GB2090870A - Nickel-Iron Alloy Electroplating Bath and Rejuvenation Thereof - Google Patents

Abstract

An aqueous bath for the electrodeposition of bright, high- levelling nickel-iron alloy deposits on a conductive substrate comprises nickel ions, iron ions, an iron solubilizing agent, a buffering agent, a brightening agent, hydrogen ions to provide a pH of about 2.6 to 4.5 and one or more bath soluble additive agents having the structural formula: <IMAGE> wherein: R is H or a C1-C4 alkyl group, n is 0 to 4, m is 0 to 1, and X is H, NH4<+> or a bath compatible metal atom. The additive agent I reduces the sensitivity of the bath to organic contaminants such as oils, greases and organic degradation products of the bath additives used. Used nickel-iron alloy plating baths can be rejuvenated by adding an additive agent of formula I.

Description

SPECIFICATION Bright Nickel-iron Alloy Electroplating Bath and Process The present invention relates to nickel iron electroplating baths and processes for using them.

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 resistance and are particularly useful for providing decorative finishes on corrosion susceptible substrates over which a subsequent electrodeposit of chromium is applied. It is extremely important that such nickel-iron decorative deposits should have highleveling properties, exceptional brightness and good ductility and that these beneficial characteristics are uniform over the entire electrodeposit.

Typical of known nickel-iron electroplating bath 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 organic 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 baths designed to electrodeposit alloys containing high percentages of iron, such as for example, 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 employed, have been found to cause a progressive deterioration of the quality of the electrodeposit and to greatly restrict the permissible bath operating parameters requiring relatively stringent control to maintain high quality electro deposits. The progressive deterioration of the bath is typically evidenced by eiectrodeposits 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 is 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 diminishes the detrimental effects of bath contamination during operation, which permits operation at a higher pH level to achieve excellent brightness and leveling, which permits more latitude in the parameters of bath control, and which facilitates the attainment 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 rejuvenating 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.

Thus according to the present invention there is provided an aqueous acidic bath of the type suitable for electrodepositing a bright, highleveling 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 concentration of iron ions in solution, a buffering agent, a brightening agent, preferably a primary brightener preferably in combination with one or more secondary brightening agents, 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 effective to improve the appearance of the deposit and preferably in an amount of at least about 2 milligrams per litre (mgl) of the structural formula:

wherein:: R represents a hydrogen atom or a C, to C4 alkyl group, n is an integer from 0 to 4, m is an integer from 0 to 1, and x represents a hydrogen atom or an ammonium group or a bath compatible metal atom or mixtures of such additives.

A particularly preferred additive agent corresponding to the foregoing structural formula is propargyl sulphonic 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 300 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, highleveling nickel-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 1 800F (40 to 820C) for a period of time to effect the electrodeposition of the nickel-iron alloy until a desired thickness is obtained. 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) (0.54 to 10.8 amperes per square decimetre (ASD)).The present invention further contemplates the process of replenishing a nickeliron bath by periodic and/or continuous addition of the additive agent to maintain the bath at optimum operating efficiency as well as the process of rejuvenating a contaminated, inefficient bath by the addition of the rejuvenating agent to restore the bath to its optimum operating condition.

The present invention is particularly applicable to the electrodeposition of decorative nickel-iron alloy deposits on electrically conductive substrates which can be utilized as a base for the subsequent electrodeposition of chromium in order to achieve the desired decorative and/or corrosion resistant properties. While the present invention is primarily applicable to the electrodeposition of nickel-iron alloys on metallic substrates, it is also contemplated that the invention can be applied to plastics substrates which have been subjected to a suitable pretreatment in accordance with well-known techniques to achieve an electrically conductive coating thereover such as a nickel or copper layer rendering the plastic substrate receptive to the nickel-iron alloy electroplating operation.Typical of such plastic materials which can be electroplated are ABS, polyolefin, polyvinyl chloride, and phenol-formaldehyde polymers.

In accordance with the composition aspects, the aqueous electroplating bath contains as essential constituents, a source of nickel ions, a source of iron ions, and an iron solubilizing agent present in an amount to maintain the desired concentration of iron ions in solution, a buffering agent, a carrier brightener, preferably a primary brightener, preferably in combination with one or more secondary brightening agents to produce a bright, preferably 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 agent preferably present in an amount of at least 2 mg/l having the structural formula:

wherein:: R represents a hydrogen atom or a C, to CA alkyl group, n is an integer from 0 to 4, m is an integer from 0 to 1, and X represents a hydrogen atom or an ammonium group or a bath compatible metal atom or mixtures of such additives.

Additive agents corresponding to the foregoing structural formula include 1-butyne-3-sulphonic acid, 1-pentyne-5-sulphonic acid, propargyl sulphonic acid and the alkali metal and ammonium salts thereof.

Of these, propargyl sulphonic acid and its bath compatible salts comprises the preferred additive agent. The additive agent of mixtures thereof is usually employed in amounts of about 2 to about 300 mg/l with amounts of about 5 to about 80 mg/l being preferred. When the preferred propargyl sulphonic 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 permits the electrodeposition of nickel-iron alloys of relatively high iron content, e.g. about 35% and higher employing a bath operating pH at the upper end of the 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 to occur without imposing the need for stringent control of the bath operating parameters to avoid blotchy or nonuniform deposits.The present invention further contemplates the replenishment and rejuvenation of contaminated baths which have lost their effectiveness 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 introduced into the bath as bath soluble and compatible nickel and iron compounds.

Preferably, inorganic nickel salts are employed such as nickel sulphate or nickel chloride, as well as other nickel materials such as nickel sulphamate. When nickel sulphate or sulphamate salts are used they are preferably employed in amounts ranging from 40 up to about 300 g/l (calculated as nickel sulphate hexahydrate). 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 so introduced provide for satisfactory conductivity of the bath and also provide for satisfactory corrosion properties of the soluble anodes.

The iron compounds preferably comprise inorganic ferrous salts such as ferrous sulphate, or ferrous chloride. 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, or ferrous sulphamate.

The concentration of nickel and iron ions in the bath is usually controlled to provide a weight ratio of nickel to iron ranging from about 5:1 up to about 50:1. The concentration of nickel ions in the bath is at least about 10 g/l while the concentration of the iron ions is at least about 0.2 g/l with the specific amount present being controlled to provide the appropriate weight ratio as hereinabove set forth.

In order to maintain the ferrous and ferric ions in solution 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 or by a reducing function or both. The reducing function reduces ferric ions to ferrous ions to avoid precipitation of ferric hydroxide. The iron solubilizing agent employed may include any of those heretofore used in the art and typically includes hydroxy substituted 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, glucoheptonic acid, glycollic acid, and tartaric acid as well as the water soluble and bath compatible salts thereof such as ammonium or alkali metal salts, as well as the nickel or iron salts thereof.

The iron solubilizing agent is employed in an amount sufficient to maintain the desired iron ion concentration in the solution and is typically employed in amounts in total of about 5 up to about 100 g/l with amounts of about 10 to about 30 g/l being preferred (calculated as the free acid or acids). Usually, 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 degradation products over prolonged operating periods of the bath. 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 constituent may precipitate out while at ratios above about 20:1 excessive concentrations of the solubilizing agent may be present resulting in the disadvantages and potential problems set forth above.

A further essential constituent of the bath is a buffering agent such as boric acid, or acetic acid as well as the alkali metal, ammonium, nickel or 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 60 g/l with concentrations of about 40 to about 50 g/l being preferred. Particularly satisfactory results are obtained employing boric acid and the bath soluble salts thereof.

The bath further contains as an essential constituent, a controlled amount of a brightener preferably a primary brightener or so-called carrier brightener preferably in further combination with secondary brighteners to attain exceptional brightness 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 gIl 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 or ammonium ions.

Primary brighteners suitable for use include those described in U. S. Patent No. 3,974,044, the substance of which is incorporated herein by reference. Such primary brighteners as described in the aforementioned patent comprise sulphooxygen compounds of sulphur-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, sulphobenzaldehyde, benzenesulphonamide and sodium allyl sulphonate, as well as mixtures thereof. Other bath soluble sulpho-oxygen compounds are those such as the unsaturated aliphatic sulphonic acids, mononuclear and binuclear aromatic sulphinic acids, mononuclear aromatic sulphonamides and sulphonimides.Of the foregoing, saccharin itself or saccharin in combination with allyl sulphonate and/or vinyl sulphonate comprises a preferred primary brightener.

Suitable secondary brighteners include acetylenic nickel brighteners such as the acetylenic sulpho-oxygen compounds and acetylenic nickel brighteners as described in U. S.

Pat. No. 3,366,667 such as the polyethers resulting from the condensation reaction of acetylenic alcohols and diols such as, propargyl alcohol or butyndiol, with the lower alkylene oxides such as, epichlorohydrin, ethylene oxide or propylene oxide.

Additional secondary brighteners that are suitable include nitrogen heterocyclic quaternary or betain nickel brighteners which are usually employed in amounts of about 1 to about 150 mg/l. Suitable compounds of this type are those decribed in U. S. Pat. No. 2,647,866 and the nitrogen heterocyclic sulphonates described in U.S. Pat. No.3,023,151. Preferred compounds described therein are the pyridine quaternaries or betains or the pyridine sulphobetains. Suitable quaternaries that may be employed are quinaldine propane sultone, quinaldine dimethyl sulphate, quinaldine allyl bromide, pyridine aliyl bromide, isoquinaldine propane sultone, isoquinaldine dimethyl sulphate, and isoquinaldine allyl bromide.

In addition, secondary brighteners further include the reaction product of a polyamine-type brightener which has a molecular weight ranging from 300 to about 24,000, and an alkylating agent of the type described in U. S. Pat. No.

4,002,543 the substance of which is incorporated herein by reference. Exemplary alkylating agents are dimethyl sulphate, chloroacetic acid, allyl bromide, propane sultone, benzyl chloride or propargyl bromide. The polyamine brightener may be sulphonated utilizing as exemplary compounds sulphamic acid or chloro sulphonic acid. The ratio of polyamine to alkylating agent or to the sulphonating agent can be varied so that every amino group need not be alkylated or sulphonated 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. Pat. No. 3,806,429, the substance of which is incorporated herein by reference Such optional special additives are not required in achieving the exceptional brightness and high-leveling in accordance with the present invention but their inclusion in 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 densities.Such speciality additives comprise organic sulphide compounds which are normally employed in amounts ranging from about 0.5 to about 40 mg/l and are of the formula:

where R' represents a hydrogen atom or a carbon atom of an organic radical, R2 represents a nitrogen atom or a carbon atom of an organic radical and R3 represents a carbon atom of an organic radical. R' and R2 or R3 may be linked together through a single organic radical.

Typically, the bath soluble organic sulphide compounds can be 2-amino thiazoles or iso thioureas. 2-aminothiazole and 2-aminobenzo thiazo[e can be reacted with bromethane sulphonate, propane sultone, benzyl chloride, dimethylsulphate, diethyl sulphate, methyl bromide, propargyl bromide, ethylene dibromide, allyl bromide, methyl chloro acetate or sulphophenoxyethylene bromide, to form compounds suitable for use. Substituted 2-aminothiazoles and 2-aminobenzothiazoles, such as 2-amino-5chlorothiazole or 2-amino-4-methylthiazole, can also be employed. Thiourea can be reacted with propiolactone, butyrolactone, chloroacetic acid, chloropropronic acid, propane sultone or dimethyl sulphate. Also, phenyl thiourea, methyl thiourea, allyl thiourea and other similar substituted thioureas can be used to form suitable reacted compounds.

The bath further contains as an essential constituent, hydrogen ions to provide a pH of about 2.6 to about 4.5 and preferably from about 3.2 to 3.8. The hydrogen ions can suitably be introduced by means of any of the acids conventionally used in nickel-iron plating baths of which sulphuric acid and hydrochloric acid are preferred.

The bath may further contain as an optional constituent, a controlled amount of a reducing saccharide. The reducing saccharide or mixture of saccharides which can 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 simplest 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 monosaccharides, in which one sugar forms a glucoside with an -OH group of some other sugar.

Disaccharides suitable for use in the practice of the present invention include lactose, maltose and turanose. Other disaccharides in which the second monosaccharide may, at least momentarily, 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 additionaliy provides for exceptional brightness and leveling of the nickel-iron electrodeposit in combination with the tartrate-type complexing solubilizing agents and primary and secondary brighteners providing a synergistic 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 or isoascorbic acid or both 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 solubilizing agent, it can be employed in amounts up to about 100 g/l. Preferably, this stabilizing agent is employed in combinatioon with other iron solubilizing agents as hereinabove set forth at concentrations ranging from about 0.5 to about 3 g/l with amounts of about 1 to 2 g/l being preferred.

The use of the reducing saccharide and/or stabilizing agent inhibits the formation of ferric ions in the bath resulting from the oxidation of the ferrous salts 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 anode area at which oxidation occurs in addition to the oxidation due to dissolved oxygen which also occurs particularly when air agitiation 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 (0.54 to 10.8 ASD), preferably 30 to about 60 ASF (3.2 to 6.5 ASD), for periods of time to provide the desired plating thickness.

Usually plating thickness for decorative purposes range from about 0.1 mils to about 2 mils (0.25 to 5.1 microns) with thicknesses of about 0.2 to about 0.5 mils (0.50 to 1.25 microns) being typical. The operating bath is usually maintained at a temperature ranging from 1 050F up to about 1 800F (40 to 820C) with temperatures of about 1300to about 1400F (54 to 600C) being preferred. Plating durations of from about 5 minutes to about 30 minutes are usually satisfactory in consideration of the specific current density employed and the thickness of the plating deposits desired. Agitation of the bath during electroplating is not necessary but it is preferred to employ conventional agitation means such as mechanical agitation or air agitation.

The invention can be put into practice in various ways and a number of specific embodiments will be described to illustrate the invention with reference to the accompanying examples.

Example 1 A nickel-iron electroplating bath was prepared having the following initial composition: Ingredient Concentration NiSO4-6H > O 150 g/l NiC12.6H2O 75 g/l H3BO3 50 g/l FeSO4-7H2O 40 g/l Sodium gluconate 20 9 Primary brightener 7 g/l Secondary brightener 20 mg/l The sodium gluconate comprised the iron solubilizing agent. The primary brightener comprised a mixture of sulpho-oxygen carrier brighteners comprising 2.5 g/l saccharin and 4.5 g/l sodium allyl sulphonate. The secondary brightener comprised 2-amino thiazole, and propynoxy ethylene oxide, a reaction product of polyethylene imine (molecular weight 1200) with suiphamic acid.The bath temperature was controlled at 1 400F (600C) and the pH of the bath was adjusted to 3.5. A clean rolled steel panel was plated at 30 ASF (3.24 ASD) for 10 minutes leaving a used bath 1 B. The resulting deposit was bright but had a dark recess area and an overall white blotchiness in the intermediate current density areas. The concentration of the constituents of the bath had purposely been selected to insure that an unacceptable deposit was obtained with a high iron alloy content of about 42.5% iron.

Example 2 The nickel-iron electroplating bath 1 B of Example 1 was replenished to provide the same initial bath composition as in Example 1 and in addition, 5 mg/l of propargyl sulphonate was added. A clean rolled steel panel was plated under the same conditions as described in Example 1 and the resulting deposit was overall bright with excellent recess areas and the white blotchiness was eliminated.

Example 3 This is a comparison Example.

A nickel-iron plating solution which had been in commercial operation for about one year was analyzed and found to have the following composition of constituents: Ni+2 73.75 gIl NiSO,.6H2O 187.50 g/l NiCI2.6H2O 138.85 gIl H3BO3 44:24 gel Stabilizer (1) 17.40 g/l Fe+2 2.67 gIl Fe+3 1.61 g/l Primary Brightener (2) 3.8% Secondary Brightener (3) 2.3% pH 3.1 (1) Calculated as tartaric acid and comprised a mixture originally added to the bath containing 65% tartaric acid, 15% lactose and 20% by weight isoascorbic acid.

(2) as in Example 1.

(3) as in Example 1.

A clean 3"x5" (7.6x12.7 cms=0.0097 sq.

decimetres) polished brass panel was plated in the above described plating solution using a standard Hull cell apparatus at 2 AMPS for 10 minutes at 1 400F (600C). The resulting deposit was overall bright and cloud free across the entire panel. The deposit contained 1314% iron.

Example 4 This is a comparison Example.

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/l 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. The deposit contained 2324% iron.

Example 5 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 mg/l of propargyl sulphonate was added to the bath. The Hull cell panel tests were repeated and the resulting deposit was overall bright and cloud free across the entire panel. The deposit contained 2324% iron.

Example 6 The pH of the solution described in example 5 was further increased to 3.8, the brighteners and iron replenished to the values given in Example 3 and the Hull cell panel tests were repeated. The resulting deposit plated at 2 AMPS for 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. The deposit contained 2324% iron.

Example 7 An additional 5 mg/l of propargyl sulphonate was added to the nickel-iron solution described in Example 6, the brighteners and iron replenished to the values given in Example 3 and the Hull cell panel tests were repeated as described in Example 3. The resulting deposit was now bright and cloud free over the entire panel. The deposit contained 2324% iron.

Example 8 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 bath was increased to 3.8 and the total iron content was increased to 5.0 g/l.A Hull cell panel was plated at 2 AMPS for ten minutes at 1450 F (630C). The resulting deposit 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. The deposit contained 2324% iron.

Example 9 15 mg/l of 1-butyne-3-sulphonic acid, sodium salt, was added to the bath described in Example 8, the brighteners and iron replenished to the values given in Example 3 and the Hull cell panel test was repeated. There was a slight improvement in deposit quality in that there was some reduction in the intermediate current density cloudiness. The deposit contained 2324% iron.

Example 10 The concentration of the 1-butyne-3-sulphonic acid, sodium salt, described in Example 9 was increased to 60 mg/l, the brighteners and iron replenished to the values given in Example 3 and the Hull cell panel test was repeated. The resulting deposit was overall bright and leveled over the entire panel with only a very slight cloudiness along the meniscus of the plated deposit. The meniscus is the line at which the test panel emerged from the test solution when it was in the bath being plated. The deposit contained 2324% iron.

Examples 11A and 11B The commercial plating bath specifically described in Examples 3 and 8 was again used to check the effectiveness of 1 -pentyne-5-sulphonic acid. The appearance of the plated panel without the additive of the present invention was exactly as described in Example 8 (Example 11 A). 50 mg/l of 1-pentyne-5-sulphonic acid, sodium salt was added to the bath, the brighteners and iron replenished to the values given in Example 3, and the Hull cell panel test repeated. The resulting deposit was overall bright and leveled over the entire panel as well as the meniscus.

Examples 12A and 12B The commercial plating bath specifically described in Examples 3 and 8 was again used to check the effectiveness of 3-heptyne-7-sulphonic 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: CH3-CH2-C=-C-CH2-CH2-CH2-SO3Na The appearance of the plated panel without the additive of this Example was exactly as described in Examples (Example 12A). 50 mg/l of 3heptyne-7-sulphonic acid was added to the bath, the brighteners and the iron replenished to the values given in Example 3 and the Hull cell panel test repeated. The resulting deposit showed no improvement.

Example 13 The concentration of the 3-heptyne-7sulphonic acid, sodium salt was increased to 100 mg/l, the brighteners and iron replenished to the values given in Example 3 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.

Claims (37)

Claims

1. An aqueous bath suitable for the electrodeposition of bright, nickel-iron alloy deposits comprising a source of nickel ions, a source of iron ions, an iron solubilizing agent present in an amount to maintain the desired concentration of iron ions in solution, a buffering agent, a brightening agent present in an amount sufficient to produce a bright nickel-iron deposit, hydrogen ions to provide a pH of 2.6 to 4.5 and one or more bath soluble additive agents present in an amount effective to improve the appearance of the deposit, the additive agents having the structural formula:

wherein: R represents a hydrogen atom or a C1-C4 alkyl group, n is an integer from 0 to 4, m is an integer from 0 to 1, and X represents a hydrogen atom or an ammonium group or a bath compatible metal atom, or mixtures of such additives.

2. A bath as claimed in claim 1 in which X represents an alkali metal atom.

3. A bath as claimed in claim 1 or claim 2 in which the said additive is present in an amount of at least about 2 mg/l.

4. A bath as defined in claim 1,2 or 3 in which the said additive agent is present in an amount of 2 up to 300 mg/l.

5. A bath as claimed in claim 4 in which the said additive agent is present in an amount of 5 up to 80 mg/l.

6. A bath as claimed in any one of claims 1 to 5 in which the said bath soluble additive agent comprises 1-butyne-3-sulphonic acid or a bath compatible and soluble salt thereof.

7. A bath as claimed in any one of claims 1 to 5 in which the said bath soluble additive agent comprises 1 -pentyne-5-sulphonic acid or a bath soluble and compatible salt thereof.

8. A bath as claimed in any one of claims 1 to 5 in which the said bath soluble additive agent comprises propargyl sulphonic acid or a bath soluble and compatible salt thereof.

9. A bath as claimed in claim 8 in which the compatible salt of the said propargyl sulphonic acid comprises an alkali metal or ammonium salt.

10. A bath as claimed in claim 8 or claim 9 in which the said additive agent is present in an amount of 2 to 200 mg/l.

11. A bath as claimed in claim 8 or claim 9 in which the said additive agent is present in an amount of 5 to 40 mg/l.

12. A bath as claimed in any one of claims 1 to 11 in which the said nickel ions are present in an amount of at least about 10 g/l and the said iron ions are present in an amount of at least about 0.2 g/l.

13. A bath as claimed in any one of claims 1 to 12 in which the weight ratio of nickel ions to iron ions ranges from about 5:1 to about 50:1.

14. A bath as claimed in any one of claims 1 to 1 3 in which the said hydrogen ions are present to provide a pH of 3.2 to 3.8.

1 5. A bath as claimed in any one of claims 1 to 14 in which the said buffering agent comprises boric acid or acetic acid, or the bath compatible and soluble salts thereof, or mixtures thereof.

16. A bath as claimed in any one of claims 1 to 1 5 in which the said iron solubilizing agent is present in an amount of 5 to 100 g/l.

17. A bath as claimed in claim 16 in which the said iron solubilizing agent is present in an amount of 10 to 30 g/l.

18. A bath as claimed in any one of claims 1 to 1 7 in which the said iron solubilizing agent comprises a hydroxy substituted lower aliphatic carboxylic acid having 2 to 11 carbon atoms, from 1 to 6 hydroxyl groups, from 1 to 3 carboxyl groups or a bath soluble and compatible salt thereof or mixtures thereof.

19. A bath as claimed in any one of claims 1 to 1 8 in which the said iron solubilizing agent comprises ascorbic acid or isoascorbic acid or a bath soluble and compatible salt thereof, or mixtures thereof.

20. A bath as claimed in any one of claims 1 to 1 9 in which the said iron solubilizing agent comprises a reducing saccharide.

21. A bath as claimed in any one of claims 1 to 20 in which the said iron solubilizing agent comprises at least one of tartaric, ascorbic, isoascorbic, gluconic, citric, glucoheptonic, malic, glutaric, muconic or glycollic acids or a bath soluble and compatible salt thereof or mixtures thereof.

22. A bath as claimed in any one of claims 1 to 21 in which the brightener comprises a primary brightener.

23. A bath as claimed in claim 22 further including at least one secondary brightening agent.

24. A bath as claimed in claim 23 in which the secondary brightening agent is present in an amount of 0.25 mg/l up to 1 g/l.

25. A bath as claimed in claim 24 in which the secondary brightening agent is present in an amount of 10 to 100 mg/l.

26. A bath as claimed in claim 1 substantially as specifically described herein with reference to any one of Examples 2, 5, 7, 9, 10 or 11 B.

27. A process for electroplating a bright, highleveling nickel-iron alloy deposit on an electrically conductive substrate comprising the steps of immersing the substrate in an aqueous bath as claimed in any one of claims 1 to 26, applying a cathodic charge to the said substrate to effect a progressive deposition of a nickel-iron electrodeposit thereon, controlling the bath at a temperature of about 1 050F (400 C) to about 1 800F (820C), and continuing the electrodeposition of the said nickel-iron electrodeposit until a desired thickness is obtained.

28. A process as claimed in claim 27 substantially as specifically described herein with reference to any one of Examples 2, 5, 7, 9, 10 or 11 B.

29. A substrate carrying a bright nickel-iron deposit whenever made by a method as claimed in claim 27 or claim 28.

30. A replenishing agent comprising one or more compounds having the structural formula:

wherein: R represents a hydrogen atom or C1-C4 alkyl group, n is an integer from 0 to 4, m is an integer from 0 to 1, and X represents a hydrogen atom or an ammonium group or a bath compatible metal atom, for use in replenishing an aqueous bath suitable for the electrodeposition of bright, high-leveling nickel-iron alloy deposits containing 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, and hydrogen ions to provide a pH of about 2.6 to about 4.5.

31. A replenishing agent as claimed in claim 30 which comprises propargyl sulphonic acid, the bath soluble and compatible salts thereof and mixtures thereof.

32. A replenishing agent as claimed in claim 31 in which the said salts comprise alkali metal and ammonium salts.

33. A process for rejuvenating an aqueous bath to restore its capacity to electrodeposit bright, high-leveling nickel-iron alloy deposits, the said bath containing nickel ions, iron ions, an iron solubiiizing agent present in an amount to maintain the desired concentration of iron ions in solution, a buffering agent, a primary brightening agent and hydrogen ions to provide a pH of about 2.6 to about 4.5, the said process comprising the steps of adding to the said bath a rejuvenating agent in an amount sufficient to restore the capacity of the said bath to electrodeposit a bright, high-leveling nickel-iron alloy, the said rejuvenating agent comprising one or more compounds as claimed in any one of claims 30 to 32.

34. A process as claimed in claim 33 in which the said rejuvenating agent is added in an amount of 2 to 300 mg/l.

35. A process as claimed in claim 33 or claim 34 in which the said rejuvenating agent is added in an amount of 5 to 80 mg/l.

36. A process as claimed in claim 33 and claim 31 or claim 33 and claim 32 in which the said rejuvenating agent is added in an amount to maintain a concentration of 2 to 200 mg/l.

37. A process as claimed in claim 36 in which the said rejuvenating agent is added in an amount to maintain a concentration of about 5 to about 40 mg/l.