US1527576A - Process of coating conducting materials with tin - Google Patents

Description

' Patented Feb. 24, 19.25."

I v 1,527,576 1 UNITED STATES PATENT oFn-ca.

, ISAAC M. SCOTT AND SAMUEL PEAOOCK,

F WHEELING, WEST VIRGINIA,- AND WIL- LIAJYLEABL ARMSTRONG, OF MARTIN'S FERRY, OHIO, ASSIGNORS T0 WHEELING STEEL 8c IRON COMPANY, OF WHEELING, WEST VIRGINIA, A CORPORATION 0F c d WEST PROCESS OF coarme connuc'rrae MATERIALS 'wrrrr TIN,

No Drawing. Application filed February To all whomitmg/concem: v Be'it known that we, ISAAC M. Soo'rr, SAMUEL PEACOCK, and'WIiJLIAM EARL ARM- 'STRQNG, all citizens of the United States, the said ISAAC M. Scorr and SAMUEL PEA- COCK residing at Wheeling, in thecounty of Ohio and State of West Virginia, and the said WILLIAM EARL ARMSTRONG residing at Martins Ferry, in the county of Belmont and State of Ohio, have invented certain new and useful Improvements in Processes of Coating Conducting Materials with Tin, and we do hereby declare the following to be a full, clear,and=exact description of the invention, such as will enable'others skilled a in the art to which it appertains to make v and use the same. V

's invention relates to improvements in electro-tinning and more particularly to the whereby said electroinning can be carried out on a commercial scale and in a manner more .economical'than has been heretofore attained. y

With these andother objects in view the invention consists in the novel steps and combinations of steps constituting the process, all as will be more fully hereinafter dis-' closed and particularly pointed out in the ac claims. a

' In order that. the preciseinvention may be the more clearly understood it is said In the electro-deposition of tin, great'difliculty has been heretofore experienced in producm'g' a dense and coherent deposit. This is especially. emphasized when the objects to ;be electro-tinned are constructedof metals higher in the electro chemical series thanis tin, "such for example, as steel or iron. Heretofore, articles' constructed of metals, such as iron, were firstelectro'-plated with a metal lower in the electrochemical series such for example as copper, and upon this last named metal the 'But, solutions that areavailable for epositing the tin'directly on iron or steel deterioirate rapidly, and cannot 'be" operated son la ,commercial scale, economically, unless, as-

sociated with a suitable restoring solution;

These difficulties are all well known'in this 'art." A. On the other hand, this inventiogi involves h electroa solution and a method "by :wh}

solution or electrol te, and to a process 'tm was de osited.

19, 192?. Serial'No. 620,009.

.tinning can be carried out without diflichlty and much more efliciently' than heretofore;

and this solution can be used for plating directly on steel and other metals higher in the electro chemical series. Further this method may beused. for large scaleyopera tions with different concentrations and without causing a formation of. colloidal or spongy deposits as in the prior procedures.

he solutions contain a lower percentage of tin than those heretofore employed, they do not deteriorate o'r'hydrolize to an objectionable extent, and, they operate with almost 100% efliciency. This bat-h does not require a periodical addition of tin salts as heretofore, or in other words it is self. sustainm k It will be understood by those skilled in the art that the thickness 'of deposit .or amount .of tinplated' per unit of surface will depend upon the length of time and the number of amperes used, irrespective of the .voltagefiaut of course, the lower the voltage 1 employed the more economical will be the deposition. I w

It has been found in practice that with say to 1% volts, good deposits are obtamed with this solution. f r p In carrying out the invention in its preferred form, one may take, for example 3 parts by weight of a commercial hydrofluoric acid HF) and dissolve therein 1.6 parts by weig t of boric acid H BO These acids react with an evol form an acid known as fluoboric acidior ution of heat and .borofluohydric acid, the simplest formula r 1 of which is HBF In this acid, one dissolves stannous oxide SnO until the acid has taken up the equivalent. of 1.35 parts by Wei ht of metallic tin, leaving about 31% of t e acid present in the free state.

By this means there is produced a solution of stannous fluoborate Sn(BF.,) containing an excessof free fluoboric acid HBF 'Tojncrease the conductivity of this solution one adds a metallic saltof a metal higher in the electro-chemical, series than iron, and prefers for this purpose the addition of 1.3 arts by weight of aluminum sulphate A1 0 or 1.3 arts by weight of magnesium sulphate Mg0,. This solution is'then diluted with water. to such a concentration that it will contain about 1% ounces of metallic tin to one gallon. In this diluted solution there is suspended metallic tin as an anode on a positive bus bar, and one suspends the articles to be plated such as sheet steel, in the solution and connects them to the. negative bus bar whereby on the passage of a suitable electric current, the steel articles become plated with metallic tin.

It has been found it is also desirable to add so-called addition agents or brightening agents, such as molasses, gelatine, etc., to the solution for the purpose of obtaining somewhat improved and bright deposits. It is preferred to use ordinary glue for this pur-' pose and in a quantity of about .03 ounce per gallon of solution, but a larger amount will not interfere with the success of the process. I \p Instead of using stannous oxide $110 for introducting the tin into this solution, one may add other tin salts, such as stannous hydrate Sn(OH) or may dissolve in the solution metallic tin with or without the aid of the electric current. It has been found that the economical addition of tin may also be obtained by suspending metallic tin as anodes in the solution, connected with a positive bus bar and-suspending metal strips, surrounded by porous cups in the solution,

7 the metal strips being connected to a negative bus bar. By the passage of a suitable electric current, such as that above disclosed, the tin is dissolved from the anodes into the solution and being unable to pass into the porous cups, it is taken up by the acid.

' When sufiicient tin has been dissolved the cups are removed and the plating continued.

In the foregoing. description there is disclosed a tin solution in a somewhat diluted form with an acid reaction, but the solution can be used in more concentrated forms such for example as in those having a plurality of times the concentration of that above mentioned. The solution can also be used in the neutral state and for certain purposes one prefers a neutral solution, for such last named solution is especially desirable when chemically pure tin is being deposited.

The above solution has proved satisfactory for the deposition of tin on various metals such as iron, steel and copper. and therefore, it is not desired to be limitedto the pro cedure set forth 'in the description.This

' solution and process may also be usedwith various modifications for numerous purposes that will readily suggest themselves to those skilled in the art without departing from the spirit of my invention.

plating baths, a bath suitable for carrying out this process'is disclosed and claimed What is claimed is 1. The process -of coating tin on electric conductors which consists in providing an electrolytic solution containing tin dissolved in boro-fiuohydric acid; immersing the article to be coated in said solution; and passing "a current of electricity from said solution to said article to obtain the desired 0 coating. v 2. The process of coating tin on an electric conductor which consists in. providing an electrolytic solution containing stannous fiuoborate and a salt ofa metal more electropositive than iron, immersing the article to be coated in said solution as a cathode; and passing a current through said solution to said cathode to obtain the desired coating.

3. The rocess of coating iron or steel with tin w ich consists in providing a bath consisting essentially of stannous fluoborate; immersing the iron or steel article to be coated in said bath and making the same a cathode in an electrolyticcircuit; and passing a current to obtain the desired coating. 4;. The process of coating iron or steel with tin which consists in providing a bath consisting essentially of stannous fiuoborate admixed with free boro-fluohydric acid; immersing the iron or steel article to be coated insaid bath and making the same a cathode in an electrolytic circuit; and passing a current to obtain the desired coating.

v5. The process of coating iron or steel with tin which consists in providing abath .consisting essentially of stannous fluoborate oated in said bath and making the same a c thode in an electrolytic circuit,- and passi g a current to obtain the desired coating.

tures.

ISAAC M; SCOTT. f' SAMUEL PEACOCK.

In testimony whereof we'aflix our signa- WILLIAM EARL' ARMSTRONG. I