DE1088311B - Process for the production of firmly adhering protective coatings on surfaces made of titanium, zirconium or their alloys - Google Patents

Description

GERMAN

In recent years, the production of titanium metal has been greatly increased through improvements. The extremely valuable properties of this metal and its alloys have led to it found an increasingly broad field of application because it is processed by pressing, hot and cold rolling, pulled and otherwise stretched and deformed. Also zirconium metal and its alloys were recognized in their extremely valuable properties, even if there are still few to be had is. As with others. Metals was also tried with these metals titanium and zircon with the help of protective coatings to facilitate processing and to protect the metals themselves. Titanium metal oxidizes and reacts very easily with nitrogen in the heat. Therefore a tightly adhering protective coating of great value during the processing of the metal, especially during wire drawing. The usual phosphate and oxalate baths do not give satisfactory results on titanium or zirconium Coatings. Either the metal is not provided with a coating at all with these solutions, or you just get a loose, dusty coating that is not suitable for pulling.

It was already known that the addition of fluorides to phosphating solutions containing oxidizing agents has a beneficial influence on the phosphating of metals (U.S. Patent 2,487,137). Since, however, as an area of application of this process from manufacturing process

firmly adhering protective coatings

on surfaces made of titanium, zirconium

or alloys thereof

Applicant:

Metallgesellschaft Aktiengesellschaft,
Frankfurt / M., Reuterweg 14

Claimed priority:
V. St. v. America August 5, 1954

Edwin W. Goodspeed, Royal Oak, Mich.,

and Frank G. Pollard, Ferndale, Mich. (V. St. A.),

have been named as inventors

formation of iron, the presence of an aluminum compound suppresses the formation of a coating on iron it was stated that it had ameliorating effects on various 30. Even if a solution here consists of ferrous metals, Zinc and its alloys and aluminum can eventually be applied to one of these metals

If, for example, aluminum is phosphated, it is advisable to use a soluble iron compound or in the phosphating of iron a soluble

minium and its alloys are used
the expert could not infer from this,
that an addition of fluorides taking into account certain further procedural measures is suitable for the application of coatings on titanium for the aluminum compound added to the solution. will. So there will be no connection of each

treated metal used. In addition, in this known process, in addition to that in double fluorides bound fluorine does not use excess fluoride ions.

It has now been found that surfaces made of titanium, zirconium or alloys of the same with a uniform, hard and firmly adhering protective coating can be provided when the metal surface phating solutions in addition to a monophosphate a 45 with an aqueous solution of a coating-forming Double fluoride, an oxidizing agent and a soluble phosphate, which consists predominantly of monomanganese phosphate Compound each of these three metals. The meaning, consists, brings in touch that a stable oxydie these soluble compounds of the metals alu- dating agent and fluoride in a concentration demini lim, iron and zinc in the solution are here- held, which are kept higher than the amount of the gebei discussed in more detail, and it can be seen from this that dissolved titanium or zirconium corresponds. One can do good

The use of fluorides is also known in a phosphating process, the simultaneous or separate throughput of iron, aluminum and / or zinc surfaces is permitted, d. H. at a process that is specially tailored to these three metals and in which the disturbances that were previously occurred due to aluminum contents in the solution. For this purpose, the phos-

Do not consider the metal as a soluble compound in the Phosphating solution is required that is to be treated, but that just for the formation of the coating A Verbin coating on zinc and / or aluminum can be obtained in these treatment baths, if these do not contain dissolved titanium or zirconium. The quality of these coatings as they are obtained in large-scale operations will, however, be improved and an equal

009 589/397

1088

"Moderate treatment" is ensured if a small amount of titanium or zirconium is added to the bath from the start. For this purpose, the titanium or zirconium can be added in the form of a soluble salt, for example as titanyl sulfate (Ti OSO ₄ ) or as calcium fluoride titanate (K ₂ TiF ₆ ) or in the form of a soluble zirconium compound. However, the bath can also be enriched with titanium or zirconium in the presence of metallic titanium or zirconium until a sufficient amount is dissolved of the bath of titanium and zirconium is at least about 0.05 percent by weight. The effect of the dissolved titanium on the coating formation of the solution against zirconium is not as great as that of the dissolved zirconium. The effect of the dissolved zirconium on the coating formation on titanium is analogously lower than that of dissolved titanium. For this reason, when titanium is used with a Coating is to be provided, and dissolved zirconium when a coating is to be made from zirconium. For example, hard coatings with excellent adhesion are obtained in solutions which contain titanium in concentrations of 0.5% up to saturation.

Under ordinary process conditions, both batch and continuous use of the solution, the content of free titanium and zirconium ions in the bath increases slowly on, and thus the effectiveness of the bath with regard to its coating formation gradually decreases. It has now been found that the full effectiveness of such a bath is restored and easily maintained can be achieved by adding fluoride ions from time to time. In this way the treatment baths according to the invention are adapted to the procedure in operation.

It has also been found that particularly good layers and a satisfactory and reliable Working of the treatment baths can be achieved that ions of ammonium and / or Sodium and / or potassium are present in the solution, although layers without their presence can be obtained with satisfactory adhesive strength and layer weight. The most favorable is the effect of the Ammonium ions and the combined use of sodium and potassium ions. To this beneficial effect A small amount of ammonium and / or sodium-h potassium ions is sufficient to achieve this. in the generally only 0.02% ammonium ion or equivalent amounts of sodium + potassium are required. Better results are obtained with 0.03 to 0.04%. More than 0.2% ammonium ions or equivalent amounts of sodium and potassium ions are of no use noticeable improvement, if they don't bother either.

You can also use solutions of other coating-forming phosphates, not just manganese phosphate, Apply coatings to titanium or zirconium. However, these coatings are not uniform or otherwise unsatisfactory. For example, zinc phosphate coatings do not improve drawing or other forming operations in the same way as manganese phosphate coatings. Solutions in which manganese phosphate is the main ingredient or the coating The predominant component is to give harder, more adhesive and thicker coatings on titanium and Zirconium metal and on their alloys. Coatings obtained with manganese phosphate solutions, are also superior in terms of quality in metalworking processes. The proportions for the Manganese phosphate in the coating solutions are not as critical.

A characteristic bath according to the invention contains 2 to 10% monomanganese phosphate. The effectiveness the bath rises with the monomanganese phosphate content from 3 to 9 per cent. The solutions can vary considerably in terms of their free acid content and total acid content. (Under free Acid is the number of cubic centimeters of n / 10 sodium hydroxide solution understood that it is necessary to make 2 ecm phosphate solution against bromophenol blue to neutralize, and below total acid is the number of cubic centimeters of n / 10 sodium hydroxide solution understood that is required to add 2 ecm of the solution to neutralize against phenolphthalein.) The solutions according to the invention are excellent Coatings are obtained when the ratio of free acid to total acid is between about 1: 4 and 1: 7 lies. One can use stable concentrated stock solutions

ao produce that at least twice the concentration of the applied solutions of monomanganese phosphate urtd the other ingredients, which are above which you only have to dilute with water before use or which can be added to an existing bathroom as a supplementary solution.

The concentration of oxidizing agent is not critical as long as there is sufficient oxidizing agent is present to ensure the formation of a coating.

With only 0.7% sodium nitrate (about 0.5% nitrate ions), which is a preferred oxidizing agent for the process according to the invention excellent, uniform and firmly adhering coatings are obtained .. However, preference is given to using somewhat larger amounts to ensure a small excess of oxidizing agent. At in practice Usual baths which contain 2 to 10% monomanganese phosphate are preferably used about 1.5 up to 1.75% sodium nitrate or its equivalents.

However, concentrations up to saturation of the salt in question can advantageously be used. Other Oxidizing agents that are somewhat weaker than, for example, potassium permanganate or potassium persulfate, can be used satisfactorily, e.g. B. ammonium nitrate, sodium chlorate, sodium nitrite, saccharine, Cane sugar and others Sacharine in quantities of 0.2 to 20% leads to even, firmly adhering coatings. With cane sugar or grape sugar, only 0.2 to 2% are required for similarly good coatings.

Sodium nitrite, which decomposes in acidic solution at elevated temperatures, leads to uniform, firmly adhering coatings, if it is added slowly and continuously in such amounts that a Concentration of about 0.01% is maintained.

Sodium chlorate improves coating formation when used in amounts from 0.7 to 2.5%. Independent of the particular oxidizing agent used, the oxidizing agent is in Quantities used in their effect on the

Coating of the solution corresponds to about 0.7% or more sodium nitrate.

The concentration of free fluoride ions is also not critical, if only a small amount is present 'which is not complex with titanium, zirconium or other polyvalent metals in the solution is bound. Solutions that are saturated with fluoride ions form firmly adhering coatings on titanium and zirconium metals aü * s. Already 0.03% is sufficient for solutions that only have a lower titanium and zirconium content to have. Thicker, better adhering coatings are

08a31t

obtained when at least 0.2% free fluoride ions are present. The total amount of fluoride ions in the bath is not decisive for the quality, weight and adhesion of the coating obtained. It is only necessary that fluoride be used in at least a slight excess over the amount which is theoretically necessary to form TiF ₀ ions or other complex ions with the titanium or zirconium content of the bath. In a bath containing about 8% monomanganese phosphate, thick, firmly adhering, very good coatings are obtained on titanium or zirconium if fluoride is at least 0.09% in excess of the theoretically required amount for the formation of Ti F ₆ Ions or other complex ions from the titanium or zirconium dissolved in the bath is present. In order to avoid too frequent replenishment of the bath in its fluoride content during use, it is desirable to provide a considerable excess of fluoride ions. 0.15 to 2.5% free fluoride ions are usually sufficient for this.

The fluoride content can be introduced by any water-soluble fluoride or bifluoride, for example as an alkali metal or ammonium fluoride or bifluoride. Ammonium bifluoride (NH ₄ HF ₂ ), sodium bifluoride and potassium bifluoride are preferably used because this also brings the desired ammonium, sodium and potassium ions into the solution.

The process according to the invention can be satisfactory at temperatures between 88 ° C. and the boiling point be performed. If the temperature is increased above 88 ° C, the required treatment time is reduced. For example, at around 90 ° C., satisfactory, firmly adhering coatings are produced in 30 minutes obtain. At 93 ° C and higher, satisfactory coatings are obtained in about 15 minutes.

There is no special pretreatment of the titanium or zirconium metal before the coatings are applied necessary. In general, however, it is desirable to pretreat the metal by activation with nitric acid - hydrofluoric acid, as is customary applied to stainless steels and then rinsed with hot water. Grease, oil or dirt can be done by wiping, spraying or immersion in mineral acids or other solvents or with The help of alkaline cleaners before the nitric acid-hydrofluoric acid treatment removed.

The coatings that are applied with the method according to the invention and its means protect the metal surface also protects against corrosion. Should the coatings be used as a primer for paints then a conventional chromic acid rinse is preferably followed by the formation of the coating. If the titanium or zirconium covered with a coating is to be deformed, one brings preferably following. the application of the phosphate coating a common drawing lubricant, for example stearate soap, before the actual shaping.

The solutions can also contain a mineral acid in such an amount that the individual bath components be kept in solution, for example nitric acid. The treatment baths are in supplemented in the usual way with phosphate and oxidizing agents. Because of the low solubility of the Fluoride these are generally separated from the supplement solution for phosphates and oxidants added, in such an amount that the fluoride concentration of the bath is higher

will hold than corresponds to the amount of dissolved titanium or zirconium. Bifluorides are preferably used for this purpose used.

The invention will be explained in more detail using a few specific examples.

example 1

A solution was made from the following components 42 g / l Mn (H ₂ PO ₄ ) ₂ · 2 H ₂ O, 7 g / l NaNO ₃ ,
10 g / l NH ₄ HF ₂ ,

built up. A sheet of titanium of commercial grade was immersed in the bath for 15 minutes and the temperature was kept at 93 ° C. during this process. One that could be used for cold working was formed Coating.

Example 2

A concentrated aqueous stock solution was prepared which contained the following components: 285 g / l Mn (H ₂ PO ₄ ) ₂ ■ 2 H ₂ O, 48, SgANaNO ₃ ,
24.3 g / l NH ₄ HF ₂ .

With solutions obtained by diluting the stock solution up to a content of 80 g / l monomanganese phosphate excellent coatings are applied to titanium.

Example 3

The process will be explained in more detail using a bath that is continuously in operation, with a bath approach von 5601 used and the workpieces at 93 to 99 ° C bath temperature were gradually enforced.

The bath had the following composition: 90.8 g / l Mn (H ₂ PO ₄ ) ₂ · 2 H ₂ O, 7.3 g / l NH ₄ HF ₂ ,
9.7 g / l NaNO ₃ .

The bath was incorporated by dissolving 0.9 g / L titanium sponge before using the solution. At the beginning of the first use, the ratio of free acid to total acid was 1: 4.7. With this procedure, uniform, firmly adhering coatings on titanium could be obtained over a period of several months. _{Small amounts of NH 4} HF _{2 were} added from time to time in order to keep the fluoride content at the desired level. After a larger volume of metal had passed through, the rest of the bath components would also have had to be supplemented. This bath showed that it was stable for a long time.

Example 4

The effect of ammonium was proven with the following bath:

83.3 g / l Mn (H ₂ PO ₄ ) ₂ · 2 H ₂ O, 6.7 g / l NaHF ₂ ,
6.7 g / l NaNO ₃ .

Sheets made of titanium of commercially available purity were treated in this solution at 93 to 99 ° C. for 70 minutes, with practically no coating forming. At this point in time, the solution had a ratio of free acid to total acid = 1: 4.1. By adding only 3.3 g / l (HN ₄ ) ₂ HPO ₄ to this solution, it was achieved that the following sheet received an excellent, thick, hard and firmly adhering coating in one minute at 93 to 99 ° C.

Example 5

A bath of the following composition would be prepared;

83g / lMn (H ₂ PO ₄ ) ₂ -2H ₂ O, -,

6.7 g / l NaNO ₃ , ■ - 6.7 g / l NH ₄ HF ₂ .

The bath was heated to 93 ° C and held at a temperature of 93 to 99 ° C for 2 to 3 hours. A tube made of commercially available zirconium was pretreated in nitric acid-hydrofluoric acid, in hot Rinsed water, immersed in the bath for 15 minutes at 93 ° C, rinsed again in hot water and dried. During this treatment, only a thin coating formed on the pipe. The bathroom was closed this time a ratio of free acid to total acid of 1: 4.5. When the treatment time is extended this tube resulted in a considerable improvement in the coating. From these attempts it follows that the presence of zirconium ions, in the ao> Bath that had gone into solution during the first 15 minutes, the coating of the solution on Zircon improved considerably. If you treat zircon sheets in a similar way. Bathroom that has been used was to provide titanium with a coating, then one obtains a thick, uniform coating, the but does not adhere as firmly as a coating obtained in the presence of zirconium ions. That with the zirconium tube covered with the coating in the zirconium-containing solution was lubricated with stearate soap and drawn. This significantly improved the drawing process compared to drawing not zircon coated with such a coating.

Example 6

35

For the application of coatings on titanium in the factory, a process was developed that uses two Treatment agents works, with a solution to approach the bath and a concentrated one Supplementary solution. The solutions had the following composition:

Aqueous make-up solution

600 g / l Mn (H ₂ PO ₄ ) ₂ 2H ₂ O, 22.6 g / l HNO ₃ (42 ° Be), 82 g / l NaNO ₃ ,
6.8 g / l NaHF ₂ ,
15.8 g / l K ₂ TiF ₆ ;

Supplementary solution

593 g / l Mn (H ₂ PO ₄ ) ₂ · 2 H ₂ O,

57.1 g / l nitric acid (42 ° Be), 27.4 g / l KNO ₃ .

In these solutions, nitric acid or another mineral acid is used to convert the components keep in solution. Before use, the acidity of the prepared bath was checked by adding Manganese carbonate adjusted to an acid ratio of 1: 4.5. The acidity of the supplementary solutions, as stated above, is sufficient to ensure the exact acidity of the prepared bath with prolonged use maintain. Since sodium bifluoride has only limited solubility in the cold, it cannot be used to a considerable extent Do not incorporate the amount in the make-up solution or in the supplementary solution. One must therefore this Add component alone from time to time.

To produce the treatment bath, 146 l of solution were diluted to 1000 l with water, the diluted solution was heated to 93 to 99 ° C. and 2040 g of manganese carbonate were added in order to reduce the acidity. After adding a further 2380 g of sodium bifluoride, the bath was ready for use.

When using the bath, the total acidity gradually decreases. The addition of 8.25 1 Supplementary solution per 10001 bath reduces total acidity the approach solution increase by one point. With repeated use, small amounts of sodium bifluoride are generated added as necessary to the level of free fluoride and the effectiveness of the bath. The specified proportions ensure excellent coatings Titanium of commercial purity.

Example 7

In the starting and supplementary solution according to Example 6, the sodium or potassium nitrate was through Replaces ammonium nitrate. Baths according to this example are being layered on titanium and zirconium superior to those of Example 6.

Example 8

A simple concentrated solution that can be used both as a make-up solution and as a make-up solution has the following composition:

40 percent by weight Mn (H ₂ PO ₄ ) ₂ 2H ₂ O, 3.75 percent by weight 70% nitric acid, 1.7 percent by weight NaNO ₃ , 1.85 percent by weight KNO ₃ ,

Rest water.

The acid ratio of the solution was 1: 7.6.

The treatment solution was prepared by diluting 210 kg of the above solution to 1000 l with water. After heating to 93 to 99 ° C and adding 5.15 kg of manganese carbonate, 2.17 kg of K ₂ TiF ₆ and 3.4 kg of NaHF ₂ per 10001 solution, titanium of commercial purity was added to the solution after pre-pickling in 3% HF and 10% HNO ₃ (1 minute at room temperature) treated for 15 minutes. A uniform, excellent coating with an average layer weight of 1.12 g / m ^{2 was} obtained.

Claims (10)

Patent claims: 1. Process for the production of firmly adhering protective coatings on surfaces made of titanium, zirconium or alloys of the same with the aid of fluoride ions and an oxidizing agent Phosphating solutions, characterized in that the metal surface with an aqueous solution a coating-forming phosphate consisting predominantly of monomanganese phosphate, which an oxidizing agent and containing fluoride ions, treated and the concentration of fluoride higher is kept than the amount of dissolved titanium or zirconium. 2. The method according to claim 1, characterized in that the metal surface is treated with a solution, the fluoride concentration of which is kept greater than is theoretically _{required for the formation of TiF 6} with the titanium dissolved from the surface, and preferably 0.15 to 2 Contains 5% free fluoride ions. 3. The method according to claim 1 and 2, characterized in that the metal surface with a Solution is treated, the ammonium ions and optionally sodium and / or potassium ions in Contains amounts of at least 0.02%. 4. The method hach claim 1 and 2, characterized in that the metal surface with a 1 088 3ί Solution is treated, the sodium and potassium ions contains in amounts of at least 0.02%. 5. The method according to claim 1 to 4, characterized in that in the treatment of titanium in the solution with the approach of titanium and in the treatment of zirconium zirconium in the form of metals or one of its compounds is introduced, preferably each in amounts of at least 0.05%. 6. The method according to claim 1 to 5, characterized in that the metal surface with a Solution is treated, which contains nitrate as an oxidizing agent, preferably in amounts of 1.5 up to 1.75% with 2 to 10% monomanganese phosphate. 7. The method according to claim 1 to 5, characterized in that the metal surface with a Solution is treated, which contains saccharine as an oxidizing agent, preferably in amounts of 0.2 to 20%. 8. The method according to claim 1 to 7, characterized in that the metal surface with a Solution is treated, the monomanganese phosphate, Contains ammonium bifluoride, potassium fluorotitanate and sodium nitrate and their fluoride concentration is preferably at least 0.09% above the _{amount theoretically required for the formation of TiF 6} with the dissolved titanium, and the titanium content is preferably at least 0.05% and the ammonium content is at least 0.02%. 9. The method according to claim 1 to 8, characterized in that the metal surface with a Solution is treated, which contains a mineral acid and whose fluoride concentration is kept so high that the formation of precipitates in the solution is prevented. 10. The method according to claim 1 to 9, characterized in that following the phosphating rinsing with chromic acid is carried out. Considered publications: German Patent No. 853 695;
U.S. Patent No. 2,487,137. © 009589/397 8.60