US2162129A - Fluorine containing layer on light metals - Google Patents

Description

Eatented June 13, 3939 UNITED STATS FLUO RINE CONTAINING LAYER ON LIGHT METALS Julius Still, Leverkusen-I. G. Wei-k, Germany, as-

signor, by mesne assignments, to Magnesium Development Corporation, a corporation of Delaware No Drawing. Application July 23, 1936, Serial No. 92,251. In Germany July 27, 1935 3 Claims.

This invention relates to the manufacture of fluorine containing layers on light metals or.

10 In accordance with the present invention fluorine containing layers are prepared on light metals or alloys thereof, such as magnesium, the alloy thereof known under the trade-mark "Elektron", byelectrolysis using as an electrolyte 15 a poly-acid fluoride having the composition YF.::(HF) wherein a: is at least 2 and YF stands for a member of the group consisting of the alkali metal fluorides, ammonium fluoride, amido fluorides and amino fluorides. Besides the alkali 20 metal poly-acid fluorides and ammonium polyacid fluorides, there may be used the poly-acid fluorides of amides or amines, such as of urea, acetamide, aniline, methylamine, ethylamine, diphenylamine, diethylamine, tetramethyl-ammo- 25 nium hydroxide and the like. Mixtures of the above mentioned poly-acid fluorides may be employed as well as mixtures of the same with neutral fluorides or bifluorides, The poly-acid fluorides used in accordance with the present-invention are characterized by having a comparatively low melting point, so that the process can be performed at low temperatures and with slight consumption of energy, due to which fact the process can also be applied to such metals or 35 alloys with a comparatively low melting point.

As suitable poly-acid fluorides there may be mentioned by way of example the potassium poly-. acid fluorides of the composition 'KF.2HF to KLMHF, the melting points of the said poly-acid 40 fluorides being between 60 and '10v C.; furthermore, ammonium poly-acid fluorides of the composition NH4F.2HF to '-NH4F.5HF. melting between about 20 and 30 0.; further a mixture of poly-acid fluorides of the composition 45 msnr+nmnnr in various proportions, for example in the ratio 1:1; or a mixture of 80% of NH4F.2HF and 20% of NHJHF, the latter mixture melting at 20 C.

Example 1.A magnesium sheet is placed into a melt of NH4F.2HFand used as the anode. At 55 40-50 C. an electric current which is regulated by means of a regulating resistance to 1 ampere per square decimeter is passed through for about minutes. Thereby the tension rises from about 50 to about 135 volts. In this manner a fluorine containing layer is produced on the magnesium sheet.

Example 2.In the same manner a fluorine containing layer is'produced on a plate of Elek- 5 tron" metal. The Elektron plate is used as the anode. As the electrolyte the salt of ZEEEHF is used and a current of ampere per square decimeter is passed through for about minutes at 80-90" C. The final tension is about 10 56 volts. 7

Example 3.'In an analogous manner a fluorine containing layer is produced on a magnesium plate while working with a,mixture of KF.2.5HF+NH4F.HF in the proportion 1:1 and passing through a current of l ampere per square decimeter for 10 minutes at 100 C. The tension during the process rises to 58-62 volts.

,1. A process of forming a protective fluorine containing layer on articles made of a metal of the group consisting of magnesium and magnesium base alloys, which comprises subjecting a fused electrolyte, comprising at least one polyacid fluoride having the composition YF.:r(HZF),

wherein a: is at least 2 and not more than 5 and YF stands for a member of the group consisting of the alkali metal fluorides, ammonium fluorides, amide fluorides and amino fluorides, to electrolysis while employing such metal article as the anode.

2. A process of forminga protective fluorine containing layer on articles made of a metal of the group consisting of magnesium and magnesium base alloys, which comprises subjecting a fused electrolyte, comprising at least one polyacid fluoride having the composition YF.a:(HF), wherein a: is at least 2 and not more than 5 and YF stands for a member of the group consisting of the alkali metal fluorides, ammonium fluorides, amido fluorides and amino fluorides, andat least one fluoride of the group consisting of' neutral fluorides and bifluorides, to electrolysis while employing such metal article as the anode. -3. A process of forming a protective fluorine containing layer on articles made of a metal of the group consisting of magnesium and magnesium base alloys, which comprises subjecting a fused electrolyte having a melting point not exceeding about 100 C. and substantially consisting of at least onepoly-acid fluoride having the composition YF.a:(I-IF),.wherein a: is at least 2 and not more than 5 and Y5 stands for a member of the group consisting of the alkali metal fluorides, ammonium fluorides, amido 5 fluorides and amino fluorides, to electrolysis while employing such metal article as the anode. JULIUS sou.