US2420403A

US2420403A - Electrodeposition of iron

Info

Publication number: US2420403A
Application number: US477131A
Authority: US
Inventors: Jr William B Stoddard
Original assignee: Champion Paper and Fibre Co
Current assignee: Champion Paper and Fibre Co
Priority date: 1943-02-25
Filing date: 1943-02-25
Publication date: 1947-05-13
Anticipated expiration: 1964-05-13
Also published as: GB577621A

Description

Patented May 13, I947 sates OFFICE 2,420,403 ELEornoDErosrrroN .oF IRON No Drawing. Application February 25, 1943,

.Serial No. 477,131

22'Claim's. 1

invention relates to the electrodeposition of iron and is herein described as embodied in a plating bath of improved composition with which it is possible to secure deposits which are uniform-1y fine-grained and smooth and possess a combination of strength and ductility not heretofore obtained in electrodep-osited iron without subsequent heat treatment.

Electrodeposition of iron has in the past found relatively little practical use, due in part to the hardness and brittleness of the deposits commonly secured by this method, and in part to the difiiculty of controlling the deposition to maintain the desired uniformity and consistency in the results secured.

Iron deposits have been made from solutions of ferrous salts, usually the chloride or sulfate. Deposits from the chloride have been made with fine-grained structure of good strength at the beginning of the deposition but it was found that as deposition continued the grain coarsened so that the deposit had good strength only on the surface first deposited. Deposits so made could be bent in one direction but would fracture readily if bent in the other direction. Such characteristics naturally seriously limited the use of iron deposited as described.

Furthermore, it has in the past been necessary, in order to secure an iron deposit having a reasonable degree of ductility, to carry out the deposition at temperatures from about 190 to 220 or more degrees Fahrenheit, which was in many cases found to be disadvantageous. It has also been necessar heretofore to very closely control the temperature and hydrogen ion concentration in the baths from which iron was deposited, since When a relatively small change was made in either of these conditions, great differences were found in the structure and-physical properties .of the resulting iron deposit.

I have now discovered that the addition of a small amount of soluble manganese to the plating bath serves to prevent a coarsening of the grain as the deposition continues, and makes possible the deposition of iron in a uniformly fine-grained and ductile form of good strength, at temperatures materially lower than hereto fore required. I have also discovered that the addition of manganese to the bath appears to materially broaden the permissible operating range of temperature and hydrogen ion concentration within which it is possible to secure deposits of good strength and ductility. For instance, by'the addition of manganous chloride in amounts equivalent to 1.4 grams of soluble manganese per liter to a bath containing, say 300 grams of ferrous chloride (-FeClz-lI-IaO), which is equivalent to about '84 grams of soluble iron, per liter, I have been able to secure an iron deposit which is truly ductile, strong, and of uniformly fine rain structure, when the bath was maintained at a temperature between 160 and 220 and a. pH value between 1.2 and 2.6. In a ferrous sulfate bath the manganese serves to ref ne the rain structure but has not served to produce a deposit which is truly ductile without heat treatment, apparently because of the tendency of sulfate solutions ,to cause hydrogen emhrittlement. V

Manganese in the bath appears to be effective to refine the grain structure of 'electrodeposited iron when present in amounts as small as it gram of soluble manganese per liter. The effect seems to increase with increasing amounts of manganese up to about 1.4 grams per liter. Little if any advantage, however, appears to be secured by further increases in the amount, though amounts up to 17 or 20 or more grams per liter have been used successfully.

The manganese is advantageously added to the ferrous chloride and ferrous sulfate solutions in theform of manganous chlorideand manganous sulfate respectively. :It may, however, he added in any one of a variety of other forms, such as other salts of manganese or even salts of manganic or permanganic acid, which in the ferrous chloride or sulfate solutions react to liberate ions of divalent manganese. The use of salts such as the nitrate, formate, etc., carrying acid radicals which enter into the cathode reaction, should be avoided.

It may also be noted that the action of the manganese is apparently catalytic in nature, no evidence having been discovered to indicate that any of the manganese in the bath is consumed during the electrodeposition of the iron, or that even small amounts of manganese have been deposited with the iron.

When using the chloride solutions of the present invention, I find it advantageous to maintain therein a pH value between 1.2 and 2.6, and preferably between 1.8 and 2.3 as measured at room temperature by glass electrode equipment,

thegreatest ductility having been secured with 3 using a chloride solution modified according to the present invention, the required acidity is advantageously secured by addition of hydrochloric acid.

4 As in the case of the usual baths, the current densities which may be used are higher at higher temperatures and lower at lower temperatures. For example, at temperatures above 200 F. I have When using a sulfate bath containing man- 5 been able to use current densities as high as 300 ganese in accordance with the present invention, amperes per square foot; at temperatures of 170 the pH of the solution is advantageously main- F. 100 amperes per square foot; and at 160 F. 50 tained at a value materially higher than in the amperes per square foot. case of a chloridebath, since at values as low The presence in the solution of as little as 5 as 2 the anodes are attacked with great vigor milligrams of lead per liter noticeably interferes and much gas is liberated at the cathode, indiwith the deposition of iron, and 250 milligrams eating reduced efficiency. The addition of manper liter completely prevents the formation of ganese to the solution, as described, advanany useful deposit. Consequently the bath used tageously in the form of manganous sulfate, should be substantially free from lead, and the serves to impart a refined grain structure to iron use of lead-lined tanks or other lead equipment deposits made from solutionshaving pH values should be avoided. Other precautions, well unfrom 2 up to 4.5 or more. derstood by those skilled in the art, should be As in the prior art, so also in the deposition taken to insure the purity of the bath, such as of iron from the solutions of the present inventhe use of pure chemicals and anodes, specifically tion, the higher the temperature of the bath the such as are substantially free from such impurigreater the ductility of the deposit. By the use ties as arsenic, copper, tin, lead, etc. The anodes of my improved solution, however, I find it posshould be enclosed, as by any of the known desible to secure fine-grained ductile deposits of vices, e. g. porous cups, glass or asbestos bags, iron at temperatures from 30 to 50 F. lower etc. to maintain the cleanliness of the solution than those heretofore required. and prevent the resulting roughening of the de- I have frequently observed a tendency toward posit. In case of the contamination of the bath pitting of the deposit, which appears to be more by organic materials, treatment with an inert serious at lower temperatures; but I have found, adsorbent material such as activated carbon, is however, that this tendency toward pitting can sometimes advantageous. To avoid trouble be prevented and the character and smoothness caused by oxidation of the solution by contact of the deposit greatly improved by the addition with the air, it may be covered with a layer of to the solution of a small amount of a sodium mineral oil, molten paraffin, or the like, to presalt of a sulfated higher fatty alcohol. For exvent such contact, Further, it is frequently adample, the products known to the trade as vantageous to subject the baths of the present Gardinol and Tergitol have been found efinvention to the breaking-in period, well fective in amounts approximating one gram per known in the art, wherein the solution is subliter, though there appears to be nothing critical jected to electrolysis for a short time before it about the proportion used, and a considerable is placed in service. variation can apparently be made in the per- The following table gives the pertinent facts centages used while still securing the advantages regarding a number of examples which illustrate described. With the solution so modified I have the use of various solutions embodying the presfound it possible to operate successfully securent invention in the formation of electrolytic ing fine-grained deposits of good strength and iron deposits having improved rai St ucture ductility at temperatures as low as 160 F. and ductility.

No. chloride sulfate chloride Sulfate WA 1.017 a F: l000#/1n.'- per cent sands 1 84 1.4 20s 100 51 44 2,244 f gg gf f fgfgffg ductility for iron.

2 84 1.4 194 2.1 100 Fine-grained ductile deposit. Badly pitted.

3 S4 1.4 $4 104 2.1 100 Fine-grained ductile deposit. Freeirom pitting.

4 cs 0.8 1 170 23 1, 900 deposit free from pitting.

5 cs 0.8 1 50 111 12.5 1, 390 igggit ttts'iitii from pitting.

6 60 1.2 3.0 100 Smooth finegrained deposit only slightly ductile.

7 s4 1.4 205 100 47.5 50 2, s75 g g gggf fiflg i tionally ductile.

The concentration of ferrous iron in the solutions may be varied over rather wide limits.

In the foregoing table the product of percent elongation and tensile strength is included to fur- Solutions containing less than 45 and more than 70 nish a basis of comparison of the strength-duc- 200 grams of iron per liter in the form of ferrous chloride have been used successfully. With the higher concentrations it is in general possible to operate at somewhat lower temperatures than with the lower concentrations.

tility properties of the deposits with the same properties of known forms of iron. This product. in the case of commercial soft irons and low carbon steels where ductility is a requirement, has a commonly accepted value of about 1,500,000.

For example, a representative cold rolled strip steel in a soft temper, intended for forming and drawing operations Where ductility is of primary importance, may have a tensile strength of about 50,000 pounds per square inch and an elongation of about 30 per cent. Use of the solutions of the present invention is'thus seen to'make possible the production by electrolytic deposition, of iron which amply fulfills the present day strength-ductility standards set for commercial ductile iron. Even where the deposition was car ried out under conditions to yield a deposit of tensile strength which is exceptionally high for substantially pure iron, it will be noted thata good degree of ductility was nevertheless secured.

Not only do the solutions of the present inven tion make possible the production of uniformly smooth and fine=grained deposits, but they are also found to be materially less sensitive to Vari atiohs in temperature and in hydrogen ion concentration than were those of the prior art. Therefore, with my solutions it is not necessary to maintain the extremely accurate control of temperature and pd formerly required in order to produce iron deposits of satisfactory uniformity. With these solutions, also, it is possible to substantially if not entirely eliminate the evolution of gas and to secure cathode efiiciencies of 96 to 98 percent or better. Operating temperatures may be from 30 to 50 degrees F. lower than heretofore while securing an iron deposit which possesses equal or superior ductility and fineness of grain structure.

The use of my solutions is thus seen to make possible a novel combination of broad operating range of temperature and pl-l with fine grain, good strength, and ductility of the resulting iron deposit.

I claim:

1. The process of obtaining smooth, finegrained deposits of iron from an electrolytic bath consisting essentially of an aqueous solution of a salt from the class consisting of ferrous chloride and ferrous sulfate which comprises passing an electric current through the bath while maintaining therein, as a catalytic refining agent, at least one-tenth gram and not substantially more than twenty grams per liter of soluble manganese in the form of a divalent salt from the class consisting of manganous chloride and manganous sulfate, the pH of the bath being between 1 and 4.5 but not sufilciently high to cause a coarse grain structure of the deposited iron.

2. The process of obtaining smooth, finegrained deposits of iron from an electrolytic bath consisting essentially of an aqueous solution of ferrous chloride which comprises passing an electric current through the bath while maintaining therein, as a catalytic refining agent, at least one-tenth and not substantially more than twenty grams per liter of soluble manganese in the form of a divalent salt from the class consisting of mange-nous chloride and manganous sulfate, the pH of the bath being between 1 and 3.

3. The process of obtaining smooth, finegrain'ed deposits of iron from an electrolytic bath consisting essentially of an aqueous solution of ferrous chloride which comprises passing an electric current through the bath while maintaining therein, as a catalytic refining agent, at least onetenth and not substantially more than twenty grams per liter of soluble manganese in the form of a divalent salt from the class consisting of m'anganous chloride and a manganous sulfate, the pH of the bath being between 1.2 and-2. 6;

4. The process of obtaining smooth} sne grained deposits of iron froman electrolytic bat-h consisting essentially of an aqueous senses of ferrous chloride which comprises pa ssinga-n sledtric current through the bath While maintaining therein, as a catalytic refining gent; at least one-tenth and'not substantially more than twenty grams per liter of soluble manganese in the formof a divalent salt from the class consisting of manganous chloride and manganous's ulfate; the pH of the bath being between 1.8 and 2.3;

5. The process of obtaining smooth,- finegrained deposits of iron from an electrolytic bath consisting essentially of anaqueous solutionof ferrous sulfate which comprises passing an electric current through the bath while maintaining therein, as a catalytic refining agent, atleast one-tenth gram and not substantially moretha'n twenty grams per liter of soluble manganesein the form of a divalent salt from the class con sisting of manganous chloride and manganous sulfate, the pH of the bath being between 2 and 4.5.

6. The process of. obtaining smooth; finegrained deposits of iron from an electrolytic bath consisting essentially of an aqueous solution of ferrous sulfate which comprises passing an electric current through the bath While maintaining therein, as a catalytic refining agent, at least one-tenth gram and not substantially more than twenty grams per liter of soluble manganese in the form of a divalent salt from the class consisting of man anous chloride and manganous sulfate, the pH of the bath being about 3.

'7. The process of obtaining smooth, finegrained deposits of iron from an electrolytic bath consisting essentially of an aqueous solution of a salt from the class consisting of ferrous chlo: ride and ferrous sulfate, and a sodium salt of a sulfated higher fatty alcohol, which comprises passing an electric current through the bath while maintaining therein, as a catalytic refining agent, at least one-tenth gram and not substantially more than twenty grams per liter of soluble manganese in the form of a divalent salt from the class consisting of manganous chloride and manganous sulfate, the pH of the bath being between 1 and 4.5 but not suificiently high to cause a course grain structure of the deposited iron.

8. The process of obtaining smooth, finegrained de'posits'of iron from an electrolytic bath consisting essentially of an aqueous solutionof ferrous chloride and a sodium salt of a'sulfated higher fatty alcohol, which comprises passing an electric current through the bath while maintaining therein, as a catalytic refining agent, at least one-tenth gram and not substantially more than twenty grams per liter of soluble manganese in the form of a divalent salt from the class consisting of manganous chloride and manganous sulfate, the pH of the bath being between 1.2 and 2.6.

9. The process of obtaining smooth, finegrained'deposi'ts of iron from an electrolytic bath consisting essentially of an aqueous solution of a salt from the class consisting of ferrous chloride and ferrous sulfate which comprises passing an electric current tlirough'the bath while maintaining therein, as a catalytic refining agent, at least one-tenth gram and not substantiallymore than twenty grams per liter of soluble manganese in the form of a divalent salt from the class consisting of man'gan'ous chloride and nianganous sulfate, the pH of thebath being between 1' and 4.5 but not .sumciently high to cause" a course grain structure of the deposited iron, maintaining the current density between twenty-five and three hundred amperes per square foot at the cathode surface, and maintaining the bath during the electrodeposition of the iron at a temperature between 160 F. and 220 F.

10. The process of obtaining smooth, finegrained deposits of iron from an electrolytic bath of an aqueous solution consisting essentially of ferrous chloride which comprises passing an electric current through the bath while maintaining therein, as a catalytic refining agent, at least one-tenth and not substantially more than twenty grams per liter of soluble manganese in the form of a divalent salt from the class consisting of manganous chloride and manganous sulfate, the pH of the bath being between 1.2 and 2.6, maintaining the current density betweentwenty-five and three hundred amperes per square foot at the cathode surface, and maintaining the bath during the electrodeposition of the iron at a temperature between 160 F. and 220 F.

11. The process of obtaining smooth, finegrained deposits of iron from an electrolytic bath consisting essentially of an aqueous solution of ferrous chloride which comprises passing an electric current through the bath while maintaining therein, as a catalytic refining agent, at least one-tenth and not substantially more than twenty grams per liter of soluble manganese in the form of manganous chloride, the pH of the bath being between 1 and 3.

12. The process of obtaining smooth, finegrained deposits of iron from an electrolytic bath comprising essentially a solution in water of the cations of divalent manganese and divalent iron, and anions from the class consisting of chloride and sulfate which comprises passing an electric current through the bath while maintaining the divalent manganese cations therein to the extent of at least one-tenth gram per liter and sufficient to cause grain refinement of the deposited iron, but not to an extent suflicient to cause deposition of manganese along with the deposition of iron under the deposition conditions recited, and maintaining the pH of the bath during deposition between 1 and 1.5 but not suificiently high to cause a coarse grain structure of the deposited iron, the divalent manganese cations acting as a refining agent.

13. A plating bath for the electrodeposition of iron comprising essentially a solution in water of the cations of divalent manganese and divalent iron, and anions from the class consisting of chloride and sulfate, the divalent manganese cations acting as a catalytic refining agent and being present in an amount not less than about one-tenth gram per liter and in an amount sufficient to cause grain refinement but not in an amount sufiicient to cause deposition of manganese along with the deposition of iron when an electric current is passed through the bath to cause electrodeposition of iron therefrom, the pH of the solution being between 1 and 4.5, but not sufiiciently high to cause a coarse grain structure of the deposited iron.

14. A plating bath for the electrodeposition of iron comprising essentially a solution in water of the cations of divalent manganese and divalent iron, and anions from the class consisting of chloride and sulfate, the divalent manganese cations acting as a catalytic refining agent and being present in an amount between about onetenth gram and twenty grams per liter, said bath having a pH between 1 and 4.5, but not sufficiently high to cause a coarse grain structure of the deposited iron.

15. A plating bath for the electrodeposition of iron comprising essentially a solution in water of the cations of divalent manganese and divalent iron, and chloride anions, the divalent manganese cations acting as a cataytic refining agent and being present in an amount between about one-tenth gram and twenty grams per liter, the pH of the solution being between about 1 and 3.

16. A plating bath for the electrodeposition of iron comprising essentially a solution in water of the cations of divalent manganese and divalent iron, and chloride anions, the divalent manganese cations acting as a catalytic refining agent and being present in an amount between about onetenth gram and twenty grams per liter, the pH of the solution being between 1.2 and 2.6.

17. A plating bath for the electrodeposition of iron comprising essentially a solution in water of the cations of divalent manganese and divalent iron, and chloride anions, the divalent manganese cations acting as a catalytic refining agent and being present in an amount between about onetenth gram and twenty grams per liter, the pH of the solution being between 1.8 and 2.3.

18. A plating bath for the electrodeposition of iron comprising essentially a solution in water of the cations of divalent manganese and divalent iron, and sulfate anions, the divalent manganese cations acting as a catalytic refining agent and being present in an amount between about onetenth gram and twenty grams per liter, the pH of the solution being between about 2 and 4.5.

19. A plating bath for the electrodeposition of iron comprising essentially a solution in water of the cations of divalent manganese and divalent iron, and sulfate anions, the divalent manganese cations acting as a catalytic refining agent and being present in an amount between about onetenth gram and twenty grams per liter, the pH of the solution being about 3.

20. A plating bath for the electrodeposition of iron comprising essentially a solution in water of a sodium salt of a sulfated higher fatty alcohol, cations of divalent manganese and divalent iron, and anions from the class consisting of chloride and sulfate, the divalent manganese cations acting as a catalytic refining agent and being present in an amount not less than about one-tenth gram per liter and sufiicient to cause grain refinement of the deposited iron, but not in an amount sufficient to cause deposition of manganese along with the deposition of iron when an electric current is passed through the bath to cause electrodeposition of iron therefrom, the pH of the solution being not suificiently high to cause a coarse grain structure of the deposited iron.

21. A plating bath for the electrodeposition of iron comprising essentially a solution in water of a sodium salt of a sulfated high'er fatty alcohol, cations of divalent manganese and divalent iron, and chloride anions, the divalent manganese cations acting as a catalytic refining agent and being present in an amount between about onetenth gram and twenty grams per liter, the pH of the solution being between about 1 and 3.

22. A plating bath for the electrodeposition of iron comprising essentially a solution in water of ferrous chloride and manganous chloride, the manganous chloride being present as a catalytic refining agent and in an amount suflicient to provide between about one-tenth gram and 9 l0 twenty grams per liter of manganese, said solu- Number Name Date tion having a pH between about 1 and 3. 2,254,161 Waite et a1 Aug. 26, 1941 2,316,917 Wallace Apr. 20, 1943 WILLIAM B. STODDARD, J R. a FOREIGN PATENTS REFERENCES CITED Number Country Date The following references are of record-in the 288660 Germany 1915 file of this patent: OTHER REFERENCES UNITED STATES PATENTS 0 Modern Electroplatlng, special vo1., Electro- Number Name Date chemical Society 1942, page 273. (Copy in Divi- 1,215,354 Eaton Feb. 13, 1917 1,377,822 Eustis May 10, 1921