US 1811298 A
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Patented June 23, 1931 UNITED STATES PATENT OFFICE cILARLEs OULANGERQOF CLICHY, FRANCE, ASSIGNOR T0 soomrn con'rm'nm'nnn PARKER, 01 CLICHY, FRANCE PROCESS .AN'DIPRODUGT FOR PROTECTING ALU MINIUM, MAGNESIUM AND THEIR. Ad)- I LOYS AGAINST CORROSION No Drawing. Application filed October 21, 1929, Serial No. 401,384, and in Fra'nce November 10, 1928.
The present inventionhas for itsobject a process of protecting the surface of aluminium, magnesium, or their alloys, against attacks by salt solutions,- such as chloride of sodium, or by moist air loaded with particles of these solutions, for instance sea air capable of causing the alteration or corrosion of the metal. p The. process is essentially characterized by the fact that, by"means of a salt bath, a protecting deposit is formed at the surface of the metal, and that, to form this deposit, use
as chromates, vanadates, molybda-tes, tungstates, ititanates, uranates, niobates, manganates, etc., either alone, or mixed together.
' It is necessary that the metal chosen can I give at least two oxidesthe most oxygenated of which gives an alkalisalt soluble in an alkaline solution. By reduction, the corresponding oxide is brought back to the state of sub-oxide. Thus, a manganate corresponding to managanic" acid MnO H O, will be brought back to the state of'Mn Q or of Mn O which are stable, do not corrode when inuse, and form at the surface of aluminium, for instance, the. desired protecting layer.
The formation of this layer can be obtained by immersion of the metal part or member in a bath ofthe chosen salt, at a suitable degree of concentration and at a suitable temperature. 'The bath must be rendered alkaline by the'addition of an alkali'car.
bonate, droxide. For instance for protecting an article made of aluminium, it can be immersed in a boiling solution of carbonate of sodium at about 1%, and of molybdate of sodium or potassium It has been found that the following ess, derived from the preceding one, .procures special advantages concerning the practical industrial carrying'out of the process.
better preservation of-these salts in presence of moisture can be obtained by addition of a small quantity of a salt, such as borate' of soda, which is without action on the deposited oxide film be protected. 1
is made of solutions of alkali metal salts such-1 or oi? the corresponding alkali hyand on the metal to A mixture of these two salts gives, in
sti'tute an example, since use can be made of sulphoitun state instead of sulpho-molybdate, or o sulpho-uranate, with phosphovanadate or phospho-manganate, either alone or mixed together.
' By way of example, the following proportions can be indicated for protecting aluminium:
Mixture of'phospho-chromate and of sulpho-molybdate of potash0.5% of the bath.
Carbonate of Solvay soda: 1% of the solution. 1
The concentration of the solution in alkali carbonate varies but slightly inuse. The
loss of salt caused by deposition, will be compensated by the introduction of a; further quantity of salt in become weaker.
The above mentioned proportion as the bath will salts are stable, they do not alter under the action of air and moisture, they are extremely soluble. The mixing of these salts with carbonate of soda pro cures the same qualities of unalterableness and of solubility.
The treatment of the article to beprotected is efi'ected at boiling point; the duration of the treatment depends on the thickness of the deposit it is desired to obtain.
.' The protecting layer constitutes an excellent holding surface for any varnish, paint,
"fatty bodies, enamels, etc.
Claims 1. Process for protecting articles made of aluminium, magnesium, or their alloys, against corrosion, of the said articles in a bath containing carbonate of soda and an alkali salt of the most oxygenated oxide of a metal capable of forming at least two oxides the mostoxygenated' one being soluble .in alkaline solution and the less oxygenated one being insoluble.
2. Process for protecting articles made of 1M comprising the treatment aluminium, magnesium, or their alloys, against corrosion, comprising the treatment of the said articles in a bath containing carbonate of soda and a mixture of alkali sul- 5 pho-molybdate and alkali phospho chromatei 3. Process for protecting articles "made of aluminium, magnesium, or their alloys, against corrosion, comprising the treatment 0 the said'articles in a bath containing carbonate of soda and a mixture composed of 1 part of alkali sulpho-molybdate and 5 parts of alkali phospho-chromate. r 4. Product servin to reduce a protecting layer on articles 111 e o aluminium, magnesium or their alloys, comprising a carbonate of alkali metal and a salt formed by an alkali metal and by one of the following metals; I vanadium, molybdenum, tungsten, titanium,
uranium, niobium, manganese and chromium.
5. .Process for protecting articles made of aluminium, magnesium, or their alloys, comprising the treatmentof the said articles in. a
. ,ath, containing carbonate of soda and an alkali salt of, a metal capable of givin atleast two oxides, such as vanadium, moly denum, tungsten, titanium, uranium, niobium, manganese and chromium.
In testimony whereof I have hereunto so aflixed my signature.