US3563866A - Electrodeposition of nickel - Google Patents

Abstract

A METHOD OF ELECTRODEPOSITING SATIN-LIKE FINISH NICKEL PLATES. THE BATHS COMPRISE OTHER WISE STANDARD NICKEL PLATING SOLUTIONS BUT CONTAIN THE COMBINATION OF A POLYALKYLCENE GLYCOL AND A SULFONAMIDE OF THE FORMULA

1-(HOOC-),4-(H2N-O2S-),(R)N-CYCLOHEXANE

WHERIN R IS -CH3, -C2H5, OR OH AND N IS AN INTERGER FROM 0 TO 3 INCLUSIVE.

Description

United States Patent 3,563,866 ELECTRODEPOSITION F NICKEL Richard J. Clauss, Allen Park, Norman C. Adamowicz, Inkster, and Robert A. Tremmel, Utica, Mich., assignors to The Udylite Corporation, Warren, Mich., a corporation of Michigan No Drawing. Filed Dec. 26, 1968, Ser. No. 787,271

Int. Cl. C23b 5/08, 5/46 U.S. Cl. 204-49 12 Claims ABSTRACT OF THE DISCLOSURE A method of electrodepositing satin-like finish nickel plates. The baths comprise otherwise standard nickel plating solutions but contain the combination of a polyalkylene glycol and a sulfonamide of the formula (IJOOH wherein R is CH -C H or OH and n is an integer from 0 to 3 inclusive.

THE INVENTION The invention relates to the electrodeposition of nickel on a substrate to provide a finished product whose surface has a satin-like appearance, as well as having enhanced corrosion resistance properties. By satin-like appearance is meant that the deposits, rather than being fully bright and highly reflective, exhibit a soft, lustrous sheen with reduced reflectivity and gloss approaching a matte finish.

It is well known that substrates plated with semi or bright nickel, followed by an electrodeposit of chromium acquire a surface which is corosion resistant, hard-.wearing, as well as being bright and highly reflective. Over the years, the plating art has conducted a continuing search for addition agents that make possible deposits with maximum brightness and reflectivity. In only a few applications has there been a need for a nickel plating bath to provide electrodeposits, which rather than being fully bright and highly reflective, exhibit a satin-like appearance with reduced brightness and reflectivity.

In the past, satin finishes have been used to provide a contrast with the extremely bright nickel surface thereby giving a two-tone eifect. Recently, safety considerations.

have been a prime reason for a markedly increased interest in nickel electrodeposits having a satin finish and decreased reflectivity. Plating baths providing such deposits are particularly useful for the plating of motor vehicle components to reduce reflective glare on the driver of the vehicle, as well as on the operators of other vehicles. In fact, federal legislation has recently been enacted whereby certain components of military vehicles such as windshield moldings and Wiper arms and blades, rear view mirrors, mounting and trim hardware, etc., must not have a specular gloss rating beyond a stated maximum. Thus, there is an outstanding need in the art for a plating bath capable of depositing uniform electrodeposits having a satin appearance with reduced reflectivity.

In the past, satin finishes have been obtained by mechanical treatment of the metal surface prior to plating, or mechanical abrasion of the nickel surface after plating by sand blasting, brush finishing, etc. This latter step not only is expensive, but also reduces the cororsion resistance of the finish because the brush or polishing marks 3,563,866 Patented Feb. 16, 1971 penetrate into the plate, which is especially detrimental in recessed areas where the plate is thin.

A second technique to obtain satin finishes previously used has been to add fine, bath insoluble powders to the nickel plating bath. The particles are occluded in the otherwise smooth nickel deposits thereby providing an irregular surface having a lustrous, satin-like finish. See for example US. Patents 3,l52,97123. While such baths have provided outstanding results, there are certain disadvantages in using such baths. For example, it is not possible to filter these solutions without removal therefrom of the fine powders, and provisions must be made to continually agitate the baths to keep the particles dispersed.

An object of this invention is to provide a process for electro-depositing nickel having a satin-like appearance without the necessity of mechanical abrasion of the metal surface and without the use of fine insoluble particles in the plating bath. Another object is to provide nickel plating baths containing organic agents which make possible deposition therefrom of nickel electrodeposits having a uniform, satin finish of reduced reflectivity.

The present invention comprises the conjoint use of a polyalkylene glycol and a carboxy sulfonamide in a nickel plating bath of the usual composition to make possible deposition therefrom of electrodeposits having the satin appearance described above. These baths are more easily controllable, provide uniform deposits, and obviate the problems associated with other techniques previously known for obtaining satin deposits.

The baths of the invention comprise a solution of certain organic addition agents to be more fully described below, in otherwise conventional nickel plating baths. The compositions of conventional nickel plating baths are well known and include nickel salts, such as nickel chloride, sulfate, fluoborate, or sulfamate and usually contain a bufler such as boric acid. A particularly useful bath is the well-known Watts Bath with a composition of from about 50 to 200 g./l. of nickel chloride, 50 to 300 g./l. of nickel sulfate, and 30 to 50 g./l. of boric acid. The bath may also contain the usual wetting agents and/or anti-pitting agents. The baths are generally operated at a pH range of 2 to 6 and a temperature of from. 60 to F.

In order to make possible the deposition of nickel of a satin-like appearance from these baths, a number from each of two classes of organic compounds is required.

The first class of these compounds is of the following formula:

1 )n 2 wherein X is OH2CH2O or CH;

CHOHzO R and R are the same or different and are H, CH or C H and n is an integer from 6 to 15 inclusive when X is CH CH O, and is from 5 to 11 when X is CH3 -(IJHCH2O' The compounds described above are polyethylene glycols, polypropylene glycols, methoxy and ethoxy polyethylene glycols and methoxy and ethoxy polypropylene glycols having a molecular weight of from about 300 to about 700. A preferred group of compounds for use in the baths of this invention are compounds described above having a molecular weight of from about 350 to 500. The glycol compounds of this invention are used in a concentration of from about 0.25 to 15 milligrams per liter, preferably 0.5 to 4 milligrams per liter of plating bath. The polyethylene and methoxy polyethylene glycols are available from the Union Carbide Corporation under the trademark Carbowax.

The second class of compounds to be used in the plating baths of this invention is of the following formula:

wherein R is CH C H OH, and n is an integer from O were included in the above bath, and the plated panels were then inspected to determine if an acceptable satin appearance was obtained, with particular attention being given to the uniformity of the deposits, as well as the reflectivity and gloss thereof. A tabulation of the results obtained using various combinations of additives is shown in Table I.

TABLE I Concentra- Brightener system tion, g./l. Results 1 i 5 3 2 carboxy benzaldehyde 0.5 Ugacceptable, non-uniform, dark grey Benzene sulfonamide 2,5 dicarboxy benzene sulfonamide.

p-Carboxy benzene sulIonamide-Nacetic ac1d p-Carboxy benzene sulfonamide Methoxy polyethylene glycol, M.W. 350. 7 Polypropylene glycol, M.W. 425

eposits. 1.0 I nacceptable, non-uniform. 0. 5 Unacceptable, black recess. 1. Unacceptable, non-uniform. 1.0 Unacceptable, recess too bright. 0. 002 Unacceptable, non-uniform, grainy deposits 0.002 Unacceptable, non-uniform deposits, dark in low current density area.

p-Carboxy benzene sulfonamide 2. ""{Polyethylene glycol, M.W. 20 0.001 Unacceptable bright recess 9 p-Carboxy benzene sulfonamide" 1. 0

""""""" Polypgopylgne glycolmMW. 2%0. 010(1) Dicar oxy enzene s onaml e. d 10 "{Methoxy polyethylene glycol M. 0. 0005 gg non uniform grainy e 11 {Dmarboxy benzene sulfonamlde" O Unacceptable, deposits darker and gralner i wgy p lv y s v b than Example 10,

par oxy enzene su onann e 12 "{Mtthoxy ptullyethylenenglycoht Lw. 750- 0. 30% Unacceptable dark recess parboxy enzeue su onami e 13 g, g g fiif d 1 Unacceptable, bright recess par oxy enzene s onami e l 14 th glycol, 350 0 0005 Acceptable, uniform; Satin like deposits 15 p-Carboxy benzene snlfonannde 1. 0 Do Polyethylene glycol, M W 409...- 0. 003 16 p-Carboxy benzene sulfonamide" 1. 5 D o.

' Polypfiopylgne glycohllglLW. 4%5- 0. 03155 p-Car oxy enzene su onami e 17 {Polyethylene glycol, M.W. 710 0. 0005 Wmmepmble, grainy 181mm In all examples recess" refers to low current density area.

to 3 inclusive. These compounds are substituted benzene sulfonamides having as an essential requisite a carboxy group in the para position. The preferred compound of this group is p-carboxy benzene sulfonamide, i.e., where n is zero in the above formula. The sulfonamides are used in a concentration of from about 0.5 to about 5 grams per liter, preferably 1 to 3 grams per liter of plating bath.

An outstanding benefit of the baths of the invention is that satin deposits can be obtained that are uniform in appearance over the complete area of the part being plated. Because commercial parts have contours and therefore varying current densities are obtained during plating, it is very difficult to obtain uniform deposits. Thus, while the use of either of the addition agents of the invention alone, or in combination with a variety of other materials may produce deposits with reduced gloss, such deposits are not uniform and therefore unacceptable for commercial purposes. On the other hand, while it may be possible to obtain uniform deposits with such combinations, the deposits do not have the proper gloss, i.e., they are either too dull or they approach being fully bright, and therefore not acceptable for the purpose of this invention. It is only when the specific additives of the in vention are used in combination are deposits with the requisite properties obtained.

To more fully describe the invention, a series of tests are detailed below wherein various addition agents were added to a plating bath to determine their effectiveness in producing nickel deposits having the requisite satin appearance. In all tests, a Watts bath having the following composition was used:

G./l. NiCl 6H O 43 3 Boric acid 43 The bath was operated at temperatures of 150-157 F. and at a pH of 3.8-4.1. Steel panels 6" x 1%", bent in the form of a I with a 1" base and 1" leg were plated for approximately 15 minutes at an average current density of -45 amperes per square foot. Various additives As is apparent from the results shown in Table I, only the specific additives of this invention in combination make possible deposits having the desired appeaarnce. Neither the sulfonamide compound used alone nor the polyoxyethylene compound used alone has the desired effect (see Examples 5-7). However, when the compounds are used conjointly, uniform deposits having a satin-like appearance are obtained (see Examples 14-16). This combination is very specific for the purpose intended, and when other compounds, even those structurally sirnilar to the claimed compounds are substituted therefor the desired results are not obtained. For example, substitution of a polyethylene material having a molecular Weight outside the limits of from 300 to 700 leads to poor and unacceptable results (see Examples 8, 9, and 12). Similarly, the use of compounds structurally similar to the benzene sulfonamide gives poor results. Thus, the use of dicarboxy benzene sulfonamide (Examples 10 and ll) does not give acceptable deposits.

Optimum results are obtained by appropriate variation of significant parameters within the limits defined above. In general, it has been found that gloss increases with an increase in polyethylene compound concentration and/or bath nickel chloride content, and decreases with an increase in carboxy benzene sulfonamide concentration, temperature and pH level. Thus, by variation of these parameters a deposit can be obtained with the desired finish for the particular application.

The baths of this invention may be used for the deposition of nickel with a satin-like appearance on a variety of basis materials. For example, the plating can be carried out directly on the basis metals such as steel, zinc die castings, or other metals, or the basis metal may be first plated with copper or a semi-bright nickel, or both. Also, plastic materials such as ABS or polypropylene, approximately made conductive by conventional techniques may be plated using the baths of this invention.

To further investigate the properties of the baths of this invention, additional plating tests were carried out using some of the preferred additives. The testing was carried out by plating 4" x 6" steel panels in a 60 gallon pilot laboratory tank containing a Watts solution of the following analyses:

NiCl -6H 43 g./l.

Boric Acid-43 g./l.

p-Canboxy benzene sulfonamide'1.48 g./l.

Steel panels were plated in the above solutions for 15 minutes at 150-157 F., at an average current density of 30-45 amperes per square foot. The electrodeposits were inspected and found to be fairly uniform, but unacceptable because of a bright low current density area.

To the bath was then added methyl polyethylene glycol (sold as Carbowax 350 by Union Carbide Corp.) in a concentration of 0.75 milligram per liter of solution. Five smaller steel panels were then plated under the same conditions as the prior panel. The deposits on all five panels were observed to be uniform, with a soft, satin-like appearance.

The panels were then chromium plated using a conventional chromium plating bath and then subjected to a specular gloss test in accordance with the widely accepted A'STM method for specular glass determination identified as ASTM Designation: D 523-62T, revised 1962. using a Gardner Glossmeter.

With this test, light beams from a lamp are directed on the test specimen at a specified angle and the rays reflected therefrom are directed to a photosensitive device. Readings are then compared to a known standard. To meet the requirements established by Federal Regulations for automotive trim parts, readings on theGardner Glossmeter (manufactured by Gardner Laboratory, Inc., Bethesda, Md.) must be below 40. Readings on the five plated panels were 11, 19, 22, 10, and 12, for an average reading of 15. Thus the gloss of each of the five panels was well within the acceptable limit of 40.

The foregoing tests were repeated under the exact conditions as described above except that the concentration of the methoxy polyethylene glycol was increased to 1.0 milligram per liter. The average reading on the glossmeter for the five panels was 38, just under the maximum limit of 40. Thus, it is evident that under these conditions a concentration of 0.751.0 milligram per liter of methoxy polyethylene glycol is optimum to meet the automotive safety specification. Of course for other applications, such as furniture and other decorative systems, higher gloss readings can be tolerated and different concentrations of the additives, or different plating conditions may be utilized to achieve the desired level of gloss.

Deposition of the satin-nickel deposits of this invention is generally followed by chromium plating thereon, using any of the chromium plating baths well known to the art. Such baths may comprise mixtures of chromic acid or chromic acid anhydride, or dichromates or polychromates with appropriate amounts of certain anions such as sulfate, fluoride, fluosilicate, etc.

While specific benzene carboxy sulfonamides have been described, it is understood that the various soluble salts of these compouids such as potassium, sodium, magnesium, nickel salts are also usable.

We claim:

1. An electroplating bath for the deposition of nickel comprising an aqueous acidic nickel salt solution containing therein a polyalkylene glycol of the formula:

R and R are the same or different and are H, CH or C H and n is an integer from 6 to 15 inclusive when X is --CII CH O, and is from 5 to 11 when X is CH 3H-oH20- and a carboxy sulfonamide of the formula:

([IOOH wherein R is CH C H OH; and n is an integer from 0 to 3 inclusive, said glycol and said sulfonamide each being present in an amount such that the combination is effective to produce a satin-like finish nickel electrodeposit.

2. The bath of claim 1 wherein said polyalkylene glycol has a molecular weight of from about 300 to about 700 and is present in a concentration of from about 0.25 to about 15 milligrams per liter of solution.

3. The bath of claim 1 wherein said carboxy sulfonamide is p-carboxy benzene sulfonamide and is present in an amount of from about 0.5 to about 5 grams per liter of solution.

4. The bath of claim 3 wherein said polyalkylene glycol has a molecular weight of from about 300 to about 700 and is present in a concentration of from about 0.25 to about 15 milligrams per liter of solution, and said carboxy sulfonamide is present in an amount of from about 0.5 to about 5 grams per liter of solution.

5. (The bath of claim 4 wherein said polyalkylene glycol is a polyethylene glycol.

6. The bath of claim 5 wherein said polyalkylene gly col has a molecular weight of from about 350 to about 500.

7. A method of electrodepositing nickel on a conductive substrate which comprises the step of electrodepositing nickel from an aqueous acid nickel plating bath containing dissolved therein a polyalkylene glycol of the formula:

1 n Z wherein X is -CH2CI'I20 0! CH3 -oHcH o R and R are the same or different and are H, CH

or --C H and n is an integer from 6 to 15 inclusive when X is CH CH O, and is from 5 to 11 when X is l S OzNHz wherein R is CH C H OH; and n is an integer from 0 to 3 inclusive, said glycol and said sulfonamide each being present in an amount such that the combination is effective to produce a satin-like finish nickel electrodeposit.

8. The method of claim 7 wherein said polyalkylene glycol has a molecular weight of from about 300 to about 700 and is present in a concentration of from about 0.25 to about 15 milligrams per liter of solution.

9. The method of claim 7 wherein said carboxy sulfonamide is p-carboxy benzene sulfonamide and is present in an amount of from about 0.5 to about 5 grams per liter of solution.

10. The method of claim 7 wherein said polyalkylene glycol has a molecular weight of from about 300 to about 700 and is present in a concentration of from about 0.25 to about 15 milligrams per liter of solution and said carboxy sulfonamide is p-carboxy benzene sulfonamide and is present in an amount of from about 0.5 to about 5 grams per liter of solution.

11. The method of claim 10 wherein said polyalkylene glycol is a polyethylene glycol.

12. The method of claim 11 wherein said polyalkylene glycol has a molecular weight of from about 350 to 500.

8 References Cited UNITED STATES PATENTS 2,782,155 2/1957 Du Rose et al 204-49 2,784,152 3/1957 Ellis 20449 3,017,333 1/1962 Waite et al. 20449 3,282,810 11/1966 Odekerken 20441 3,312,604 4/1967 Wells et al 204-49 GERALD L. KAPLAN, Primary Examiner