US2383798A - Electroplating - Google Patents

Description

Patented Aug. 28, 1945 I ELECTROPLAT ING Richard 0. Hull, Lakewood, Ohio, assignor to E. I.

du Pont de Nemours -& Company, Del., a corporation of Delaware No Drawing.

12 Claims.

This invention relates to the electrodeposition of cadmium and is more particularly directed to processes and'compositions adapted to produce I cadmium deposits which are bright but subject to pitting, a small amount of a sulfonated vegetable oil being used as an anti-pit agent.

Wilmington, I

Application December 11, 1940, Serial 100,369,533

The development of the cadmium plating art has led in recent years to the production of .brighter and brighter deposits and as a result the problem of pitting has become important. Cadmium deposits produced by most prior art practices have a matte surface orat the most are only moderately bright. With such deposits pitting is hardly noticeable unless it is unusually severe and it is rarely considered objectionable. With the bright, mirror-like cadmium deposits which the art is now able to make even a small amount of pitting produces major blemishes. n bright deposits pitting is a major imperfection.

Pitting is apparently caused by any of anumber of things some of which are known and some of which are not. One of the principal causes of pitting is the presence of traces of thallium terious eifects which result from using it in addition agent concentrations. When used with addition agents which lead to mirror-like deposits, a sulfonated. vegetable oil acts synergetically to produce brilliant deposits over a wide current density range and the deposits are not water-repel- Y lent and they are free from pitting.

Any sulfonated vegetable oil may be used as an anti-pit agent and for examples reference may be had to the Westbrook Patent 1,826,159. Salts such as monopole soap or a cadmium salt may be used as suggested in the Westbrook patent or the sulfonated oils may be added in solvents or,

in another suitable manner as suggested in the Westbrook patent.

'cording to the present invention are obtained which find their way into the bath with the" cadmium. Pitting also seems to be a property of certain plating baths, some one or more of the bath constituents probably being to blame.

Now I have found that pitting may be decreased in cyanide-cadmium plating baths by the inclusion of not substantially more than about 0.5 gram per liter of a sulfonated vegetable oil' as an anti-pit agent. It is more specifically preferred to use sulfonated castor oil.-

Westbrook in Patent 1,826,159 shows the use of sulfonated vegetable oils as addition agents for cadmium plating. These sulfonated oilsaccording to the practices of Westbrook are used in amounts equivalent to from about 5 to 15 grams per liter and deposits of good character are obtained as explained in the patient. Unfortunately, sulfonatedvegetable oils liave certain deleterious effects when used-in such amounts with other brightening agents which are capable .of producing truly mirror-like deposits. When Turkon Oil is present in addition agent amounts the cadmium plating bath has a limited bright current density range, the deposits produced are likely to be streaked, and the cadmiumsurface is water repellent. This last leads to particularly great diificulty if the deposits produced are to be bright-dipped or it they are to receive a further electrodeposit.

When. not substantially more than about 0.5 gram per liter of a sulfonated vegetable oil is used it serves as. an anti-pit without the delewhen a sulfonated castor oil is used as an antipit agent and it is still more specifically preferable to use the commercial grade of sulfonated castor oil, Turkon Oil, mentioned in the Westbrook patent.

A cyanide-cadmium plating composition adapted to produce deposits which are bright but subject to pitting is improved according to the present invention by the inclusion as an anti-pit agent of a sulfonated oil in an amount equiva-- lent to not substantially more than about 0.5 gram per liter. More specifically it is desirable to use from about 0.01 to about 0.5 gram per liter and it is still more specifically preferred to use from about 0.05 to about 0.3 gram per liter ofa sulfonated vegetable oil. When not substantially more than 0.5 gram per liter of a sulfonated vegetable oil is used as indicated the agent serves efiectively as an anti-pit but does not impart the deleterious effects'which result from the use of the material as an addition agent. It is further to be noted that when a sulfonated vegetable oil is used at a concentration suitable for an anti-pit according to the'present invention there upon the brightness of is no substantial efiect The anti-pit agents of this invention may advantageously be used to prevent pitting in any cyanide-cadmium plating system, but the best results are obtained when the agents areused in conjunction with an addition agent which promotes the formation of. brilliant, mirror like deposits. While any addition agent may be used, particularly good results have been obtained using isoamketaldoresins as set out in Henricks 2,085,750

and as further described in Henricks 2,085,747,

Henricks 2,085,748, Henricks 2,085,749, Hull I 2,085,754, Hull. 2,090,049, and 'LutZ 2,097,630.

While any isoamketaldoresin may be used, it is By far the best results ac-- preferred to use amketaldoresins, while still more specifically it is preferred to use amaldacets. It is still more specifically preferred to use the antipit agents of this invention with cyalda'cets as specifically set out in Henricks 2,085,747.

Metal brighteners as shown in the Westbrook Patent 1,681,500 such as iron, cobalt, and nickel may be used in baths of the present invention.

It is preferred to use cobalt and this or the other of the metals may be used as shown in the abovementioned patents to Westbrook, Henricks, Hull,

or Lutz.

The anti-pit agents of this invention are used in cyanide-cadmium plating baths and any bath may be employed. Illustrative of cyanide-cadmium plating baths are those shown in the Westbrook, .I-Ienricks, Hull and Lutz patents above mentioned.

The anti-pit agents of this inventiorrmay most advantageously be included in compositions com- EXAMPLE A cyanide-cadmium platingbath was made-up with the following: a

Grams per liter Sodium cyanide (NaCN) 130 The addition agent employed is the concentrated agent of Example I of Henricks 2,085,747

the agent being used in very much the same fashion as in Example III of the patent. Using the above-described bath brilliant mirror-like deposits were obtained in a barrel plating installation and the work produced was-free from visually discernible pits. g

A similar bath was made up using additionally grams per liter of cobalt sulfate (COSOr'IHaO) and excellent result were btam a sun Plating installation.

While I \have described certain illustrative products in the foregoing, it will be understood that one skilled in the art may readily employ a sulfonated vegetable oil as an anti-pit agent in cyanide-cadmium plating baths in a variety ,of ways without departing from the spirit of this invention.

I claim:

1. In a process for the electrodeposition of cadmium from an aqueous cyanide-cadr'iium bath, the step comprising 'eflecting deposltim in the pr a e of anisoamketaldoresin and t substantially more than about 0.5 gram per liter of a sulionated vegetable oil.

2. In a process for the electrodeposition oi cadmium froman aqueous cyanide-cadmium bath, the step comprising reflecting deposition in the presence of an amaldacet and not substantially more than about 0.5 gram per liter of a sulfonated vegetable oil.

3. In a process for the electrodeposition of cadmium from an aqueous cyanide-cadmium bath, the step comprising eflecting deposition in the presence of a cyaldacet, a compound of co- 1 halt, and not substantially more than about 0.5 gram per liter of a sulfonated vegetable oil.

4. In a process for the electrodeposition of "cadmium from an aqueous cyanide-cadmium the presence of an amaldacet and not substanbath adapted to produce deposits which are bright but subject to pitting, the step comprising eflecting deposition in the presence of an anti-pit agent comprising not substantially more than about 0.5 gram perv liter of sulfonated castor oil.

5 In a process for the electrodeposition of cadmium from an aqueous cyanide-cadmium bath, the step comprising efiecting cleposition'in tially more than about 0.5 gram per liter of sulfonated castor oil.

6. In a process for the electrodeposition of cadmium from an aqueous cyanide-cadmium bath, the step comprising eflecting deposition in the presence of a oyaldacet and about 0.1 to 0.5 gram per liter of sulionated castor oil.

'7. In a process for the electrodeposition of cadmium from an aqueous cyanideecadmium bath, the step comprising effecting deposition in I the presence of a compound of a metal selected Cadmium oxide (CdO) 43 'Sodium sulfate (Nazsol) Addition agent 3 2 Turkont oil 0.2

from the group consistingof cobalt, nickel, and copper and about 0.1 to 0.5 gram per liter of sulfonated castor oil.

8. In a process for the electrodeposition of cadmium from an aqueous cyanide-cadmium bath, the step comprising effecting deposition in the presence of a cyaldacet, a cobalt compound, and about 0.5 to 0.3 gram per liter of sulfonated castor oil.

9. A composition of matter adapted to improve the character of deposit obtainable from cyanide cadmium plating baths comprising about two parts by weight of a cyaldacet and about 0.01 to 0.5 part by weight of a sulfonated castor oil.

10.. A composition of matter adapted to lm-'- prove the character of deposit obtainablefrom cyanide-cadmium plating baths comprising about two parts by weight of a cyaldacet and about 0.05 to 0.3 part byweight of a sulfonated castor 11. A composition of matter adapted to improve the character of deposit obtainable from cyanide-cadmium plating baths comprising about two parts by weight oi an amaldacet and about 0.01 to 0.5 part by weight of a sultonat'ed vezetable .011.

12. A composition ofmatter adapted to improve the character of deposit obtainable from' cyanide-cadmium plating baths. comprising about a two parts by weight of a cyaldacet and 0.2-

par castor oil.

by weight of sulfonated RICHARD OJHULL.