US815875A - Process of deep etching of zinc by electrolysis. - Google Patents

Description

UNITED srArEs imer orrron.

OF WAINZ, GERMANY. 4 a

, eno ct-zss or- DEEP sToHme F zmc BY ELECTROLYSIS.

Specification of Letters Patent. Applicatich filed May 26; 1904. Serial No. 209,977.

. Patented March 20, 1906.

To-aLZ-Z whom it may concern:

Be it known that we, Or'ro CARL STRECKER,

v residing at the city-of Darmstadt, and HANS and useful Improvements in Processes for HERMANN STREoKnR, residing at the city of Mainz, German Empire, doctors of hilosoby and subjects [of the Grandj= uke of l Iesse-Darmstadt, have invented certain new the Deep Etching of Zinc by Electrolysis and we do hereby declare that the following is a full, clear, and exact description of the invention:

pure zinc, was used. T

This invention relates to processes for the deep etchingof Zinc by electrol sisfor the SP 'P ose of rmting impressionst erefrom. In the eectrol tic-production of deeplyetched zincograp s and reliefetchings for litho aphic metal printing there could hith erto e obtained a serviceable-etched ground (especially deeply-etched parts) only inthe eventthat a perfectly plure metal, such as e impurities-such as lead,'iron,- andcarbon occurring even in thebest commercial brands of the article bring about an irregular solution of the zinc,

j andthere is obtained a mu h unequally-bitten etched ground, which ta es the color. and

1 is printedoff. The limits of the relative proplate, there appears under it a smooth etched current strength effects thera orti ons of zinc and the principal impurities ound in commercial'zinc' are 94.4 71 Z1110 and- 99.378 zinc, 2.393 lead and 0.503 le ad 0.136 iron and 0.041 iron. (See Graham. Otto,

Manual "of Chemistry, Vol. 1-11, page 755.) According to the present invention, however,

a good smooth etched ground is obtainable even with 3 the use of impure zinc, provided, that during the etching ofthefzinc plate employed as ano currentstrength'of at east two amperes torieach square decimeter of metallic one si'ded ployed. The m twelve amperes.

current density is The application of thishigh id and smooth solution ofthe zinc from the zinc. late',,w'hich "plat'e'must be regarded a'san a loy o i'rlead with zinc containing carbon. Moreover, the

impurities, whichare either the insoluble carbon or the hardly-soluble lead, remain behind as a'soft coating loosely adherentto the plate;

If this coating be then removed from the ground. If, on the other hand, the work is effected by means of a low current strength,

later.

gan'ode surface be em OTTOCARLSTRECKER, or DAR'MSTADT, AND HANS HERMANN sTREoKER,

machine even large zinc plates may-be etched according tothe new invention.v

The coating ofimpurities formed in consequence of the action of the current upon the etched plate adheres 'sufficiently firmly that it can be taken, together with the plate, out

of the bath, whereby the bath is kept free 7 If zinc ace- 'tate or zinc formiate be made use of, the.

from muddiness and impurities.

bath is, kept clean in the above-described manner and at the same time the cathode is so proportioned that it also corresponds to a hig currentstrength, then the operation on a permanent scale is rendered possible. With the use of a high current intensity also at the cathode of at least two amperes'per square decimeter of metallic one-side cathode surface the zinc at the cathode is electrolytically separated in acontinuous firmly-adherent layer. In this manner there are avoided,-

first, short circuits through conducting metal brid es between the plates, and, secondly, the ath may be maintained constant in its composition even in continuous working.

In place of acetate or formiate ofzinc other zinc-salts might be used for the bath in so far as they possess the same properties as the zinc acetate and zinc formiatenamely, thatthe precipitate electrolytically zinc at the cat ode in a continuous layer under high two amperes per square decimeter of metallic one-side cathode surface. For the operation of continuous working attention mustbe given consequently, on the one hand, to the 'gh current strength at'the cathode, and on the other hand, also and at thesametime a suitable zinc-salt must be employed. With a lower current strength at the anode the sediment or skin of impurities remaining thereon falls into the bath and causes dis- 95 current strength at the cathode of at least fei'e with the printin or else into a soluble turbances of the working through the sedi- Inent. Moreover, at the cathode disturbances of the continued working may arise by the zinc separating in the form of a sponge or tree. Thisinconvenience is obviated by having a high current strength at the cathode also and at the same time making use of such zinc-salts for the bath as will separate the zinc at the cathode in continuous form under high current strength. Such zinc-sal ts therefore should not be used which would tend to separate the zinc at the cathode with the fonmation of spongy or tree-shaped formations even at high current strength.

The new process is referably carried out as follows: The Zinc p ate provided with the greasy drawing or print is rolled with color, gurnr'ned, and washed with washing tincture or turpentine over the dry gum. The drawing is then protected by a coating of greasy asphalt solution or the like, dried, and washed. The plate thus prepared is then suspended as anode in a bath, which consists of about ten per cent. of zinc-acetate solution and has a zinc cathode. Hereupon an electric current is sent through the bath, which possesses a current strength of at least two ampere's per square decimeter of metallic one-sided anode surface. Obviously several baths may be arranged in series. The plates may be suspended vertically, or they may he placed horizontally in the baths, because neither spongy zinc nor hydrogen are produced and the adherence of the impurities to the anode does not prevent the horizontal arrangement. After an action of the current for about twenty minutes the etching is usually sufliciently deep'for lithographic or other lightly-etched printing-plates, The plate'is then removed from the bath and replaced by a new one. The plate after removal, to which adhere all the impurities and foreign bodies of ordinary rolled Zinc, is first 'Wiped with a soft wet cloth or the like. It is then again treated with zince'tc'hing fluid or acid, which precipitates or dissolvesthe lead in order to convert the last particles of lead still adhering to it into colorles's white substance, which will not intersalt which can be was ed off.

square decimeter of the active su In place of a plate a cylinder electrolyticany provided with a zinc coating of sufiicient thickness can be subjected to the etching process. In this case the process only needs alteration in that the cylinder which acts as anode is rotated during the etchin process.

. e deep etching has the drawback for certain kinds of print, especially for rotary print, that too much water collects and adheres to the highly-etched drawing, which thus reaches the printing-rolls and causes a gray feeble not sufficiently-pronounced rint. This drawback may be avoided by pl ticing the Zinc plates after previous cleansing in a bath consisting of a salt solution and subjecting them as anodes to the action of an electric current until the upper surface layer, which during the rolling has received another physical coi'istitution in consequence of the mechanical pressure thus exercised upon it, has been removed. In this manner there is attained, first, that the surface of the zinc plate can be more easily scoured and ground, and that, secondly, in the case of dee etching the zinc plate can be etched shaiiower than without the aforesaid treatment is possible by electrolysis. In the presence of a superficial layer of different physical properties the etching must be continued to a great depth. 'lhis process is preferably conducted as follows: The plate of rolled zinc is first cleaned, then brought into the salt solution serving as the bath and exposed to electrolysis as anode. The cathode is preferably also constructed of zinc, and the electrolytic fluid is preferably a solution of a zinc-salt. For the current strength two amperes for each square decimeter of surface is usually sufficient. In the case of a less current strength the etchin does not proceed quickly enough, whereas t the increase of the current strength over one ampere usually better results are obtained.

After the above-described electrolytic prc aration the zinc plate is washed, the acid d irectly removed, provided with print, or else again ground and further treated.

Having now described our invention and in what manner the same is to be performed, what .we claim, and desire to secure by Letters Patent, is i I 1. The herein-described electrolytic process of deeply etching zinc which consists in exposing a zinc plate as an anode to an electric current of at least two am eres per rface while submerged in a bath of zinc-salt, substantially as described.

2. The herein-described electrolytic process of deeply etching zinc which consists in providing said zinc, with a print or transfer, sprinkling it with asphaltuln dust and then exposing said zinc plate as an anode to an electric current of at least two amperes per square decimeter of the active surface, while submerged in a bath of zinc-salt, substantially as described.

3. The herein-described electrolytic process of deeply etching zinc which consists in exposing a zinc plate tric current while submerged in a salt solution and removing the surface-layer, washing the plate during transferring and then exposing it as an anode to an electric current of at least two amperes per square decimeter of the active surface while submerged in a bath of zinc-salt, substantially as described.

4. Process for deep etching of zinc by electrolysis for the purpose of printing impresas an anode to an elecsi ons therefrom, whiehprocess consists in 1 In witness whereof we have hereunto set preparmg a zme eyhnder, and exposmg 1t as ourha'nds 1n presence of two wltnesses.

anode to a current of at least two amperes OTTO CARL STRECKER.

per square decilneter 0f the surface facing HANS HE-RMANN STRECKER. 5 the cathode, in a bath of a suitable zine-salt, Witnesses: I

thereby se arating the zinc at the cathode, WALTER HOUSING,

substantia 1y as described. -WALTER SCHUMANN.