DE1235107B - Aqueous, chromium compounds and reducing agents containing application solution and process for the production of colored, corrosion-resistant protective layers - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

JmPk
if / »PATENT OFFICE

EDITORIAL

Int. Cl .:

C23f

German class: 48 dl -5/00

Number: 1 235 107

File number: H 39465 VI b / 48 dl

Filing date: May 18, 1960

Opened on: February 23, 1967

There are aqueous, chromic acid and suitable reducing agents containing application solutions known which form a chrome coating in situ capacity and are intended for the production of corrosion-resistant protective layers. It results in 5 a very good protection against corrosion, and in general the appearance of the treated area also suffers not, but the upper parts are not exactly decorative. With suitable recipes of the Treatment solution, brownish-colored coatings can be obtained, but their brown color is obtained often blotchy and therefore unsightly as a result of interference fringes, probably because of the layers are pretty see-through.

The object of the present invention is to enable the production of colored, corrosion-resistant protective layers which avoid these disadvantages. The invention relates to a colored for producing corrosion-resistant protective layers certain aqueous, chromium compounds and Re. Advice! containing application solution, which is characterized in that it contains a water-soluble dichromate of an at least divalent metal, e.g. B. zinc or magnesium dichromate, and so much of a reducing agent compatible with this contains that only when heated to at least 138 ° C at least about 70 to 95 ° / »of the hexavalent chromium of the dichromate are reduced to trivalent chromium, and that they also still Contains pigments in amounts of about 10 to about Ψ5 percent by weight of the dichromate and preferably still dispersed resin particles , the weight of which is advantageously not more than twice the weight of the dichromate.

The invention also relates to a process for passivating and coloring metal fiii using the aqueous dispersions just identified. It is characterized in that the dispersion is applied to the iMetflüflache to be treated and then the surface is heated to a temperature between about 138 and 232 ° C, the application of the dispersion preferably being adjusted so that after heating the coating layer is at least 100 mg / Weighs 900 cm ² . The dispersions can be applied by spraying. It is advisable to work with the aid of a compressed air stream in such a way that at least three quarters of the dispensing agent evaporate before the spray jet reaches the metal surface.

For the treatment of surfaces made of simple carbon steels, the dispersion can also be metallic.

Aqueous, chromium compounds and
Application solution containing reducing agent
and methods of making colored ones
corrosion-resistant protective layers

Applicant:

Heintz Manufacturing Company,

Philadelphia, Pa. (V. St. A.)

Representative:

Dr.-Ing. Dr. jur. H. Mediger, patent attorney,

Munich 9, Aggensteinstr. 13th

Named as inventor:

Ludwig Karl Schuster, Dresher, Pa .;

Alfonso L. Baldi Jr., Drexel Hill, Pa. (V. St. A.)

Claimed priority:

V. St. v. America May 19, 1959 (814 200),

from! February 1960 (6021) -

Zinc particles with particle sizes contained in the tpr Sf) micron_ ". The dispersions of the invention can advantageously also be used on iron surfaces that have been plated with zinc or tin after etching, and on metal surfaces that have already been coated with an adhesive Oxide or other substances such as phosphate, chromate, oxalate, sulfide, or with coloring coatings, including adhesion promoting, zinc blackening or lubricating coatings. They are also suitable for the treatment of porous objects such as porous metal blocks, as well as for the treatment of glass surfaces their protection against the attack of caustic agents, especially on glass surfaces adjacent to metal surfaces. $? ^

Pigments suitable for seducing the present invention are particularly recommended inert, such as titanium dioxide, carbon black. Iron oxide ^ Mülybdate orange, Ferrite yellow, chromium oxide, the chrome yellow, as well as the phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green. Finely divided metallic zinc, which is a

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has a relatively low coloring effect, but the anti-corrosion effect of the coating layer increases considerably. The pigments result the best opacity when it is very finely divided Shape are located and their particle size is, for example, 1 micron or even less. in the In the case of zinc powder, however, the protective effect reaches a maximum when the particle size is around 50 microns. In general, the pigment should be present in the coating solution in an amount of from 10 to 75 percent by weight of the dichromate present must be present. Wetting agents, especially those of the nonionic group, can be applied to the pigment particles during application to keep the metal surface in dispersion.

In order to achieve layers with a more brilliant appearance and a good corrosion protection effect, the weight of the finished coating layer should weigh at least about 100 mg per 900 cm 'surface. Resins are also expediently incorporated into the dispersions and coating layers, as described in British Patent 793,242. These resin additives further improve the anti-corrosive effect and facilitate the production of very heavy coating layers. In this way one can easily produce coating layers which weigh ^{1000 to 2000 mg or more per 900 cm 2.}

Too high a resin content makes the finished coating layer resistant to the action of solvents sensitive, so that the color of the layer becomes streaky or cloudy. The maximum resin content should therefore expediently not more than 1 part by weight per 3 parts by weight of dichromate in the coating dispersion be. But you also get an excellent protective effect if you:> The ratio of resin to dichromate increases up to 1.75: 1 or up to 0: 1 lowers. In general, the best results are obtained with ratios of 1.5: 1 to 1: 3. The proportions given are calculated by dividing the resin weight to the difference between the weight of the metal dichromate and the weight of the cation of the dichromate puts. It is noteworthy that the presence of pigments according to the invention by the Coating layer granted corrosion protection improved even if no resins are present.

Resins based on methyl acrylate, ethyl acrylate and methyl methacrylate are used as resins for the purpose of the invention preferred. You can choose from degrees of hardness of KHN number 2 or higher (ASTM Bull. 138, 39, January 1946; Henry A. Gardner and George G. Sward, Paint Testing Manual, 18th Edition, 1962, P. 135). When the coated product is further manipulated must, softer resins, especially if they are present in quantities greater than 1: 2, lead to the dichromate are easy to fingerprint and the like on the finished layer. Hard pigments, such as titanium dioxide, reduce the risk of such unwanted marks.

The method of the invention with the pigment-containing coating layers can be used in all cases where the surface to be treated can withstand the conditions of use. Even paper can be provided with a coating layer in this way. This is of particular importance Process of the invention, however, for the production of coating layers on metal surfaces, because this is where the high corrosion protection of the coating layers comes into play. This corrosion protection is of such a size that even surfaces made of stainless chromium-nickel steels (e.g. Type 18-8) can be made even more resistant to corrosion, which in itself only corrodes relatively slowly. The coating layers produced by the method of the invention adhere very well to corrodible ones Metal surfaces, although in some cases

ίο z. B. with aluminum and stainless steels one slight roughening of the metal surface or at least a not too strong polishing of the surfaces in the Manufacturing can be beneficial. The roughening can be done by etching or mechanically, e.g. B. with the Sandblasting or by rolling the sheet metal between two rollers with a roughened surface be effected. With normal carbon steels and iron there is a roughening under the The aspect of the adhesion of the coating layer is not required, but the anti-corrosion effect can be increased significantly in these cases by first etching the surface can be, as described in the two cited patents.

The coating layer according to the method of the invention can also be applied very effectively to metal surfaces that previously had an adhesive Coating made of an oxide or other substances such as phosphate, oxalate, sulfide or other chromate coatings or coloring coatings including those that prevent paint from adhering to ferrous metals promote or blacken zinc or have a lubricating effect during machining operations. Examples of such pretreatment measures are described in U.S. Patent 2,768,104.

If coating layers are applied in this way by the method of the invention to metal surfaces which have already been coated beforehand, an even more effective protection against corrosion is achieved than before. An aqueous paint on such a double-coated metal surface also gives much better corrosion resistance, and for this purpose the coating layer applied by the method of the invention does not need to contain resin and can even be applied in very thin layers. For example, on a carbon steel phosphated according to Examples 13 and 14 of US Pat. No. 2,768,104, a coating layer consisting of an aqueous solution of zinc dichromate and an amount of reducing sucrose or the like results in 70 to 95% of the hexavalent chromium being reduced to trivalent chromium If the spread is subjected to the heating according to the invention, even in a thickness of only 20 mg per 900 cm ² a very favorable coating layer. The solution of the zinc dichromate and the reducing agent only needs to be applied to a certain extent as a rinse after the phosphating of the carbon surface, especially if it is an already formed structure, such as a frame or a chassis for motor vehicles. A comparable improvement is achieved with objects of this type which are first subjected to grain etching, then treated according to the method of the invention with a solution of zinc dichromate and reducing agent, heated and finally provided with a coating of an aqueous paint. In these

In some cases, the zinc dichromate can also be replaced by CrO ₃ .

In addition to stainless steels, carbon steels are suitable for the treatment according to the invention and aluminum also simple chromium steels, beryllium, cadmium, chromium, cobalt, chromium, copper, Lead, manganese, magnesium, molybdenum, nickel, silver, tantalum, tin, titanium, vanadium, zinc, Zirconium and any alloys of these metals with one another.

Zinc dichromate or magnesium dichromate can be replaced by strontium dichromate, calcium dichromate or CrO ₃ without significantly reducing its effectiveness. The aftertreatment can take place at any temperature between 12.1 and 232 ° C.

example 1

An aqueous dispersion is produced

64 cm ^{3 of} an aqueous solution of zinc dichromate containing 0.75 g of chromium, calculated as CrO ₃ , per cubic centimeter;

60 cm ^{3 of} an aqueous dispersion of 3 parts of carbon black and 1 part of phthalocyanine blue with 0.3 g of solid substance per cubic centimeter and stabilized with 0.1 percent by weight of oxyethyl cellulose;

32 cm ^{3 of} an aqueous solution of sucrose with 0.5 g of sugar per cubic centimeter;

30 cm ^{3 of} an aqueous dispersion of polymethyl methacrylate with 13 g of polymer with an average molecular weight of 10,000 and the KHN number 4, stabilized with 0.1 percent by weight of 4-isopropylnaphthalene ammonium sulfonate;
600 cm ^{3 of} water.

Steel strips are immersed in the dispersion, passed between corrugated rollers and heated to 177 ° C in an air oven. In this way, the tapes are given a coating layer of 200 mg per 900 cm and a very pleasing black appearance. They survive 100 hours at 98 ⁰ O humidity and 35 ° C without any signs of corrosion. The layer adheres well, cannot be scratched off with a fingernail and does not accept finger marks.

Corresponding results are obtained with the above-mentioned variations of the recipe. However, other resins, such as polystyrene or copolymers of styrene and butadiene, give because they only have a Tukon hardness of 2 or less, possibly finger marks. Also in But the coatings are their case if they contain no resin at all or no more than 1 part resin to 3 parts Dichiomat included, free of finger marks.

The coating layers described also result in a very pleasing leather-like surface Metal that has previously been roughened by rolling. For example, stainless steel is obtained in this way Steel sheets great looking layers. Sufficient for pigment-free coating layers Post-treatment at 121 ° C. Coatings containing pigments require at least one post-treatment at 138 ° C.

TiO ₂ is a white pigment, but generally gives the coating layers a pastel green color, and in combination with phthalocyanine blue the result is an even darker green. When mixed with soot, the result is a pleasing gray. Phthalocyanine green gives a green colored coating. Red iron oxide gives a red color and phthalocyanine blue gives a strong blue color.

The coating dispersion can also be applied by spraying on, and by suitable coordination it can be achieved that a large part of the aqueous medium of the applied dispersion evaporates before the sprayed particles reach the surface to be coated. If you surround the spray nozzle with additional air nozzles, it can be achieved in this way that up to 75% of the water contained in the dispersion evaporates on the way from the spray nozzle to the surface to be treated. In this way, the particles of the dispersion settle in a more or less viscous form and therefore no longer run down the surface and easily build up coating layers that weigh ^{up to 5000 mg per 900 cm 2.} This type of coating is particularly useful for the treatment of processed articles in which the coating layers must be prevented from running down. Regardless of the thickness of the coating layer, the thermal aftertreatment can be carried out in a few seconds.

When hard resins such as the above-mentioned acrylic resins are to be used in large amounts and the metal surface is still somehow deformed or otherwise processed after the coating layer has been applied it is convenient to use the resins

.35 to plasticize with polyvinyl stearate or other plasticizers such as acrylic resins with molecular weights of about 2000. The polyvinyl stearate can be fully esterified or still contain about half of the hydroxyl groups of the polyvinyl alcohol in an unchanged state (cf. US Pat. Nos. 2,188,864 and 2,562,965). The plasticizer can be used in amounts up to about 25 percent by weight of the resin, and sheet metal coated with such layers is particularly suitable for stamping at high speeds, e.g. B. in the production of lids and bases for the cans required by the food industry. Such a sleeve has a cylindrical body formed from a single strip of brightly polished black plate, the ends of which are folded back on to form interlocking flanges. This cylinder is closed at the top and bottom with lids, which are flanged at the edge and formed with flanges. In addition, circular reinforcing ribs can be provided both in the lid and in the base. For the production of the can body as well as the cover and the base sheet metal is suitable which is provided beforehand with a coating layer according to the method of the invention. Before applying the dispersion according to the invention, the black plate is cathodically cleaned in an aqueous solution containing 16 g of KOH per liter at a current density of 15 amps per 900 cm ² cathode at 60 to 71 ° C for 10 seconds, then with cold water rinsed, then anodically in an aqueous solution with 16 g of KOH per liter for 10 seconds at 60 to 71 ° C with a current density of 15 amps

900 cm ² each anode cleaned, rinsed again with cold water, then to prevent passivation with a solution of 0.5 weight percent H ₂ SO ₄ flushed for 0.5 seconds at 27 ^: C, rinsed again with cold water for 8 hours at 27 ° C with a 2% aqueous nitric acid and a pressure of 2.7 kg per 6.25 cm ² , rinsed again with cold water, then freed of all residues by brushing in the water and now for 2 seconds with a 24 ° C hot aqueous solution of

840 cm ^{3 of} a dispersion of a butadiene-styrene resin that hardens in the heat, according to Example 1 of US Pat. No. 2 683 69S, but with styrene instead of vinyl toluene and without sodium bicarbonate, with 46% solids content,

12 g p-octylphenyltriethylenoxyethanol, 112 g sucrose,

375 g of a 36% dispersion of TiO ₀ in

Water,

600 cm ³ aqueous zinc chromate solution with 0.75 g salt, calculated as CrO ₃ ,

600 g zinc dust,

filled up with water to 6000 cm ³ ,

washed up.

The plate, which is still wet, is turned between two rubber rollers and treated for 5 seconds in a drying cabinet equipped with red-hot ceramic gas burners, during which the plate reaches a temperature of 177 to 204 ° C. If the sheet is in long strips, it can be wound up immediately after this treatment. The coating layer produced weighs approximately 200 mg per 900 cm ² and the sheet is colored pale green. In this form, it can be processed into the bushings described by punching, flanging or soldering. The cans produced in this way can be sterilized, heated, evacuated or pressurized in the usual way after filling; their corrosion resistance is excellent and better than tin-plated cans. The vessels manufactured with sheets coated according to the process are particularly suitable for filling goods such as detergents, soaps, other alkaline preparations, but also for chemicals and other goods with a neutral and acidic reaction.

When punching can ends, etc., the presence of the pigment does not noticeably affect it the deformation operation. However, if the amount of resin in the coating layer is less than that Weighs amount of dichromate, the resin is expediently mixed with 10 to 25% plasticizer or a resin based on butadiene-styrene applied.

For the application of a coating layer with a softer resin, for example, the following is used Suitable for dispersion:

37 g

48 g CrO ₃ , reacted with ZnO to form zinc

dichromate,

16 g sucrose,

60 cm ^{3 of} a 26 percent strength by weight aqueous dispersion of phthalocyanine blue,

a 46% aqueous dispersion of methyl acrylate with a KHN number of 1.2,

filled up to 500 cm ³ with water.

The procedure is as for the treatment of the sheet of Example 1, but using rough Rubber rollers for rolling the wet sheet and

ίο with an aftertreatment temperature of approx 160 ° C. A very pleasing dark blue coating layer with a high protective effect is obtained.

Since the layers according to the invention also provide ^{a good protective effect with weights of about 20 mg per 900 cm 2} , such coatings are also valuable for other materials, such as porous metal blocks for the production of bearings, filter surfaces and the like, or for masks or TV tube screens. In this way, the bearings can be

ao pressed and sintered bronze powder or similar Well-made sintered porous steel bearings with a dilute aqueous solution of 2% Chromic acid and 0.65% reducing agent, such as triethanolamine, impregnated and after draining the excess solution can be post-treated at 121 ° C. In this way objects are obtained which are still porous, behave very well as bearings, but are less susceptible to corrosion.

For picture tubes in color television, the masks that set the DT color separation for the individual can be used Effect shield parts, are produced by od in a metal sheet made of iron, copper. fine openings made by etching or in some other way and this mask then 'in the same Way how the porous bearings are coated. Replacement of part or all of the quantity Chromic acid through zinc dichromate should be avoided in such cases, as the adequate degassing otherwise the tube becomes more difficult.

Example 2

408 cm ^{3 of} a polyacrylic resin dispersion, 33 cm ^{3 of} an aqueous 20 weight percent solution of pn-octylphenoxytetraethoxyethanol, 6.8 cm ^{3 of} an aqueous 67 weight percent solution of sucrose (specific weight 1.33) and 200 cm ^{3 of} an aqueous dispersion with 36 weight percent TiO are mixed. , and 3.3 percent by weight oxyethyl cellulose (specific weight 1.4), add 133.5 cm ^{3 of} an aqueous solution of zinc dichromate (0.75 g chromic acid per cubic centimeter) to ^{the mixture and dilute it with water to 1000 cm 3} . The mixture can be applied immediately to the substrate by spraying, dipping or using an applicator roller. It has a resin to chromic acid ratio of 2: 1 and can be stored for 1 week or more.

Example 3

Mix 455 cm ^{3 of} a polyacrylic resin dispersion, 33 cm ^{3 of} a 20 weight percent aqueous solution of pn-octylphenoxytetraethoxyethanol, 6.8 cm ^{3 of} an aqueous 67 weight percent solution of sucrose (specific weight 1.33), 200 cm ^{3 of} an aqueous dispersion of a mixture of 95% Carbon black and 5% phthalocyanine blue with 25 weight percent solids content and stabilized with 0.05% pn-octylphenoxytriethoxyethanol and

54 cm ^{3 of} an aqueous dispersion of 36 weight percent - weight percent TiO ₂ and 3.3 weight percent Oxyäthylccllulose. The mixture is combined with zinc dichromate and made up with water in the same way as in Example 2.

. The mixture can be done in the same way as that of Example 2 can be applied. The ratio of resin to chromic acid is 2.25: 1.

Example 4
The dispersion contains water ^{per 1000 cm 3}

100 g MgCr ₂ O ₇ , made from 7 parts magnesium carbonate and 11 parts chromic acid,

4OgH ₃ PO ₃ ,
30 g red iron oxide,
4 grams of dioctyl sodium sulfosuccinate.

It results on steel if the aftertreatment is carried out by flaring at a maximum of 191 ° C Resin-free red coating layers have a very good protective effect. Flaring can also be used for post-treatment can be used by resinous coatings and is convenient for drying or post-treatment any kind of organic coating layers such as aqueous paints, water-dispersed Resin and even paints with organic thinners are suitable. When the diluent are flammable, most of them should be evaporated before the application layer reaches the flame zone achieved.

The coating dispersions according to the invention can contain a small amount of excess chromic acid tolerated, as can be seen from the above recipe. Along with the excess of chromic acid resin can also be incorporated, e.g. B. 50 g of alkyd resin according to Example 1 of the USA patent 2,634,245, emulsified with 25% of those described there Polyethylene glycols.

In some use cases, e.g. B. for packing cotton bales with sheet metal strips, The coloring plays a bigger role than the corrosion resistance. The sheet metal strips can be made from There are normal types of steel that are expediently subject to a particularly strong post-rolling for improvement subjected to elasticity and hardness. This steel sheet is made according to the method of the invention treated before or after it is cut to the desired bandwidth. A premonition, as indicated in Example 1 is advantageous. In this way, the sheet metal strip can easily and cheap to be given the color that the cotton industry has been putting on them for the past 50 years or more more used.

The grain etching, e.g. B. with nitric acid according to Example 2, is also recommended for electrically deposited coatings of metals such as zinc and tin. Coatings of these metals on black plate, which was pre-etched so far in the manner indicated, to a 900 cm ^"2300 mg of metal to remove, has a much better corrosion resistance both with and without the application of a coating with reduced chromic acid or reduced dichromate. In particular, unprotected acidic zinc and tin plating on ordinary low carbon steel sheet improved by this pre-etch.

The dichromate coating dispersion of the invention can be applied to the metal surface by dipping, washing, spraying, roller application, electrostatic Spraying, etc. are applied. Dipping, roller application or flooding are recommended especially for the continuous treatment of metal in strip form. The thickness of the application layer depends on the concentration of the mixture, but also on the contact pressure and the surface properties of any used application rollers.

It is noteworthy that the pigment-containing coating dispersions of the invention generally do not need additional wetting agents to ensure adequate wetting of the metal surfaces to be treated to reach. Apparently, the dispersions containing the pigment have, in addition to the ability, the pigment to keep in a suitable distribution, also very good wettability for all for the treatment eligible metals. This becomes even more noticeable when the dispersions are next to the pigments also contain resin in a stable dispersion. The application of dispersions does that too Pre-cleaning less critical.

The dispersing or wetting agents used to stabilize the dispersions can be any Be kind. In addition to those already mentioned, there are also long-chain alkyl sulfates and tert-butyl alcohol to call. The latter is effective, although it does not cause any appreciable chemical reduction and im generally in higher concentrations, e.g. B. 0.5%, must be present in order to bring about effective wetting. In general, anionic, cationic and nonionic surfactants are inclusive the quaternary ammonium compounds of long-chain alkyl or aralkyl amines, are suitable.

The coating layers according to the invention are also suitable for glass in order to prevent it from being attacked Caustic agents such as hydrofluoric acid.

This is significant for the manufacture of television tubes with glass envelopes that are on the outside with Metal supports are provided, which are anchored with the help of a fritted block or a pane of glass are, which is melted onto the glass envelope, so that an internally expanded base is formed inside which a metal arm is held. If you have this glass frit and possibly the provides abutting parts of the metal arm with a coating layer according to the invention, so the Tubular envelope are subjected to the usual processing operation without the glass frit so far is attacked that it loses its hold in the glass envelope appreciably. Both resin-free ones are suitable such as resin-containing coating layers and the dichromate can be wholly or partially replaced by chromic acid will. In this case, the dispersions do not need to contain pigments, although they do can be useful.

The coating layers according to the invention are also suitable for reducing the corrosion of razor blades made of simple carbon steel during shaving. Here, too, the coating layers can be resin-free or contain resin and are applied in relatively thin layers directly over the cutting edge of the blade. A coating weight of about 30 mg per 900 cm ² is adequate for this purpose, and these coatings also reduce the initial sharpness of the blade somewhat

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leads to the fact that you always cut yourself with a new blade. The corrosion protection of the coating has an effect between the individual shaves, so that a blade treated according to the invention at least can be used as often as an untreated one.

Since the resin-free coatings according to the invention have a purely inorganic character, with them coating layers are made on objects that are used for other types of protection have high temperatures. This applies, for example, to metal castings which begin to oxidize as soon as they have been removed from the mold and have not yet cooled to room temperature. Aluminum or Zinc castings can be sprayed with the coating dispersions of the invention even if they are still have a temperature of 260 ° C or higher. At these temperatures the coating layer cured immediately and if the temperature is very high, the coating can even begin to ao decompose. But even in the latter case the oxidation of the metal surface becomes sufficient for the cooling period and also inhibited for a few days afterwards. In such coatings there can even be a small Amount of resin must be present and the pigment omitted. To protect cast blocks that serve to fill molten metal baths, a very thin coating of simple solutions of chromic acid and a polyhydric alcohol, such as sugar, as a reducing agent.

In this way, less foreign matter is introduced into the bath, although not much is added when a dichromate is used _{instead of CrO 3.}

Claims (9)

Claims: ' 1. Aqueous chromium compounds specific to the production of colored, corrosion-resistant protective layers and reducing agent containing application solution, characterized in that that they have a water-soluble dichromate of at least a bivalent one in aqueous dispersion Metal and contains so much reducing agent compatible with this that only when heated to at least 138 ° C at least about 70 to 95% of the hexavalent chromium of the dichromate are reduced to trivalent chromium, and that they also contain pigments in quantities of about 10 to about 75 percent by weight of the dichromate, and preferably still dispersed resin particles contains, the weight of which is expediently not more than twice the weight of the dichromate amounts to. 2. Dispersion according to claim 1, characterized in that it is titanium dioxide as pigment, Contains carbon black, iron oxide or a phthalocyanine dye. 3. Dispersion according to claim 1 and 2 for the treatment of simple carbon steels, characterized characterized in that the dispersion contains metallic zinc particles, the particle size of which is below 30 microns. 4. A method for passivating and coloring metal surfaces using the dispersion according to claim 1 to 3, characterized in that the dispersion is applied to the metal surface to be treated and then the surface is heated to a temperature between about 138 and 232 ° C, the Application of the dispersion is preferably adjusted so that, after heating, the coating layer weighs ^{at least 100 mg per 900 cm 2.} 5. The method according to claim 4, characterized in that the dispersion is sprayed is applied. 6. The method according to claim 5, characterized in that the dispersion with the aid of a Compressed air stream is applied such that at least three quarters of the dispersant evaporate before the spray reaches the metal surface. 7. Use of the method according to claim 4 to 6 for treating an iron surface, which was plated with zinc or tin after etching. 8. Use of the method according to claim 4 to 6 for the treatment of metal surfaces, which was previously covered with an adhesive coating made of an oxide or other substances, such as Phosphate, chromate, oxalate, sulfide, or with coloring coatings, including adhesion-promoting, zinc-blackening or lubricating coatings are provided. 9. Use of the method according to claims 4 to 6 for # treatment of glass surfaces to protect them against attack by caustic agents, especially on metal surfaces adjacent glass surfaces. Considered publications:
W. Machu, "Die Phosphatierung", 1959, p. 243; "Non-metallic inorganic coatings", 1952, p. 193. 709 510/543 2.67 Q Bundesdruckerei Berlin