US3135671A - Electrolytic treatment of articles - Google Patents

Description

United States Patent ELECTROLYTIC TREATMENT 9F ARTHILES .lohn C. Grade, Warren, Ohio, and Arthur Kenneth Graham, fienhintown, Pa., assignors to Rockwell- Standard Corporation, (Zoraopolis, Pa, 21 corporation of Pennsylvania No Drawing. Filed Dec. 1, 1%(2, Ser. No. 2,889

6 (Ziaims. (Cl. 294-34) The present invention relates to electrolytic treatment of metallic articles, such as anodic or cathodic treatments in aqueous electrolytes of acids, alkalies, or plating bath compositions. More particularly the present invention relates to a method of preventing the development of magnetism in articles of magnetizable metal so as to obtain electrodeposits of superior smoothness and protective value by electrically demagnetizing the articles at predetermined stages in the electrolytic treatments.

During the electrolytic treatment of articles of magnetizable metal in their preparation for electroplating and in the electrodeposition of metals, a major problem in obtaining satisfactory quality is that of overcoming roughness. From a visual standpoint, this is more serious in bright plating, so prevalent today, than when many electrodeposits were heavily buffed, as in the early s. From the standpoint of corrosion resistance, roughness is always bad. If the plate is bufied to eliminate roughness, particles are torn out of the coating, thus greatly reducing resistance to corrosion and often creating a pitted appearance. Roughness, like pitting, may also be so fine and widely distributed as to be confused with lack of brightness.

Roughness, when plating articles of magnetizable metal such as steel, is commonly caused by chips, slivers and other forms of metal debris which adhere to or are otherwise held to the surface of an article being electrolytically treated. Chips and sliver-like metal particles are probably the most common type particles formed during machining and polishing operations. For a more detailed explanation and description of such small metallic particles produced during these operations reference is hereby made to W. L. Pinner, Proc. Amer. Electroplaters Soc. 40, 83-89 (1953). Furthermore, such articles may also be magnetized in machining or polishing, as well asunder the influence of direct current fields present'in the electrolytic treatments of the plating cycle. Even though adhering metal slivers may be removed in these treatments, such magnetized articles will attract metal particles present in the solutions, including the plating bath itself, and roughness will result. (See also R. B. Saltonstall, Electroplating Engineering Handbook, Reinhold Publishing Corp, New York ,pp. 231-232, 1955.)

With certain configurations of articles of magnetizable metallic materials to be coated by an electroplating process, as for example steel automobile bumpers, an elecrolytic treatment such as electrocleaning, anodic acid etching and electroplating, create a magnetic field and induce magnetism into the articles. The magnetism thus induced into the articles is of suficient strength to attract small magnetizable metallic steel or nickel particles which may be suspended within the treatment baths, so that they adhere to the surface of the articles. The induced magnetism may also cause attached slivers of metal resulting from polishing the article to stand up on end from the surface of the metallic article.

As a consequence, when the articles are carried into the plating bath metal deposits over these metallic particles result in rough coatings of inferior quality. Where the slivers stand out from the article surface this is even more pronounced.

A further problem resulting from the magnetism of "ice electroplated articles made of magnetizable metallic materials arises in measuring the plating thickness. It is the general practice to measure the plating thickness as a production control by means of some conventional form or magnetic thickness tester, as for example a Magne-Gage. It has been found that the residual magnetism in the electroplated article of magnetizable metal produces readings in the instrument Which may vary from the true value for the thickness being measured to both high and low values, depending on the degree of induced magnetism in the plated articles and the relative location of the point of measurement with respect to the magnetic poles. This is explained in more detail in G. S. Bowman, Monthly Review, Am. Electroplaters Soc. 33, 10445, 1902 (1946); and A. K. Graham and H. L. Pinkerton, Proc. Am. Society for Testing Materials, vol. 59 (1959).

The present invention has among others, the advantage of overcoming ditliculties arising from magnetism induced in articles to be electroplated. Briefly, this is accomplished by changing the magnitude and type of current which is normally used in the various electrolytic treatments, over a predetermined period of time at the end of the electrolytic cycle steps, to a current characterized by periodic reversals of the current flowing combined with a simultaneous diminution of the magnitude of the current during said period to substantially zero.

Accordingly, it is a primary object of the present invention to provide a novel process of preventing magnetism from being induced in articles made of magnetizable metal as a result of electrolytic treatment prior to electroplating.

It is a further object of this invention to substantially completely remove any magnetism in an article to be electroplated.

It is yet another object of this invention to improve the quality of electroplated articles of steel or any other magnetizable material produced by an electroplating process by eliminating roughness of electroplated articles caused by magnetic attraction of the articles to small metal particles during electrolytic treatments prior to plating.

It is also an object of this invention to provide a novel process for improving the quality of electroplated articles of steel or magnetizable material by eliminating roughness on the surfaces of the articles caused by attached metal particles in general and more especially metallic slivers resulting from polishing by eliminating the tendency for these slivers to stand up on the surface of said articles under magnetic forces.

It is still another object of this invention to provide a novel process to remove the magnetism induced into articles of magnetizable metal during electroplating thus permitting accurate measurements which may subsequently be made with a magnetic type of thickness tester as a convenient, non-destructive, routine production control with acceptable accuracy.

It is still another object of the present invention to provide a novel electrolytic process to substantially completely remove any magnetism which may have been induced in metallic articles by treatments such as machining or polishing prior to plating. 1

Further objects and advantages of the present invention will become apparent to those skilled in the art from the appended claims and following description.

The method of electrolytic treatment of magnetized articles, according to the present invention, will be described particularly as applicable in the production of steel automobile bumpers, but automobile steel hardware and grilles, household appliances, and other plated metallic articles may be successfully processed in the same manner.

In general, automobile bumpers are made by first .stamping out a form from a flat sheet of steel which has ducea smooth finish. After forming the blank it is transferred to other presses and shaped to a particular design of bumper.

The shaped bars are then racked on plating racks to be run through the plating cycle. The'platin'g cycle usually consists of an alkali electrocleaner, an anodic acid dip followed by another alkali electrocleaner and acid dip prior to electroplatingwith suitable rinses in between each treatment step. 'After nickel plating the bars are 'usually inspected and bufied and again cleaned and chrostitute soils which must be removed first. This is acmium plated. The bufling after nickel plating is usually mild, commonly referred to as a wiping buff, when applied to proprietary bright plated coatings. Buffing is usually done to correct for any irregularities in surface appearance as well as roughness.

The apparatus for accomplishing the electrolytic treatments normally given to an automobile bumper is similar to that which might be applied in cycles for other articles made of magnetizable metal. Each of the treatments involving the use of electric current will inducemagnetism into the parts being treated. The apparatus in any case will consist of a tank made of suitable material which holds the waterisolution of the alkali chemicals, acidsor plating compositions, commonly known as the electrolyte, used in the treatment. The articles ofirnagnetizable material arepositioned on a rack or carrier and placed in a particular treatment bath, so that it Will make electrical contact with a source of current as either ananode or a cathode as many he required; The other'el ectrode in each' case will be either a cathode or an anode and will be connected to the other pole of the current generating equipment. A source "of direct current, or direct cur rent source which can be periodically reversed according to some predetermined cycle, is connected to the electrodes and articles in the treatment tank-through conventional buses attached to the anode and cathode rods.

The source of current may be a direct current-source, such as a battery, generator or rectifier, combined with suitable relays, reversing switches, rheostats and timing L mechanisms for controlling the magnitude of the current and for reversing the current at predetermined times and to cause the current to decay from maximum value to substantially zero over-selected and predetermined periods in accordance with the requirements of this inven- Such apparatus is conventional and is disclosed tion. in United States Letters Patent to Grainger, No. 2,494,121, issued Jan. 10, 1950; the United States Letters Patent to iernstedt, No. 2,451,341, issued Oct. 12, 1948, or Electroplating Engineering Handbook, Reinhold Publishing Corporation, New York; 1955.

It will be appreciated that any suitable apparatus may be devised to produce the desired electrolytic current cycle and that the cycle may be produced by simply reversing the flow of current from separate direct current sources which may be alternated in accordance with the requirements of the present invention.

In accordance with the present invention, the method for producing finished nickel-chrome electroplated products having basis metals of'magnetizable materials first involves manufacturing steps such as machining and/or forming, followed by polishing, and sometimes buffing, in order to produce the final article in the desired configuration :and with the specified surface finish. Bumpers are ordinarily not bufied prior to plating, so that following the conventional operations, the polished bumper of desired configuration is spray washed in some instances and is then ready for processing through the plating cycle. A group of bumpers are usually mounted on a rack for simultaneous immersion and treatment in the various treatment steps of the replating and plating cycle.

It is the usual practice to prepare the surface of the articles for plating by a series of electrolytic cleaning, pickling and polishing treatments in order to remove organic soil, oxides, and polishing and buflin-g residues from the sur complished by treating the articles in an alkaline electrocleaner, either anodically or cathodically. The cleaner may consist of an aqueous solution'of 8 to 12 oz. gal of a'proprietary formulation or an equivalent composition compounded from 'a group of alkali chemicals consisting of hydroxides, carbonates, phosphates and silicates of sodium 'or potassium. The article is then rinsed to remove alkali prior to the next step.

In the case of steel articles, the next step is usually an anodic acid treatment in a Water solution of sulfuric acid or a mixture of acids.

This treatment serves to remove a certain amount of loose metal from the surface and to etch the metal in such a Way as to improve the adhesion of the subsequent electrodeposit. A very thorough rinsing must follow this treatment to remove the concentrated acid from the surface of the article being processed. n

It is not uncommon to again immerse thearticle in a second alkaline electrocleaning step similar to the one previously described, the purpose of which is to insure more complete removal of any residual organic soil. A

rinse following this treatment is used to remove traces of alkali. v

In the next step the article is usually dipped in a pickling solution, such as 10% by volume hydrochloric acid, to neutralize any alkali and to reactivate the surface after which it is rinsed in water to remove traces of the acid. 7

The current used in the alkaline electrocleaning steps may be a simple direct current or a cyclic current which i ficiently strong to attract small metallic particles of magnetizQable material which are produced by prior manufacturing treatments and which have become dispersed in the electrolytic treatment bath.

It has been found that merely periodically reversing the flow of the current does not remove magnetism or prevent magnetism from being induced into articles of magnetizable material. For instance, an ordinary alkali electrocleaning treatment using periodic current Willmagnetiz'e a rack of automobile bumpers to substantially the same extent as one using simple direct cleaning and the same total current flow. This has been found to be true Whether the periodic reverse current cycle is made up of equal or unequal portions of positive and negative current. As a consequence, magnetism Will be induced into the articles being treated whether a simple direct current is utilized or Whether a current characterized by periodic reversals is employed. The polarity of magnetisminduced in a bumper or a rack of bumpers being treated is determined by the direction of the current after the last reversal in the electrolytic treatment step.

While it is less likely that small steel particles will exist The intensity of the magnetic field produced by the magnetized bumpers may be suftric current at the end of the electrocleaning treatment, and by simuitmeously diminishing the magnitude of the current from its maximum processing value to substantially zero over the last ten to twenty second interval of the periodic reversals. The periodic reversal cycle for this purpose may be made up of equal or unequal portions of anodic and cathodic current flow as will become apparent by reference to the examples hereinafter appearing. The preferred cycle has proportions of three second anodic and three second cathodic. As will become apparent from the subsequent examples, a cycle having the proportions of twelve seconds anodic and three seconds cathodic is also effective to demagnetize the article when the current reversals are made concomitantly with the diminution of the current over the last l20 seconds of the operation. When a simple non-reversing direct current is being used during the electrolytic treatment, it is sufficient to begin the mriodic reversals of current flow simultaneously with the diminution of the current.

As a consequence, the magnetism induced into the bumpers and other articles of magnetizable materials as a result of the electrolytic treatments and the prior manufacturing operations is substantially removed and the steel particles clinging thereto become detached for dispersement into the treatment bath.

Following the various electrolytic pickling and cleaning treatments, the bumpers are then prepared for the final operation of plating with a metal, such as nickel. Ordinarily electroplating utilizes low voltage direct current and moderate current densities, but for very rapid plating the current density may be further increased. When high current densities are used, more rapid deposition occurs but inferior deposits may result in that metal deposited at very high current density usually becomes pulverulent, rough and burnt after a short interval. It has been found that high current densities can be used for a limited period of time as disclosed in the above-identified Grainger patent, and it is advantageous to follow such operations by a reverse in the direction of flow of the plating current in such a manner as to remove a portion of the plated coating, that is, that portion which tends to be burnt or unsatisactory. By alternate plating and deplating operations, that is, by a series of operations alternately applying and removing metal, high amperage can be successfully employed and satisfactory results obtained. The time interval of such operations for removing the undesirable metal is predetermined to obtain desired results.

During the electroplating operation it has been found that numerous small particles from the anode become suspended in the electroplating bath. If these particles are magnetic material, as is the case with nickel, they are magnetically attracted to the steel bumpers which again become magnetized whether a simple direct plating current is used or whether a current characterized by periodic reversals is employed. As soon as the particles adhere to the cathode surface, such as a bumper, they too become cathodic and the metal being plated deposits on and around the particle so that it ultimately becomes secured to and a part of the plated coating and causes roughness. Any solid particles suspended in the bath during plating, whether of magnetic material or not, may also settle upon the object being plated, particularly the upper horizontal or socalled shelf surfaces, and become secured to the plated coating in much the same manner and cause roughness. The conventional means of eliminating roughness under these conditions is by using anode bags or diaphragms to prevent anode particles from reaching the cathode, and by providing a sufliciently high rate of solution circulation through a filter to keep the solution substantially free from suspended particles. Shop dirt or air-carried solids in the plating room also are a source of suspended solids in the plating solutions and roughness resulting from these sources is controlled by good housekeeping and somet mes air conditioning the plating area.

Because particles in the plating bath causing roughness during electroposition of a metal become more or less so cured to the surface of the cathode, demagnetizing article: of magnetizable metal during the final states of the electro plating operation will not necessarily completely eliminate roughness. However, articles of magnetizable metals such as steel bumpers, may be effectively demagnetizec' by this means and from that point any attraction of particles and roughness resulting therefrom is substantially completely avoided.

This is accomplished in accord with the present invention by reversing the electroplating current at a fast cycle of approximately /6 cycle per second (i.e., 3 seconds anodic and 3 seconds cathodic) during the last thirty seconds of the plating operation and simultaneously steadily diminishing the current over this last thirty second interval from full value to substantially zero.

It will be appreciated that by demagnetizing the bumpers, a magnet type of thickness tester can be used to accurately measure the thickness of the deposited coating. thus providing for a convenient, non-destructive and much favored production control.

in order to demonstratevthe demagnetizing effect oi periodically reversing the electric current simultaneously with diminishing the current at the end of the electrolytic and the electroplating operations, the following examples provide a comparative analysis of passing various forms of current through an article of magnetizable material. For each of the examples, specially formed miniature automobile bumpers were utilized in which the bumper size was scaled down for the purpose of .convenience to approximately of the actual production size. Eight bumpers of scaled-down size were used in each example and were mounted back in a rack in two vertical rows of four each. The rack of bumpers, simulating in every re spect racking in production, was immersed in a suitable alkaline electrolytic treatment bath and the current passed through the bumpers was limited for convenience to of the normal magnitude generally used during production.

As a consequence the magnetic fields produced were only approximately /3 of that intensity normally experienced during production. The direction and intensity of the induced magnetism was measured by means of a sensitive compass by placing each of the bumpers along the east-west line passing through the north (i.e., south) pole of the compass needle. The magnetism was measured at each end of each bumper in the rack at two different vertical distances above the ends of the bumpers which are hereinafter referred to as the near and far positions. The square'of the ratio of the two vertical distances corresponding to the near and far positions was maintained for each bumper end at 13 and the deflection of the compass needle was observed in degrees. If the north pointing compass needle was attracted, the end of the bumper was called north and if the compass needle was repellent, the end of the bumper was called south. These compass measurements were made before and after electrolysis in an alkaline electrolyte. The bumpers were to all practical purposes demagnetized before electrolytic treatments, at least to the extent that any deflection on the compass needles was less than 10 degress in the near composition and Zero in the far composition.

EXAMPLE 1 Mild steel model bumpers arranged as described on the model rack were electrolyzed anodically for 3 minutes in an alkaline solution at amperes total current without reversing the current. Compass deflections measured at both the near and the far positions for each end of the bumper were taken before the current was passed through the bumpers and after the current was passed through the bumpers. These compass deflections before and after application of current are tabulated in degrees in Table 1 in the horizontal columns identified as be- 7 r fore and after. The ends of each bumper are identified in Table 1 as end A and end B.

In order to characterize the results of the experiment, the algebraic difference of the compass deflections before and after application of current is tabulated in Table 1 in' degrees for each position of the compass. For example, at the near position, end A of bumper No. 1 was observed to have a compassdeflection of 8 degrees north before application of current and a compass deflection of 33 degrees south after application of'current in accordance with the current flow provided in Example 1. The algebraic difierence, which is tabulated in the horizontal column identified as difierence, is indicated to be 41 degrees,

In the last horizontal column in Table l, the summation of these differences. are tabulated separately for the near and far? compass positions and are referred to as the characteristics of the experiment. Thus, in the near position, the sum of the dilferences in compass deflections for each of the ends of the numbers are:

degrees. Simila ly, the sum of the differences of the compass deflections in the far position is tabulated as 31 degrees for Example 1. Thus, the magnitudes of 341 degrees and 31 degrees characterize the increase in the degree of 'magnetism induced into the rackof model bumpers when a total current of 100 amperes is. passed through the bumpers for a period of 3 minutes.

Table 1 Compass Deflections Bumper No. Near Position Far Position End A End B End A End B 1 (Top bumper on N8 S3 0 rack). S33 N 40 S N7 41 43 5 7 2 N 3 0 0 0 S12 N23v 0 N2 15 23 O 2 3 N8 0 0 0 55 N 0 0 13 10 0 0 4 (Bottom bumper)- S2 N8 0 0 i S2 N8 0 0 a Difference." 0 0 0 0 5 (Top bumper) Before S2 N10 0 0 After N45 S60 N7 1 86' 47 70 7 6 'N 2 S1 0 0 N35 S17 N3 81 Difiereuce... 33 16 3 1 7 Before S4 N7 0 0 After N4 S5 0 0 Difference." 7 l2 0 0 8 (Bottom bumper). Before S3 N8 0 0 After a. 0 0 0 0 Difference..- 3 -8 O 0 Characteristic (Sum of all differences). 341 31 EXAMPLE 2 A rack of model bumpers was electrolyzed according to Example 1, except that the direction of the current was reversed every 3 seconds. The characteristics (i.e., the sum of all the differences of compass deflections before and after application of current) of this run was 389 degrees in the near position and 60 degrees in the far position.

EXAMPLE '3 run were 12 degrees and 0 degree in the ?near and far positions, respectively.

8 EXAMPLE 4 The experiment of Example 3 was repeated, except that the time during which the current was diminishedwas reduced to 12 seconds. The characteristics of this run were 14 degrees and 0 degree, in the near and far positions, respectively.

EXAMPLE 5' A rack of model bumpers was electrolyzed according to Example 2, except that the periodic. reversal cycle of the current was changed to 12 seconds anodic and 3 seconds cathodic. The characteristics 'of this run were .379 degrees and 37 degrees, in the near and far positions respectively.

' EXAMPLE 6 will induce substantial magnetism in the article beingelectrolyzed. From Example 2, it will be appreciated that merely reversing the direction of the current every 3 fseconds, Withoutcausing the current to decay to zero value in the final period of the operation, will not cause the article to become demagnetized and will not prevent 'magnetism from being induced into the article.

From Example 3, it is apparent that when'the electrolyzing current is gradually diminished to zero over the last thirty seconds simultaneously with the periodic reversal of the current flow in accordance with the present invention, the degree of magnetism remaining in the articles is substantially negligible, particularly in comparison with the magnetism induced and remaining under the conditions given in Examples 1 and 2.

Examples 4 and 6 indicate that the period over which the current is'diminished may vary from 12 seconds to 30 seconds for the purpose of demagnetizing the article.

It has been found that diminution of the current over the last lO-20 seconds ofanelectrolytic alkali or acid treatment is satisfactory to demagnetize the article when the flow of current is simultaneously reversed. The preferred period'of current diminution following an electroplating step, however, is 30 seconds in order to demagnetize the article.

Example 5 exemplifies the fact that the degree of magnetism induced into the article is not diminished by only applying a periodic reversal cycle made up of unequal portions of anodic and cathodic current.

. From Example 6 it is apparent that the current may be reversed at other than a rate of cycle per second (i.e., 3 seconds anodic and 3 seconds cathodic) in order to' demagnetize the article and to produce a product from each electrolytic treatment step that is free of appreciable magnetism induced during that or prior operations.

I Alternating current of the common 60 cycle frequency has been found not to induce magnetismwhen thearticle is subjected to conditions similar to those associated with using a direct or periodicallyreversing current. On the other hand, such an alternating current does not demagnetize the article so that any magnetism induced by prior treatments or manufacturing operations will remain.

Since the ditference between periodically reversing the flow of a direct current as compared with 60 cycle alternating current is primarily a matter of frequency, there is, consequently, some periodic reversal cycle which, like 60 cycle is not eifective for demagnetizing the article.

As a practical matter, however, cycles'faster than 3 secondscathodic and 3 seconds anodic (i.e., cycle per second) are not readily obtainable since the only practical method for reversing the large currents employed in electrolytic treatments is to reverse the exciting field current of a D.-C. generator. The time required to overcome the hysteresis effect in the generator field coil and to thereby accomplish a current reversal is dependent upon the characteristics of the generator and varies on the order of two to four seconds. As a consequence, the fastest current reversal obtainable with a conventional D.-C. generator is about 3 seconds minus and 3 seconds plus or cycle per second.

The electrolytic treatment of articles of magnetizable metal according to the present invention and the plated articles produced thereby are particularly applicable to automobile bumpers, hardware, household appliances and the like which are subject to induction of magnetism as a result of the electrolytic treatment or prior manufacturing operations.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come Within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In a process of plating a magnetizable article with an electroplating cycle including at least one treatment in which magnetism is induced into the article by the flow of electrical current therethrough and wherein the magnetism induced in said article is destroyed to prevent the adherance of magnetically attractable particles to the article and improve the quality of the plating produced thereon, the steps of:

(a) immersing said article in an electrolyte;

(b) passing a direct current through the immersed article to efiect said treatment;

(c) then passing an electrical current through the immersed article at the end of the treatment, periodically reversing the direction of flow of the current, and gradually reducing the magnitude of the current from full value to substantially zero to thereby demagnetize said article.

2. The process as defined in claim 1, wherein the electroplating cycle includes at least one magnetism inducing electrolytic treatment prior to plating and the periodically reversed, gradually diminished demagnetizing current is passed through the immersed article at the end of the electrolytic treatment.

3. The process as defined in claim 1, wherein the electroplating cycle includes at least one electrodeposition treatment and the periodically reversed, gradually diminished demagnetizing current is passed through the immersed article during the terminal portion of the electrodeposition treatment.

4. The process as defined in claim 1, wherein the direction of flow of the demagnetizing current is reversed approximately every three seconds.

5. The process as defined in claim 1, wherein the electroplating cycle includes at least one electrolytic treatment prior to plating and at least one electrodeposition type plating treatment and a periodically reversed, gradually diminished demagnetizing current is passed through the immersed article at the end of each of said treatments.

6. The process defined in claim 1 wherein the current is periodically reversed and the magnitude of said current is diminished over the last 10 to 30 seconds of the treatment.

References Cited in the file of this patent UNITED STATES PATENTS 2,118,174 Doane May 24, 1938 2,451,341 Jernstedt Oct. 12, 1948 2,494,121 Grainger Jan. 20, 1950 2,807,363 Hendrickson et a1 Sept. 24, 1957 2,915,444 Meyer Dec. 1, 1959 2,939,826 Gulick June 7, 1960 OTHER REFERENCES Metal Industry, November 1925, volume 23, No. 11, pages 451, 452.

Claims (1)

1. IN A PROCESS OF PLATING A MAGNETIZABLE ARTICLE WITH AN ELECTROPLATING CYCLE INCLUDING AT LEAST ON TREATMENT IN WHICH MAGNETISM IS INDUCED INTO THE ARTICLE BY THE FLOW OF ELECTRICAL CURRENT THERETHROUGH AND WHEREIN THE MAGNETISM INDUCED IN SAID ARTICLE IS DESTROYED TO PREVENT THE ADHERANCE OF MAGNETICALLY ATTRACTABLE PARTICLES TO THE ARTICLE AND IMPROVE THE QUALITY OF THE PLATING PRODUCED THEREON, THE STEPS OF: (A) IMMERSING SAID ARTICLE IN AN ELECTROLYTE; (B) PASSING A DIRECT CURRENT THROUGH THE IMMERSED ARTICLE TO EFFECT SAID TREATMENT; (C) THEN PASSING AN ELECTRICAL CURRENT THROUGH THE IMMERSED ARTICLE AT THE END OF THE TREATMENT, PERIODICALLY REVERSING THE DIRECTION OF FLOW OF THE CURRENT, AND GRADUALLY REDUCING THE MAGNITUDE OF THE CURRENT FROM FULL VALUE TO SUBSTANTIALLY ZERO TO THEREBY DEMAGNETIZE SAID ARTICLE.