US1851219A - Method of electrodeposition of zinc - Google Patents

Description

Patented Mar. 29, 1932 ,umranzys'rn UBLYN o.- rmron. communes-nae. rnansvm, son'm AFRICA METHOD OF ELEGTRODEPOSITION 01 ZINC Ho pavin This invention relates to an improved -method of electrodeposition of zinc and has 5 ri tyand high for its purpose of a new type,

of pure lead and to add to the solution a a greater or ter of the deposit.

lue to improve the charac- The zinc metal so ob tained,'however, is always contaminated to less degree with lead derived small amount of from the anode and the deposited metal is but having brittle and relatively difficult to work mechanically. According to the present invention, I employ an anode consisting mainly of lead alloyed with it a certain propor- 29 tion of a metal or metals standing belowlead in the electro-chemical scale, such as silver, arsenic, bismuth, etc. I further add to the solution a small proportion of an inorganic colloid such as silicic acid. It is frequently desirable to couple with the inorganic colloid the addition of an organic colloid not as gum -arabic precipitated by zinc sulphate solution, such or agar jelly. Under these conditions the zinc deposit obtained is much purer than by the ordinary method and at the same time the deposits are of exceptionally good quality, being very smooth, malleable, and ductile. It has been found possible to produce, directly from the cathode deposits, zinc foil-only one-sixteen thousandthsof an inch in thickness, and the metal may be rolled out indefinitely without annealing.

In carryingthis invention into ploy an anode "consisting mainly of lead but containing a small percentage, say 1%, of silver, bismuth, or arsenic. Other metals or combinations of metals electro-negative 'to lead may be employed although my preference is for. those mentioned, in the order named. To the electrolyte I add a solution of silicic acid orsodium silicate in the proportion of about one to five pounds of soluble silica per ton of zinc deposited. To insure a smooth deposit, and more especiallyif impurities are likely to effect, I embe present in the Application filed August 27, 1928. Serial No. 302,444.

electrolyte, the addition of a similar quantity of gum arabic, or of one quarter the amount of agar, is beneficial. The electrolysls is preferably conducted under conditions descrlbed in prior patents of the present applicant, namely, in, the presence of a large proportion of acid and at a high current density. Other conditions of electrolysis may, however, be employed.

It will be found that the zinc deposited un-. so der the above conditions carries only about one-tenth as much lead as does electrolytic zinc made in the usual way. Moreover the deposited metal, both in the form. of cathode and after melting, is remarkably ductile and 6a malleable and may be put through severe mechanical operations such as drawin \spinrung, and stamping, to an extent to w ich it is impossible to subject ordinary zinc with success. 3e

It will be found further, that under the above conditions the power required for electrolysis is substantially reduced as compared with ordinary practice, because not only is the current efiiciency exceptionally high, but the terminal voltage is lower than when using the ordinary conditions.

The metal obtained is also of special value in the plating of thin zinc deposits on other metals as, for example, in the roduction of galvanized iron and steel. wing to the high purity of the metal, the resistance to corrosion is greater and'the adhesion of the zinc to the underlying metal is much stronger than when made by the ordinary method.

Having thus described my invention, what I claim and desire to secure by Letters Patcut is:

1. In the ele'ctro-deposition of zinc, the method of producing zinc deposits of great purityv and ductility which consists in using an anode composed of an alloy of lead with a small proportion of a metal electro-negative to lead, and carrying out the electrolysis in the presence of silicic acid.

2. In the electro-deposition of zinc, the method of producing zinc deposits of great purity and ductility which consists in usin an anode composed of an alloy of lead an silver, and carrying out the electrolysis in the presence of silicic acid.

3. In the electro-deposition of zinc, the method of producing zinc deposits of great purity and ductility which consists in using an anodecomposed of an alloy of lead with a small proportion of metal electro-negative to lead andcarrying out the clectrolysis in the presence of silicic acid and gum. arabic.

URLYN C, TAINTON.