US3288574A

US3288574A - Metal laminates and method of forming by electroplating

Info

Publication number: US3288574A
Application number: US358872A
Authority: US
Inventors: Rose Arthur H Du; William J Pierce
Original assignee: Harshaw Chemical Co
Current assignee: HARSHAW/FILTROL PARTNERSHIP A PARTNERSHIP OF
Priority date: 1964-04-10
Filing date: 1964-04-10
Publication date: 1966-11-29
Anticipated expiration: 1983-11-29
Also published as: GB1081794A; DE1496823B1

Description

Nov. 29, 1966 A. H. DU ROSE ETAL 3,238,574

METAL LAMINATES AND METHOD OF FORMING BY ELECTROPLATING Filed April 10, 1964 CORROSION CHROA/IIUM PLATE BRIGHT NICKEL PLATE IIIPLEA IEEALEAEQLLIEE NICKEL PLATE F/ BRIGHT NICKEL PLATE NICKEL-ARSENIC ALLOY PLATE (0. 0/-o.2 M/L., O.25%-8% ARSEN/C) NICKEL PLATE METAL BASE CORROSION CHROMIUM PLATE V/l VT /7\4/ s\\ w R L/ BRIGHT NICKEL PLATE NICKEL-ARSENIC ALLOY PLATE R I- 0-2 M/L., 0.25-8'Z ARSEN/C) NICKEL PLATE METAL BASE FIG} ARTHUR H. DUROSE AND WJLLIAM J. PIERCE, INVENTORS ATTORNEY United States Patent Office 3,283,5'3'4 Patented Nov. 29, 1966 3,288,574 METAL LAIVHNATES AND NHETHUD 6F FGRPv HNG BY ELECTROPLATING Arthur H. Du Rose, Euclid, and William 3. Pierce, Lyndhurst, Qhio, assignors to The Harshaw Chemical Company, Cleveland, Ohio, a corporation of Ohio Filed Apr. 10, 1964, Ser. No. 358,872 20 Claims. (Cl. 29-194) This invention relates to a composite coating of three adjacently bonded layers of nickel and more particularly this invention relates to such a composite coating wherein the intermediate layer thereof comprises a thin nickel deposit containing a desired amount of arsenic.

In recent years much work has been done to provide an article with a decorative plate of chromium over two or three underlying layers of nickel. The composition and electrochemical properties of these layers of nickel are balanced to obtain good protection of the base surface against corrosion without compromising the decorative appearance. To be effective the series of nickel layers must be deposited from plating baths adapted to impart not only the desired electrochemical properties to the nickel layers but also the other physical and chem ical properties necessary for a good plate. Moreover, thebrightness and other surface characteristics of the top layer must be such that the chromium deposit be smooth, lustrous and substantially free from color, spots and the like.

When using three layers of nickel, the composition of the intermediate layer is adjusted so as to be anodic to both the upper agnd lower layers and preferably the composition of the upper layer is adjusted so as to be anodic to the lower layer. The decorative chromium layer is more noble than the said nickel layers. Moreover, the intermediate layer advantageously is made very thin, the reasons for which will be explained more fully hereinafter.

Originally, the triple-layer systems were made using as the intermediate layer metals usually different from nickel but anodic thereto. With the use of some systems, marked corrosion protection was observed (see Knapp, Trans. Inst. Met. Finishing, 1958, 35, 139-165). In most cases, however, the systems were found not to be useful, either because the metal corroded too rapidly causing blistering or scaling or because the metal stained or colored the decorative surface.

Within the last few years triple-layer systems have been made using a nickel-containing deposit for each layer and wherein relative potentials of the layers are controlled by the amounts of sulfur deposited with the nickel. The sulfur may be controlled in the bath by adjusting the contents of the various organic brightening additives comprising sulfur with o-r without additional sulfur-containing compounds. Sulfur-free brighteners with sulfo-oxygen carriers also may be used to enhance the sulfur in the nickel deposit. This control of the addition agents ultimately controls the amount of sulfur in the electrodeposits and thereby the relative potential which is considered to be the important factor.

Several problems have confronted the industry in accepting the triple-layer system because sulfur as such not only provides differences in potential in electrodeposits of nickel but also affects other physical properties such as ductility and brightness and continuity of the deposit. For instance, if the proper potential is to be maintained between the intermediate layer and the top layer, the sulfur contents of each layer must be controlled. However, there is evidence that the electronegative potential (its relative susceptibility to corrosion) of sulfur-containing nickel does not vary as a straight line function in relation to the sulfur content and tends to level off at sulfur concentrations in the range of from about 0.2-0.3 percent by weight. Thus it is seen that the degree in which the concentration of sulfur may be varied in the nickel layer to adjust potential is very narrow. Moreover, if a manufacturer prefers to deposit a lower layer of nickel from a sulfur-containing bath, he necessarily will have to increase the amounts of sulfur in the intermediate and upper nickel layers necessitating the adjustment of the other additives in the bath.

It has now been discovered that triple layer systems using arsenic-containing intermediate layers are not only more durable than the systems using sulfur in the intermediate layer but they are more easily and advantageously prepared; they may be deposited merely from a standard bath having the proper concentration of a water-soluble arsenic compound. Moreover the arsenic compounds are more stable in the bath than the sulfur compounds which may be used in the bath to impart sulfur into the deposit especially in regard to air oxidation, thus permitting air agitation to any degree desired.

in accordance with the present invention there is provided an improved composite coating comprising three adjacently bonded layers of nickel deposits, the lower layer of a conventional low-sulfur nickel electroplate preferably 0.3 to 2 mils thick and having from 0 to about 25 percent cobalt by weight alloyed therewith and a sulfur content preferably less than 0.01 percent, a top layer of a conventional bright nickel electroplate preferably 0.15 to 1 mil thick and having from 0 to 50 percent cobalt alloyed therewith and preferably from about 0.03 percent to about 0.3 percent sulfur by weight; and characterizing the invention, an intermediate layer 0.01 to 0.2 mil thick of which comprises a deposit of nickel having from about 0 to about 25 percent cobalt alloyed therewith and containing from about 0.025 percent arsenic to about 8 percent arsenic based on the total weight of said deposit.

For reasons to be explained more fully hereinafter, the triple-layer composite coatings of the present invention are generally more advantageously prepared using intermediate layers having arsenic concentrations in the range of from about 0.25 percent to about 4 percent. More preferably the arsenic concentration is kept in the range of from about 0.50 percent to about 2.5 percent.

The mechanism by which the triple-layer coating system of the present invention acts to protect a corrodible substrate is more easily understood by referring to the accompanying drawing in which:

FIG. 1 illustrates schematically a triple-layer system with a corrosion pit in its incipient stage.

FIG. 2 illustrates the same triple-layer system with the corrosion pit in an advanced stage where the pit has reached and has attacked the intermediate layer.

FIG. 3 illustrates the same triple-layer system with the corrosion pit widened laterally but where the lower layer has not been attacked substantially.

The composite electroplate of the present invention advantageously is employed over various substrates and particularly substrates susceptible to corrosion. Iron, steel, copper, brass, aluminum, zinc and magnesium with or without a copper deposit, are substrates protected by the composite electroplates of the present invention.

The arsenic present in the intermediate layers of the instant triple-layer composites provides surprisingly good corrosion protect-ion to the substrate covered by the system. The electroplate composites of the present invention are three to four times more effective than those prepared using sulfur in the intermediate layer. The projected rust-free life of the instant composite may approach 5-6 years, based on the results of the standard Corrodkote and CASS corrosion tests. The corresponding triple-layer composites having sulfur-containing intermediate layers have at best a 2 to 4 year projected rustfree life based on these tests.

Corrodkote is the name given to an accelerated test in which a synthetic road soil slurry is applied to the plated surface of an article and the article is then exposed to a warm humid atmosphere. A Corrodkote slurry formulation includes both soluble and insoluble elements and sufficient liquid to give proper spreading consistency. The slurry is applied to the surface being tested by means of a paint brush, or similar device, to produce a fairly uniform coating, after which the coated specimen is exposed to specified humidity conditions.

A standard Corrodkote mixture, efiective in testmg chromium-nickel combinations over steel, is:

Kaolin, grams 30 Ferric chloride, gram 0.165 Cupric nitrate, gram 0.035 Ammonium chloride, gram 1 Water, ml. 50

The CASS test involves exposing the plated parts to a salt spray containing small concentrations of cupric chloride and acetic acid.

Both the Corrodkote and the CASS tests have been accepted by the industry as well established accelerated tests for corrosion. For a complete description of the tests see Plating, vol. 44, p. 763, 1957.

In some instances neither the Corrodkote test nor the CASS test are absolutely reliable in predicting service life of plated parts on cars. When some plated panels are rated good by the Corrodkote test,-the same panels are less highly rated by the CASS test and the reverse would be observed with other plated panels. Therefore the test results set forth hereinafter to show the advantages of the present invention are obtained by submitting the sample panels to 3 or 4 Corrodkote cycles, and instead of using more Corrodkote cycles, further submitting the panels to the CASS test. Controls or panels for comparison are always employed. A representative test would be 3 or 4 Corrodkote cycles plus 48 hours of CASS exposure.

The advantage of using the triple-layer composite systems to protect a corrodible substrate becomes significant when reference is made to FIGS. 13 of the drawing. These figures illustrate in sequence the progressive corrosion of a typical three-layer composite. As a corrosion pit is formed in the top nickel layer as shown in FIG. 1 (usually through a pore or other defect in the chromium decorative coat), the pit progressively enlarges hemispherically. This corrosion site continually enlarges until it reaches the more anodic intermediate layer.

In FIG. 2 the corrosion pit has attacked the intermediate layer, progressed until the pit has become substantially cylindrical rather than hemispherical and has undercut the intermediate layer slightly below the top layer of nickel. Because the lower layer is more noble than the two upper layers of nickel, the lower layer remains relatively free from corrosion.

As the intermediate layer corrodes beneath the top or upper layer, the intermediate layer becomes more inaccessible to the corroding electrolyte and the total polarization increases due to localized changes in concentration causing increase in the resistance of the electrolyte and other ohmic eifects. Thus the rate of the corrosion of the intermediate layer decreases and the top layer begins to corrode again and exposes the intermediate layer renewing the anodic protection of the top layer. This cycle continually is repeated while the lower layer is protected by the sacrificial action of both the intermediate layer and the top layer. In FIG. 3 there is shown a plate with the corrosion pit widened with the lower layer of nickel being attacked only very slightly. The rate of corrosion of the lower layer in relation to i the top and intermediate layer is usually less than 1 to 100.

In the triple-layer system the intermediate layer acts as the sacrificial anode primarily, while the top layer provides the bright surface for the decorative chromium; the composition of the intermediate layer need not be controlled as rigidly as the composition of the top layer in a duplex system.

The reasons that the triple-layer systems of the present invention manifest such excellent corrosion resistance is not completely understood. From a superficial study of the electrochemical properties of arsenic-containing nickel deposits, it is observed that the relative potentials obtainable from theses deposits generally are higher than those obtainable from sulfur-containing nickel deposits, usually at least millivolts, measured 5 percent sodium chloride solution adjusted to a pH of 3 with acetic acid. Thus, it appears that the intermediate layer of the instant triple-layer composites is prepared consistently anodic to the upper and lower layers of nickel.

As mentioned hereinbefore, the triple-layer system is most effective when the intermediate layer is anodic to the lower layer and the upper layer and wherein the lower layer is cathodic to the upper layer. Supposedly the mechanism taking place is that the intermediate layer acts as a primary sacrificial anode and the upper layer acts as a secondary sacrificial anode, protecting the lower layer while the intermediate layer is temporarily less active. Moreover, the use of arsenic as the alloying constituent with nickel in the preparation of the intermediate layer provides advantages other than that of providing higher potentials than those obtainable from the use of sulfur as the alloying constituent with nickel.

In order to carry the present invention into effect, the substrate is plated first with a lower layer of nickel and then with the intermediate layer of nickel and the upper layer of nickel. Any solution of nickel ions designed for electroplating nickel may be used.

The solutions contain at least one of the following salts: nickel sulfate, nickel chloride, nickel fluoroborate and nickel sulfamate, wherein the solution is adjusted to an operating concentration of nickel. Included among the various baths useful in carrying out the present invention are (1) the various barrel plating baths generally comprising nickel sulfate and nickel chloride as the source of the nickel ion and buffer systems comprising boric acid alone or in conjunction with magnesium sulfate or ammonium chloride, (2) the all-chloride bath designed for use Where a high current density is desired, comprising nickel chloride as the source of nickel ion and boric acid as the buffer, (3) the fluoroborate bath comprising nickel fluoroborate as the source of nickel ion and free boric acid as the buffer alone or in combination with fluoroboric acid, (4) the common Watts-type bath designed for all purpose nickel plating and generally comprising nickel sulfate and nickel chloride as the source ofnickel ion buffered with boric acid, (5) the all sulfamate bath comprising nickel sulfamate including boric acid as the buffer, (6) the chloride-sulfamate bath comprising nickel chloride and nickel sulfamate with boric acid as the buffer and (7) other nickel baths made from nickel salts and complexing agents.

After the desired thickness is obtained for the first or lower layer of nickel, the arsenic-containing intermediate layer of nickel is deposited. An arsenic-supplying compound is added to one of the above baths adjusted to the appropriate concentration and a thin layer of arseniccontaining nickel is deposited directly on the surface of the first or lower layer of nickel.

The composition is then completed by plating a third deposit of nickel directly on the surface of the intermediate plate. Normally this plate is fully bright to provide an optimum surface for the decorative chromium plate. The decorative chromium layer advantageously is from about 0.005 mil to about 0.2 mil thick. Each of the above layers of nickel may be deposited using more than one step such as for example by interrupting the plating cycle for one reason or another.

In its preferred form the composite coating of the present invention comprises a first or lower layer of ductile sulfur-free nickel. This preferred plate is deposited from a typical Watts-type or fluoroborate-type bath containing an effective amount of a sulfur-free leveler such as coumarin and the like. The top layer of nickel preferably being fully bright is deposited upon one of the above baths using a brightener of the first class (sulfo-oxygen carrier) and a brightener of the second class. Where the top layer is high in sulfur content (0.1 to 0.3 percent) the lower layer also may be deposited from a bath containing in addition to a brightener of the first class (sulfo-oxygen compound) small amounts of a brightener of the second class. The baths disclosed in US. Patent 3,090,733, as being useful for preparing the upper layers of nickel in the composite disclosed and claimed therein may be used to deposit the upper layers of nickel for the present invention.

As indicated hereinbefore, the lower and top layers of nickel may be deposited from baths of conventional compositions and in the baths there may be present one or more brighteners of the first class. These compounds generally comprise an aryl ring, a substituted aryl ring or an unsaturated aliphatic chain with a sulfur-containing radical in the form of sulfonic acids, sulfonates, sulfonamides, sulfimides, sulfinic aacid and sulfones. The aryl ring advantageously may be derived from benzene, naphthalene and the like, the substituted aryl ring may be derived from toluene, xylene, naphthylamine, toluidine, benzyl naphthalene and the like and the alkylene chain may advantageously be derived from vinyl compounds or allyl compounds and the like. Examples of sulfo-oxygen compounds of the above described type and which are useful particularly in the instant nickel plating baths are found in US. Patents 2,757,133 and 2,766,284.

Almost uniformly, the top layer of nickel is deposited from baths containing, in addition to brighteners of the first class, brighteners of the second class including organic compounds dependent on the carbonyl C=O) radical for the brightening action such as the various ketones, aldehydes, carboxylic acids, some proteins (gelatin) and the like; those compounds dependent on the ethylenic (CH=CH--) radical for the brightening action such as the alkylenic carboxylic esters, the alkylenic aldehydes, the aromatic compounds dependent on the in-ring ethylenic radical such as the aryl aldehydes, the sulfonated aryl aldehydes, allyl and vinyl substituted compounds, coumarin and its derivatives, and the like; those compounds dependent on the acetylenic radical including the acetylenic alcohols, nitrogen heterocyclics having an N-substituted acetylenic radical and the like; those compounds depending on the azo and azine type nuclei @N- and N=N) for the brightening action such as the azine, thiazane and oxazine dyes, the triphenyl methane dyes, the quinidines, pyrimidines, pyrazoles and imidazoles, the pyridinium and quinolinium compounds, and the like; those compounds dependent on the cyano radical for the brightening action such as the nitriles, thionitriles and the like; and those compounds dependent on the thiuoreide radical (NC=S) such as the cyclic thioureides and thiourea.

Compounds considered useful as brighteners of the second class include the water-soluble acetylenic compounds set forth in US. Patent (Kardos et al.) 2,712,522; the aryl, alkylene and arylalkynoxy sulfonic acids set forth in US. Patent 2,800,442; the alkynoxy sulfonic and carboxylic acids having the triple bond separated from the acid radical by at least one oxygen atom set forth in US. Patent 2,841,602; and the nitriles set forth in US. Patents 2,524,010; 2,647,866; 2,882,208; 2,978,391 and 3,093,557.

Where cobalt is desired as an alloying constituent in the nickel layers the instant bath may be adjusted by adding any of the cobalt salts well known to those skilled in the art. For example, the halides of cobalt are particularly useful including cobalt chloride, cobalt bromide, and the like. Cobalt sulfate may be used also.

Nickel electroplating baths particularly useful in combination with these brightener systems include the Wattstype and fiuoroborate-type baths having increased nickel content. Such baths are designed for use with organic brighteners in general; they may be operated at the higher current densities desirable for the effective use of the organic brighteners. The preferred Watts-type bath essentially comprises an overall nickel content ranging from 70 to 115 grams per liter provided by 270 grams per liter to about 450 grams -per liter of nickel sulfate and from about 20 grams per liter to about grams per liter of nickel chloride with about 30 to 40 grams per liter of boric acid as the buffer and the preferred fiuoroboratetype bath essentially comprises an over-all nickel content ranging from 75 to grams per liter provided by about 440 grams per liter of nickel fiuoroborate with about 30 grams per liter of boric acid as the buffer.

For purposes of the present invention, boric acid is preferred as the buffer-as an additive to maintain the desired pH. However, acetic acid, borax (sodium tetraborate), formic acid, the fiuoroborates, and other compounds commonly known to have utility as buffers, may be used with the baths of the present invention with no apparent undesirable efiects.

Illustrative examples of Wetting agents which may be employed in the baths for carrying out the present invention include a great majority of the anionic surfactants. The sulfate type particularly may be used. Included among this type are certain of the alkylsulfates, aralkylsulfates, alkylsulfonates, and the aralkylsulfonates. Trisulfonyl methanes such as tri(hexylsulfonyl)methane, tri(heptylsulfonyl) methane and the like may be used effectively also as wetting agents.

The use of a wetting agent in baths used in carrying out the present invention is optional; excellent deposits are obtained from baths having no wetting agent provided they are free of Water-insoluble and hydrophobic matter.

The preparation of the arsenic-nickel plating baths advantageously is carried out merely by adding from about 0.05 gram per liter to about 5.0 gram per liter and'preferably 0.5 gram per liter to about 2 grams per liter of an arsenic-supplying compound to any one of the above enumerated baths used for depositing nickel. The amounts of the particular arsenic-supplying compound necessary to impart a desired amount of arsenic in the nickel deposit vary with each compound; and, of course, with the temperature of the bath and cathode current density. Moreover, many arsenic-containing compounds which can be used to impart arsenic into the nickel deposit are not very soluble in water which therefore restricts or limits 7 the amounts which can be used.

Preferably, the operating temperature of a typical bath (Watts-type) is in the range of from about F. to about F. This range is not critical; however good deposits may be obtained at temperatures as low as 50 F. or lower and at temperatures as high as F. or even at the boiling point of the electrolyte. The arsenic compounds particularly useful are those which are capable of supplying arsenic in a form which permits codeposition of arsenic with the nickel, preferably those compounds capable of supplying arsenite ions or other trivalent arsenic ions.

The operative current density at the cathode is dependent also on the operating current density for the chosen bath composition free from arsenic. Where the Wattstype bath is employed, current densities ranging from about 10 to 50 amperes per square foot are preferred.

When using acid nickel baths the arsenic-containing nickel deposits are plated more advantageously from baths having lower pH values. Broadly the pH should be in the range of from 1.5 to and preferably in the range of from 2 to 4.

For purposes of the present invention, the arsenic com- 3 large amounts of arsenic but manifested proportionately low anodic potentials when compared to nickel deposits using the arsenites and having similar arsenic concentrations.

pounds which may be used most effectively in forming the 5 The reasons for this disparity in the relative potentials arsenic-containing intermediate layers are those comof nickel deposits obtained using arsenates is not clear. pounds capable of supplying arsenite ions to the bath One possible explanation for this difference in electrosuch as arsenious oxide (arsenic trioxide) and arsenious chemical activity between nickel deposits is that the acid, the alkali metal arsenites, nickel arsenite and cobalt arsenic contained in the deposits from baths using the arsenite and the dilute acid-soluble alkaline earth metal arsenate largely is present in an occluded form, possibly arsenites, such as calcium arsenite and strontium arsenite. unchanged arsenate. The nickel deposits manifesting Hydrolyzable compounds of arsenic may also be uwd adhigh anodic potentials (much higher than those obtained vantageously such as, for example, arsenious chloride using arsenates) probably have the arsenic present as (arsenic trichloride). Generally this class of compounds nickel arsenide. When the arsenic is obtained in the plate includes substantially all of the compounds capable of in this form, there is very little advantage in having more hydrolyzing to form arsenious acid. than about 4 percent arsenic in the deposit.

The organic esters of arsenious acid including both the While the arsenates in general are less desirable as a fully substituted and partially substituted esters may be source of arsenic in the bath, good corrosion results have used if they are sufiiciently water soluble or hydrolyze to been obtained from composites made using certain arsearseniou-s acid or other water soluble compounds. These nates or other pentavalent arsenic compounds. Allyl esters generally may be represented by the following arsonic acid particularly gives good results, in many ingeneral formula: stances as good as the results obtained using sodium arsenite as the source of arsenic.

(R nAS {OR1)3n P'henyl arsonic acid and benzylarsonic acid are ad- Wherein is an integer from O to zlnelllsive, R is a Inemvantageously used as the arsenic-supplying compound. Selected from the group hlg of hydroge lkyl, (See US. Patent 2,211,535.) Organic arsenic compounds aryl alkaryl hydroxyarylane-th111w and a member containing a triple bond such as propargyl arsonic acid selected from the group consisting of hydrogen, a monoand .butyne arsenic acid also may be used valeriiimetal. g g aryl hydroxyalkyand Wlth As a further refinement of the present invention a sul'foprovision is or 1 may represent a Walent .meta oxygen compound or brightener of the first class is added atom, an alkanylene, alkenylene, arylene and substituted h t b n t P f divalent organic radicals. In this instance R represents to t e arsenic C on ammg m sma amoun a single divalent radical bridging two oxygen atoms, conably the arsemc 1s pres,ent the: baths arsemte, i nficbsd directly to the arsenic atom. or any other form WhlCh W111 provide ions containing Examples of some Specific compounds represented by trivalent arsenic. The sulfo-oxygen compound surpris- Formula I include the trialkyl esters of arsenious acid ingly acts to Provide a semi-bflght to a y P such as the trimethyl, triethyl, triisopropyl derivatives; Pending 011 the amount of arsenic Present in the deposit the triaryl esters of arsenious a id such as th triphenyl Whereas for similar arsenic concentrations a dark to black esters; the :mixed alkyl and and triesters of arsenious acid deposit is obtained without the sulfo-oxygen carrier. The such as ethylphenylene arsenite; the organic substituted 40 concentrations of the sulfo-oxygen carrier useful in overarsenious acids such as his phenyl) arsenious acid, hycoming the blackening of 'the deposit generally are similar droxyphenylphenyl arsenious acid, ethylphenyl arsenious to the concentrations useful with arsenic-free baths. From acid and the like; and the diesters having a hydrocarbon about 0.5 gram per liter to about 2 gnams per liter of the radical connected directly to the arsenic atom such as for sulfo-oxygen compound cover effective amounts but example dibutoxyphenyl arsine. amounts outside this range are useful also.

Generally these organic derivatives are limitedly soluble It has been found that relatively small amounts of sulfur in Water and offer o advantage over th very wat are imparted into the deposit; an amount which is much soluble arsenious acid and the metal arsenite salts. less than is obtained in the deposit using a fully bright The arsenates may be used also but the composites nickel bath containing a brightener of the second class. made using the arsenates often act erratically when tested The following Table A sets forth specific compositions for corrosion properties; the amounts of arsenic deposited of baths useful for depositing the lower layer in preparing with the nickel from baths containing arsenates do not the triple-layer composite electroplate of the present inafiipear to be correlata'ble with the relative potentials of the vention.

TABLE A Boric Bath Nickel Salts, g./l Addition Agent, g./l. Other Additives, g./l. Wetting Agents, g./1. Big; pH

1a {fiiefikhiiqail Sodium lauryl sulfate, 0.02. 37 3. 5 2a }Ooumarin, 0.2 Formaldehyde (40%), 0.1 c.c./1 do 37 4. 0

NiSO4.6Hz0,3O0 3a {NiClz.6H20, 45 }Nickel Formate, 4.5 Formaldehyde, 0.5 cc./ 30 2. 5 00804-61120, 30 v 4a. {i%?: q 6q: }3 Bromocoumarin, 0.2 30 4. 0 5a {ifilf f fif fi}: }Butynediol, 0.1 Chlora1,0.05 30 4.0 w {asaaaat acumen, {aaaaaiaaainae: podium 35 7a 39 }Ooumarin, 0.2 Chloral, 0.05 do 35 3. 5

deposit. In many instances deposits from baths containing derivatives of arsenic pentoxide contained relatively The following Table B sets forth specific compositions of baths useful for depositing an upper layer or top layer in preparing the triple-layer composite electroplate of the present invention:

10 Three panels per Examples I VIII were submitted to the Corrodkote Test for 80 hours and to the CASS test for 48 hours.

TABLE B Boric Ex. Nickel Salts, g./l. Organic Sulfa-oxygen cpd., g./l. Brighteners, g./l. Wetting Agents, g./l. Acid pH N0. Buffer,

1b lNaphthalenedisulfonic acid, 4. Reduced fuchsin, .007 Sodium lauryl sulfate, 0.03-. 37 3. 5

NiSO- GH2O 3O Saccharin, 1--- Butynediol, 0.2. iNgonenzofaz. Allyl sulfonate, Coumariu, 0.1.. 37 3b.. Dibenzenesulfonimide, 3.-.. Allylpyridinium bromide, 0.05 .do 37 4. 0 4b {i%)16}l[ 6O,3Z:/00. }p,p oziygbgs(dibenzenesullon- B,B thiodipropionitrile, 0.003--. Sodium oetyl sulfate, 0.1 37 4. 0

"" 1 2 ami e NlSO4.6HzO, 150. Saecharin, 2 Nronerno, 150 Allyl sulionate, 1. 37 5 6b j g }Same as 2D e s 211 Same as 37 4.0 7b..... {}%gfgf%gi9 }Benzenesullouamide, 2- -.d0 37 3. 5

The panels of Examples I-VIII remained substantially unattacked, manifesting no rust spots.

By comparison the same bath and conditions were used to plate another series of steel panels using varying amounts of sodium benzenesulfinate in the bath used to deposit the intermediate layer. The thickness of the nickel layers for each panel and the amounts of the sodium benzene sulfinate used in the bath are set forth in the following table.

The following examples set forth the preparation of composite electroplates according to the present invention. Example I Using bath Zn from Table A, a 0.45 mil layer of nickel was deposited on steel panels. The coated panel was rinsed with water and a 0.13 mil layer of nickel was deposited from the following bath at a current density of 40 amps/sq. ft. The bath was kept at a temperature of about 140 F. and a pH of about 4.0. C stitue t A t TABLE III.THICKNESS OF LAYER IN MILS NiSO -6H O, g./l. 300 NiCl '6I-I O, g./l. 45 .?mgunt H3BO4, g./ 41 Example No. Lower Inter- Upper b r z ie NaAgo g /1, 1 ed ate sulfiraate Wetting agent, cc./l. 3 fis i f F f The arsenic in the plate had about 2.0 percent by weight based on the total weight of the second or intermediate .45 07 .37 4 layer. 1%?) 8? i The panel was rinsed again and a 0.55 mil top or upper .50 10 .57 4 layer of bright nickel was deposited from bath 4b of 1%? :93 :23 :2 Table B. .45 07 .46 .5

After rinsing again, a 10-12 millionths of an inch coat :2; fig 12. 3 of chromium was plated on the surface of the upper layer. .ig 1 8 .32 Examples Il-VIII I 12 14s is Using the same baths and conditions as were used in Example I, a series of steel panels was coated with three The following Table IV sets forth corrosion tests relayers of nickel and a layer of chromium. The thicksults of the panels of Table III.

1168868 Of each layer are set forth in the following Table TABLE IV NO RUST SPOTS OBSERVED AFTER COR I. The amount of arsensic in the intermediate layer of DK T YCLE each was about 2.0 percent by weight based on the weight of the intermediate layer. Example N o. 1 2 3 4 0.45s 2 TABLE I.THICKNESS OF LAYER IN MILS 13 31 51 62 02 Example No. Lower Intermediate Upper 0 2 2 5 18 0 7 21 09 0 2 6 14 20 0.47 0.13 0.53 0 0 1 22 45 0.45 0.15 0.45 0 3 1s 34 58 0.45 0.12 0.46 1 12 45 53 83 0.45 0 .12 0 .46 0 1 21 40 58 0.50 0.10 0.52 2 3 20 a9 72 8 43 3g 66 27 4 54 The same bath and conditlons were used to plate an- 3 21 34 36 51 other series of steel panels except 1.27 grams per liter of allyl arsonic acid was substituted for the sodium arsenite in the bath used for plating the intermediate layer.

The thicknesses of each layer are set forth in the following Table II. The amount of arsenic in the intermediate layer of each sample was about 2 percent by weight based on the total weight of the intermediate layer.

TABLE II.THICKNESS OF LAYER IN MILS 70 Each cycle equals 20 hours exposure. 48 hours.

Duplex (double layer) nickel panels, plated frornthe same baths as cited above for the bottom and top layers, under the same conditions, were Corrodkote-CASS tested and showed 38 to 100+ rust spots.

Example XXI Lowe Inwmediate Using the bath of Example I with one gram per liter of saccharine added thereto, panels are coated accord- Example No. Upper VII..

81%; gig ing to the procedure outlined in Example I. The sodium arsenite (NaAsO concentrations are adjusted in the bath from 0.5 gram per liter to 3.0 grams per liter using increments of 0.5 gram per liter. The nickel deposited from the baths containing the different concentrations of sodium arsenite range from being semi-bright to a metallic gray color. The corrosion resistance of each of the composites is comparable to those obtained according to Examples I through VIII. The semi-bright and metallic gray deposits are in definite contrast with the black deposits obtained from baths not using saccharine where the amount of sodium arsenite in the bath exceeds 2.5 grams per liter.

The present invention in its broadest form includes composites or laminates of nickel layers having more than three layers of nickel and composites or laminates wherein the arsenic-containing nickel layer is sandwiched between layers of nickel which may have relative potentials equal substantially to each other or be slightly more cathodic than the intermediate layer.

Where the composite has more than three layers of nickel, the arsenic-containing nickel layer is always bonded to layers of nickel on both sides. Moreover, at least one of the nickel layers should be cathodic to the arsenic-containing layer and be substantially free from arsenic, phosphorus, sulphur and substantially all other nickel alloying constituents.

Examples of systems for the composites of the present invention include composites having, in addition to those already described, (1) a sulfur-free lower layer and a sulfur-free upper layer, (2) a bright lower layer and a bright upper layer and (3) a sulfur-containing lower layer and a sulfur-containing upper layer. Thus it is easily understood that composites may be made according to the present invention where the lower layer contains from to about 0.15 percent sulfur and'the upper layer contains from 0 to about 0.4 percent sulfur. Higher amounts of sulfur can be obtained in the nickel deposits but there is no advantage in using the higher amounts (1.0 percent) of sulfur.

While specific examples of the invention have been set forth hereinabove, it is not intended that the invention be limited solely thereto, but to include all of the variations and modifications falling within the scope of the appended claims.

What is claimed is:

1. As an article of manufacture a laminate comprising three firmly bonded layers of nickel including an intermediate layer of a nickel-arsenic alloy sandwiched between and in adherent contact with an arsenic-free lower lower layer of nickel and an arsenic-free upper layer of nickel, said nickel-arsenic alloy consisting essentially of nickel and about 0.025 percent to about 8.0 percent arsenic.

2. As an article of manufacture a laminate comprising three firmly bonded layers of nickel including an intermediate layer of a nickel-arsenic alloy sandwiched between and in adherent contact with a relatively noble lower nickel-containing layer and a top layer of bright nickel anodic to said lower layer, said alloy consisting essentially of nickel and from about .025 percent to about 8 percent by weight arsenic and being anodic to said lower layer and said top layer.

3. As an article of manufacture a composite coating bonded to a metal substrate susceptible to atmospheric corrosion comprising as its essential layers three adjacently bonded layers of electrodeposits, the lower layer of which consists essentially of a nickel electrodeposit having from 0 to about 25 percent cobalt by weight therewith and an average sulfur content of less than 0.15 percent by weight based on the weight of said electrodeposit, a top layer of which consists essentially of a bright nickel electrodeposit having from 0 to about 50 percent cobalt alloyed therewith and from about 0.03 percent to about 0.4 percent sulfur by weight and the intermediate layer of which consists essentially of a nickel alloy electrodeposit having from 0 to 25 percent cobalt alloyed therewith and also 12 having alloyed therewith from about 0.25 percent to about 4 percent arsenic based on the total weight of said electrodeposit.

4. The article of claim 3 wherein, said lower layer has a thickness of from about 0.3 mil to about 2 mils, said top layer has a thickness from about 0.15 mil to about 1 mil and said intermediate layer has a thickness ranging from about 0.01 mil to about 0.2 mil.

5. As an article of manufacture a composite coating bonded to a metal substrate comprising as its essential layers three adjacently bonded layers of nickel, the lower layer of which consists essentially of nickel deposits having a sulfur content of less than about 0.15 percent selected from the group consisting of nickel and a nickelcobalt alloy containing less than about 25 percent cobalt based on the weight of said lower layer, the upper layer of which consists essentially of nickel deposits having a sulfur content of from about 0.03 percent to about 0.4 percent, selected from the group consisting of nickel and a nickel-cobalt alloy containing less than about 50 percent cobalt based on the weight of said upper layer and the intermediate layer of which consists essentially of a deposit selected from the group consisting of a nickelarsenic alloy consisting essentially of from about 0.25 percent to about 4 percent arsenic and a nickel-cobalt arsenic alloy consisting essentially of from about 0.25 percent to about 4 percent arsenic containing less than 25 percent cobalt, the remainder being nickel.

6. As an article of manufacture a composite coating bonded to a metal substrate selected from the group consisting of iron, steel, copper, zinc, aluminum, magnesium and alloys thereof comprising as its essential layers three adjacently bonded layers of electrodeposits, the lower layer of which consists essentially of nickel electrodeposits having from 0 to about 25 percent cobalt by weight alloyed therewith and an average sulfur content of less than about 0.15 percent by weight based on the weight of said electrodeposit, a top layer of which consists essentially of a bright nickel electrodeposit having from 0 to about 50 percent cobalt alloyed therewith and from about 0.03 percent to about 0.4 percent sulfur by weight and a nickel alloy intermediate layer consisting essentially of from 0 to 25 percent cobalt and from about 0.25 percent to about 4 percent arsenic based on the total weight of said intermediate layer.

7. The article of claim 3 wherein said top layer of nickel is electroplated with a chromium deposit having a thickness ranging from about 0.005 to about 0.2 mil.

8. In a method of electroplating from aqueous solutions a corrosion-protective composite nickel coating comprising as its essential layers three adjacently bonded layers of electrodeposits on a metal surface susceptible to atmospheric corrosion wherein a lower layer is cathodic to an intermediate layer and an upper layer and said intermediate layer is anodic to said lower layer and said upper layer, the improvement consisting essentially of electrodepositing said intermediate layer from an aqueous solution of nickel salts and compounds capable of permitting codeposition of arsenic with the nickel to form a layer of nickel having a thickness of from about 0.01 to 0.2 mil and an arsenic content of from about .025 percent to about 8 percent by weight of the intermediate layer.

9. The method of claim 8 wherein said lower layer is deposited from an aqueous solution comprising nickel salts and at least one sulfur compound to provide a layer consisting essentially of nickel electroplate having from 0 to about 25 percent cobalt by weight alloyed therewith and an average sulfur content up to about 0.15 percent by weight, and wherein said top layer is deposited from an aqueous solution comprising nickel salts and sulfur comprises a bright nickel electroplate having from about 0.03 percent to about 0.4 percent sulfur by weight and the intermediate layer of which consists essentially of a deposit of nickel containing from about 0.25 percent to about 4.0 percent arsenic based on the total weight of said intermediate layer.

10. The method of claim 8 wherein said lower layer is deposited from a sulfur-free aqueous acid solution comprising nickel salts and at least one sulfur-free compound capable of leveling action and wherein said top layer comprises a bright nickel plate having from about 0.03 percent to about 0.4 percent sulfur by weight and said intermediate layer consists essentially of a deposit of nickel containing from about 0.25 percent to about 4.0 percent arsenic based on the total weight of said intermediate layer.

11. The method of claim 10 wherein said compound capable of leveling action is coumarin.

12. The method of claim 8 wherein said intermediate nickel layer is plated from an aqueous ac'dic bath containing from about 0.5 gram per liter to about grams per liter of a compound capable of supplying triple valent arsenic ions.

13. The method of claim 8 wherein said intermediate nickel layer is plated from an aqueous acidic bath containing from about 0.5 gram per liter to about 5 grams per liter of a compound capable of supplying pentavalent arsenic ions.

14. The method of claim 12 wherein said intermediate layer is plated from an aqueous nickel plating 'bath containing from about 1.0 gram per liter to about 8 grams per liter of a compound capable of supplying arsenic to said bath in a form which permits codeposition of said arsenic with said nickel.

15. A method of electroplating from an aqueous solution a corrosion protective composite coating on a metal surface susceptible to atmospheric corrosion which comprises the'steps of (1) electroplating on said surface in at least one electroplating step an adherent layer consisting essentially of nickel having a thickness of about 0.3 mil to about 2.0 mils and a sulfur content of less than about 0.15 percent, to form an adherent lower layer, (2) electroplating directly on said lower layer in at least one plating step an adherent intermediate layer consisting essentially of a plate selected from the group consisting of nickel plate and nickel-cobalt alloy plate containing at least about 75 percent nickel, said intermediate layer having a thickness of about 0.01 mil to about 0.2 mil and an arsenic content of about 0.25 percent to about 4 percent, (3) electroplating directly on said intermediate nickel layer an adherent upper layer in at least one electroplating step consisting essentially of an electroplate selected from the group consisting of nickel electroplate and nickel-cobalt alloy electroplate containing at least about 50 percent nickel, said upper layer having a thickness of about 0.15 to about 1 mil and an average sulfur content of 0.03 to 0.3 percent, said upper nickel layer containing a higher percentage of sulfur than said lower layer.

16. The method of claim 15' wherein said intermediate layer is plated from an aqueous acidic nickel bath containing from about 0.5 gram per liter to about 15 grams per liter of a water-soluble compound capable of supplying arsenic in a form which permits codeposition of said arsenic with said nickel.

17. In a method of electroplating from aqueous solutions a corrosion-protective composite coating comprising as its essential layers three adjacently bonded layers of nickel electrodeposits on a metal substrate susceptible to atmospheric corrosion wherein a lower layer is cathodic to an intermediate layer and an upper layer and said intermediate layer is anodic to said lower layer and said upper layer, the improvement comprising electrodepositing said intermediate layer of nickel from an aqueous acid solution of nickel salts, sulfo-oxygen compound and at least one compound capable of supplying arsenic in a form which permits codeposition of arsenic with the nickel to form a layer of nickel having a thickness of from about 0.01 mil to about 0.2 mil and an arsenic content of from about 0.025 percent to about 8 percent based on the weight of said intermediate layer.

18. The method of claim 17 wherein said lower layer is deposited from a sulfur-free aqueous acid solution comprising nickel salts and at least one sulfur-free compound capable of leveling action and wherein said top layer comprises a bright nickel plate having from about 0.03 percent to about 0.4 percent sulfur by weight and said intermediate layer comprises a deposit of nickel containing from about 0.25 percent to about 4.0 percent arsenic based on the total Weight of said intermediate layer.

19. The method of claim 17 wherein said intermediate nickel layer is plated from an aqueous acidic bath containing from about 0.5 gram per liter to about 5 grams per liter of a compound capable of supplying arsenite ions to a bath and a sulfo-oxygen carrier.

20. The method of claim 19 wherein said compound is sodium arsenite and said sulfo-oxygen carrier is saccharine.

References Cited by the Examiner UNITED STATES PATENTS 3,090,733 5/1963 Brown 29-19616 HYLAND BIZOT, Primary Examiner.

Claims

1. AS AN ARTICLE OF MANUFACTURE A LAMINATE COMPRISING THREE FIRMLY BONDED LAYERS OF NICKEL INCLUDING AN INTERMEDIATE LAYER OF A NICKEL-ARSENIC ALLOY SANDWICHED BETWEEN AND IN ADHERENT CONTACT WITH AN ARSENIC-FREE LOWER LAYER OF NICKEL AND AN ARSENIC-FREE UPPER LAYER OF NICKEL, SAID NICKEL-ARSENIC ALLOY CONSISTING ESSENTIALLY OF NICKEL AND ABOUT 0.025 PERCENT TO ABOUT 8.0 PERCENT ARSENIC.