US1801808A - Process for covering metals or alloys with layers of metallic beryllium - Google Patents

Description

Patented Apr. 21, 1931 UNITED STATES PATENT OFFICE HELLMUT FISCHER, 0F BERLIN-FRIEDEN'AU, GER-MANY, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO METAL.& THERMIT' CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY PROCESS FOR COVERING METALS OR ALLOYS WITH LAYERS 0F METALLIC BERYLLIUM No Drawing. Application filed October 3, 1927, serial No. 223,836, and in Germany August'20, 192G.

My invention relates to a process for c'overing metals or alloys with layers of metallic beryllium.

It is well known to produce coatings of aluminium or aluminium alloys by immersing the article to be coated in the melt of a sa t of the coating metal as free as possible from water and electrolyzing the melt or fused salt with the aid of soluble anodes of the coating metal, the article to be covered being connected as the cathode. This well known process is, however, not applicable to the production of perfect coatings of metallic beryllium or beryllium alloys, because it is necessary for this, purpose first to determine the correct temperature at which the electrolysis of the melt is to take place as well as the correct composition of the melt.

It is furthermore impossible to employ in this case soluble anodes as in the aluminium coating process mentioned above.

There is also known a process for producing tin or zinc coatings upon iron or steel articles for the purpose of preventing rust-.

ing or corrosion, by electrolyzing a melt. Apart from the fact that this process has a difi'erent object, it is also for the reasons specified above not directly applicable for producing perfect coatings of beryllium by means of electrolysis of a melt.

It is also well knownto separate beryllium in solid form by the electrolysis of a melt consisting of a beryllium-containing mixture of salts. Experiments have proved that this process is not directly applicable for the production of coatings of metallic beryllium upon articles of metal or metal alloys.

There existed thus up to now no process by means of which coatings or coverings of metallic beryllium useful for vengineering purposes could be produced-in a technical manner. i

According to my invention thisproblem is solved b immersing the article in a melt produce by the application of heat and which consists of at least one halide of an alkali metal or of an alkaline earth metal and a beryllium compound and electrol n this melt with the article to be coate COD.-

nected as the cathode. It is essential that the temperature of the'bathbe kept during the electrolysis below the fusing point of the article to be coated. Preferably the blast of cold air or gas is sufiicient to keep,

their temperature lower, for instance about 100 O., lower than the temperature of the melt.

The character of' the beryllium coating may be modified orimproved by carrying out the electrolysis at a temperature either slightly or far below the fusing point of the article to be coated. The deposited layer is then always smooth, very dense and adheres firmly to the metallic surface. Generally it is's'uflicient to maintain the electrolysis during a few seconds only. Should it, however, be desired to obtain a more substantial coating of beryllium the duration of the electrolysis may be correspondingly extended, for instance up to a few minutes. Parts of the melted salt or a light film of oxides which may happen to adhere to the deposited layer may be removed by sudden immersion into a cooling liquid or mechanically by carefulscr'aping, bufling or the like. The extremely hard beryllium coating is smooth and firmly adheres to the metallic surface. According to the difference between the temperature at which the electrolysis coated. In this case the deposited metal diffuses more or less deeply into the base metal and may even form an alloy with it. This layer of alloy is then particularly strong and sion it imparts to the surface of the coated metal or metal alloy the characteristic qualities of pure beryllium alloys with such metals, such as great hardness, imperviousness to corrosion and so on.

If, on the other hand, it is desired to obtain layers of pure beryllium, the process is referably carried through at temperatures of the bath which lie as far as possible below the fusing point of the metal to be covered. The desired temperature ratio may be attained by an appropriate cooling of the article to be coated and connected as the cathode. In this case there is formed upon the base metal a surface coating of pure beryllium which is of great hardness andadheres firmly,'but does not alter the characteristic qualities ofthe foundation metal.

The best results were obtained upon metals of not too low a fusing point, such as aluminium, copper, iron and the like. My improved process may, however, also be employed for numerous other metals or metal alloys. As suitable electrolytes for the production of beryllium coatings the halides of beryllium are used with special advantage. According to the nature of the metal to be coated the fusing point of the melt used may be varied by adding to the beryllium compound or compounds one or more halides of the alkali metals or of the alkaline earth metals.

As an example of my improved process I will now describe the production of a deposit of beryllium upon an article of copper. Sodium'fluoride and beryllium fluoride are mixed in the proportion of their molecular weights and the mixture is fused or melted in a crucible of graphite heated externally. The copper article to be coated is then immersed as the cathode into the liquid mixture and the graphite crucible is connected as the anode. After a short time, for instance after a few seconds, a dense and very firmly adhering coating of metallic beryllium or a copper-beryllium alloy is obtained which by careful bufiing or scraping may be cleaned from any adhering. traces of the salt.

If it is desired to modify or improve the physical properties of the beryllium coating so deposited, and particularly its hardness, the process is conducted as follows: a layer of another metal is first deposited upon the article to be coated, for instance by electrolysis in an aqueous bath. For such an intermediate layer metals are particularly suitable which on the one hand adhere firmly to the base metal due to surface diffusion and on the other hand have the property of absorbing beryllium. Metals such as iron, copper and mckel are particularly suitable for this intermediate layer. A plurality of such intermediate layers may be provided.

After such an intermediate layer complying with the specified conditions has been applied to the article, the article is covered with beryllium in the manner described above by electrolyzing the fused salts.

The following may serve as examples for the application of the last described process:

1. Upon an article of tungsten there is first deposited a layer of iron, for instance by the electrolysis of an aqueous solution of an iron salt, and upon this layer beryllium is deposited by the electrolysis of a melt kept liquid by heating to about 1200 0., the above specified temperature conditions being carefully observed.

2. Articles of molybdenum may first be galvanically plated with copper. The beryllium coating is then applied to this copper layer in the above described manner at a temperature of the bath of 700 to 800 C.

3. Articles of tantalum may first be galvanically nickel-plated. The subsequent deposition of the coating of beryllium may preferably take place at a temperature of the bath of about 1100 C.

In a similar manner intermediate layers may be produced upon vanadium, niobium and so on before the final coating of beryllium is applied to them. Generally speaking such intermediate layers are advisable for such metal articles as melt considerably above the fusing point of beryllium (about 1285 C.). It will be understood that such intermediate layers may equally well be applied to articles which consist of alloys.

Various modifications and changes may be made without departing from the spirit and the scope of the invention, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art. It will be understood that for the purpose of my present invention, the halide of an alkaline earth metal is to be considered the equivalent of the halide of an alkali metal, and the appended claims are to be interpreted as covering such equivalent.

I claim as my invention 1. The process of producing a permanently adhering coating of a beryllium allo upon a metal article having a surface whicl i readily alloys with beryllium, which consists in'preparing a melt of a sodium fluoride and beryllium fluoride kept liquid by the application of heat, immersing in said melt the article to be coated, connected as the cathode, and electrolyzing said melt with the aid of an insoluble anode whilemaintaining the melt at a temperature which lies below the fusing point of beryllium and slightly below the fusing point of the said article.

2. In the production of a permanently adhering coating of a beryllium alloy upon a metal article, the process which comprises depositing a layer of a metal alloying with beryllium upon the article to be coated, preparing a melt from a beryllium halide and at least one alkali metal halide, maintaining said melt liquid by the application of heat and at a temperature slightl below the fusing point of said .article and elow the fusing Eomt of beryllium, immersing the article earing the said metal layer deposited thereon in said melt, the said article being connected as the cathode, and electrolyzing the said melt with the aid of an insoluble anode.

testimony whereof I afiix my signature.

HELLMUT- FISCHER.