WO1991019833A2

WO1991019833A2 - Electrolytic zinc-plating process and devices

Info

Publication number: WO1991019833A2
Application number: PCT/DE1991/000326
Authority: WO
Inventors: Hermann Clasen
Original assignee: Löwe-Lack-Werk Otto Löwe Gmbh & Co. Kg
Priority date: 1990-06-11
Filing date: 1991-04-19
Publication date: 1991-12-26
Also published as: DE4018649C2; WO1991019833A3; DE4018649A1; EP0489875A1

Abstract

In order to avoid corrosion damage in the non-bath galvanizing , using hand-held electrodes, of e.g. iron adjacent to masonry, aqueous ammonia is used as the starting electrolyte and zinc as the cathode, so that only inert zinc oxide and no corrosive salts remain behind after drying. Several hand-held rub electrodes are described which render possible the use in practice of the new, simple, low-conductivity electrolyte. In the simplest case, the hand-held electrode comprises a piece of zinc wire (1) 3 mm in diameter and 40 mm long, one half of which passes hermetically (3) through the bottom of a soft plastics beaker (2) 5 mm wide so that the rim of the beaker extends 2 mm beyond the end of the wire, the free end of the wire being connected to positive (4), and the beaker holding the electrolyte (E). The electrode with its bevelled mouth can be used equally well in any position. It gives about 40 mA at 12 V, and one fill lasts for more than 5 min. Zinc plated on to polished iron (5) adheres and covers well, is ductile and is suitable for the direct application of a paint coating.

Description

description

Methods and devices for electrolytic galvanizing

The present invention relates to a method and associated devices for the electrolytic deposition of adherent and opaque coatings of metallic zinc on metals, in particular on iron or on zinc and on galvanized iron, here briefly called galvanizing. The generate

The main purpose of galvanizing on iron is to protect it against corrosion from atmospheric influences. The galvanizing then excludes the deposition and impure or alloyed zinc.

There are numerous recipes for the aqueous electrolyte solutions, here called electrolytes for short, which serve as a bath in which the objects with the negative polarity, to be galvanized and the positive electrodes with zinc are immersed. For bath-free galvanizing by hand g electrodes were suggested, so-called hand electrodes, in which brushes, sponges, felts and paste-forming agents serve as carriers for the aqueous electrolyte. Alien known electrolytes are the use of non-volatile acids or the non-volatile alkali bases and electrolytically particularly conductive salts, so-called conductive salts. The tendency of the zinc to acicular deposition (dendrite) is due to the special recipe (material composition of many components, distance and area ratio of the electrodes, electrical voltage and current density, acid strength temperature, etc.) and the movement of the bath or the electrodes bath-free galvanizing counteracted by rubbing the hand electrodes (so-called friction electrodes) on the surface to be galvanized.

Such electrolytes and hand electrodes have been recommended for the repair of damaged areas on galvanized or painted iron sheets, in particular a motor vehicle. The strongly acidic or alkaline electrolytes quickly attack any zinc that is still present and, like the tiniest residues of the salts, lead to rust formation in unprotected areas, where the electrolyte runs in an uncontrolled manner. Furthermore, the known hand electrodes are not suitable for every surface contour and spatial position and not for narrow parts, they mechanically damage the paintwork in the vicinity of the repair point and decimate the galvanization produced. In addition, the electrolytes attack the zinc electrode when de-energized.

The object of the present invention is to find a corrosion-free electrolyte, in particular a bath-free priming galvanizing, which the aforementioned should be found for repair purposes

Does not have bad conditions. As a very special task, which has not yet been set, it should be possible to repair galvanize iron parts that border on concrete or masonry. The known electrolytes are completely unsuitable because they destroy concrete or masonry mortar and are absorbed by them, so that a non-removable reservoir of rust-forming salts would arise. It has now been found that an aqueous solution of ammonia, so-called ammonia spirit, al

Electrolyte when using zinc as a positively polarized electrode, or positive for short, is suitable and the described shortcomings can be overcome.

REPLACEMENT LEAF If, according to the invention, at 15 ° C in the bath from 10% aqueous ammonia, a perpendicular iron wire negative of 3 mm in diameter at a distance of 2 mm is compared with a zinc wire positive made of a pair of wires each 3 mm in diameter and electrolyzed at about 1 volt with 6 mA corresponding to an electrical current density of 0.3 A / dm ² longitudinal zinc cut surface, so after a start-up time of a few seconds, which is associated with a clear hydrogen development on the negatives, a light gray zinc coating is formed on the negatives. The great uniformity and the large dispersion of the deposit, which also leads to the galvanizing of the back of the negatives in a few minutes, is impressive. However, after a total of about 15 minutes of polarization with a power standstill, this can be remedied by increasing the voltage to 2 V. In the electrolysis according to the invention, zinc goes from the positive into solution and separates out from the negative. After passage of current, the known zinc aminohydrides Zn (NH ₃ ) _n (OH) ₂ with n = 4 or 6 are present in the solution. Instead of starting with pure aqueous ammonia, ma can accordingly also start with the electrolyte that has already been used. A further possibility is accordingly to mix zinc aminohydroxides before or during the electrolytic galvanizing. Instead, it is also possible to simply add finely divided zinc oxide, for example zinc white, or salt-free zinc hydroxide, since these compounds slowly dissolve moderately in aqueous ammonia to form the zinc aminohydroxides. Powdered zinc can also be mixed in, since it also reacts with aqueous ammonia with evolution of hydrogen to form zinc aminohydroxides.

Another possibility of enriching the electrolyte with zinc aminohydroxides is, according to the invention, prior electrolysis of the aqueous ammonia solution between zinc electrodes b, the greatest possible current density, which entails a large hydrogen evolution on the negatives and repeated polarity reversal of the electrodes. In each period, as a result of the simultaneous formation of hydrogen, more zinc is dissolved than is deposited.

Finally, the electrolyte according to the invention can also be produced by reacting zinc nitride with water or aqueous ammonia.

The process according to the invention requires no conductive salts and no alkali bases. Of course, traces of ammonium carbonate or other reaction products of aqueous ammonia with the carbon dioxide in the air are not to be mentioned as a lead acid content.

Incidentally, the above-mentioned salt-free zinc hydroxide can only be produced approximately by laboriously washing zinc hydroxide precipitated from zinc salt solution. The solubility of the same in aqueous ammonia increases with the residual salt content.

The electrolyte according to the invention can contain soluble zinc phosphates which are added or originate from a coating of the iron materials to be galvanized with zinc phosphates. Zin phosphate is not a salt that leads to corrosion, but is known as an anti-corrosion pigment. The additives mentioned all increase the electrolytic conductivity of the aqueous ammonia and, under otherwise identical circumstances, enable higher current densities. Zinc phosphate is more soluble in aqueous ammonia and can significantly increase the viscosity of the electrolyte. The admixture of the zinc oxide and / or zinc hydroxide can go as far as paste formation, in particular to prevent the electrolyte from draining off from the damaged area during bath-free galvanizing.

In order to increase the electrolytic dissolution rate of the positively polarized zinc, zinc is used according to the invention in granular form, in particular from roundish granules produced from the melt flow or in the form of a large number of small wire sections. Grains made of fine zinc (99.99% Zn), which are larger than 0.5 mm, are not attacked by aqueous ammonia at room temperature or below, as long as no external electrical current flows. These forms of zinc enable the construction of advantageous hand electrodes.

The low electrolytic conductivity of the electrolytes according to the invention is taken into account by the fact that, in contrast to previous practice, b

Hand electrodes - preferably no electrolyte carriers, which take up the entire cross-section of the power line and have a considerable thickness. There are only in certain cases thin fabrics, knitted fabrics, nets, sieves, perforated foils, nonwovens or the like made from as largely as possible permeable to electrolytes, compatible with electrolytes, wettable by the electrolyte, electrically non-conductive, possibly abrasion-resistant and soft-elastic materials, here abbreviated separators, used, which do not significantly restrict the electrolytic conductivity between positive and negative, because they also allow a particularly small electrode spacing. If wicks are used as the electrolyte carrier, they may not cover the main current-conducting cross-section between the electrodes. It has been found that the known particularly strong tendency of zinc, in the electrolytic

Galvanizing from ammonical solutions does not grow firmly and does not form a layer, but forms loose dendrites or a black sponge, and the tendency towards poiarization until the current comes to a standstill, which can otherwise only be remedied by a strong voltage surge for a limited time, is therefore the easiest and safest way can be countered that friction bodies slide over the separating surface, the necessary speed of movement of which generally increases with the current density. By matching the applied voltage, the current density of the distance and the area ratio of the electrodes, the ammonia content, possibly de electrolyte movement and this rubbing movement, it is possible that on the metal base, in particular iron and zinc or the already existing galvanizing, no black and Loc keres zinc forms or already formed - if necessary with increased speed of movement - detaches again and largely dissolves. In this way, firmly adhering galvanizing can be achieved up to such high current densities, whose further exceeding is no longer possible for reasons of current overheating.

Without the use of friction bodies, galvanizing is only possible at very low current densities. But even then, after hours, dendrite growth and / or polarization occurs until the current comes to a standstill. There are fewer requirements for zinc as a deposition support than for iron: a thin coating of zinc with weathering products such as zinc oxide or basic zinc carbonate does not interfere with the deposition because the aqueous ammonia frees the metallic zinc

REPLACEMENT LEAF sets. Iron rust, on the other hand, can only be covered by the galvanizing to a limited extent, whereby the adhesive strength suffers. Zinc-phosphated iron can be readily galvanized in aqueous ammonia after the electrically insulating coating has dissolved.

A prerequisite for the current flow and the area-wide deposition is that the electrolyte wets the negative base. It has an advantageous effect that aqueous ammonia can saponify and wash away greasy soiling. Aqueous ammonia is a good wetting agent. It can e.g. To wet polyethylene so that we can use this material for the manufacture of hand electrodes. The rubbing movement can do the rest. In principle, the iron surface must also be metallically clean in order to achieve a firmly adhering, uniform and area-wide galvanizing. Without the rubbing movement, a strong hydrogen evolution spontaneously sets in on the black zinc that is immediately deposited at a higher current density. Adequate movement completely or almost completely dissolves black zinc. A hydrogen evolution means loss of electricity yield and danger of hydrogen embrittlement of a steel base. Rapid movement prevents or at least minimizes the development of hydrogen. In the bath process e.g. Felt strips, in the rotating drum also a moving bulk material to be galvanized, e.g. iron wire pins, work yourself. In the case of dip-free galvanizing in electrolyte-filled hand electrodes, the mouthpieces of the same are preferably used as rubbing elements, which consist of electrically non-conductive material.

Various hand electrodes have been found to carry out the method according to the invention and in particular the repair galvanizing which is the task. Common to all is an integrated space that holds a limited amount of the electrolyte. This is designed so that as little ammonia as possible can outgas. In addition, if the hydrogen evolution is kept low, the consumption or loss of electrolyte is small. Therefore, the amount of electrolyte and the electrolyte space can be small. Otherwise, the hand electrodes are easily refillable. After the hand electrode has been filled to the brim with electrolyte, the mouthpiece is placed as flush as possible on the surface to be galvanized with light pressure so that it is wetted by the electrolyte at the place of application. If the current density is limited to approximately 3 A / dm ² zinc end face of the positive, it can be galvanized for a long time without movement. For this purpose, the hand electrode can be fixed in the correct position with an iron binding wire and with the help of a permanent magnet.

With larger current densities, on the other hand, the hand electrode is guided so quickly in the frictional contact over the surface to be galvanized that the black zinc does not form or at least largely dissolves again immediately after the electrical current is switched on.

Preferably, the electrolyte vessels of the hand electrodes are designed so that they are airtight - apart from the open mouthpiece. So you have the general form

Bechers, without restricting this term to the circular cylindrical shape. If the width of the cup mouthpiece is limited to approximately 8 mm, it is possible with such hand electrodes to use the same in every room, i.e. Also galvanize the undersides and vertical side surfaces, because the electrolyte runs out when handling the filling or after the flush fitting, because it passes through the top

REPLACEMENT LEAF voltage and the atmospheric pressure free hanging liquid acid. If the mouthpiece has an oval shape, the "width" is to be understood as the smaller diameter.

The electrolyte vessel includes not only the space between the electrodes, but also a resume that can also receive and release electrolyte. This reserve space is - also without the use of carrier substances for the electrolyte - mainly gap-shaped and the gaps are up to 3 mm wide. When galvanizing surfaces with the mouthpiece directed downwards, small hydrogen bubbles that may rise or the air trapped when they are placed on top (if the filling is not filled to the brim) collect at the top of this gap, without the internal zinc positive losing contact with the electrolyte. The loss of electrolyte in the hand electrodes is limited to the amount that remains on the entire surface to be galvanized and is more or less evaporated on it as a wetting layer, as well as the mostly very small amount that results from the electrolyte being displaced by the usually very low hydrogen evolution . When galvanizing bottom views, i.e. with the mouthpiece pointing upwards, the hydrogen bubbles leave the mouthpiece laterally outwards. In the case of galvanizing vertical surfaces, the current-carrying cross-section is correspondingly reduced by gas accumulation, and it is only necessary to replenish it in the event of larger gas accumulation, which prevents the flow of electricity or reduces it too much. It is therefore advantageous for the galvanizing of vertical surfaces to bevel the mouth piece and put it on in such a way that the gas bubbles can withdraw upwards into the open or into the spare compartment from the mouthpiece space. As already mentioned, the evolution of hydrogen can be achieved by moving the hand electrode faster and by reducing the current, e.g. by increasing the electrode gap, who minimized the. It was found that a strong intermixing in the electrolyte space, which preferably has no flow resistance in the form of the known electrolyte carrier but is free, is caused by the rubbing movement, which serves the zinc ion transport and thus counteracts the competing hydrogen separation.

If the mouthpiece is covered by a sufficiently fine-meshed separator, the electrolyte will not leak, even if the mouthpiece is a few cm in diameter, regardless of the spacing, even if the mouthpiece is placed on the surface to be galvanized and then moved. The better the wetting and mechanical tension of the separator, the greater the retention capacity of the separator. For example, a knitted nylon stocking stretched over the edge of a cylindrical cup can carry a hanging column of 10% aqueous ammonia with a diameter of over 9 c of the cup rim. Such large diameters are, however, forbidden in practice due to the power supply and the dissipation of the current heat and because of the shock sensitivity. The separators can at the same time ensure that the granular zinc filled in does not fall out, as does the electrolyte. Of course, the separators must be made of non-conductive material if they come into contact with the positive and the negative at the same time.

If the zinc positive has the shape of a cup, e.g. are known from dry cell batteries then it can serve directly as an electrolyte vessel. So that the open side of the cup can serve as a mouthpiece, all that is required is a border made of electrically non-conductive material, which projects somewhat. At least from a mouthpiece width of about 8 mm, the coverage by a Se

REPLACEMENT LEAF parator necessary, which can also represent the electrically insulating border itself. The cup may then contain granular zinc without losing it. Of course, the cup - also to enlarge the zinc solution area - can also contain other loose or solid zinc internals that are in electrical contact with the cup. If the electrolyte space is not only open at the bottom, but also open at the top, slit-shaped, free and so closely formed that, due to its capillarity, the electrolyte fills up to a considerable height when the electrolyte is soaked in, the electrolyte will run downwards when the wetting contact is flush directed mouthpiece on the surface to be galvanized, but the split pillarity ensures restraint. Such electrodes can be made very narrow and are therefore suitable for galvanizing in narrow places. Gas bubbles can escape upwards into the open. Since wetting and outgassing losses occur during the movement, they are refilled every few minutes by briefly soaking them up.

It has been found that mouthpieces made of soft, elastic and abrasion-resistant material give very good galvanizing results when used as the rubbing electrode. The paint in the vicinity of the damaged area is not damaged. Zinc that has already been deposited will not be abrasively removed. In the simplest case, the mouthpiece of this type consists of a tube made of ammonia-resistant and abrasion-resistant soft rubber. Rubber glides smoothly and effortlessly on the wetted surfaces. no porous materials are used in the manufacture of the mouthpiece edges because they are not sufficiently abrasion-resistant and too blunt when moving and because they promote ammonia outgassing.

For the purpose of processing larger, also corrugated and curved surfaces, several small Han electrodes are bundled so that the mouthpieces of the individual hand electrodes sit on the surface to be galvanized and at least in the case of curved and corrugated surfaces are also mutually parallel, so that at the same time all Mouthpieces with the surface in constant contact This can be achieved in the simplest case by bundling with a rubber band that is so tightly stretched around the entirety of the individual electrodes that they experience the necessary bundling, but that the rubber band is also sufficiently loose is so that each individual electrode bundle can adapt to the surface contour as a result of gravity, manual operation, pressing on a foam pad, etc. If the radius of curvature is not too small and only 3 individual electrodes are combined, e.g. a spherical surface can also be machined with a rigid bundle.

The simplest, most cost-effective and most widely applicable hand electrode of the present invention consists of a section of a zinc wire which, on the one hand, forms a gap-like reserve storage space for the electrolyte with a soft-elastic sheathed tube and protrudes somewhat beyond the wire and forms the mouthpiece here, and the cavity on the other hand , ie is closed between the hose and the zinc wire, and the other end of the zinc wire is connected to the electrical line and the positive pole of the direct current source. The closure and sealing of the gap space is preferably carried out in the simplest manner by a second hose on which the hose and in which the zinc wire are difficult to move. This second hose, in addition to its extension, can provide the contacting of the clamped, stripped end of the lead wire with the zinc wire and can further serve to support the lead. The tightness and an adjustable The electrode gap can be ensured by additional means such as a screw hose clamp or a rubber band, which can be easily loosened or tightened as required. The two hoses can also be combined in a uniform molded rubber body, which can be equipped, for example, with sealing lips against the zinc wire. Instead of fixed internals made of zinc, the zinc cup electrode can also contain granular zinc or zinc wire or zinc tube sections of the same length, which are arranged so as to be loosely movable parallel to the casing wall, and which are in electrically conductive contact with the cup. A resilient material placed on the inner cup base, for example high density polyurethane foam, ensures that the end faces of the inserts on the mouthpiece press against the mouthpiece separator so that this automatically follows the contour of the surface to be galvanized.

In order to avoid damage to the Separato drawn over the sharp edge of the zinc cup electrode by this edge, the latter can be covered by an aluminum foil of e.g. 0, mm thickness can be defused. It has been found that in the case of empty, i.e. only electrolytically filled zinc cup electrode there is no wear on the separator fabric if its protruding edge is squeezed between the outer wall of the zinc cup and the mouthpiece hose and the latter jumps little. In another embodiment, the electrolyte vessel consists of a soft rubber or soft plastic body, which not only contains a zinc wire positive and the lead, but also has space for granular zinc or longer zinc wire sections that are in electrical contact with the lead, the latter being movable parallel to one another are and can follow the surface contour via a separator

An advantage over the cylindrical zinc cup electrode is that the electrolyte vessel can be reversibly deformed to form a gap in the case of zinc grain filling, so that narrow throats or gaps to be galvanized can also be achieved, and that special external insulation is unnecessary. In the case of filling with the longer zinc wire sections, the elastic vessel can also take over the function of the spring insert. A coarser sieve tray is sufficient as separator for this filling. The one for a finer

The finely meshed separator required for zinc grain filling can be used with the more wear-resistant sieve bottom, e.g. perforated vessel bottom, can be combined, the fine-meshed separator is preferably arranged on the inside.

The fine-meshed separator can also be at the bottom of a bag which contains the granular zinc and in which the feed line, preferably a zinc wire, is inserted and the bag has plat in the electrolyte vessel. The feed line is inserted airtight into the vessel. The vessel can be composed of several parts.

The hand electrodes described in detail in claims 33 and 34 are characterized in addition to great performance, flexibility and rapid interchangeability of the separator fabrics. The capillary electrode already mentioned with free, only electro-filled gaps and not covered

Mouthpiece is advantageously made from a piece of zinc sheet as a positive, which is partially surrounded by an electrically insulating sheath that forms capillary wetting gaps with the sheet. The shell slightly protrudes below the sheet and forms the narrow, gap-shaped mouthpiece. The cover is preferably made of hard polyvinyl chloride and is made airtight against the outstanding sheet metal preferably by air-self-vulcanizing silicone material. With this seal, it becomes

REPLACEMENT LEAF it is sufficient that the electrode can also be used for galvanizing undersides, because without the seal, the wetting-friendly aqueous ammonia will follow gravity. When filling by soaking, you must ensure that the air escapes by slanting the mouthpiece and pointing upwards in between. German patent 34400 describes a brush electrode which consists of a narrowly wound zinc sheet, the gap distance being determined by inserted bristles, d emerging from the winding roller in a brush-like manner. By installing it in a zinc cup, it is made usable for lower teeth.

Contains the electrolyte vessel, preferably a zinc cup, zinc in the form of parallel displaceable Zinröhrchen, the mouthpiece-side openings carry slightly projecting Isolierkö by, so they can serve as spacers and as rubbing elements against the surface to be galvanized, so that a separator is unnecessary.

In the end, a solution was found that made use of the possibility of porous and capillary-active electrolyte carriers such as soft-elastic open-pore foams, tissue packs and the like. However, without using these less abrasion-resistant materials too much by friction and without impairing the current path too much , and without zinc short-circuits forming in them: In a zinc cup, the insulating mouthpiece of which is again formed by an overlaid and slightly protruding hose, there are fitted those carrier materials that protrude what, but which come into contact with the hose nozzle on the Fläc to be galvanized compressed and pushed into the cup. These wick-like materials adapt to the shape of the surface and supply the annular space between the zinc cup rim as a positive and the surface to be galvanized as a negative with electrolyte. The mainly current-conducting annulus is essentially not used by these carrier materials. Despite the low electrode spacing, the overall height of the foam can be very large, and thus the electrolyte absorption capacity as well as softness and conformability can be very large without the electrolytic conductivity and the leic activity of the rubbing movement of the mouthpiece being appreciably impaired.

The galvanizing according to the invention is not dependent on compliance with certain formulations and narrow working conditions. The ammonia content of the aqueous solution can vary within wide limits. The maximum electrolytic conductivity is approximately 10% by weight of ammonia. Handling with aqueous ammonia of this concentration can be done without odor. The current densities that can be used are also not critical and within a wide range variable current densities from 5 to 50 A / dm ^{2 of} active zinc surface are practicable with moving electrodes. At higher current densities there are problems with the dissipation of the current heat. The electrode spacing results from the separator thickness and, in the case of the uncovered hand electrodes, from the fact that short circuit v should be avoided. If you are working with 12 volts and the current density in stationary operation is to be limited to a maximum of 3 A / dm ² , an electrode spacing of approximately 25 mm is necessary if you do not want to switch on a special series resistor. The method according to the invention works at any room and outside temperature.

REPLACEMENT LEAF In order to limit the current at a given voltage of the motor vehicle battery, ma can replace the long lead wire, which is necessary in order to be able to reach all points of the vehicle, in whole or in part by a resistance wire in order to save a special series resistor

An environmentally friendly simplification is that the galvanizing does not have to be washed a after the end of the electrolysis, but it suffices to wipe dry or to dry in the air.

The properties of the galvanizing of fine zinc on iron and on zinc according to the invention are summarized in claim 45. All zinc parts mentioned can consist of fine zinc and / or impure zinc and / or alloyed zinc.

The described designs of the devices and of the method can be applied to other metallic substrates such as copper, nickel and tin in a manner analogous to that for iron, zinc and galvanized iron

Similar to zinc, copper can also be used with an oxidized surface.

The particularly ductile and wetting-friendly zinc coatings obtained by the present process are suitable as lubricant carriers for mechanical deformations of the metal base.

Examples

In the examples which follow, which are intended to explain the invention further, without restricting it thereto, functionally analogous parts are provided with the same number designation. This is intended to illustrate the common principle.

It means: 1 zinc parts = positive

2 = parts of the cup-shaped electrolyte vessel

3 = parts for sealing 1 against 2

4 = lead wire with fastening parts

5 = surface to be galvanized = negatives 6 = separator and fastening parts

7 = lacquer layer

8 = iron wire

9 = permanent magnet

10 = rubber band, 11 = wetting gusset 12 = resilient buffer, 13 = adhesive film, 14 = wick.

example 1

Galvanizing steel with a stationary, small, very simple hand electrode and with aqueous ammonia as the starting electrolyte The hand electrode according to Fig. 1 consists of a wire section (1) made of fine zinc (99.99%) with a diameter and 40 mm length, a soft and elastic one and transparent molded body (2, 3) and a stranded wire (4). The molded body on the one hand protrudes from one end of the zinc wire by an adjustable length (d) and forms the open and 5 mm wide mouthpiece through which commercially available ammonia is filled as a starting electrolyte with an ammonia content of 10% by weight and that of the zinc wire and filled the shaped body cylindrical and slit-cylindrical cavity

The molded body, on the other hand, encloses the zinc wire tightly and airtight, and its extension (4 'presses the stripped end of the strand against the zinc wire. The extension supports the insulated strand further elastically and prevents it from kinking. The molded body can also be fitted with two matching hose sections (2 and 3) of φ 2.8 x 1, 3 x 25 and φ 5 x 0.4 x 35 mm. Surface tension and air pressure as well as capillarity ensure that the electrolyte does not leak in any position of the electrode when handling, except in the case of sudden acceleration, very strong deformation of the electrolyte vessel or when vacuuming with, for example, absorbent paper.

The electrode, which is filled to the brim and air-free, is applied vertically and flush to the damaged area (5) of an ia kized (7) steel sheet, which has been removed from rust and paint residues by scratching with a steel nail, with a slight pressure by hand and flush with the mouthpiece sets on, whereby the electrolyte wets the bare area. A molded iron wire (8) and a permanent magnet (9) hold the electrode in this position.

The stranded wire is conductively connected to the positive pole and the steel sheet to the negative pole of a dry battery of approximately 1.5 volt terminal voltage. If d = 4.5 mm, a current of 1 mA flows immediately and remains fairly constant over the entire electrolysis period of 1 hour. The current flow can also be recognized by a magnifying glass by the fact that small gas bubbles rise from the damaged area. They collect at the upper end of the gap and take 5 mm in height after 1 h, corresponding to 62 m of hydrogen gas. The temperature is 15 ° C. The current loss due to hydrogen gassing would be 62/602 = 10%, because the 1.4 mA times 3600 s would develop 602 mm ³ H2 of 15 ° C. D

Current density is 1.4 mA / 7.0 mm ² = 2 A / dm ² , based on the end face of the zinc solution electrode.

During the electrolysis period, the small amount of electrolyte corresponding to the amount of hydrogen formed flows out at the edge of the mouthpiece. The electrolyte is not refilled. Apart from this small amount of runoff, there is no loss of electrolyte. Since the mouthpiece closes quite tightly, no appreciable amount of ammonia evaporates. There is therefore no odor pollution.

After removing the electrode, the area is wiped dry with absorbent paper. The galvanizing is light gray, matt, when viewed under a microscope, fine-grained-metallic-crystalline and fully opaque and glittering, it is ductile and after rubbing with a rounded steel tool, it is fully shiny,

Steel stylus can be scratched, highly adhesive (bending and shear test), sharply delimited by the edge of the mouthpiece or by the paint rim. The deposition thickness is 10 μm, it can be increased by lengthening the electrolysis time, but eventually dendrite growth or polarization with current standstill can occur. The electrode can be used not only on horizontal, but on surfaces of every contour and space. Fig. 2 illustrates the application on a lower view throat (5), the mouthpiece adjusts from 2 and allows galvanizing down to the depth of the throat. In this F, however, it must be carefully placed air-free. Gas bubbles can leave the mouthpiece and the kehie laterally outwards. If the zinc wire is pushed back further, so that d becomes larger, which is favorable with the Geomet, the current flow and the gas development as well as the current loss decrease.

In particular when galvanizing repairs on the motor vehicle, the existing 12 volt battery power source can be used with the advantage that each damaged area is connected to the negative pole. With a series resistor of 10 kOhm, the current can be limited to 1.2 mA. Example 2

Galvanizing iron with moving, smaller. Hand-held rubbing electrode and 10% aqueous ammonia. Amperages greater than approximately 2 mA, corresponding to 3 A / dm ^{2 of} zinc end face, cannot be achieved with the hand-held electrode, which is described in detail in Example 1, because it deposits spongy black or dendritic zinc and the evolution of hydrogen becomes significant. Much higher currents and separating capacities are possible if the hand electrode b is moved, the mouthpiece of the electrode being rubbed lightly over the surface to be galvanized when it is used by the electrolyte as flush as possible back and forth or rotating. In order to achieve the same good galvanizing as on horizontal top and bottom views even with vertical walls, a beveling of the mouthpiece is practical. As a result, the Glasbläs Chen can be made to disappear from the mouthpiece in this position, in which this can be derived outwards (strand end directed downwards) or - preferably - inwards upwards (strand connection nac directed upwards).

Table 1 provides guide data on the achievable currents I as a function of the electrode distance d at 12 volts, using an aqueous ammonia as a starting electrolyte with an ammonia content of approximately 10% by weight, and at a temperature of 15 ° C. In addition, the time t is given in minutes after which a refill of the aqueous ammonia is necessary or opportune.

The highest achievable current of 100 mA is not

recommended because the heat is so great that a mouthpiece made of soft PVC loses its elasticity and strength and becomes sticky. In addition, the refilling time and the galvanizing current yield are poor. Ad = 2 to 4 mm is practically advantageous.

It is necessary to set the hand electrode in motion immediately after switching on the power. Otherwise, the black zinc forms, initially in a thin coating of the iron, then with an excessively voluminous sponge and sometimes conifers growing up to a short circuit between the electrodes. This is associated with very strong hydrogen development. These complications do not arise due to the movement. Black and dendritic zinc can be completely avoided and the evolution of hydrogen reduced so that the refill times shown in Table 1 are achieved. Fresh black zinc created by a short standstill or insufficient movement

REPLACEMENT LEAF can be brought back to solution by - if necessary only temporarily - increasing the speed of movement. The formation of black zinc, like the development of hydrogen, represents a loss of electricity yield for the galvanizing.

The necessary speed of movement increases with the current density. With d = 2 to 4 mm and 40 to 10 m, high-quality galvanizing can be achieved if sufficient movement is carried out by hand. That soft

The mouthpiece does not cause any damage to the intact paint around the galvanizing when moving. In addition, the 10% ammonia synthetic resin varnish does not attack at all and an existing galvanizing only to the extent that it is favorable for the adhesion of the new deposition.

The galvanizing achieved can be easily painted after drying. The minimum electrolysis time should be about one minute per cm ² .

Since the zinc electrode is encapsulated and the wire is insulated, there is no risk of an external cure. The movement is sure to avoid the internal short circuit. A series resistor is not required.

In order to be able to carry out repair galvanizing on the motor vehicle, an approximately 8 mm long, thin, flexible strand is used, which is connected to the positive pole of the vehicle battery by clamping the stripped bare end between the iron pole clamp and an applied holding magnet.

Example 3 Bundling of hand electrodes

In Fig. 3 four electrodes are shown in plan and in side view, which are loosely bundled by the rubber block (10) and placed on the curved surface (5). If a slight pressure is exerted on the electrodes by hand, the electrodes adapt to the curvature by placing the Mun pieces of the electrodes 2 and 2 'lower than that of 2 "and 2". The mouthpieces deform somewhat on the one hand, on the other hand they form wetting gussets (11) with the filled electrolyte.

A spherical surface can be galvanized with 3 bundled electrodes, the mouthpieces of which lie on a smooth surface; they can therefore be bundled together so that they cannot move.

Such bundles make galvanizing faster than with individual electrodes and are advantageous when galvanizing larger areas.

example

Zinc oralia separator hand electrode with soft PVC molded body

In Fig. 4, a zinc wire section (1) of 3 mm in diameter is airtight and tight in a molded body (2, 3) made of soft polyvinyl chloride. The 16 mm wide circular mouthpiece of the molded body is covered with 2 layers of polyester fabric (6) as a separator, which is attached to the outside of the molded body with adhesive tape and has a layer thickness of 2 times 0.125 mm. The interior of the molded body is filled with zinc granules (1 ') made of fine zinc (99.99% Zn) with a grain size of 0.5 to 2 mm.

10% aqueous ammonia is pipetted onto the upward-pointing mouthpiece until it reaches the edge and has fully wetted the separator (1.6 ml).

REPLACEMENT LEAF The electrode can be used in any position. Under current flow, it must be moved quickly who the. The current density at 12 volts is approx. 50 A / dm ² mouthpiece area. Cover a 3 x 3 cm ² area i with 3 µm zinc coating in 3 minutes. There is no refill. The thin sheet iron underlay heats up considerably. After use, the electrode is placed on the absorbent paper with the mouthpiece, since the remaining electrolyte sucks off. The electrode can be used again at any time. However, the fabric is a wear spare part.

In order to galvanize very narrow and wavy surfaces, the molded body on the mouthpiece can be pressed into a gap with your fingers, see longitudinal section and plan in the lower part of Fig. 4. The separator and granules emerge in a bead-like manner.

If the electrode was first used on the horizontal and has already lost electrolyte for wetting and then should be used for bottom-view galvanizing without refilling, it is also recommended to press the mouthpiece together, as this will push out the electrolyte and it must be readily available on the mouthpiece. The narrow gap mouthpiece, which is placed on the hole with one of the two corners, is also recommended for galvanizing small holes.

Otherwise, the loosely clamped fabric adapts easily to any mountainous and tired surface contours, and the large scatter also ensures the galvanizing in the depth of threads, into which no electrode fits. With only one layer of the polyester fabric of 0.125 mm normal layer thickness, 100 A / dm ^{2 is} sufficient. Then the heating by the current is so strong that the galvanizing must be interrupted after 1 minute.

Due to the use of zinc granules, which have a large surface area, and the strong current heating, the highest galvanizing performances are achieved with such electrodes.

Example 5

Granule double separator hand electrode

In Fig. 5 the thin-walled, slightly conical, cup-shaped rubber container (2) together with the soft, matching rubber stopper (3) forms the electrolyte container, inner diameter 26 mm. The bottom of the rubber cup is perforated. The textile fabric (6) is on the inside, which is fixed by the rubber plug. The zinc wire (1) is passed airtight through the plug, which is in electrical contact with the granule filling (1 ') and has a positive polarity. The electrolyte is applied with the polyethylene bottle pipette to a bottom hole up to the edge.

When galvanizing from below, the cup is pressed together a little to make good wetting contact between the electrodes. The movement of the cup base as a mouthpiece is flush with the negatives, the mouthpiece can follow the surface contour and is most easily guided in a spirally rotating manner with changes in direction.

150 mA at 12 V, corresponding to 105 A / dm ² total area of the hole cross sections, are achieved with a floor thickness of almost 2 mm and a fabric thickness of 0.13 mm. The separators are wear-free.

REPLACEMENT LEAF Example 6 Power Current Hand Electrode

An electrode that brings 1.5 amps at 12 V with 10% aqueous ammonia is shown in Fig. 6 ge. It consists of a rubber tube (2) φ 28 mm by 2 mm wall thickness, which, together with the two-layer tissue separator (6) and the rubber stopper (3), forms the electrolyte container in which the granules (1 ') and the zinc wire (1 ) are located. The tissue separator is clamped between the hose 2 and a rubber hose (6 ') φ 28 times 0.5 mm. Flat textiles can be used as a separator, diameter 95 mm. The electrode has a good grip and is also suitable for rough hands.

Example 7

Zinc cup wire bundle hand electrode

In Fig.7 the separator (6) is made of strong, soft elastic, coarse mesh polyamide (Lycra fibers) with a layer thickness of 0.6 mm using the rubber tube (4 ', 6') over the mouthpiece of a zinc alloy cup (0, 3% bei and cadmium) of 13 mm diameter and 48 mm length g. The hose is also used for the external electrical insulation and for contacting the cable (4). The sharp edge of the mouthpiece is covered with aluminum foil 0.1 mm thick so that the knitted separator (6) cannot be injured. On the bottom of the cup there is a tight polyurethane foam pad (12), which removes 10 zinc wire sections φ 3 mm (V) against the separator, so that it can follow the surface contours (5.5 ', 5 "). (13) is an insulating adhesive film .

With 10% aqueous ammonia, 200 to 300 mA (= 42 A / dm total surface area of the zinc wires) are achieved at a voltage of 2 V. One filling of the electrolyte is sufficient for 5 minutes of galvanizing. An injection syringe is practical for the introduction of the electrolyte.

With zinc granules (fine zinc 0.5 to 2 mm grain size) instead of the zinc wires and three-ply fine-mesh polyester fabric with a total thickness of 0.4 mm, 400 to 600 mA (= 100 A / dm ² mouthpiece cross section) are achieved.

Instead of the zinc wire sections (1), zinc bite tubes can also be used, in particular those in whose mouthpiece sides plastic wedges are crimped, which, like the enveloping hose (4 ', 6'), protrude beyond the zinc end faces and the distance to the surface to be galvanized (5) guarantee and make a separator obsolete.

Example 8 Wick Electrode

Over a beaker made of alloyed zinc (0.3% lead and cadmium) φ 13.3 mm x 0.4 x 46, Fig. 8 (1, 2), i a soft PVC tube (2 ') φ _t = 13, wall thickness 1.5 mm, length 50 mm, pulled, which stripped the

Press the end of the lead wire (4) against the cup, electrically isolate the cup from the outside, al

Handle serves, and especially forms the edge of the mouthpiece by the hose protruding from the cup edge u almost 1 mm. The soft, elastic, open-pore foam (12, 14) is flexibly fitted into the cup, which in the decompressed state protrudes over the edge of the mouthpiece. The foam soaks up the electrolyte. When the mouthpiece is placed on the surface to be galvanized, the foam of this surface adapts to its contours by receding accordingly, Fig. 8 below flat surface (5).

The foam soaked in the electrolyte wets the surface to be galvanized and the zinc wall, in particular the edge of the zinc cup, and ensures electrolytic conduction between the cup positions and the negatives (5).

It is advantageous over the known foam tampon electrode, in which a thin foam layer is arranged as an electrolyte carrier between parallel electrode surfaces that de

Foam here is much less stressed by the rubbing movement, that the current path through the foam in the edge area is not covered at all and less so inside that di

Foam thickness is not equal to the electrode spacing, and that fasteners are omitted.

The electrode is suitable in every room. With 10% aqueous ammonia, 125 mA at 15 ° C are achieved.

Instead of the foam wick, you can also use a wick made of textile fibers, especially in the shape of a rectangular piece of woven fabric made of cotton, which is tightly wound into a matching cylindrical wick. Such a wick has an unsurpassed absorption and holding capacity for the electrolyte. Such a wick is not just a particularly long galvanizing process with a filling of 4 m

Electrolyte possible in every room and on edges, etc., but this electrode construction shows a special ability to cover rust scars on steel sheet, which is greatest when ma stays calmly over the rust-scarred area with the electrode for a few seconds, so that a circular circle is full Spot of black zinc becomes visible, and then continues with the movement which then visually makes the black deposit spot disappear. However, the adhesive strength of such galvanizing is lower on such surfaces that are not completely pure metal.

Example 9

Zinc cup electrode without internals In Fig. 9, compared to Fig. 8, the wick is omitted and the zinc cup mouthpiece with one

Textile fabric (polyester, polyamide) covered, the protruding edge of which is clamped between the outer wall of the cup and the inner wall of the tube by means of slipping over the lower 17 mm high tube section. Hose protrusion d = 0.2 mm, textile fabric thickness 0.1 mm. The cup is expediently filled with electrolyte beforehand. It was surprisingly found that such a separator shows no signs of wear after a long period of use and has not been damaged by the unprocessed edge of the zinc cup produced by the extrusion process.

REPLACEMENT LEAF With 12 V, a warm-up time of up to 3000 mA is achieved in every room. Surprisingly, bottom and vertical galvanizing can also take place with partial filling if the separator is occasionally rewetted by briefly turning the mouthpiece downwards. It is beneficial to press the circular mouthpiece into an oval, as this also makes narrow places accessible. The current intensity does not decrease as a result, the current density increases. Because when the electrode stops for a short time, a black ring of the oval zinc rim with a width of approx. 2 mm forms on the negative surface.

Example 1Q Zlnkgranalien-double egg cup hand electrodes

In Fig. 10 the zinc wire (1) is passed airtight through the bottom (3) of a soft rubber cup (2,6 '). The cup contains a stiffer soft PVC hose (2 ', 6 ") of 20 cm inner diameter, 2 mm wall thickness and 20 mm height, the mouthpiece of which is somewhat opposite the rubber rim, and the one with the foam rubber perforated disc (12) The bulging filling with 12 g zinc granules (1 '; 99.99% Zn, 0.5 to 2 mm grain size) is covered and prevented from falling out by a four-layer polyester fabric (6), φ = 58 mm, total layer thickness = 0 , 5 mm, the edges of which are squeezed and fixed in the narrow gap between the cup wall and the tube with a screwdriver, which is easy to do if one presses the thumb on the tissue and the granules. The electrode delivers 0.8 A. After A cooling break must be taken every 1 minute of electrolysis.

The electrolyte hold is good and galvanizing is equally possible in any position. A second rubber cup similar to the outer one can also be used as the inner cup.

Example 11

Cardillary gap hand electrode

A piece of hard polyvinyl pipe with a height and diameter of 15 mm and a wall thickness of 0.8 m is compressed in the heat to a gap of 1 mm in width and fixed in this shape by cooling, Fig. 11 (2). Zinc sheet (titanium zinc) 40 mm long, 17 mm wide and 0 mm thick (1) is tightly inserted into the gap, so that free gaps of 0.2 mm in width are created on both sides of the zinc sheet Zinc sheet are stabilized. The protruding end of the positively polarized sheet, which is electrically insulated by adhesive film (4 ', 13), is sealed against the casing by self-vulcanizing silicone compound (3). The sleeve projects over the other end of the tin plate by d = 0.5 mm and forms the mouthpiece of the electrode. The shell, together with the silicone seal, represents the cup-shaped electrolyte vessel, which has to be refilled approximately every 2 minutes by inclined soaking and air vents with the mouthpiece pointing upwards.

The lower part of Fig. 11 shows a cross section through the electrode. The maximum current when filled with 25% aqueous ammonia is 150 mA. This electrode is particularly suitable for galvanizing in narrow throats and gaps and for every position g.

REPLACEMENT LEAF Example 12

Galvanizing steel with aqueous ammonia-zinc phosphate electrolytes

14 g metaphosphoric acid HPO ₃ and 50 g water are converted into orthophosphoric acid H3P0 by heating to 80 ° C and then 23 g zinc oxide (zinc white red seal quality) are dissolved in it, finally mixed with 52 g 25% aqueous ammonia, which results in a clear, viscous solution arises, which is used as an electrolyte in the hand electrode, construction as in Example 1, Fig. 1, see Table 2.

It can be seen that working conditions have been found in which there is no hydrogen evolution on the negatively polarized steel. This process variant is therefore suitable, e.g. To galvanize spring steel, which is easily brittle due to hydrogen absorption. At the same time, the development of oxygen at the zinc positive can be minimized, so that long galvanizing times can be achieved in stationary operation.

Washing off after the galvanizing has ended is also unnecessary in this electrolyte because, in contrast to the known conductive salts (mostly chlorides and sulfates), zinc phosphate is not a corrosive salt.

Table 2

II \ II - M nute

Example 13

Bathroom ginGes A negatively polarized horizontal iron axis carries a perforated drum made of non-conductive

Plastic. The drum rotates in an iron trough that contains the electrolyte. Zinc sheets are arranged around the trough as fixed positives. The encapsulation has a gas vent. The drum is filled 3/4 with iron wire pins (Nägein) freshly pickled in hydrochloric acid and washed with water. Galvanizing with 10% ammonia as the starting electrolyte proceeds with a moderate current density almost without gas evolution and very evenly. The galvanizing is matt light gray. The dried ones

REPLACEMENT LEAF Wire sticks are dipped in mineral oil and centrifuged. They are served so that they are permanently rust-proof.

Example 14 Periodic Pre-Enrichment Electrolysis

A test tube contains 10% aqueous ammonia, into which 2 zinc electrodes in the form of a wire double, wire diameter 3 mm, are inserted vertically and parallel to each other. is initially electrolyzed with 12 volts. The current increases from 75 to 230 mA in 7 minutes. Zinc is deposited on the negatives as a black sponge. The voltage is reduced to 10 volts and after 5 minutes to 5 volts as the temperature rises. After another 10 minutes, d

Current 300 mA and the sponge threatens to fall off or form a short circuit bridge. It is reversed that the zinc sponge dissolves and a new zinc sponge forms on the new negative. This periodic direct current electrolysis is continued for a few more periods, which become ever shorter, with strong hydrogen evolution taking place on the negatives. Finally, the electrolytic conductivity is measured and according to the invention with others

Electrolytes compared, see Table 3.

Advantages of the invention

After the above detailed explanation of the invention, finally, in part to summarize and in addition, the advantages which it offers compared to the prior art will be discussed in the end.

The invention has shown that in the electrolytic galvanizing on corrosive Sal alkali bases and acids can be completely dispensed with, in the simplest way. As a result, the use of electrolytic galvanizing has only become practical for iron parts that border on Mauerwe masonry mortar, concrete and other porous materials, since it is inevitable that these will be wetted by the electrolyte and soak it up. An electrolyte that contains corrosive non-volatile constituents - and this applies to all known galvanizing electrolytes - would then be the source of a bottom rust that cannot be switched off. But even when galvanizing repairs on motor vehicles, it cannot be ruled out that the electrolyte will get into gaps where it can cause rust damage if it contains corrosive constituents that are non-volatile, and if rinsing down to the smallest residual traces is not guaranteed Electrolyte for galvanizing has been described which contains only volatile (water and ammonia) and inert (zinc oxide, zinc hydroxide) as well as anti-rust (zinc phosphate) components.

REPLACEMENT LEAF It is known (WS Sebborn, Transactions Faraday Society (J. of Cem. Soc.) 29 (1933) 659 bi

663) that a "dilute solution of zinc oxide in excess ammonium hydroxide solution" in de

Electrolysis with "high current density" between static zinc sheet electrodes, sponge zinc deposits, the presentation and investigation of which are the subject of the publication. However, there is no indication that or how galvanizing can be achieved.

Attempts to deposit on zinc have been carried out with ammoniacal zinc salt solutions. The dendritic growth, which interferes with the application, could be avoided by using very low current densities and adding cresoisulfonate for a longer electrolysis time (F. Foerster and K Klemm, Z. Elektrochemie 35 (1929) 409 to 426). There is also no indication of how perfect galvanizing without salts and additives or at higher current densities can be achieved. In addition, the adhesive strength on zinc says nothing about that on iron and other metals.

No special electrolyte is mentioned in the special literature on hand electrodes. Although the rubbing movement is known in this water ("rubbing electrodes"), the fact that in it and in combination with the aqueous ammonia is the key to galvanizing without the use of sait has apparently not been recognized so far.

In fact, only a single hand electrode for electrolytic repair galvanizing a motor vehicle has recently appeared on the market. It corresponds to DE OS 3630919 A 1 (C 25 D 19/00), whereby the positive is not made of zinc and not a solution electrode, but consists of carbon, about 0.3 mm behind the abrasive ring that surrounds it. It works with zinc chloride-containing, strongly acidic electrolyte that is thickened. During the movement of this rubbing electrode, a considerable part of the deposited zinc is ground again - for the purpose of smoothing - so that the current yield is poor. A short circuit is prevented by a built-in series resistor, which, however, limits the usable current strength to approximately 100 mA when using the motor vehicle battery with a 12 volt terminal voltage. The electrode is quite large for this performance (outer diameter 15 mm, carbon diameter 6.5 mm, length 110 mm) and not suitable for narrow spaces. Since there is no zinc solution electrode, the small amount of electrolyte between the electrodes is electrolyzed extremely quickly, and care must always be taken to get fresh electrolytes under the carbon positive. The passage of electricity is hampered by the strong gas formation (hydrogen and chlorine), a viscous foam quickly forms. The zinc chloride is the most corrosive of all zinc salts. A fresh portion of electrolyte is required after just 1 minute.

The electrode according to the invention preferably works with a soft-elastic mouthpiece that does not grind off zinc and does not damage the paint environment of the repair site. The new electrolyte is not only free of salt and corrosion, it does not develop toxic chlorine, but at most a little hydrogen. The electrolyte is hardly used up and in principle only a very thin electrolyte layer is required as a vehicle for the absorption and release of zinc ions. A series resistor is not necessary. The electricity yield is over 90%. The refill times are usually longer than the galvanizing times.

For the first time, the process according to the invention achieves perfect galvanizing without the need to contain a specific recipe, and this even with the commercially available ammonia and the simplest electrodes available in every drugstore. An approximately 10% aqueous ammonia is optimal, but it can also be much more concentrated or weaker, so that the process is inefficient.

T reacts to outgassing of ammonia. Outgassing is also very limited due to the flush-fitting mouthpiece designs. The electrode spacing, the current density, the voltage, the temperature, the area ratio from positive to negative are also variable, all parameters that are otherwise precisely prescribed. Galvanizing without the use of corrosive substances brings advantages not only for repair galvanizing, but also for bath galvanizing. Because the galvanized goods do not have to be washed until the smallest traces of these substances have been removed. The method according to the invention is therefore more environmentally friendly and less expensive. There is also no danger, since corrosive substances are trapped in the galvanizing and later wreak havoc. In many cases, it is sufficient to simply drain the galvanized material and let it air dry. It is also environmentally friendly and inexpensive that the electrolyte consumption is minimal, because the production of every chemical is environmentally harmful. The extremely small amount of ammonia that escapes into the atmosphere benefits agriculture as a fertilizer through the rain and reduces its acidity. That the low electrolytic conductivity of the aqueous ammonia need not be a handicap is demonstrated by the numerous electrolysis devices which are described here and which are competitive

Enable current densities. Aqueous ammonia and these devices form a uniform solution to the inventive problem.

Conversely, the new devices are adaptable and unsuitable for other electrolytes. Just as aqueous ammonia does not attack the fine zinc solution electrode in the de-energized idle state, it does not attack existing and already generated zinc coatings, while the known electrolytes are all aggressive.

The aqueous ammonia dissolves the weathering products of zinc, copper and nickel and therefore exposes the metal base necessary for the electroplating. Since copper and nickel form metal amminohydroxides just like zinc, these metals are deposited analogously to zinc. Without additional oxidizing agents such as Air, hydrogen peroxide, etc. but copper and nickel are not attacked by ammonia, and in contrast to zinc also not with electrolytic current flow. in general, it is not necessary to rinse out the electrodes according to the invention after use. When the zinc oxide and hydroxide which precipitate out and, if appropriate, zinc phosphate dry out, they re-dissolve with the filled-in aqueous ammonia when used again. You can simply place electrodes with the mouthpiece on absorbent paper, which then sucks the electrolyte. When stored in the air, residual ammonia forms ammonium carbonate with the carbon dioxide in the air, but this is a volatile and decomposable salt and is therefore not of a corrosive nature.

The service life of the electrodes is determined either only by the consumption of zinc parts for the galvanizing itself or by the service life of the separator, which is, however, easily replaceable.

Compared to the short-bristled brush electrodes, which are not very supple and sticky, the plastic or rubber mouthpieces according to the invention slide very easily and comfortably on the wetted, wet surface. With the densest and thus the most capillary-active pack, the evenly thick

REPLACEMENT LEAF Round bristles cover this geometrically 91% of the free cross-section, which the present invention does not restrict or only as little as possible.

Long-haired brush electrodes, which work softer than short stiff bristles, are less hard-wearing and, incidentally, hardly practical even for highly conductive electrolytes. It is therefore proposed where to use the brush electrodes, the bristles of which partially. are shorter and electrically conductive (US PS 15

934).

Instead of fine zinc, impure and alloyed zinc can also be used. A preliminary test can quickly determine whether a zinc alloy is suitable for the present process. Compared to the known sponges and foams with an open pore structure as electroly carriers, which take up the entire wire cross-section with a large thickness (tampon electrodes are the advantages of the electrodes according to the invention the unimpeded or only slightly hindered current passage, the abrasion resistance and the avoidance of short-circuit bridges, as they occur due to zinc deposition in the pore passages of the tampon electrodes. As regards the design of the hand electrode according to claim 32, it has compared to d

Hand electrode according to German PS 673 190 the advantages that the electrolyte carrier does not cover all the positives in a thick layer, the electrolyte carrier is nevertheless much thicker and more adaptable, the distance between the electrodes is smaller and the storage capacity for the electrolyte is greater because the electrolyte vessel - apart from that Mouthpiece - is sealed airtight, and that no short-circuit bridges made of zinc form in the carrier, probably because it does not cover the annular main flow path and the soft-elastic foam carrier in the mouthpiece area is in strong movement.

The construction of a brush electrode, in which the hair bundle is in a platinum cup and extends beyond the edge of the same, is described in German GM 81 29 270.8. In comparison z the hand electrodes e.g. According to claims 28 and 32, it should be noted that the protruding brush hairs do not ensure a constant electrode spacing, because, depending on the pressure exerted by Han, they bend and wear more or less, apart from the fact that the volume of the hair bundle and the strong gas evolution on the inert positive leads to disturbances in the current flow.

An open mouthpiece with an otherwise airtight electrolyte vessel has already become known for a handheld electrode which is used "for point-like electrolytic treatment of metallic objects, in particular for polishing and etching" (German PS 1 130 245). However, it is only the narrow mouth through which the used electrolyte, driven by the gas generated during the process, is to escape. It is not a traveling friction electrode and it has no positive solutions. A the nature of the mouthpiece are mentioned above only made the requirements that it should be electrically non-conductive and narrow at points. In contrast, the mouthpiece according to the invention should be as wide as possible and the width is only limited by the opposite stipulation that as far as possible no electrolyte should leak.

If a comparison is made between the capillary-active gap electrode according to the above claim 2 with the pin electrode according to the German PS 34 400, it should be noted that the gap formed by the rolled zinc sheet is filled with brush bristles that the gap width and the electro

REPLACEMENT LEAF guarantee the distance and give the friction effect, while the above-mentioned design of the electrodes according to the invention has free capillary flattening and only a rubbing mouthpiece on the circumference. Furthermore, the electrode according to claim 26 is suitable for galvanizing in any spatial position, which is not the case with the known because its - Similar to painting a ceiling with a brush - the electrolyte can flow out on the handling side because the brush is not encapsulated. Finally, the known electrode is only suitable for larger flat surfaces, while the inventive both for narrow gaps and - bundled according to claim 38 - can be used for contoured surfaces.

The claim 27 includes an improvement of the electrode according to the aforementioned DE PS 3 400 by encapsulating it with a zinc cup, so that it can be used in any position. Few bristles are sufficient as a gap width holder and the bristle protrusions are unnecessary when using the protruding insulator border of the zinc cup rim as a means of maintaining the electrode spacing and as friction elements.

Further advantages of the present invention listed below have already been described in detail above: 1. Unsurpassed simple electrolyte and simple hand electrodes.

2. No electrolyte flow, but the lowest consumption

3. Typical application: repair galvanizing of garage door sills, the galvanizing has worn off or is adjacent to concrete.

4. Hand electrodes that can be used in any position. 5. Substantially free electrolyte space, so there is no difficulty in the exchange of materials and

Current flow through inert electrolyte carriers.

6. Hand electrodes that can be adapted to any surface contour.

7. Thin separators allow a very small electrode gap and the use of granular zinc, which has a high dissolving activity. 8. Very good current spreading, so that galvanizing e.g. Thread recesses is possible.

9. The advantages of galvanizing as a lacquer carrier: no pre-lacquer and no filler required.

10. No abrasive properties of the soft mouthpieces.

11. Absorbent, wick-like electrolyte carriers only to the extent that the power line cross-section between the electrode constrictions remains free, i.e. the electrodes in the most active area are not covered. 12. Use of foam as an electrolyte carrier, which is relieved of abrasion and more adaptable to the surface, and a constant electrode distance is specified by the mouthpiece.

13. The good wetting ability of aqueous ammonia.

14. The minimization of hydrogen gassing. 15. High current efficiency.

16. No polarization with current standstill with the friction electrode.

17. Galvanizing is also possible and cheap at winter temperatures.

18. Coverage of rust scars.

19. Immediate galvanizability of phosphated iron sheets 20. Capillary gap sucks faster than tampon without increasing the electrolytic resistance.

REPLACEMENT LEAF 21. Flexible bundling of hand electrodes for processing larger, even curved surfaces.

22. Use of the galvanizing as a lubricant and lubricant carrier for mechanical deformation.

23. Use and deposition of zinc alloys.

24. No series resistor is required because there is no risk of short-circuit and the electrical resistance can be selected by the electrode spacing.

Literature reviewed

Publications of the German Patent Office of the classes

48 a 5/00, 5/10, 5/70, 5/72, 5/74, 5/76; C 07 D 231/18;

C 25 D 3/02, 3/22, 5/00, 5/04, 5/06, 5/08, 5/10, 5/22, 17/14, 19/00.

Chemical Abstracts 1916 ff.

Gmelin, Handbook of Inorganic Chemistry, Bank Zink, Hauptwerk 1924 and supplementary volume

1956, publishing house chemistry. Etc.

REPLACEMENT LEAF

Claims

1. A process for the electrolytic production of adherent and opaque coatings made of zinc on negatively polarized metals, in particular iron and zinc, by means of an aqueous ammoniacal electrolytic solution and a positively polarized electrode made of zinc, characterized in that an electrolyte is used which at the start in essentially consists only of pure aqueous ammonia, or that it already contains the electrolytic reaction products (zinc aminohydroxides), or that these are added before or during electrolytic galvanizing, in particular by admixing zinc oxide and / or zinc hydroxide or / and powdered zinc, or are produced by prior electrolysis of the aqueous ammonia solution between zinc electrodes at high current density and high hydrogen evolution at the negatively polarized zinc electrode and repeated polarity reversal of the electrodes.

2. The method according to claim 1, characterized in that the electrolyte is made from zinc nitride and water or aqueous ammonia.

3. Process according to claims 1 and 2, characterized in that the electrolyte contains no conductive salt or alkali bases.

4. The method according to claim 1, characterized in that the ammoniacal electrolyte additionally i contains soluble zinc phosphates, which are either added or / and from the coating of the iron materials to be galvanized with zinc phosphates.

5. The method according to claims 1 to 4, characterized in that excess zinc oxide and / or zinc hydroxide is added for the purpose of thickening, which can go to paste consistency.

6. The method according to claims 1 to 5, characterized in that the electrical voltage, di electrical current density, the electrode spacing, the area ratio of the electrodes, the ammonia content and the relative movement of the electrolyte and / or of friction bodies on the required for larger current densities Negatives or on the already formed zinc plating should be set in such a way that no black or loose zinc forms on the negatives, be or already formed - if necessary with increased movement - detaches again and largely dissolves and on the negatives a firmly adhering and opaque Galvanizing forms, so that preferably only little or no hydrogen is produced on the negative in the case of iron and zinc as negative.

7. The method according to claims 1 to 6, characterized in that in the moving electrolyte bath be moved to be galvanized bulk material acts as a friction body.

8. The method according to claims 1 to 6, characterized in that when electrolytically bath-free galvanizing m electrolyte-filled hand electrodes whose mouthpieces made of electrically non-conductive material serve as Rei body.

REPLACEMENT LEAF

9. The method according to claims 1 to 4, characterized in that a hand electrode is used, the space between the electrodes contains only the electrolyte, that the electrode is placed on the surface to be galvanized so that it is wetted by the electrolyte, and that the electrode is held in this position, especially when galvanizing iron with the help of a magnet

, 5 th and an iron wire, a current density of approximately 3 A / dm ² zinc end face not being exceeded.

10. hand electrode for performing a bath-free electrolytic galvanizing with the electrolyte according to claims 1 to 5, characterized in that at the same time a. the electrolyte vessel is cup-shaped, 10 b. the cup-shaped vessel consists of positively poled zinc and / or receives such. c. the edge of the open cup mouthpiece is made of electrically insulating material, d. the electrode spacing is 0.1 to 5 mm, e. the volume of the vessel is greater than the volume between the area of the open mouthpiece and the nearest zinc area (electrolyte reserve and gas storage),

15 f. the edge of the mouthpiece can be placed flush on the surface to be galvanized, g. the electrolyte-wetted edge of the mouthpiece can serve as a gentle rubbing element, h. the electrolytically wetted area of the positively polarized zinc is larger than the area of the open one

Mouthpiece, i. the cup-shaped vessel - apart from the open mouthpiece - is hermetically sealed, 20 j. the electrolyte liquid is prevented from running out when the mouthpiece is directed downwards, preferably by the fact that the filled electrolyte liquid - in particular without the use of voluminous absorbent electrolyte carrier substances - forms a free-hanging liquid column, which at least with open mouthpiece widths over 8 mm with an electrolyte-permeable, from Electrolyte-wettable, thin separator such as woven fabric, 25 knitted fabrics, mesh, sieve, perforated film, fleece or the like made of electrically insulating material

Stabilization is covered in one or more layers on the open mouthpiece.

11. The method according to claims 6 and 8 by means of a hand-rubbing electrode according to claim 10, characterized in that it is filled with the electrolyte and is placed on the surface to be galvanized so that it is first wetted on the seat parts and that the electrode after

30 Switching on the electric current is moved so quickly in the frictional contact that no black zinc is deposited on the surface or this largely dissolves again.

12. Hand electrode according to claim 10, characterized in that the zinc lies behind the mouthpiece - by 0.1 to 5 mm.

35 13. Hand electrode for performing the method according to claims 1 to 4, characterized gekenn¬ characterized in that the zinc is wholly or partly in lumpy and freely movable form and is prevented from falling out of the mouthpiece by a separator defined in claim 10.

REPLACEMENT LEAF

14. Hand electrode according to claim 13, characterized in that the zinc is in granular form, in particular special round granules or angular, short wire sections.

15. Hand electrode according to claim 13, characterized in that the zinc is in the form of zinc wire or zinc tube sections which are displaceable in parallel with one another.

16. Hand electrode for performing the method according to claims 1 to 5, characterized in that the electrolyte vessel contains zinc in the form of mutually parallel displaceable zinc tubes chen, the mouthpiece-side openings 0.1 to 5 mm projecting insulating body, di as spacers and friction elements serve.

17. Hand electrode according to claims 10 to 16, characterized in that the electrolyte space is not completely filled by electrolyte carriers at least in the region of the closest electrode spacing and preferably contains no electrolyte carriers at all or only the separators defined in claim 10 or the insulating bodies mentioned in claim 6 .

18. Hand electrode according to claims 10 to 17, characterized in that the edge of the mouthpiece consists of soft-elastic material which is electrically non-conductive.

19. Hand electrode according to claims 10 to 18, characterized in that the electrolyte vessel is formed of electrically non-conductive material and contains zinc as a wire, rod or sheet, since these parts or their leads are inserted airtight through the wall of the vessel.

20. Hand electrode according to claim 19, characterized in that the electrolyte vessel consists of soft-elastic material.

21. Hand electrode according to claims 19 and 20, characterized in that in the cup-shaped

Electrolyte vessel a zinc wire is inserted through the cup bottom, that a gap is formed between the zinc wire and the side cup wall, that the gap is up to 3 mm and the open mouthpiece, which is preferably beveled, up to 8 mm wide, and that the mouthpiece is unconditional .

22. Hand electrode according to claim 21, characterized in that a shorter piece of a tight-fitting hose is pulled about a piece of a zinc wire approximately in the middle, and that a sleeve tube seals on this one hand and on the other hand projects beyond one end of the zinc wire.

23. Hand electrode according to claims 21 and 22, characterized in that the zinc wire in the B cherboden or in the tight-fitting piece of hose is displaceable, and that the Dic activity by means of tools such as screw, rubber band or the like. can be guaranteed, the zwec

Moving the wire can be loosened or tightened as required.

24. hand electrode according to claims 13 to 15 and 19 and 20, characterized in that d mouthpiece carries a separator sieve, which can also be part of the electrolyte vessel by z. the bottom of which is perforated, that the electrolyte vessel can consist of a cup part and a stopper, that the end faces of zinc wire sections are stored on the sieve bottom, which are arranged in parallel and preferably mutually parallel, and fill in free space and whose diameter is larger than the holes or mesh of the Siebb dens, or that the sieve bottom is covered with a sufficiently fine-meshed separator and d zinc filling is granular.

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25. Hand electrode according to claim 14, characterized in that the granular zinc is combined in a textile bag into which the electrical lead leads, and that the bottom of the bag can be a separator.

26. Hand electrode according to claims 10 and 19, characterized in that zinc is surrounded by narrow gap-shaped free spaces, that in particular sheet-like zinc with the electrically non-conductive electrolyte vessel forms capillary-active narrow gaps which are not covered on the mouthpiece side, and that as a sealing material for the introduction parts of the zinc into the vessel made of preferably hard polyvinyl chloride, preferably air-self-vulcanizing silicone mass is used.

27. Hand electrode according to claims 10, 19 and 26, characterized in that a positively polarized zinc cup receives an electrode according to DE PS 34 400, which is in electrical contact with the cup.

28. Hand electrode according to claims 10, 12 and 18, characterized in that the zinc cup to be filled with electrolyte is covered on the mouthpiece with a separator, preferably textile fabric, which is fixed in that its protruding edges between the zinc cup and the which elastic border is constrained on the mouthpiece, and that the border preferably protrudes slightly compared to the separator surface, so that the separator is protected against fretting at least on flat and concave surfaces to be galvanized

29. Hand electrode according to claim 28, characterized in that the mouthpiece of a cylindrical zinc cup is deformed from the circle to the oval.

30. Hand electrode according to claims 28 and 29, characterized in that the zinc cup contains additional zinc parts.

31. Hand electrode according to claims 10, 15, 28 and 30, characterized in that in the zinc cup parallel to the wall of the zinc wire or tube sections are loosely movable and which are in electrically conductive contact with the cup that on the cup bottom resilient material is placed, and that the resilient material presses the wire and tube sections against the separator.

32. Hand electrode according to claims 10 and 12, characterized in that the zinc has the shape of a cylindrical cup, the open side of which is the mouthpiece, the electrically insulating border of which projects somewhat that the cup contains a wick, preferably made of soft elastic open-pore foam or from textile aggregates, in particular from cotton, that the

In the decompressed state, the wick preferably protrudes somewhat over the edge of the mouthpiece, so that the cup and the wick take up the electrolyte, and that during the galvanizing the wick preferably leaves the annular space between the zinc cup rim and the corresponding counter surface to be galvanized free.

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33. hand electrode according to claims 10, 14 and 20, characterized in that the cup-shaped electrolyte vessel made of soft rubber with tightly inserted zinc wire a fitted stiffer hose, e.g. made of soft polyvinyl chloride, the mouthpiece of which is slightly recessed relative to the mouthpiece of the rubber cup, and which has a gap with the inner rubber cup wall, that preferably a disc made of soft-elastic foam rubber lies on the cup base, that the rest of the hose space is plump with granular to the edge of its mouthpiece Zinc is filled because its protruding edge is forced into the gap and thus fixed.

34. Hand electrode according to claim 33, characterized in that the fitted hose is replaced by a fitted rubber cup.

35. Electrode according to claims 10, 12, 18, 8, characterized in that a hose or a plurality of hose parts is tightly pulled over a zinc beaker as an electrolyte vessel in its entire length, which firstly electrically insulates the zinc beaker from the outside, secondly that over the Beche rand forms a slightly protruding friction mouthpiece, which can also serve to fix a separator, and thirdly enables contacting with the supply line according to claim 36.

36. Hand electrodes according to claims 10 to 35, characterized in that the cylindrical, in particular wire-shaped or cup-shaped zinc electrode or the feed line is connected to the feed line by a hose which tightens over the stripped end of the strand and the zinc or d intermediate feed line is slipped on, and which in the case of the zinc wire in its extension can serve as a flexible support for the strand running outwards.

37. hand electrode according to claims 21 to 23 and 36, characterized in that cup u

Hoses represent a uniform molded body, in which the zinc wire is sealed so that it is difficult to slide, preferably by means of sealing lugs in the molded body.

38. The method according to claim 6, characterized in that a plurality of manual electrodes are bundled for processing larger, also corrugated and curved surfaces, and that the bundle can allow parallel movement of the individual electrodes, preferably by not being too tight

Rubber bands.

39. The method according to claim 6, characterized in that the hand electrode is placed on the surface to be galvanized and possibly moved so that the gas formed during the electrolysis can either withdraw to the outside or collect in the vessel part of the electrode remote from the mouthpiece.

40. The method and electrodes according to claims 1 to 39, characterized in that the tines are made of fine zinc or / and impure zinc or / and alloy zinc.

41. The method according to claims 1 to 40, characterized in that with aqueous ammonia v 5 to 25 percent by weight, preferably about 10 wt .-% at current densities of 1 to 100 A / dm ² , v preferably 10 to 50 A / dm ² Zinc end face, a distance between the edge of the mouthpiece and zinc v

0.1 to 25 mm, preferably 0.2 to 0.5 mm in separator operation and in the capillary gap electro (claim 26) and approximately 3 mm with a free mouthpiece, and at voltages of preferably around volts.

42. The method according to claim 41, characterized in that the electrode distance is adjusted depending on the applied electrical voltage so that the desired electrical current density is achieved and no series resistor is required.

43. The method according to claim 41, characterized in that the e.g. The long lead wire required for the galvanizing of repairs on the motor vehicle with its power source consists entirely or partially of insulated electrical resistance wire in order to save a special series resistor.

44. The method according to claims 1 to 43, characterized in that the galvanizing after completion of the electrolysis is not washed off but only wiped dry or air-dried.

45. Galvanizing on iron and zinc produced according to claims 1 to 44, characterized in that it is of adherent, opaque, largely scratchable with a steel stylus, largely metallic, macroscopically on the surface mostly smooth and matt, by vigorous rubbing with steel tools to shine Coming and such only microscopically rough condition is that it is penetratingly penetrated by water and solvent-based paints, and that the paints - as well as enamel and sintered coatings - are thereby well anchored and require no further priming.

46. Method and devices according to claims 1 to 44, characterized in that they are applied to the galvanizing of galvanized iron, copper, nickel and tin.

47. The method according to claims 1 to 46, characterized in that the zinc coatings obtained are used as a lubricant and / or lubricant carrier for mechanical deformations.

48. The method according to claim 4, characterized in that iron coated with zinc phosphate is treated like uncoated metallic iron, i.e. without prior mechanical removal of the

Phosphate coating.

49. Process and devices according to claims 1 to 44, characterized in that an ammoniacal electrolyte is used which, in addition to zinc aminohydroxides, also contains nickel aminohydroxide and / or copper eramminohydroxide.

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