CA1193223A - Bright nickel-iron alloy electroplating bath and process - Google Patents

Abstract

Abstract of the Disclosure An aqueous bath and process suitable for the electrodeposition of bright, high-leveling nickel-iron alloy deposits on a conductive substrate comprising controlled, effective amounts of nickel ions, iron ions, an iron solubilizing agent, a buffering agent, a primary brightening agent, hydrogen ions to provide a pH of about 2.6 to 4.5 and a bath soluble additive agent present in an amount of at least about 2 mg/l of the structural formula:

Description

U 10,909/]0?952 BRIGEIT ~IC~EL-IRO~ ALLOY ELECTROPLATING BATH AND PROCESS
-sackground of the Invention A variety of aqueous electroplating baths and processes are known in the art and are in widespread commercial use for electrodepositing a nickel-iron alloy on electrically conductive substrates. Such nickel-iron alloy deposits possess excellent corrosion resist-ance and are particularly useful for providing decora-tive finishes on corrosion susceptible substrates over which a subsequent electrodeposit of chromium is applied.
It is extremely important that such nickel-iron decora-tive deposits are characterized by their high-leveling properties, e~ceptional brightness and good ductility and tha~ these beneficial characteristics are ~niform over the entire electrodeposit.
Typical of known nickel-iron electroplating ~ath compositions and processes are those described in U.S.
Patents Nos. 3,354,059; 3,795,591; 3,806,429; 3,812,566;
3,878,067; 3,974,044; 3,994,694; 4,002,543; 4,089,754;
4,101,387; 4,134,802 and 4,179,343. While certain of the nickel~iron plating bath compositions and processes as described in the aforementioned United States Patents have provided satisfactory electrodeposits for use in decorative applications, a continuing problem associated with such and other nickel-iron plating baths is their ,.. .

susceptibility or sensitivity to contaminants and oryanic degradation products formed during prolonged use of such baths detracting from the character and properties of the electrodeposit. This problem is particularly pronounced in electroplating ba-ths designed to e]ectrodeposit alloys containing high percentages of iron, such as for eY.ample, alloys containing above about 35% iron and operating at a pH above about 3.4~ The progressive contamination of such electroplating baths with greases, oils and organic degradation products of the organic bath additives ernployed, have been -found to cause a progressive dete-rioration of the quality of the elec-trodeposit and to greatly restrict the permissible bath operating para-meters requiring relatively stringent control to main-tain high quality electrodeposits. The progressive deterioration of the bath is typically evidenced by electrodeposits which contain white, blotchy or black areas that form in the intermediate and low current density areas of the conductive substrate being plated.
Additionally, adverse physical properties of the electrodeposit are also evidenced, including high stress, poor ductility and inadequate adhesion in some instances.
In accordance with the present invention, an improved bath composition and process is provided which overcomes the detrimen-tal effects of ba-th contarnina-tion dllrirlg operation, which permits operation at a higher pH level to achieve excellent brightness and leveling, ~hlch permits moxe la-titude in the parameters of bath control, and which facilitates the at-tainment of the desired high quality nickel-iron alloy deposit on a consistent basis.
The invention further contemplates the use of a particular replenishing agent for conventional nickel-iron baths which when employed in controlled amounts is effective to achieve the aforementioned benefits. Additionally, the invention also contemplates a process for rejuvena-ting conventional nickel-iron electroplating baths which have been rendered inefficient or ineffective to achieve the desired high quality deposits due to the accumulation of contaminants therein by the controlled addition of a rejuvenating agent effective to restore the electroplating bath to its original operating efficiency.

Summary of the Invention The benefits and advantages of the present inven-tion in accordance with the composition aspects thereof are achieved by an aqueous acidic bath of the type suit-able for electrodepositing a bright, high-leveling nickel-iron alloy deposit on a conductive substrate containing nickel ions, iron ions, an iron solubilizing agent present in an amount to maintain the desired concentra-tion of iron ions in solution, a buffering agent, a primary brightening agent, preferably in combination with one or more secondary brightening agents of the types ~3~3 known in the art present in an amount sufficient to produce a bright, leveled nickel-iron deposit, hydrogen ions to provide a pH within a range of about 2.6 to about 4.5 and a bath soluble addition agent present in an amount of at least about 2 milligrams per liter (mg/11 of the structural formula: -~
[HC---C- (CH ) -1CH) -SO ] X

Wherein^
R is H or Cl to C4 alkyl n is an integer from 0 to 4, m is an integer from 0 to 1, and X is H, NH4, or a bath compatible metal, as well as mixtures thereof.
A particularly preferred additive agent corres-ponding to the foregoing structural formula is propargyl sulfonic acid and the alkali metal and ammonium salts thereof as well as mixtures thereof. The additive agent is generally employed in amounts up to about 800 mg/l with amounts of about 5 to 80 mg/l being preferred.
In accordance with the process aspects of the present invention, a bright, decorative, high-leveling nic]cel-iron electrodeposit is produced on a conductive substrate by immersing the substrate while cathodically charged in an electroplating bath of the aforementioned type controlled at a temperature of from about 105 to 180F fox a period of time to effect the electro-deposition of the nickel-iron alloy until a desired -~3~3 thickness is ob-tained. The electrodeposition of the nickel-iron alloy can be achieved over a broad current density range such as from about 5 to about 100 amperes per square foot (ASF). The present invention further contemplates the process of replenishing a nickel-iron bath by periodic and/or continuous addition of the addi-tive agent to maintain the bath at optimum operating efficiency as ~ell as the proeess of rejuvenating a contaminated, ineffieient bath by the addition of the rejuvenating agent to restore the bath to its optimum operating eondition.
Additional advantages and benefits of the present invention will beeome apparent upon a reading of the description of the preferred embodiments taken in eon-junction with the speclfie examples provided.

Deseription of the Preferred Embodiments The present invention is particularly applicable for the electrodeposition of deeorative niekel-iron alloy deposits on electrieally eonduetive substrates whieh can be utilized as a base for the subsequent eleetro-deposition of ehromium in order to achieve the desired decorative and/or corrosion resistant properties. While the present invention is primarily applicable for the electrodeposition of niekel-iron alloys on metallic substrates, it is also eontemplated that the invention ean be applied to plastie substrates which have been ~3~33~3 subjected to a suitable pretreatment in accordance with well-known -techniques to achieve an electrically con-ductive coating thereover such as a nickel or copper layer rendering the pl.astic substrate rece~tive to the nickel-iron alloy electroplating operation. Typical of such plastic materials which can be elec-troplated are ABS, polyolefin, polyvinyl chloride, and phenol-formal-dehyde polymers~
In accordance with the composition aspects, the aqueous electroplating bath contains as essential constituents, nickel ions, iron ions, and iron solu-bilizing agent present i.n an amount to maintain the desired concentration of iron ions in solution, a buffering agent, a primary carrier brightener, preferably in combination with one or more secondary brightening agents to produce a bright, high-leveling nickel-iron alloy deposit, hydrogen ions to provide a pH of from about 2.6 to about 4.5, and preferably 3.2 to about 3.8, and a bath soluble acetylenic additive agent present in an amount of at least about 2 mg/l of the structural formula:
[HC-=C-lcH2)n~(cllI)m~S3] X

Wherein:
R is H or C1 to C4 alkyl n is an integer from O to 4, m is an integer from O to 1, and X is H, NH4, or a bath cornpatible metal, as well as mixtures thereof.

Additive agents corresponding to the foregoing structural formula include 1 butyne - 3 - sulfonic acid, 1 - pentyne - 5 - sulfonic acid, propargyl sulfonic acid and the alkali metal and ammonium salts thereof. Of these, propargyl sulfonic acid and its bath compatible salts comprise -the preferred additive agen-t. The additive agent or mixtures thereof is usually employed in amounts of about 2 to about 300 mg/1 with amounts of about 5 to about 80 mg/l being preferred. When the preferred propargyl sulfonic acid compound is used, it is usually employed in amounts of about 2 to about 200 mg/l, with amounts of about 5 to 40 mg/l being preferred.
The addition of the organic additive agent of the present invention enables the electrodeposition of nickel-iron alloys of relatively high iron content, e.g.
about 35% and higher employing a bath operating pH in the upper range at which improved brightness and leveling of the deposit is attained. The additive agent further reduces the sensitivity of the bath to organic contaminants such as oils, greases, and organic degradation products of the organic additives present in the bath enabling continued operation without imposiny stringent control of the bath operating parameters to avoid blotchy or non-uniform deposits. The present in~
vention further contempla-tes the replenishment and rejuvenation of contaminated baths which have lost their effectiveness 3~2~
and capacity to produce high quality nickel-iron alloy deposits by the addition of controlled effective amounts of the additive agent whereby proper bath operation is restored.
In accordance with the composition aspects of the present invention, the nickel and iron ions are intro-duced into the bath employing bath soluble and compati-ble nickel and iron compounds. Preferably, inorganic nickel salts are employed such as nickel sulfate, nickel chloride, and the like as well as other nickel materials such as nickel sulfamate and the like. When nickel sulfate or sulfamate salts are used they are conventionally employed in amounts ranging from 40 up to about 300 g/l (calculated as nickel sulfate hexa-hydrate). Nickel chloride can also be used and is normally employed in an amount ranging from about 40 to about 250 g/l. The chloride or halide ions intro-duced provide for satisfactory conductivity of the bath and also provide satisfactory corrosion properties of the soluble anodes.
The iron compounds preferably comprise inorganic ferrous salts such as ferrous sulfate, ferrous chloride, and the like. Such ferrous salts are usually employed in amounts ranging from about 2 up to about 60 g/l.
Additionally, other bath soluble compatible iron salts can be employed such as soluble ferrous fluoborate, sulfamate, and the like.

The concentration of nickel and iron ions in the bath is usually controlled -to provide a weiyht ratio of nickel to iron ranging from ahout 5:1 up to about 50:1. The concentration of nlckel lons in -the bath is at least about 10 g/l while the concentration of the iron ions ls at least about 0;2 g/l with the specific arnount present being controlled to provide the appropriate weight ratio as hereinabove set forth.

In order to malntain the ferrous and ferric ions ln solutlon an iron solubilizing agent is employed in an amount to maintain the desired concentration thereof in the bath in a form available for electrodeposition on the substrate. The solubilizing agent maintains the iron ions in solution by a complexing function and/
or a reducing function of ferric to ferrous ions to avoid precipitation of ferric hydroxide. The iron solubilizing agent employed may comprise any of those heretofore used in the art and typically comprise hydro~y substi-tuted lower aliphatic carboxylic acids having from 2 to 11 carbon atoms, from 1 to 6 hydroxyl groups and from 1 to 3 carboxyl groups such as ascorbic acid, isoascorbic acid, citric acid, malic acid) glutaric acid, gluconic acid, muconic acid, gluco-heptonic acid, glycollic acid, tartaric acid and the li~e as well as the water soluble and bath compatible salts thereof such as ammonlum, alkali metal, as well as nickel and iron salts thereof.
The iron solubilizing agent is usually employed in amounts of about 5 up to about 100 g/l wi-th amounts of about 10 to about 30 g/l being preferred. Usuall~, concentrations of the iron solubilizing agent above about 50 g/l are unnecessary and in some instances are undesirable due to the formation of organic degra-dation products over prolonged operating periods of the bathO Such higher concentrations are also undesirable from an economic standpoint.
The ratio of the iron solubilizing agent relative to the iron concentration in the bath is preferably within the range from about 1:1 up to about 20:1. At ratios below 1:1, the iron consti-tuent may precipitate out while at ratios above about 20:1 excessive concen-tra-tions of the solubilizing agent may be present resulting in the disadvantages and potential problems hereinabove set forth~
A further essential constituent of the bath is a buffering agent such as boric acid, acetic acid and the like as well as the alkali metal, ammonium nickel and iron salts thereof and other bath soluble and compatible salts as well as mixtures thereof. The buffering agent is usually employed in an amount of about 20 up to about ~3~

60 g/l wi-th concentrations of about 40 to about 50 g/l being preferredO Particularly satisfactory results are obtained employing boric acid and the bath soluble salts thereof~
T~e bath further contains as an essential con-stituent, a con-trolled amount of a primary or so-cal]ed carrier brightener preferably in further cornbination with secondary brighteners to attain the exceptional brighteness and high-leveling of the nickel-iron deposit. The primary brighteners are usually employed in amounts ranging from about 0.5 to about 20 g/l with amounts of about 2 to about 8 g/l being preferred. The secondary brighteners, when used, are usually employed in amounts of about 0.25 mg/l up to about 1 g/1 with amounts of about 10 to about 100 mg/l being preferred. The primary and secondary brighteners, when an acid is involved, can be introduced into the bath in the form of the acid itself or as a salt having bath soluble cations such as the alkali metal ions including ammonium~
The primary brighteners suitable for use include those as described in U.S. Patent No. 3,974/044. Such prirnary brighteners as described in the aforementioned patent comprise sulfo-oxygen compounds of sulfur-bearing compounds as further described in "Modern Electroplating"
published by John Wiley and Sons, second edition, page 272 Included among such primary brighteners are saccharin, sulfobenzaldehyde, benzenesulfonamide, sodium allyl sulfonate, and the like as well as mix-tures thereof. Other bath soluble sulfo-oxygen compounds are those such as the unsaturated aliphatic sulfonic acids, mononuclear and binuclear aromatic sul~inic acids, mononuclear arornatic sulfon-amides and sulfonimides, and the like. Of the foregoing, saccharin itself or saccharin in combination with allyl sulfonate and/or vinyl sulfonate comprise a preferred primary brightener.
Suitable secondary brighteners include acetylenic nickel brighteners such as the acetylenic sulfo-oxygen compounds and acetylenic nlckel brighteners as described in U.S. Pat. No. 3,366,667 such as the polyethers re-sulting from the condensation reaction of acetylenic alcohols and diols such as, propargyl aleohol, butyndiol, and -the like and lower alkylene oxides such as, epichlorohydrin, ethylene oxide, propylene oxide and the like.
Additional secondary brighteners that are suitable include nitrogen heterocyclie quaternary or betaine nickel brighteners which are usually employed in amounts of about 1 to about 150 mg/l. Compounds o~ this type suitable are those described in U.S. Pat. No. 2,647,866 and the nitrogen heteroeyclic sulfonates described in U.S. Pat.
No. 3,023,151. Preferred compounds described therein are the pyridine quaternaries or betaines or the pyridine sulfobetaines. Suitable quaternaries that may be ~12-employed are quinaldine propane sultone, quinaldine dimethyl sulfate, quinaldine allyl bromide, pyridine allyl bromide, isoquinaldine propane sultone, iso-quinaldine ~dime-thyl sulfate, isoquinaldine allyl bromide, and the like.
In addition, secondary brighteners further include -the reaction product of a polyamine-type brig'nt-ener which ~as a molecular weight ranging from 300 to about 24,000, and an alkylating agent of the type described in U.S. Patent No. 4,002,543. Exemplary alkalating agents are dimethyl sulfate, chloroacetic acid, allyl bromide, propane sultone, benzyl chloride or propargyl bromide.
me polyamine brightener may be sulfonated utilizing as exemplary compounds sulfamic acid, chloro sulfonic acid and the like. The ratio of polyamine to alkylating agent or to the sulfonating agent can be varied so that every amino group need not be alkylated or sulfonated as the case may be.
In addition to the essential primary and optional secondary brighteners and other bath constituents, a further optional addition agent comprises special carrier agents of the type described in U.S. Patent No. 3,806,429.
Such optional special additives are not required in achiev-ing the exceptional brighteners and high leveling in accor-dance with the present invention but their inclusion in ~3~3 the bath is usually preferred to assure bright nickel-iron deposits over the entire surface of the substrate, even those exposed to very low current densi-ties. Such specialty additives comprise organic sulfide cornpounds which are normally employed in amounts ranging from about 0.5 to about 40 mg/l and are of the formula:-:
RlN = C-S-R

where Rl is hydrogen or a carbon atom or an organic radical, R2 is nitrogen or a carbon atom of an organic radical and R3 is a carbon atom of an organic radical.
Rl and R2 or R3 may be linked together through a single organic radical.
Typically, the bath soluble organic sulfide com-pounds can be 2-amino thiazoles and isothloureas. 2-aminothiazole and 2-aminobenzothiazole can be reacted with bromethane sulfonate, propane sultone, benzyl chloride, dimethylsulfate, diethyl sulfate, methyl bro-mide, propargyl bromide, ethylene dibromide, allyl bromide, methyl chloro acetate, sulfophenoxyethylene bromide, to form compounds suitable for use. Substi-tuted 2-aminothiazoles and 2-aminobenzothiazoles, such as 2-amino-5~hlorothiazole,2-amino-~-methylthiazole, etc. can also be employed. Thiourea can be reacted with propiolactone, butyrolactone, chloroacetic acid, chlo-ropropionic acid, propane sultone, dimethyl sulfate, etc.

~3;~23 Also, phenyl thiourea, methyl thiourea, allyl thiourea and other similar substituted thioureas can be used to form suitable reacted compounds.
The ba-th further contains as an essential constitu-ent, hydroyen ions to provide a pH of about 2.6 to abou-t 4.5 and preferably from about 3.2 to 3.8. The hydrogen ions can suitably be introduced employing any of the acids conventionally used in nickel-iron plating baths of which sulfuric acid and hydrochloric acid are pre-ferred.
The bath may further contain as an optional con-stituent, a controlled amount of a reducing saccharide.
The reducing saccharide or mixture of saccharides which càn satisfactorily be employed in accordance with the present invention can be either a monosaccharide or a disaccharide. The monosaccharides can be defined as polyhydroxyaldehydes or polyhydroxyketones with at least three aliphatically bound carbon atoms. The sim-plest monosaccharides are glyceraldehyde (generally termed aldose) and dihydroxyacetone (generally termed ketose). Other suitable monosaccharides useful in the practice of the present invention include dextrose, sorbose, fructose, xylose, erythrose and arabinose.
Disaccharides are glucoside-type derivatives of monosac-charides, in which one sugar forms a glucoside with an -O~ group of some other sugar. Disaccharides suitable for use in ~he practice of -the present invention include lactose, maltose and turanose, Other disaccharides in which the second monosaccharide may, at least momen-tarily, possess a free carbonyl group may also be utilized.
The reducing saccharide if used, can be employed in amounts ranging from about 1 to about 50 g/l with amounts of about 2 to about 5 g/l being preferred. The reducing saccharide functions as a mild reducing agent for ferric ions present but additionally provides for exceptional brightness and leveling of the nickel-iron electrodeposit in combination with the tartrate-type complexing agents and primary and secondary brighteners providing a syner-gistic effect which is not completely understood at the present time.
Further stabilization of the iron ions in the ferrous state is achieved by the addition of ascorbic and/or isoascorbic acid as well as the bath soluble and compatible salts thereof such as the alkali metal salts. When ascorbic and/or isoascorbic acid is employed as the sole iron solu-bilizing agent, it can be employed in amounts up to about 100 g/l. Preferably, this stabilizing agent is employed in combination with other iron solubilizing agents as here-inabove set forth at concentrations ranging from about 0.5 to about 3 g/l with amounts of about 1 to 2 g/1 being preferred.
The use of the reducing saccharide and/or stabili-zing agent inhibits the formation of ferric ions in the bath resul~ing from the oxidation of the ferrous salts 3i~

originally employed for bath make-up to the ferric state during bath operation. The rate of ferric iron ion formation is a function of the anocle area at which o~idation occurs as well as by oxidation particularly when air agitation of the bath is used. It is usually preferred to control the ferric ion concentration in the bath below about 40% of the total iron present.
In accordance with the process aspects of the present invention, substrates to be electroplated are immersed in the electroplating bath while cathodically charged and are electroplated at average current densities of about 5 up to about 100 ASF, preferably 30 to about 60 ASF, for periods of time to provide the desired plating thickness.
Usually plating thicknesses for decorative purposes range from about 0.1 mils to about 2 mils with thicknesses of about 0.2 to about 0.5 mils belng typical. The operating bath is usually maintained at a temperature ranging from 105F up to about 180F with temperatures of about 130~F to about 140F being preferred. Plating durations of from about 5 minutes to about 30 minutes are usually satisfac-tory in consideration of the specific current clensity employed and the thickness of the plating deposits desired. Agitation of the bath during electroplating is not necessary but is preferred employ~
ing conventional agitation means such as mechanical agitation, air agitation, and the like.

3~3 In order to further illus-trate the electro-platiny bath and process of the present invention, the follo~Jing specific examples are provided. It ~7.ill be understood that the examples are provided for illustra-tive purposes and are not intended to be limiting of the scope of the present invention as herein described and as set forth in the subjoined claims.

A nickel-iron electroplating bath is prepared having the following composition:
Ingredient Concentration NiSO 6H O ~150 g/l 6H2o 75 g/l H3BO3 50 g/l FeSO4^7H2O 40 g/l Sodium gluconate 20 g/l Primary brighteners 7 g/l Secondary brightener 20 mg/l ~- The sodium gluconate comprises the iron solu-bilizing agent. The primary brighteners comprise a mixture of sulfo-oxygen carrier brighteners comprising

2.5 g/l saccharin and 4.5 g/l sodium allyl sulfonate.
The secondary brightener comprises propynoxy ethylene oxide, a reaction product of polyethylene imine (molecular eight 1200) with sulfamic acid and 2-amino thiazoleO The bath temperature is controlled at 140F and the pH of the bath is adjusted to 3.5. A clean rolled steel panel ,

3~

is plated at 30 ASF for 10 minutes and the resulting deposit was bright bu-t had a dark recess area and an overall white blo-tchiness in the intermediate current density areas. The concentxation of the constituents of the bath are purposely selected to insure that an unacceptable deposit is ob-tained ~7ith a high iron alloy content of about ~2.5~ iron.

I~XAMPLE 2 The nickel-i.ron electroplating bath of Example 1 is replenished to provide the same bath com-position and in addition, 5 mg/l of propargyl sulfonate is added. A clean rolled steel panel is plated under the same conditions as described in Example 1 and the resulting deposit is overall bright with excellent recess areas and the white blotchiness is eliminated.

A nickel-iron plating solution which has been in commercial operation for about one year was analyzed and found to have the following composition of constituents:

Ni+2 73.75 g/1 NiSO4.6H2O 187.50 g/1 NiCl2.6H2O 138.85 g/1 H3BO3 44.24 g/1 Stabilizer* 17.40 g/1 Fe+2 2.67 g/1 Fe+3 1.61 g/1 Primary Brightener 3.8%
Secondary Brightener 2.3%
pH 3.1 *Calculated as tartaric acid and comprises a mixture originally added to the bath containing 65% tartaric acid, 15% lactose and 20% by weight isoascorbic acid.
A clean 3" X 5" polished brass panel was plated in the above described plating solution using a standard hull cell apparatus at 2 AMPS for 10 minutes at 140°F. The resulting deposit was overall bright and cloud free across the entire panel.

The pH of a fresh sample of the nickel-iron plating solution described in Example 3 was increased to 3.5, the iron content increased to 5.0 g/1 and the hull cell panel test was repeated. The resulting deposit was bright in the high current density area with a white smokey cloud in the intermediate current density areas and dark and blotchy gray in the low current density areas.

°

3~3 The pH of a fresh sample of the nickel-iron plating solution of Example 3 was again increased to 3.5, the iron content increased to 5.0 g/l and 5 rng/l of propargyl sulfonate was added to the bath. The hull cell panel tests were repeated and the resulting deposi.t was overall bright and cloud free across the entire panel.

EX~ PLE 6 The pH of the solution described in Example 5 was further increased to 3.8, the brighteners and ixon replenished and the hull cel]. panel tests were repeated. The resulting deposit plated at 2 ~lpcfor 10 minutes was similar to the panel described in Example 4 but the cloudiness and darkness were not as severe, especially in the intermediate current density areas.

EXA~lPLE 7 An addi-tional 5 mg/l of propargyl sulfonate was added to the nickel-iron solution described in Exa.nple 6, the brighteners and iron replenished and the hull cell panel tests were repeated as described in previous E~amples. The resulting deposit was now bright and cloud free over the entire panel.

2~

E~AM?LE 3 The commercial nickel-iron plating bath described in Example 3 was placed in a standard hull cell equipped with air agitation. The pH of the ~ath was increased to 3.8 and the total ir-on content was increased to 5.0 g/l. A hull ce]l panel was plated at 2 A~IPCfor ten minutes at 145F. The resulting deposi-t was bright in the high current density areas with severe smokiness and grayness in the intermediate current density areas with dark low current density areas.

EX~IPLE 9 15 mg/l of 1-butyne-3-sulfonic acid, sodium salt, was added to the ~ath described in Fxample 8, the brighteners and iron replenished and the hull cell panel test was repeated. Results revealed a slight improvement in deposit quality in that there was some reduction in the intermediate current density cloudiness.

E~AMPLL I0 The concentration of the l-bu-tyne-3-sulfonic acid, sodium salt, described in Example 9 was increased to 60 mg/l, the brighteners and iron replenished and the hull cell panel test was repea-ted. l'he resulting deposit was overall bright and leveled over the entire panel with only a very slight cloudiness along the meniscus of the plated deposit.

~3~

The commercial plating bath specifically described in Examples 3 an~ 8 was again used to chec~
the effectiveness of l-pentyne-5~sulfonic acid. The initial pan~l without adding the test material was exactly as described in Example 8. 50 mg/l of l-pentyne-5-sulfonic acid, sodium salt was added to the bath, the brighteners and iron replenished, and the hull cell panel test repeated. The resulting deposit was overall bright and leveled over the entire panel as well as the meniscus. ---The commercial plating bath specificallydescribed in Examples 3 and 8 was again used to check the effectiveness of 3-hep^tyne-7-sulfonic acid, sodium salt. The structure of this compound which is outside the scope of usable compounds encompassed by the generic structural formula hereinabove set forth is as follows:
CH -CH2-C=C-CH2-CH2-CH2 3 The initial panel before adding the test material was exactly as described in Example 8. 50 mg/l of the above described hep-tyne derivative was added to the bath, the brighteners and the iron replenished, and the hull cell panel test repeated. The resulting deposit showed no improvement.

3~

EX~PL~ 13 The concentration of the 3-heptyne-7-sulfonic acid, sodium salt was increased to 100 mg/l, the brlghteners and iron replenished, and the hull cell panel test was repeated. The resulting deposit showed no improvement~
In fact, the intermediate current density cloudiness worsened and the recess areas appeared even darker.

While it will be apparent that the preferred embodiments of the invention disclosed are well calcu-lated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

~2~-

Claims (22)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An aqueous bath suitable for the electrodeposition of bright, high-leveling nickel-iron alloy deposits com-prising nickel ions, iron ions, an iron solubilizing agent present in an amount to maintain the desired concentration of iron ions in solution, a buffering agent, a primary brightening agent present in an amount sufficient to produce a bright nickel-iron deposit, hydrogen ions to provide a pH of about 2.6 to about 4.5 and a bath soluble additive agent present in an amount of at least about 2 mg/l of the structural formula:

Wherein:
R is H or C1-C4 alkyl group, n is an integer from 0 to 4, m is an integer from 0 to 1, and X is H, NH4, or a bath compatible metal, as well as mixtures thereof.

2. The bath as defined in claim 1 in which X comprises H, NH4, and the alkali metals.

3. The bath as defined in claim 1 in which said additive agent is present in an amount of about 2 up to about 300 mg/l.

4. The bath as defined in claim 1 in which said additive agent is present in an amount of about 5 up to about 80 mg/l.

5. The bath as defined in claim 1 in which said nickel ions are present in an amount of at least about 10 g/l and said iron ions are present in an amount of at least about 0.2 g/l and the weight ratio of nickel ions to iron ions ranges from about 5:1 to about 50:1.

6. The bath as defined in claim 1 in which said hydrogen ions are present to provide a pH of about 3.2 to about 3.8.

7. The bath as defined in claim 1 in which said buffering agent is selected from the group consisting of boric acid, acetic acid, and the bath compatible and soluble salts thereof as well as mixtures thereof.

8. The bath as defined in claim 1 in which said iron solubilizing agent is present in an amount of about 5 to about 100 g/l.

9. The bath as defined in claim 1 in which said iron solubilizing agent is present in an amount of about 10 to about 30 g/l.

10. The bath as defined in claim 1 further including at least one secondary brightening agent present in an amount of about 0.25 mg/l up to about 1 g/l.

11. The bath as defined in claim 1 further including at least one secondary brightening agent present in an amount of about 10 to about 100 mg/l.

12. The bath as defined in claim 1 in which said iron solubilizing agent comprises a hydroxy substituted lower aliphatic carboxylic acid having from 2 to 11 carbon atoms, from 1 to 6 hydroxyl groups, from 1 to 3 carboxyl groups and the bath soluble and compatible salts thereof and mixtures thereof.

13. The bath as defined in claim 1 in which said iron solubilizing agent comprises an acid selected from the group consisting of ascorbic and isoascorbic acid and the bath soluble and compatible salts thereof.

14. The bath as defined in claim 1 in which said iron solubilizing agent includes a reducing saccharide.

15. The bath as defined in claim 1 in which said iron solubilizing agent comprises at least one acid selected from the group consisting of tartaric, ascorbic, iso-ascorbic, gluconic, citric, glucoheptonic, malic, glutaric, muconic, glycollic as well as the bath soluble and compatible salts thereof and mixtures thereof.

16. The bath as defined in claim 1 in which said bath soluble additive agent comprises 1-butyne-3-sulfonic acid and the bath compatible and soluble salts thereof.

17. The bath as defined in claim 1 in which said bath soluble additive agent comprises 1-pentyne-5-sulfonic acid and the bath soluble and compatible salts thereof.

18. The bath as defined in claim 1 in which said bath soluble additive agent comprises propargyl sulfonic acid and the bath soluble and compatible salts thereof.

19. The bath as defined in Claim 18 in which the compatible salts of the said propargyl sulfonic acid comprise the alkali metal and ammonium salts.

20. The bath as defined in Claim 18 in which the said additive agent is present in an amount of about 2 to about 200 mg/l.

21. The bath as defined in Claim 18 in which the said additive agent is present in an amount of about 5 to about 40 mg/l.

22. A process for electroplating a bright, high-leveling nickel-iron alloy deposit on an electrically conductive sub-strate comprising the steps of immersing the substrate in an aqueous bath as defined in Claims 1, 2 or 3, applying a cathodic charge to said substrate to effect a progressive deposition of a nickel-iron electrodeposit thereon, controll-ing the bath at a temperature of about 105 to about 180°F, and continuing the electrodeposition of said nickel-iron electrodeposit until a desired thickness is obtained.