US2664392A - Nickel plating - Google Patents

Description

Patented Dec. 2 9 1953 2,664,392 NICKEL PLATING Newell F. Blackburn,

sylvania 7 Fort Belvoir, Va., assignor to The Pennsylvania Salt Manufacturing Com-- puny; Philadelphia, Pa., a corporation of Penn.-

N Drawing. Application November 23', 1949,

Serial No.

9"Clain1s'. (01. 204-49).

This invention relatesto' nickel plating and more particularly to the depositing. of bright nickel coatings on various types ofmetals' such as steel, copper, brass; etc- In the electro-depositing of nickel directly on base metals various types of electrolyte 'baths have heretofore been used, the most common of these being baths of the Niso4NiC12 type. In most of these baths, however, considerable difficulty has been. encountered due to metallic impurities, such, for example, as chromium, coppeigand zinc, interfering with the nickel deposit so as to produce a dull or off-color plating. This is particularly objectionable where a bright nickel deposit is desired. Another objection to baths of theNiSO4--NiClz type is that there is considerable sludge formation at the nickel anode. A build-up of sludge increases the resistan'ceat' the anode surface reducing the current for a given, voltage. To compensatefor this; more anode area is needed to reduce the.

totalanode resistance and thus'obt'ain'an equivalent nickel deposit, other factors being equal, to that which would be obtained if there were no substantialamountof' sludge formation. The

large amount of sludge'formed is also wasteful of nickel and is difii'cult to keep out of the main body of theelectrolyte where its presenceacts as an impurity which affects deleteriously the nickel deposit being" obtained.

After considerable experimentation with various types ofplating baths, it was noted that a plating bath of thenickel fluoborate type was considerably superior to'the conventional plating baths in many respects. The nickel fluoborate baths were found to have a substantiallyhigher' tolerance for metallic impurities, such as chromium, copper; zinc, etc., than the conventional nickel plating baths. The formation of anode sludge, with the resulting objectionable effects, was also considerably reduced providing a substantial saving in cell operation. Besides these advantages over the conventional NiSO4-NiClz plating baths, the use of nickel fluoborate baths time required. with the nickel fluoborate bath being, only about two-thirds of that required. when using baths ofthe conventional nickel chloride-nickel sulfate type. Also, the fiuoboratesalts themselvesare ideal buffers. Due to this,.

nickel. platingebaths, containing. no other buffer than the fiuoborate radical, maintain a constant pH during operation to a far greater degree than the conventional NisO4NiC12 type baths.

These advantages, obtained by the use of the nickel fluoborate baths, naturally made the use of this bath preferable to those of the conventional type. However, where bright nickeldeposits were desired, the nickel fiuoborate bath alone was found to be unsatisfactory.

In order to obtain. bright nickel deposits from fiuoborate plating baths, numerous conventional brightening agents were tried. These tended to improve the brightness of the plating to alimited extent but did not give a satisfactory brightness or the desired combination of brightness and ductility which was deemed desirable. After trying numerous addition agents, both conventional brighteners and others, I have found thatif a small percentage of sulfurized quinoidine (a product obtainedby sulfurizingthe mother liquor of cinchona bark after extraction of the medicinal alkaloids therefrom as described in the patent to Lutz, No. 1,908,773 of May 16,

1933) is added to the bath, together with a small amount of benzoic sulfimide, an excellent bright deposit of nickel is obtained. The nickel deposit obtained when using small amounts of sulfurized quinoidine and benzoic-sulfimide had a bright, lustrous appearance. and did not have the objectionable brittleness so often found in bright nickel deposits obtained by the use of many conventional brighteners. The deposits also showed a satisfactory adherence to the metals on which they were plated.

In carrying out my invention I have found that the addition of 1- to 4 grams per liter of benzoic sulfimide together with .01 to .03 gram per liter of sulfurized quinoidine to any nickel fluoborate electroplating bath would produce considerably better bright nickel deposits than obtained by use of these baths without the adbenzoic sulfimide is approximately 1.5 to 2.3 grams benzoic sulfimide per liter of electrolyte. In preparing nickel fluoborate baths to be used with the above ingredients, it was found advisable to keep the concentration of nickel and fluoborate, bothv ionized and unionized, at above 1 3 grams per liter of nickel and 37 grains per liter of fiuoborate the concentration of'these materials generally being maintained within the range of 13 to gramsnickel and 37 to 230 grams BR; radical per liter of electrolyte. It is understood that the concentration of nickel arid fluoborate mentioned above and in the appended 3 claims includes both the dissociated and undissociated nickel and fluoborate dissolved in the bath.

The addition of other materials, though not absolutely necessary for the purpose of obtaining a bright nickel deposit, was found to improve the over-all operation of the bath. Among these materials might be mentioned boric acid which helps to prevent the formation of free hydrofluoric acid and tends to increase the life of the plating bath, the amount added being preferably not less than 1 gram per liter, the maximum amount being limited by its solubility in the electrolyte though it is generally preferred not to use over 45 grams boric acid per liter of electrolyte; sodium and ammonium fluoborate, which tend to improve the conductivity of the bath, may be added in amounts ranging from none at all up to approximately 30 grams per liter of electrolyte it being generally preferred not to exceed the 30 grams per liter; and a small amount of wetting agent such, for example, as sodium lauryl sulfate or an alkyl aryl sulfonate, the purpose of the wetting agent being primarily to reduce pitting in the nickel deposit and to produce a more uniform bright deposit, the amount of such wetting agent being preferably about to 15 grams per 100 gallons of electrolyte. W

Even though the fluoborate baths are extremely tolerant of soluble impurities they are somewhat sensitive to insoluble impurities and floating particles. Therefore, in order to obtain the best results it is preferred to use regular cast nickel anodes of good purity.

The nickel fluoborate, which appears to be the active plating ingredient in this type of bath, may be formed by several methods such, for example, as by reacting fluoboric acid and a nickel salt; an inert metal fluoride; a nickel salt and boric acid; a nickel salt, hydrogen fluoride and boric acid; nickel fluoride and boric acid; or by the reaction of other water-soluble compounds which would produce as a reaction product the nickel fluoborate. The nickel and fluoborate radicals are generally added together as nickel fluoborate. Preferred baths, for example, Would generally contain 80 to 110 grams per liter of nickel fluoborate, 25 to 35 grams per liter of boric acid, 1.5 to 2.3 grams per liter of benzoic sulflmide and .01 to .03 gram per liter of sulfurized quinoidine. To obtain the best results the pH of the bath is preferably maintained at between 2.5 and 5.5 the preferred pH being approximately 3 to 4. This may be done by the addition of such materials as fluoboric acid or nickel carbonate. It is also desirable to maintain the temperature when using the bath somewhere in the range of 40 to 80 C. the best results being obtained with temperatures of 45 to 65 C. Cathode current densities of between 15 to 100 amperes per square foot of active cathode surface are generally employed.

The following are a few specific formulations of bright nickel electroplating baths together with operating conditions. These are given by way of example only for the purpose of better illustrating the invention and should not be considered in any way as limiting the same.

E ramble 1 Ni(BF4)2 100 grams per liter H3303 30 grams per liter Benzoic sulfimide 1 gram per liter sulfurized quinoidine .05 gram per gallon Temperature 65 C.

Cathode current density up to 50 amperes per square foot Anode current density 50 amperes per square foot Example 2 Ni(BF4) z 200 grams per liter HsBOs 30 grams per liter Benzoic sulfimide 2 grams per liter sulfurized quinoidine .05 gram per gallon Temperature 65 C.

Cathode current density up to amperes per square foot Anode current density 50 amperes per square foot Example 3 A 100 gallon bright nickel plating bath was prepared by mixing 20 gallons of 50% nickel fluoborate solution (weight to volume, equal to 88 lbs. nickel fluoborate) with 60 gallons of water. In this bath were dissolved 12.5 lbs. of boric acid, ounce of a wetting agent of the alkyl aryl sulfonate type, 10 ounces of benzoic sulfimide and 0.1 ounce of sulfurized quinoidine. After the addition of these materials the volume of the bath was adjusted to 100 gallons and the pH adjusted, either by the addition of nickel carbonate or fluoboric acid to a pH range of 3.5 to 4.5.

Several platings were made from this bath during which the temperature of the bath was varied from to F. while the cathode current density was varied from 20 to 80 amperes per square foot. An anode current density of about 50 amperes per square foot was used throughout the plating operations. The result in each instance was a bright and uniform nickel deposit.

In each of the above examples satisfactory bright nickel deposits were obtained. These deposits Were found to have good ductility and showed a strong adherence to the base metals to which they were plated.

In describing the invention, specific examples have been given. However, it is apparent that various modifications of the electrolytic bath, both in percentage of ingredients and by the addition of other ingredients to the bath may be made without departing from the scope of the invention.

Having thus described my invention, I claim:

1. A method for electro-depositing bright ductile deposits of nickel which comprises electrolyzing an aqueous solution of nickel fluoborate having small quantities of sulfurized quinoidine and benzoic sulfimide therein sufficient to produce bright nickel deposits from said solution.

2. A method for electro-depositing bright ductile deposits of nickel which comprises electrolyzing an aqueous solution of nickel fluoborate having .01 to .03 gram per liter of sulfurized quinoidine and 1 to 4 grams per liter of benzoic sulfimide therein.

3. An electrolyte for depositing bright nickel coatings comprising a water solution containing not less than 13 grams per liter of nickel, not less than 37 grams per liter of BF4 radical, 1 to 4 grams per liter of benzoic sulfimide and .01 to .03 gram per liter of sulfurized quinoidine.

4. An electrolyte for depositing bright ductile nickel coatings comprising a water solution containing not less than 13 grams per liter of nickel, not less than 37 grams per liter of HE; radical, 1 to 45 grams per liter of boric acid, 0 to 30 grams per liter of ammonium fluoborate, 1 to 4 grams per liter of benzoic sulfimide and .01 to .03 gram per liter of sulfurized quinoidine.

5. An electrolyte for depositing bright ductile nickel coatings comprising a water solution containing 13 to 80 grams of nickel per liter of electrolyte, 37 to 230 grams of BF4 radical per liter of electrolyte fluoborate, not less than 1 gram of boric acid per liter of electrolyte, and a small amount of brightening agents consist ing of 1 to 4 grams per liter of benzoic sulfimide and .01 to .03 gram per liter of sulfurized quincidene, the pH of said electrolyte being between 2.5 and 5.5.

6. A method of electro-depositing bright ductile nickel deposits which comprises electrolyzing a water solution of nickel fiuoborate having 1 to 4 grams per liter of benzoic sulfimide and .01 to .03 gram per liter of sulfurized quinoidine at a temperature of between 40 and 80 C. and a cathode current density of between 15 and 100 amperes per square foot, the pH of said electrolyte being maintained between 2.5 and 5.5

7. A method for electro-depositing bright ductile nickel deposits which comprises electrolyzing a water solution having therein 13 to 80 grams per liter of nickel, 37 to 230 grams per liter of BE; radical, 1 to grams per liter of boric acid, 1 to 4 grams per liter of benzoic sulfimide and .01 to .03 gram per liter of sulfurized quinoidine at a temperature of 45 to C., the pH of said electrolyte being maintained between 3 and 4.

8. An electrolyte for depositing bright ductile nickel coatings comprising a water solution of substantially 13 to grams per liter of nickel, 37 to 230 grams per liter of BF4 radical, not less than 1 gram per liter of boric acid, 1 to 4 grams per liter of benzoic sulfimide, .01 to .08 gram per liter of sulfurized quinoidine, and a salt selected from the group sodium fiuoborate and ammonium fluoborate the amount of said salt being not over 30 grams per liter.

9. The electrolyte of claim 5 to which has been added 5 to 15 grams of a wetting'agent for each gallons of electrolyte.

NEWELL F. BLACKBURN.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A METHOD FOR ELECTRO-DEPOSITING BRIGHT DUCTILE DEPOSITS OF NICKEL WHICH COMPRISES ELECTROLYZING AN AQUEOUS SOLUTION OF NICKEL FLUOBORATE HAVING SMALL QUANTITIES OF SULFURIZED QUINOIDINE AND BENZOIC SULFIMIDE THEREIN SUFFICIENT TO PRODUCE BRIGHT NICKEL DEPOSITS FROM SAID SOLUTION.