DE3248932T1 - ELECTRODE FOR CATIONIC, GALVANIC COATING AND METHOD FOR COATING USING THE ELECTRODE - Google Patents

Description

Toyota Jidosha Kabushiki Kaisha
Toyota-shi, Japan

Cationic Electroplating Electrode and Method of Coating Using the Electrode

The invention relates to an electrode which is formed of a sintered Metalloxidmasse to be used for coating by cationic _{electrodeposition>} and to a process for plating using the above-mentioned electrode.

In recent years, corrosion resistance has been improving of coatings for bodywork is becoming increasingly important. The measures for corrosion resistance and rust protection are in terms of base materials, chemical treatments, paint type, the way the paint is applied, the body designs from different angles and

VII / 22

Dresdner Bank (Munich) toilet 3939 844 Baye <Viiieinsbnnk (Munich) Klo 508 941 Postal check (Munich) toilet 670-43-804

-K- DE 2880

1 was searched. The technique of electroplating coating Electrolytic plating has proven itself to be the most effective and economical process exposed, so for example the inner surfaces

5 from complex and hollow structures for example

Corrosion resistance is imparted to automobile bodies and those parts on which spray coating is not easily practicable. Thus, electroplating is used extensively nowadays.
10

In conventional methods of electroplating, mostly anionic electroplating paints were used because of the low cost of the paints so used,

! the relatively low temperature for burning in the

I ^{deleted 15} and because of the relatively low cost of doing so

! ■ related equipment used. In the process of

\ Anionic, galvanic coating is however the

Object to be coated that is used as an anode

"\ is applied in the course of the electroplating

} 20 dissolves, while the cathode is made of, for example, iron, which! immersed in the galvanic cell or the paint,

j is not resolved. Accordingly, the effectiveness of the

\ chemically formed coating decreased and the thickness

% of the coating that is on the surface of the

The object to be coated is formed

j | small amount. Accordingly, as the increase has progressed

] of corrosive environmental influences that

I do not use conventional janionic electroplating

ii is necessarily sufficient. That is why

? 30th

the technique of cationic electroplating

I have found increasing recognition recently.

; ■ '■■; To carry out the cationic, galvanic coating,

I a water-insoluble polyamine resin, R-NH _{0 is} formed,

■■■;! ■ 35 ■ ^ά

ι by a primary or secondary amine to the glycidyl

--Sr- DE 2880

-ft-

group of a water-insoluble resin such as bisphenol-type epoxy resin is added to cause ring cleavage, and then an organic acid such as acetic acid or lactic acid as a neutralizing agent (water-soluble agent) AH is reacted with the above-mentioned water-insoluble polyamine resin whereby an aqueous resin R-NH _{3 is} formed as shown by Reaction Formula I below.
10

R-NH ₂ + AH ■ £ R-NH ₃ ⁺ + A "" (I)

In a cationic, galvanic paint solution that formed from the above-mentioned water-soluble resin and optionally a crosslinking agent and a pigment becomes, an object to be coated becomes negative charged electrode (hereinafter referred to as "cathode") immersed. Separately, a positively charged one becomes Electrode (hereinafter referred to as "anode"), for example, made of stainless steel or carbon in the same Solution immersed. An electric current is generated between the cathode (the object to be treated) and the Anode allowed to flow.

When the electric current flows through, they migrate positively charged paint components electrophoretically in the solution and are upon reaching the object (Cathode) coagulates and deposited by electrical Charges are given off as shown by the following equation (II), creating a water-insoluble Coating is formed on the object.

2H _o 0 + 2e "> H ₀ + 20H"

^{2 2} (II)

OH "+ R-NH"> R-NH + HO

35 ^d dd

• "I *"

DE 2880

Metal ions are dissolved at the anode, which is made of a metal such as stainless steel and at the same time oxygen is generated, as illustrated by the formulas (III) and (IV) below.

M _ »M ^{n +} + ne" (III)

40H ~ ——— »O ₂ ? + 2H ₂ O + 4e ~ (IV)

If the anode consists of carbon which is not a metal, no dissolution takes place according to formula (III), but oxygen is generated by the reaction according to formula (IV). Accordingly, the carbon of the anode itself is oxidized. Therefore, with the lapse of time, the anode loses its weight ^ and cracks may be formed, particularly when the anode is made of a metal, the metal ions released from the anode are mixed in the solution. When the paint component is coagulated and deposited, these metal ions are simultaneously coagulated and separated off ² ^ on the article. The coating that is subsequently formed therefore suffers from poor corrosion resistance or has a rough coating surface. If the anode is formed of carbon, the oxidation causes fine particles of carbon to flake off the anode into the solution. If the electroplating with the carbon particles contained in the solution is continued, granular protrusions protrude from the surface of the coated object, with the result that the coating produced is

has a ring-like appearance and poor corrosion resistance.

As materials for the anode, the release of

Avoid metal ions, high grade stainless steel can 35

SUS-316 or the like, or a noble metal such as platinum

DE 2880

be used. In addition to the high cost of stainless steel, if only to a small extent, it is becoming inevitable Metal ions, released. The precious metal is too expensive to be in question for practical use come. Carbon and graphite have the problem that they are poor in processibility.

The invention relates to the solution to the aforementioned Problems that occurred in the prior art, where a material for the anode is provided as a solution, which consists of a sintered mass of a metal oxide that is insoluble or hardly soluble and an electrical one Head is. Furthermore, a specific structure of the anode is made using a sintered mass created a metal oxide that is little deformable and can be processed.

The inventive method for cationic galvanic Coating consists in placing an object to be coated in a paint solution , pairs of electrodes are used so that they oppose the object in the paint solution and a DC voltage is applied between the object and the pair of electrodes, whereby on the surface of the Object a cationically formed electroplating coating is produced, and the method is characterized in that, as a material for the above mentioned pair of electrodes a sintered mass of an electrically conductive metal oxide is used.

The sintered mass of metal oxide used for the pair of electrodes, ie the anode _; is used in the present invention has ample electrical conductivity. Typical examples of the sintered mass are magnetic iron oxides with the formula FeO-Fe ₃ O ₃ , which under the

- "& - DE 2880

The name magnetite is known and magnetic metal oxides with the formula MO · η Fe ₂ O ₃ , which are known under the name ferrites. In the above formula, M denotes a divalent metal ion, such as Mn, Ni, Cu, Mg, Co or Zn.

Because of the intended purpose, the sintered metal mass to be used according to the invention must be electrically conductive.

In the case of the magnetite mentioned above, there is no serious problem in electrical conductivity, since the specific resistance is sufficiently low. In the case of ferrite, the resistivity is in Quite changeable depending on the composition. In general, ferrites have ferromagnetism.

The ferrites of this type, which are used in the electronics industry for various transformers, permanent magnets,
Storage elements and magnetic elements used in television, radio, sound and telecommunication devices have different specific resistances in a wide range from 100/2 cm to 100 M fl-cm. In the case of ferrites, some, which have high specific resistance values, can have the disadvantage that a drop in current and the development of heat occur and are therefore not suitable for use as an anode. The ferrite to be used as the anode material in the present invention must have a low specific resistance level. With ferrite, the electrical conduction is mainly caused by electron jumps between Fe and Fe. For the production of ferrite with a low specific resistance value, the composition of the ferrite must therefore have an excess amount of Fe ₂ O ₃ . The metal oxide sintered mass which is used according to the invention as the anode for the cationic galvanic coating has, as desired, a composition such as

-ff- DE 2880

that the value of the volume resistivity, which is determined according to the specification of ASTM D P57-61,

5 r

at no more than 10 Ji ^- cm, preferably no more than 10 -Q'cm and in particular no more than 0.3iZ · cm, at a temperature of 20 ° and at a load voltage of 20 V. In particular, the sintered metal oxide composition has a spinel crystal structure in which iron oxide and metal oxides other than iron oxide (such as NiO, MnO, GoO, MgO, CuO, ZnO and CdO) are combined in a specific mixing ratio. In other words, the sintered mass comprises iron oxide and other metal oxides than iron oxide, the metal oxide, which is different from iron oxide, in a proportion of 5 to 40% by weight, preferably 20 to 40% by weight and in particular 40% by weight. %, based on the total molar content of the sintered mass _/ is present.

In the case of magnetic iron oxide has a composition of 30 to 50% Fe and 50 to 70% Fe is _{o Q} 0, preferably 35 to 45% FeO and 65 to 55% Fe ₃ O ₃ is desired. A sintered mass of 44.0% FeQ, 53.5 % Fe ₂ O ₃ , 1.0% SiO ₂ , 0.9% Al ₃ O ₃ , 0.5% CaO and 0.1% MgO is used as one of the most preferred metal oxides are used. In the case of magnetic iron oxide, in addition to FeO and Fe ₃ O _3, 4 to 6% SiO ₃ , 0.1 to 1.0% CaO, MgO or AlpO _{3 can be} contained.

The corrosion resistance property of the above mentioned magnetic iron oxide and ferrite as anode surpasses the property of conventional materials for anodes such as stainless steel (SUS 304, SUS 316, SUS 317) or carbon such as graphite. In particular Ferrite is suitable because it hardly dissolves.

The metal oxide electrodes are known and the manufac-

.... .. .. .- .. .. 32A8932

'■ - ■ ■ - * €> - DE 2880

- 3-

. * ■ management procedures for this are also out, for example

Japanese Patent Publication No. 30 151/1977 and

35 394/1976 known. The electrode according to the invention can

j therefore using the aforementioned magnetic

I 5 see iron oxide or ferrite according to conventional methods

j ren can be generated.

: J

; As an example of such a manufacturing process

ΐ 5 to 40 mol% of at least one of the metal oxides with the

10 Formula MO (M means Mn, Ni, Co, Mg, Cu, Zn or Cd)

'Added 95 to 60 mol% Fe ₃ O ₃ . The heating will

■ '.-. in air at 800 to 1000 ⁰ C for 1 to 3 hours after

; Mixing carried out in a ball mill and the

j chilled mass is crushed to a fine powder.

■:! 15 The fine powder is molded under pressure or it becomes

! a sludge mass produced by adding water to the fine powder

1, which is cast molded into a mold after casting

! or the sludge mass is made by a suitable method

»Ι such as extrusion to a desired shape of a molded body

I shaped 20 pers. The molded product thus obtained becomes

', I. in an inert gas with a content of less than 5

? Vol .-% O ₀ , for example in an N ₀ or C0 _o atmosphere

> ο

I re sintered at 1300 to 1400 C for 3 to 5 hours,

I and then gradually in an inert gas with a content

.., I 25 of less 0 _? Volume, for example in a N "or COp-Atmos-

5 sphere is gradually cooled, whereby the desired electrical

i de is obtained. The electrode thus obtained has a

; | relatively high mechanical strength and has a special

if specific resistance is within the foregoing

1 30 mentioned area falls.

; Although Fe _o 0_ and MO (where M is the above

Has meaning) as a starting material instead of
Fe ₀ O ₀ can be used, at least Fe, FeO 35 and / or Fe ₀ O can be used in such an amount

• ti

DE 2880 -40-

that the amount is 95 to 60 % when it is calculated _{as Fe 3} O _3. Instead of the oxide, for example MO, it is also possible to use a compound, for example a carbonate or oxalate, which forms the oxide when heated.
5

The magnetite electrode can be obtained in a manner similar to that mentioned above. For example, pure Fe., 0 / granulated as a starting material together with polyvinyl alcohol as a binder and then formed, followed by a solid-phase sintering in an inert atmosphere, such as COP gas is carried out at 1200 to 1300 ⁰ C, the desired electrode is obtained.

The anode according to the invention made from the sintered metal oxide mass alone can be in the form of a flat plate

angular column or a round rod can be used. To form a large surface area of the anode and to Avoidance of a non-uniform current distribution due to the volume resistivity of the metal oxide sintered mass arises in the electrode and which is possibly self-induced if a high current intensity is applied flows and to avoid possible breakage of the anode, e.g. due to mechanical shock loads, the anode can be designed so that the sintered mass of metal oxide is formed into a cylindrical tube, one end of which is closed, and in the cavity of the cylinder body a metal element such as an aluminum core, iron core, a stainless steel core, a copper core or twisted copper wires in particular a stainless steel material by means of an electrically conductive material such as lead, solder, or conductive resin (e.g., an epoxy resin with a Content of silver or graphite, which is commercially available under the trade name "Dotite").

.

DE 2880

When stainless steel is used as the core material in the above-mentioned structure, it is possible to use a Temperature rise or a non-uniformity of the current distribution excluded when a high current flows. Because of the characteristic of

Stainless steel, metal ions are leached out only to a small extent, even if the sintered mass is broken.

If the object to be electroplated has a large, complicated structure, and if even the inner surface of a box-like structure
must be coated thoroughly and uniformly,
as in the case of a car body, the plating tank itself becomes bulky and the anode to be used therein also becomes large. The installation of the anode only in the side part of the electroplating cell does not lead to a sufficient current distribution and a sufficient thickness. It has been found that another anode, which is additionally installed on the bottom surface of the plating cell, is necessary.

If larger dimensions of the anode are desired to overcome the aforementioned problems, it is expedient, - since the manufacture of a sufficiently large tube from the sintered metal oxide mass is difficult - to form a large anode by making a tube with a horny closed end and a tube with both ends closed are, produces, then produces a rod-shaped metal element as the core material, the core material inserts into the two tubes and the core material with the tubes through an electrically conductive material firmly .ι— connects. The connection between the two Tubing is conveniently effected by placing a rigid plastic tube around the adjoining areas of the

engages both pipes by bridging them and by the rigid plastic pipe with the two pipes the sintered mass by means of a rigid one filled in between Resin is combined into one unit. 5

The on the bottom surface of the galvanic cell too installing electrode can be obtained by a coated lead wire connected to a magnetite or ferrite electrode and a tube made of stiff Resin is arranged around the electrode so that both part of the outer periphery of the tube from the sintered Ground as well as part of the lead wire is covered j while the stiff plastic tube between. Liaison offices, the space between the stiff art

fabric tube and the connection point with the thermosetting

Fill in resin that is allowed to cure to form a bridge and, if necessary, rings or caps made of stiff synthetic resin having at the opposite ends of the stiff Plastic tube are screwed on. If the electrode, 20th

is constructed as described above, the core materials of the lead wire and the electrode not attacked by the galvanic liquid in the galvanic cell. Accordingly, the electrode can easily in an arbitrary position within the cell

are set.

ErfindungsgemäO, the surface of the electrode are increased by the metal oxide in a 03sinter Ie

tubular shape is brought. Another advantage 30th

consists in the fact that the tube into which a core is roughly made Copper or stainless steel is inserted, can be reinforced.

If the electrode consists solely of a sintered metal oxide 35

exists, the temperature around the electrode terminal will rise when a current flows and it can therefore happen that the current distribution from the electrode

1 O # · '■ If · *

** - * 32Α8932

I because of the electrical resistance of the coating

ι liquid and the specific volume resistance of the

^r '. 5

> Metal oxide itself becomes uneven. Inventive

According to me, this disadvantage does not arise because the electrode

ί [contains a metal core. The combined structure of the

ΐ electrode according to the invention leads to the further advantage

■ \ part that the manufacture of an electrode with large

! 10

Dimensions as desired is possible.

■ * In the case of the electrode according to the invention with a sheathed

I th lead wire is the outer circumference of the sheathed

I lead wire covered with metal oxide sintered, the

* 15

. is in contact with the liquid. The connection

between the lead wires is covered with resin. DA / · ago, a suitable number of electrodes to a

t suitable location of the galvanic cell in any

ι and can be arranged in a simple manner. Accordingly it is

20th
'? possible an excellent power distribution and a

'to obtain the desired layer thickness, even in the case of

Coatings in which parts with large dimensions, such as body parts _7, are to be coated.

25th

Brief explanation of the drawings:

Fig. 1 is a side cross-sectional view showing a device for carrying out the method for the cationic, 'galvanic Be-30

* layering clarified.

Fig. 2 is a side cross-sectional view showing another device for performing the

Procedure for the cationic, galvanic Be-35

layering illustrated.

DE 2880

Fig. 3 shows an elongated cross-sectional view of a further device for carrying out the method for the cationic, galvanic coating.

4 shows an elongated cross-sectional view illustrating an electrode according to the invention using a metal element as the core material.
10

FIG. 5 shows a side cross-sectional view of the electrode of FIG. 4.

6 and 7 are cross-sectional views illustrating an electrode according to the present invention, which

is formed solely from a sintered metal oxide mass.

8 shows a cross-sectional view of an electrode according to the invention in which the sintered Me

Talloxidmassen are connected to each other.

FIG. 9 shows a cross-sectional view of an essential part of the electrode of FIG. 8.
25th

Fig. 10 shows a front view of an electrode connected to a lead wire.

FIG. 11 shows a cross-sectional view of an essential part of the electrode of FIG. 10.

FIGS. 12 and 13 show cross-sectional views of the electrode shown in FIG. 10 which are used for the
practical operation is provided.
35

~ ** ~ DE 2880

The invention is explained in more detail below with reference to the examples and comparative examples. the Value for each volume resistivity in in these examples and comparative examples was obtained by measuring at 20 C and at a Voltage of 20 V was performed according to the procedure of ASTM D 257-61.

Example 1 (A) Manufacture of the anode plates

Anode plates with a length of 160 mm, a width of 50 mm and a thickness of 4 mm were sintered Manufactured by using, as raw materials, magnetic iron oxide and the ferrites A to D with different values the volume resistivity were used. The values of the volume resistivity of the so sintered masses (anode plates) obtained are in

20 of Table 1-2.

Table 1-1

Electrc ^ Component
3de - ^^^ Fe 2 ° 3 30th NOK MnO ferrite A. 53 Mole% 37 Mol% 17 mol% ferrite B. 53 Mol% 45 Mol% 10 mol% ferrite C. 55 Mol% 40 Mol% 0 mol% ferrite D. 60 Mol% Mol% 9 mol%

-Vf- ^κ · DE 2880

Fine powder is produced by a component selected from the group of NiO and MnO is mixed together with Fe _o 0 _Q at the indicated in Table 1-1 least ratios, wherein the mixing operation is carried out for example in a ball mill. The mixture is then heated in air at 800 to 1000 ° C. for 1 to 3 hours and the mass obtained in this way is comminuted after cooling. After adding water to the fine powder, a slurry is obtained, which is extruded into a desired shape of the molding material. Thereafter, the molded mass is at 1300 to 1400 ° C in an N ₂ atmosphere with a content of less than 2 vol .-% 0 ".3 to

Sintered for 5 hours and cooling is done in
Np gas with a content of less than 0 volume is gradually carried out in order to obtain the desired electrode.

(B) Electroplating

(1) Painting manufacture

An epoxy type polyamino resin having a resin base number of 80 was ^{neutralized with acetic acid bl} s to a neutralization equivalent of 0.5 and dissolved in deionized water containing ethylene glycol monoethyl ether acetate to form a varnish. The so-

Paint was put together with three parts soot and

6 parts talc, both parts each to 100 parts of the
Solids content of the paint based, dispersed in a mill for 20 hours, a cationic, galvanic paint was produced. The paint thus produced was diluted to a solids content of 12% with deionized water.

(2) Coating process

As illustrated in Fig. 1, a container was made with ^:

the paint solution 3 described above

DE 2880

¹ fills. The container consisted of a tank 1 made of steel plates with a dimension of 200 mm in length, 110 mm
Width and 150 mm depth, which was provided with a vinyl chloride resin liner 2. Thereafter, the sintered 5 ferrite plates (pairs of electrodes) of 4.4 prepared as described in (A) above were fixedly installed in the bath with an area of 10 mm

..; their respective upper ends above the surface of the

Survived the bath while an object to be coated

\ 10 stand 5 was immersed in the above-mentioned bath.

Ά Item 5 was zinc phosphate treated

4 steel plate (a cold rolled steel plate SPC with a

ί size of 150 χ 50 χ 0.8mm made in advance with Bonderite

■ | il # 137 was supplied by Nihon Company

:] 15 Parkerizing Co., Ltd.). The two pairs of electrodes 4,4

I, became symmetrical around the object 5 in the treatment

• Arranged so that on the object 5 a coating

4 was formed uniformly. This pair of electrodes 4.4

j was connected to a lead wire 6. Furthermore, was

I 20 the object 5 via a connection 8 with a current

] source 7 electrically connected, which in turn is connected to the

"% above mentioned lead wire 6 was connected. While

! the bath is kept in the state described above

I, current was flowing under the following conditions

I left to eat. The pair of electrodes 4,4 were positively

I charge and used as the anode and the object 5 as the cathode i, with the result that the cationic paint I was deposited on the surface of the object 5.

f 30 (electroplating conditions)

^I I o bath temperature

ν ο distance between the electrodes

ο anode area

35

I ο cathode area

ο DC voltage ο Current flow duration

30 ° C. mm 2 and 160 V 150 cm 2 75 cm 75 V 130 3 min

DE 2880

^A After the electroplating, tap water: was sprayed at 20 C under a pressure of 0.5 kg / cm to wash the coated article for one minute. The baking was then carried out at 180 ° C. for 30 minutes. The galvanic coating <-

■ ■ ■■. 'r

was similarly made using anodes f

made from different raw materials! were conceived. The initial current value and the thickness of each coating were determined. The results are in: Table 1-2 shown.

Comparative example 1:

In a manner similar to Example 1 (B), electroplating was carried out using carbon (graphite electrodes _{.. F} manufactured by Tokai Carbon Co., Ltd., sold under the trade name of "G 152") and SUS 316 stainless steel as Materials for the pair of electrodes (anodes) carried out. Using the above anodes, the initial electroplating current value and the thickness of each layer were determined.

The results are shown in Table 1-2.

ω ο

to ο

cn

Table 1-2

CD CD G

fr. «« ♦

t m * ■ i

DE 2880
Example 2

(A) Manufacture of the anode plate

In a manner similar to Example 1 (A), anode plates using magnetic iron oxide and Ferrite D manufactured.

(B) Test method for determining corrosion resistance

A 5% strength by weight diluted with deionized water Acetic acid solution and a 5% by weight solution of lactic acid diluted with deionized water were mixed in a ratio of 1: 1 mixed. The resulting mixture was placed in a similar container with a resinous liner used as used in Example 1 (B). In the bath, the paired anode plates that, as described in (A) above, arranged in such a position that an area of 10 mm of the respective upper ends protruded above the bath surface and a cold rolled. SPC steel plate was used in it as a cathode. The electrolysis was carried out under the following conditions:

The anode plates were checked for corrosion resistance checked by measuring the weight loss of each anode. The amount of resolution so determined is in the Table 2-1 shown.

³ ^ (electrolysis conditions) ο bath temperature ο distance between the anodes ο surfaces of the anodes and cathodes

ο direct current
35

ο duration

30 ° C and 0.01 A / dm 1000 h Inter- 150 mm alternatively at use 75 cm ² vallen of 1 h ■ 5 A / dm ² det 100 to

ω
ο I. to
cn to
O cn 2-2 I—>
O II table III NiO (Mol released amount
(g / A. year) IV 40 Resistance (Jl. Cm) Ferrite D V 30th ■. ■
0.3 Ni-ferrite VI 20th ν 0.07 ■ '.; ■ ... Ki-ferrite 10 .;: "■; ■ 0.03.; ./ ': ..;> νί Ni-ferrite 5 ■. : ^; ' 0.02 V: v ^ Ni-ferrite 2 0.01 Ki-ferrite 43 0.005 Ni-ferrite 45 3.0 Ferrite C 0.5 90.0 1.0 . 2.0 4.5 7.0 12.0 0. 3 below 0.1

DE 2880

As can be seen from Table 2-2, an NiO content provides from 5 to 40 mol% better results.

Example 3

In a galvanic coating process with an electric field, as illustrated in FIG. 2, a
Container with a lining 2 made of vinyl chloride on the inner surface of a tank 1 made of steel

is provided with a paint solution 3 filled. This coat of paint essentially has the same composition as described in Example 1 (B) is. The anode plates 4, 4 * and an object 5 to be coated were immersed in the paint solution 3, the anode plates 4,4 'with the anode of a DC voltage source 7 with the help of a lead wire 6 and the object 5 to a cathode with the power source were connected via a connection 8, in this example the anodes were made as a blank electrode structure, as shown in Fig.

1 is illustrated, or used in the form of an electrode structure covered with a membrane. The latter
Structure was obtained in particular by setting up a diaphragm box 9 around the anode plate 4 ', placing an ion exchange resin membrane 10 in the plane of the diaphragm box 9 so that it lies between the anode plate 4' and the object 5 to be treated ^ and the box 9 with it Diaphragm water 12 was filled. If the anode is formed in such a diaphragm electrode structure, the galvanic coating is produced with an improved quality because the leached material is prevented from mixing in the paint solution even if the material of the anode is somewhat leached.

3 illustrates the position of the anode in the longitudinal direction

DE 2880

a galvanic cell. In the figure, the reference number 4 denotes an anode in the blank structure and the reference number 4 'an anode in a diaphragm electrode assembly.

The electroplating was carried out according to the example 1 (B) under the conditions described there in a similar manner Way done. The materials used for the anodes in this example are stainless steel (SUS 316), Carbon (graphite) and ferrite D are used.

The anodes made from these materials were in electroplating for a period of about one year. The weight reduction each anode plate was measured. The results are shown in Table 3. This table shows that the anodes made using ferrite suffered the slightest weight loss. In terms of the quality of the electroplating was found that using the ferrite anodes produced coatings did not pose any problems. The coating made using stainless steel anodes was found to have a contained increased content of Fe ions and a fairly rough skin showed. When using carbon anodes produce layer, a part of carbon fell off and therefore it was found that the paint solution contained finely divided carbon particles, with the result that that the layer produced had a poor appearance.

30th -: i ■:;

DE 2880
Table 3

Anode material decrease in thickness

(mm / year)

Ferrite less than 0.1

Carbon 1.0

stainless steel (SUS 316) 3.0

pj From the above description it is clear that

f ^: '[ the cationic, galvanic

I j coating actually does not dissolve the electrode

I I during the electroplating process because

i «the anode plates using a sintered

'Metal oxide mass were formed, which has an excellent ι ?, \ -

f I have electrical conductivity and that it is therefore

; ■; ■; .. I not possible Y * ^ar 'that ions as an impurity in the

i? I paint solution were mixed in. As the anodes

■■ '■■' 'ti

; J cannot be oxidized by the oxygen present in the

■ i close proximity to the anodes during the electroplating process

, 1 testifies, it was not possible to get the anodes through

■ '■'}. Oxidation has been degraded or partially detached. I 25

I Thus, the paint solution was free from contamination

? '- | with impurity fine particles and the coating formed

I had smooth, flawless skin. As also the anodes

?; were not degraded, they exhibited an increased shelf life

I, eliminating the need for an exchange

■■ '■■ ί 30

> fl falls and there is an economic advantage both

: I clearly result in costs and workload.

35

The following is a typical concrete structure the anodes according to the invention described.

DE 2880 ¹ example 4

FIGS. 4 and 5 show an electrical system according to the invention ^. trode. A stainless steel rod lla was provided with a connection la at its upper end.

The shank of this rod lla of stainless steel was charged with a tube 4a made of a sintered Metalloxidmasse,% which was closed at the lower end and having a U-shaped cross-section by an electrically conductive Mate f rial 13, as lead, solder, or an electrically conductive adhesive covered. Since the sintered metal oxide mass ,, se 4a over its entire inner wall surface with the Ί

Y stainless steel rod lla through the electrically conductive | de material 13 was electrically connected, took place at

of this electrode neither a temperature rise nor a |

Loss of uniformity of current distribution when L a high amperage flows. Because of the properties jii of stainless steel there is no way that the | i sintered mass 4a gives off metal ions even if the sintered mass breaks and the rod is stainless

Steel lla is exposed accordingly.

The cationic electroplating using the electrodes used in the above-mentioned construction with ferrite as sintered metal oxide mass (hereinafter referred to as "ferrite electrodes") can be formed can be carried out in a satisfactory manner according to Examples 1 to 3, as shown by Fig. 1 or Fig. 2 is illustrated.

The above coating operation by cationic electrodeposition was performed using "Power-top U-30 long (one coat of paint, which is produced by Nippon Paint Ltd. Co.) as a color coating at a direct voltage of 250 Up to 280 V at about 1800 mm

DE 2880

1 electrodes performed around per month

• 15,000 sheet steel bodies with an area of

'. 50 sqm as objects to be coated for a total

! he coat from about a year. It was observed

j 5 that both the ferrite electrodes, which are in the blank

I construction were used, as well as those that are in the di-

i phragma container 9 were included, only one very

i showed slight weight loss to the extent that

ι that their diameter decreased from 28 mm to about 27.5 mm ♦

] 10 It was found that the electrodes are still operating

could stay. It was also found that the current from the electrodes was uniform through the entire surface the ferrite rods flow and the electrodes themselves generate little heat and no particular problems with them 15 brought.

For comparison purposes, the coating process was

^ following the procedure of Example 4 using

⁴ repeated by other electrodes. Here were the

20 received the following results:

* 1) When using electroplating

^; of ferrite electrodes was carried out, each

from a sintered metal oxide tube 41 made of ferrite with

'25 consisted of a connection 12, which with its upper end

was connected by an electrically conductive material 14 as shown in Fig. 6, heat was generated at the points where the sintered tube 41 and the terminal 12 were connected and the current division was between

i ■ 30 of the connection side and the free end side of the sintered

Tube 41 different. There was little current flow on the free end face. The decrease in the outside diameter

, after about a year of operation it was on the connection side

a little bigger; the diameter increased from 28 mm to about 35 26 mm.

DE 2880

2) If the electroplating was carried out using ferrite electrodes, each consisted of a sintered metal oxide plate 42 made of ferrite with a terminal 12 at its upper end by a connection 15, which is illustrated in Fig. 7, was similarly at the points Heat generated where sintered plate 42 and terminal 12 joined and the power distribution was different between the terminal side and the free end side of the sintered plate 42. There was only a minor one Current flow on the free end side. The reduction in wall thickness after about a year of operation was on the connection side somewhat larger. The thickness decreased from 5 mm to about 4 mm.

3) When electroplating using SUS 316 stainless steel and ferrite electrodes of the present invention, as illustrated in Figure 4, when anode was performed in a similar manner, the current flow was substantially uniform and the generation of heat by the electrodes themselves was little. However, there was a decrease the outer diameter of the electrodes after about a year of operation is very large, so that the diameter decreased from 16 mm to about 3 mm. Some of the electrodes were even broken because of the sharp decrease in diameter.

4) When the electrodeposition coating was carried out in a similar manner by stainless steel for all anodes SUS 316 has been used, the electrodes were in a similar manner sm fraction as described above under 3). The paint solution contained iron ions to such an extent that partial coagulation of the paint was induced. The coating produced developed a rough skin and was uneven

"* ^ ~ DE 2880

Appearance and poor corrosion resistance. ■.

5) If the electroplating has been carried out in a similar way, using as anode iron SS41 and ferrite electrodes according to the invention with the one shown in FIG.

4 were used together, the iron anode was dissolved and broke in a few days of operation .

6) If the electroplating was carried out in a similar way, using copper, aluminum as anodes and ferrite electrodes of the present invention having the structure shown in Fig. 4 were used together the anodes of copper and aluminum were so exposed that they broke within a few days of operation.

As described above, shows in FIGS. 4 and

The ferrite electrode shown in Fig. 5 does not increase in temperature even when a large amount of current flows, and it provides a uniform distribution of the electric current because this electrode is formed using a stainless steel as a core and the outside of this core is successively coated with an electrically conductive material and a sintered metal oxide mass covered
is.

Since this electrode has stainless steel as the metal core, the properties of stainless steel prevent that the metal core is noticeably dissolved even if the sintered metal oxide mass cracks, for example as a result of shock loads. This electrode provides a coating that does not have a rough skin, caused by the dissolution of copper ions or aluminum ions in the paint or by poor corrosion resistance

■ "" * "'" De 2880

can arise, as in the rebound where the electrode Contains copper or aluminum as a metal core.

Example 5

& '■', ■;, ■, ■

This example shows an electrode formed by connecting the respective ends of tubes, the were made from a sintered metal oxide mass.

Fig. 8 shows this electrode in its entirety. Fig. 9 shows an essential part of this electrode.

A rod-shaped metal member 11 is made of copper, iron or stainless steel. The outer periphery of one end of this metal member 11 is through an electrically conductive member 13 such as lead, solder or a
electrically conductive adhesive, with a sintered mass of metal oxide 4a, one end being closed so that the tube has a U-shaped cross-section and covered with a tube made of a metal oxide sintered mass 4b, which are kept at a distance. A connecting element 16 made of a resin in the form of a jacket is provided around the opposite parts of the upper and lower sintered masses 4a, 4b.

This connecting element 16 comprises a tubular Element 17 made of a rigid plastic, such as a fluorine-containing plastic (for example a plastic that sold under the trademark "Teflon") polyvinyl chloride or nylon, which has the outer perimeters of the opposite Parts of the sintered masses 4a, 4b covered, O-rings 18 made of Teflon, leather or rubber that surround the step sections 17a, 17b are inserted, which are at opposite points on the inner wall of the tubular element 17 are formed and between the element 17 and the

ft · · '

• *

- ■? -2- DE 2880

* Metal oxide sintered mass are inserted and annular Elements 19, 19 made of rigid synthetic resin, such as Teflon or polyvinyl chloride, which have external threads on their outer circumferences 19a, 19a are provided with the internal threads 17b, 17b around the opposite edges of the inside of the tubular member 17 are designed to be screwed. The screw fastening of the rigid plastic element 19, 19, the leading ends of the O-rings 18 are pressed down, so that a solid Contact between the rigid plastic element 17 and the sintering masses 4a, 4b is brought about. After the connecting element in the structure described above has been formed, a liquid, curable resin 20, for example a two-part curable resin of the epoxy type, a polyester resin or polyvinyl chloride sol, which is hardenable, inserted into the cavity between the sintered masses of metal oxide 4a, 4b and the rigid plastic elements 19, 19 is formed, and allowed to cure at room temperature or an elevated temperature. The liquid resin 20 is in the cavity, through the opposite edge surfaces of the sintered masses 4a, 4b, the outer circumference of the metal element 11 and the rigid plastic element 17 is defined, inserted before the rigid plastic elements 19, 19 be screwed in. This resin 20 can be any resin as long as it does not dissolve in the paint.

Because of such a design of the cover with the resin all voids around the connector 16 are filled so that no paint solution gets inside of the connecting element can penetrate. The resin itself is not dissolved in the paint solution. The connecting element 16 has sufficient flexural strength because the adhesive strength of the curable resin 20 and the mechanical strength of the rigid plastic elements

~ * f ~ DE 2880

¹ 17, 19, 19 add up.

The electrodes with the structure described above in which tubes made of ferrite or magnetite as metal oxide sintered masses were used as anodes for two years continuously in the coating process Katicnic electroplating under the same conditions as in Example 4 was used. After that the electrodes were checked. There were no irregularities in the fasteners found. The galvanically formed

Coatings were normal and acceptable.

The connection structure of the two electrodes as provided by the invention is not only applicable to electrodes for cationic electroplating but can also be used in processes other than electroplating.

Example 6

This example illustrates the establishment of a connection to a Electrode with a lead wire. Fig. 10 shows a side view of the electrode and Fig. 11 shows one Cross section of a substantial part thereof.

Numeral 4 is an electrode in which the outer periphery of a rod-shaped metal member 11 made of copper, iron, stainless steel or the like as a core with an electrically conductive material 13 such as lead, solder or an electrically conductive adhesive and a sintered mass 4a made of metal oxide. On the upper one The end of the electrode is a sheathed lead wire 22, for example a 600 V cable, which is connected to a network Polyethylene-insulated vinyl jacket or a vinyl-insulated vinyl jacket, through a connection

35 dung part 21 connected.

~ *? ~ DE 2880

- Sj -

The aforementioned connecting element 21 will be described in detail. The metal member 11 is provided at its upper end with an external thread 11a, to which a pressure connector 24 for connecting the lead wire is fixed by nuts 23, 23. At a pressure portion 24a of the pressure connection part 24, a conductor 26 of the lead wire 22, for example copper stranded wire, which is exposed by removing a sheath 25, is attached under pressure, for example by caulking. In this way, the electrode 4 and the covered lead wire 22 are connected to each other.

A tubular, rigid plastic element 27 made of Teflon, polyvinyl chloride or the like is arranged around the outer circumference of the electrode 4 and the sheathed conductor wire 22 so that it forms a bridge between them. On the side of the electrode 4 of the tubular, rigid plastic element 27, an O-ring 28, for example made of Teflon, leather, rubber or the like, is inserted around a step section 27 which is formed on the inside of the element 27, while the ring with the outer circumference of the Sintered mass 4a made of metal oxide is kept in contact. At the same time, a rigid plastic element 29, which is made of Teflon or polyvinyl chloride in the form of a hollow cap and is provided on its outer circumference with an external thread 29a, is screwed to an internal thread 27b, which is formed on the edge of the inside. By screwing this stiff plastic element 29, the O-rings 28 are pressed on by its head part, whereby a close contact between the stiff plastic outer element 27 and the sintered mass 4a made of metal oxide is brought about. On the side of the sheathed conductor wire 22 is a rigid plastic element 30 made of Teflon or polyvinyl chloride

"*?" DE 2880

is in the form of a hollow cap, and is provided on the outer circumference with an external thread 30a, screwed to an internal thread 27b, which is formed in a similar manner on the edge on the inside.
5

After the connecting element in the above-described Once a structure has been formed, a liquid curable resin 31 such as a two-part curable resin becomes of the epoxy type, a polyester resin or a vinyl chloride sol, which is hardenable, into the cavity between the sintered mass 4a made of metal oxide and the rigid plastic elements 29, 27 and into the cavity through the jacket 25 and the conductor 26 of the covered conductor wire 22, the pressure connection part 24, the nuts 23, the external thread 11a of the metal element 11 and the rigid plastic elements 30, 27 is formed, filled and then at room temperature or at an elevated temperature left to harden. This resin 31 can be any resin as long as it is a liquid or a sol and not is dissolved in the paint solution after curing.

All recesses around the connecting element 21 are filled by the treatment with the above-mentioned resin. In this way it is absolutely impossible for internal parts to be exposed directly to the solution used. In this way, a high electrical insulating property and a high liquid seal can be ensured. When the connector 21 is immersed in the paint solution on the covered lead wire 22, only flows through the sintered mass
4a of the metal oxide stream to the paint solution.

The electrode structures described above, the used in coating by iciative electroplating are to be immersed in a galvanic cell as described in FIG. 12 or FIG.

"^" DE 2880

In a manner similar to Example 4, Power-top U-30 (manufactured by Nippon Paint Co., Ltd.) was used and electrodeposition was performed with the application of a DC voltage of 250 to 300 V. Carried out for 3 minutes. If the object to be coated was a motor vehicle part, the scatter or Current distribution on the inner surface of a box-shaped part, such as a bottom part, is satisfactory. Compares one the case where an electrode of the same structure

IQ as described above, additionally at the bottom of the cell, as illustrated in Fig. 12, with a case where such an additional electrode is omitted the coating, which was obtained on the inner surface of about a base part under the same conditions.

j5 th, in the former case a greater thickness and a better quality. For assessing the shelf life of the Electroplating was carried out continuously for over a year. During the exam of the electrode, it was observed that the sintered mass 4a

2Q made of metal oxide exhibited such a small volume loss that that no particular problems arose. The resin-treated parts were found to adhere to the jacketed Lead wire 22 and the connector 21 immersed in the paint solution had no irregularities developed. Furthermore, the paint solution showed no evidence of the entry of solute Ions or other foreign materials. Each coating obtained by the treatment was excellent Quality.

Although the working examples given above with regard to electrodes for cationic, galvanic Coating are explained are those according to the invention Electrodes are not limited to them but they can be used for high power or electroplating can be used for other forms of coating.

Claims (7)

Claims 1. Electrode / around coating by cationic Electroplating, characterized by a sintered mass of metal oxide that is electrically conductive. 2. Electrode according to claim 1, characterized in that the sintered mass of metal oxide, magnetite or ferrite. 3. Electrode according to claim 1, characterized in that that the sintered mass of metal oxide is in the form of a tube, one end of which is closed is, with a metal element as a core in the cavity inserted into the tube and secured therein by means of an electrically conductive material. 4. Electrode according to claim 3, characterized in that that the metal element is a stainless steel rod. VII / 22 Dresdner Bank (Munchen) KIo 3939844 6 »v <Vefeinsbank (Munich) Kio 60Θ94! Postal check [Munich] KIn 670-43-804 ::. ':;: ϋ ·. '-Ό · ..: - 32Α8932 DE 2880 5. Electrode according to claim 3, characterized in that that the tubular sintered mass of metal oxide is composed of at least two separate tubes is, wherein the metal element is inserted into and attached to the separate tubes, a tubular stiff or rigid plastic element around the connecting part of the separate tubes and bonded therewith using a curable resin. 6. Electrode according to claim 3, characterized in that a sheathed lead wire is connected to the upper end of the electrode, the connecting part
the electrode and the lead wire is covered with a tubular rigid plastic element and the cavity of the tubular, rigid plastic element filled with a curable resin and allowed to cure into a unit. 7. Process for coating by cationic GaI vanization, characterized in that an electrode of claims 1 to 6 is used as the anode.