochloric acid eliminates any difliculty in regard to a subsequent coating of chromium. For this purpose the nickel plated article is placed in a bath comtherein for a period of 13 minutes, the current being supplied at 'a voltage of l-6'volts. The article should then be rinsed and dipped in a bath of dilute HCl and again rinsed before being placed in the chromium plating bath. The latter may be of any usual type, for example, the chromic acid, chromium sulphate bath generally known as the Sargent solution, the usual con-- the nickel and We therefore regard the bright deposit as a compound or alloy of nickel and selenium, the latter, of course, being present in extremely small proportions.

We claim:

1. An electrodeposited combination of nickel and selenium the latter being present in relatively small proportion.

2. An electrolyte for electrodeposition of nickel" containing an aqueous solution of nickel salts and an addition agent soluble in the electrolyte containing selenium in suflicient quantity to cause deposition of the nickel in brilliant form.

3. An electrolyte as in claim 2, the addition agent being a selenium acid.

4. An electrolyte for electrodeposition of nickel comprising a solution containing nickel sulphate, nickel chloride, and selenious acid, the selenious acid being present in amounts corresponding to about .05 to .5 gram of SeOz per liter of solution.

5. An electrolyte for electrodeposition of nickel containing an aqueous solution of nickel salts, a selenium compound soluble in the electrolyte and a sulphated higher alcohol having at least 10 carbon atoms in the molecule.

6. Process of electrodepositing nickel in bright form upon a base, comprising passing an electric current through a nickel electrolyte to said base as cathode, said electrolyte containing a solution of nickel salts and a compound of selenium soluble in the electrolyte.

7-. Process as in claim 6, said compound being selenious acid.

8. Process of electrodeposition comprising passing an electric current through an electrolyte to a cathode to be coated, said electrolyte containing substances yielding simultaneously cathodic deposits both of nickeland selenium.

9. The process of electroplating a base comprising coating the base with abright deposit containing nickel from a bath containing nickel sulphate, nickel chloride and a selenium compound soluble in the bath, subjecting the surface to a treatment to eliminate passivity and then plating chromium thereon.-

10. Process as in claim 9, said treatment including rubbing the surface with abrasive.

11. Process as in claim 9, said treatment including subjecting. the surface to the cathodic actionof an alkaline electrolytic cleaner.

12. An electrolyte for deposition of nickel containing nickel acetate, nickel chloride, acetic acid and a compound containing selenium soluble in g the electrolyte.

13. An article comprising a conducting base and an electrolytically deposited coating predominantly of nickel, said coating having a content of selenium to an amount sumcient to cause deposition of the nickel in brilliant form.

14. An article comprising a conducting base and a coating thereon consisting of an adherent comprises electrodepositing nickel from an acid solution of nickel salts and an addition a ent containing selenium in sufilcient quantity ,to cause deposition of the nickel in brilliant form, the addition agent being a compound soluble in said solution containing an acid radical of a selenium acid.

compound of nickel and to which has been added a smallamount of selenium di-oxide sufllcient to cause deposition of the nickel in brilliant form.

16. An electrolyte for electrodeposition of nickel comprising an acid solution of nickel salts and an addition agent containing selenium in sufficient quantity to cause deposition or the nickel in brilliant form, the addition agent being a compound soluble in saidsolution containing anacid radical of a selenium acid.

17. An electrolyte for electrodeposition of nickel comprising an acid solution containing nickel sulphate, nickel chloride, and selenic acid in amount suflicient to cause deposition of the nickel in brilliant form.

18. The process of electrodeposition, which comprises electrodepositing nickel from an acid solution of nickel salts in the presence of an amount suflicient to insure a bright nickel deposit of a selenium compound, said compound being a compound soluble in said solution containing an acid radical of a selenium acid, and a minor amount of a sulphate of lauryl alcohol.

.suflicient to cause deposition of the nickel in brilliant form.

21. An electrolyte for the electrodeposition of nickel comprising an aqueous acid solution of 9.

22. An electrolyte for electrodeposition of nickel comprising an aqueous acid solution containing nickel sulphate, nickel chloride, boricacid and to which has been added a minor quantity of selenious acid suflicient to cause deposi tion of the nickel in brilliant form.

23. An electrolyte for electrodeposition of nickel containing an aqueous solution of nickel salts and an addition agent containing selenium in suiilcient quantity to cause deposition of the nickel in brilliant form, the addition agent being selenious acid to the amount produced by the addition of approximately 0.05 to 0.5 gram SeOz per liter of solution. I

24. An article comprising a metallic base and having a brilliant and adherentelectrodeposited coating thereon composed predominately of nickel and containing a relatively minute amount of selenium.

25. An article c'omprisinga conducting base. a brilliant electrodeposited coating thereon predominately or nickel and containing a small amount of selenium, and a brilliant electrodeposited coating of chromium upon said first mentioned coating. Y

26. An electrolyte for electrodeposition of nickel comprising an acid nickel; electrolyte containinga small amount of a compound of selenium soluble in the electrolyte.

27. An electrolyte (or electrodeposition of nickel comprising an aqueous acid nickel electrolyte containing selenic acid in amount suiiicient to cause deposition of nickel in brilliant form.

28. An electrolyte for electrodeposition of nickel comprising an acid .nickel electrolyte containing selenious acid in amount sufllcient to cause deposition of nickelgin brilliant form.

29. The process of electroplating a base which comprises coating the base with a bright deposit containing nickel from an acid nickel electrolyte containing a selenium compound soluble in the electrolyte, subjecting the deposit to a treatment to eliminate passivity and then plating chromium thereon.

' HARRY C. MOUGEY.

RAH-9H 'J. WIRSHING.

CERTIFICATE OF CORRECTION. Patent No. 2, 8, 29. January 1;, 19M

HARRY c; Mommy ET AL.

It is hereby bertified 'that error appears in the printed lpecificntion of the above numbered patent"; requiring correction as follows; Pggo 1, firet Y column, line 57, for "marked" re'ad "marketed",- line 39, aftei' 'ncid" in- :a'eri: --anhy ir1de-- and secom i. c'o lumn, line 9, for "NiCL'TH 'O" read 11101 311 0; andthat the and Letters Patent should beread with this correction therein that the same mm conform tothe record of the case in the Patent orr1ce.

Signed and sealed this 29th day of Febx rary, A, I). 191414..

- Leslie Frazer (Seal) I Acting Commissioner of Patents.