US2059770A - Method of preventing corrosion, particularly of metals from the iron-group, and to a orrosion preventative - Google Patents

Description

Patented Nov. 3-, 1936 UNITED STATES- 2.059.710 rm'rnon or PREVENTING connosron.

PARTICULARLY OF IRON- GROUP, AND PREVENTATIVE "METALS mom 'rns To A conaosron Anton Bopp, Heilbronn-on-the-Neckar;

Germany v No Drawing. Application June 25, 1934, Serial No. 732,386. In Germany May 31', 1934 18 Claims.

This invention relates to a method of preventing corrosion,-particularly of metals of the iron group, and to a corrosion preventative.

There are many methods and means known for 5 preventing corrosion, especially of metals of the iron group, but they chiefly attain a mere covering of the surface to be protected." The surface is not rendered passive and, above all, rust is not consumed at all, or only during a short time until the chemical equilibrium has been established.

or as long as the protective film or paint remains sufficiently intact, whereupon corrosion will again set in. The known methods and means are further unable to produce an eflec't over distances which is of practical value. The covering layer is suificiently close and homogeneous in only a few cases, and even so, the slightest damage will cause corrosion to set in again.

, This is particularly so if covering layers are chosen which are positive against iron in the E.

M. F. S. Base and at the same time easily corroding covering layers are also practically useless. The known corrosion preventatives are, therefore, more or less nothing else but preserving coverings whose efilciency depends on the state of the covering layer or paint-film.

The present invention proposes a method and a means for preventing corrosion, especially of metals of the iron group, which diflers from the known methods in so far as the surface of the metal is provided with a substance having such a composition that the parallel and interlocking processes will take place described in the following: First, a covering of the surface to be protected; second, an anodic and cathodic refinement of the basic metal combined with a reduction of the local elements and an increase in the overtension of the local cathodes; third, a reduction of oxygen solubility; fourth, an increase of the metal ions in the electrolyte limit layers; fifth,

an effective reduction of the total electric potential difference owing to the oxide mixture contained in the composition of the substance; and sixth, the formation of a non-corroding passive protective layer which will be independent after development from the paint film and adhere to the basic metal so that it will withstand hammering.

In other words, the invention consists in providing a method which produces certain processes known per se, at least partly, but not suitably combined hitherto and extended so as to be utilized for the prevention of corrosion. These processes were incapable till now of producing a non-corroding and highly passive covering layer adapted to be exposed to great technical strain without harm and independent of the paint-film. Furthermore, a means has been found for utilizing these processes. The known processes and means provide only for some of the steps recited above with the exception of the last one. The simultaneous and interlocking arrangement of these individual processes was hitherto unknown and no means or method was available to bring about all of them at the same time. The difiiculty which the invention has overcome consisted chiefly in the fact that the constituents of the new composition were partly known as anti-corroding agents and that the various groups of these agents counteracted each other and could not thus attain a maximum of protection. The essence of the invention is the knowledge that the individual steps as brought about by the qualitative and quantitative grouping of the constituents of the new agent are required to attain greater protec- 20 tion than ever before. It has been found that a substance capable of bringing about the processes mentioned above is the following:

Example Parts by weight zirconium dioxide 5 Aluminium Aluminium silicate Tal Magnesium oxide Sodium carbonate Barium sulfate Zinc oxide Lead tetroxide Basic lead carbonate Chromic oxide, amorph Cupric oxide Nickel cy n Graphite Lead mzide Titanium, white (non-acid) 1-3 or instead of titanium white (non-acid) an ilmenite of the formula xFeTiO3+yFe2O3 (pure FeTiOa if possible) of which 1-5 parts by weight should be added to the mixture.

The quantitative composition stated depends, relative to the, graphite and lead oxide, upon the binding agent used, the lower limit of the applica-v tion of poor binding agents corresponding to the upper limit of using rich binding agents. In connection with the rolling-in and fusing methods no graphite is used. The substances stated above are mixed together. To apply the new agent in the form of a paint this mixture is then ground with a suitable binding agent into a paste and, finally,

prepared, by the addition of a further quantity of the binding agent, to have a consistency which allows easy application. 7 The fineness depends upon the particular use and should be highly dispersed if maximum protection is desired.

The finished preparation is then brushed or rolled upon the surface to be protected orfused therein.

For applying the agent by painting, particles of unequal size are chosen and of different grinding fineness, as stated, and mixed with a binding agent. Preferably, linseed oil with or without an addition of wood oil is used and diluted with petrol or benzol derivatives to suit requirements. For submarine paints a rapidly drying varnish base is employed. So far as necessary, the proportion of pigment to the binding agent is chosen on the basis of the critical oil content.

When rolling-in or fusing is resorted to the binding agent is dispensed with.

The parallel and interlocking individual steps are, in the main, the following: i

In the first place, covering is effected which does not only mean that the surface to be protected is covered so that corroding agents have no access. This is effected also by known agents, at least for a certain time. The covering according to the invention forms rather 9. protecting roof under which the other steps take place undisturbed by outside influences. n the other hand, the covering does not interfere in any way with the processes going on underneath it. This covering is produced by the choice of the binding agent and the combination of the latter with the constituents having unequal sizes of particles, of which, as film-forming elements, aluminium, silicates, barium sulfate and graphite are particularly effective. Graphite in particular has a favorable influence upon the waterproofing of the film. The covering finally culminates in the production of a protective layer having a physical and electrochemical action, as described below.

Secondly, the basic metal is refined owing to anodic and cathodic eifects taking place simultaneously between the agent and the metal, i. e., ionizing processes are going on in which the basic metal alternately forms the anode and cathode. With the known anti-corroding agents a reduction of the influences of the local cathodes is mainly intended so as to refine the surface of the basic metal. As corrosion depends on the proportion of the surfaces of the anodic and cathodic places relative to each other, the new preventative aims at a simultaneous reduction of the cathodic and anodic surfaces, i.'e., of the local elements in general. Both are provided with insoluble coatings of metal, metal-soaps,

oxides or hydroxides, which are so poor in pores that existing local current favor further growing over of pores. As anodic retarders, which are usually organic or carbon compounds capable of forming on the anodic surfaces of the local elements insoluble covering layers poor in pores for rendering the anodal potential more negative, silicates and cyanide are utilized. In so far as the formation of the covering layer does not take place directly in electrochemical manner, the decrease in the number of pores is due to the formation of metal scrap (or sebates of heavy metal), aluminium scales and pigment particles, in the latter case caused by an unequally sized grain distribution. Local cathodic overtension as improvement in approximation to the potential of the basic metal is effected also by poisoning by means of deposits of scales and pigments, such as Al-, Mg-, Pb-, Tl-, Zr-compounds, in addition to,

metals properly placed high in the E. M. F. Series, coverings and reduction of pores.

There is further a reduction in oxygen solubility, chiefly caused by the cooperation of pigment, oil and, especially, graphite which, "as stated, plays an important part in mere covering too. The reduction of oxygen solubility is of importance only in the painting process. In the rolling and fusing processes graphite is superfluous. The reduction in oxygen solubility finds expression also in overtensions. The overtension of the hydrogen, briefly referred to as overtension on the cathode metal, is the difference between the liberation potential and the potential of the reversible hydrogen electrode.

Another process is the increase of metal ions in the electrolyte limit layers, which favors depositions from saturations and increases resistance.

A fifth feature is that the oxidemixture acts with its special potential and has the advantage of being almost completely free from corrosion. Remarkable are the high transition resistances of the oxides with respect to metal. In certain cases, this special polyoxide system will act also thermoelectrically. The known anti-corroding agents contain oxides, except lead oxides, chiefly as pigments or fillers, that is, for causing a coloring effect or securing a film. According to the invention, a certain series of oxides have been selected for the purpose of utilizing their specific electric character as a polyoxide system for rendering passive the respective surfaces.

The corrosion preventative according to the invention has a grey color without the addition of a dyestufl".

The formation of the film takes place as follows: After hard drying an elastic and at the same time tough film is formed under which the rust is removed to a considerable degree, or completely if the amount of rust was originally small. Furthermore, on the basic metal -is formed an electrically conducting, very hard, elastic, extraordinarily adhering and even malleable and heatresisting protective layer which has" a metallic luster and which renders superfluous even the film of paint when fully developed.

This protecting layer is rustproof and will withstand the severest strain. When fully developed, it has a considerable distance action with respect to passivity while maintaining the refining processes mentioned above, even after its generator, the fllm, has been removed. It has been ascertained by experiments that plates of whose surface only 60% had been treated with the preventative according to the invention remained free from rust on the untreated 40% also, if the rusting was effected with the exclusion of strong acids. If the experimental metal was exposed only to atmospheric influences, in the Tropics to be sure, it sufliced to treat only 50% of the surface of the metal to keep the entire surface rustfree by distance action. Used in the form of a paint, the preventative can be easily applied, possesses great covering power, is colorable in certain shades, very adhesive, hard and tough, quickly drying, weatherand water-proof and nonsetting. Above all, only one cost is suflicient. Growth of any kind in fresh and brackish water, even in the Tropical Zone (Venezuela) could not be found.

It is thought that the method and the preventative according to the invention represent a considerable technical advance in preventing cor- ID 9 I claim:

1. A corrosion preventative of the type described, comprising zirconium dioxide, aluminium, aluminium silicate, talc, magnesium oxide, sodium carbonate, barium sulfate, zinc oxide, lead tetroxide, basic lead carbonate, amorphous chromic oxide, cupric oxide, nickel cyanide, lead oxide, and titanium white.

2. A corrosion preventative comprising parts zirconium dioxide, 4 parts aluminium, 120 parts aluminium silicate, 30 parts talc, parts magnesium oxide, 1 part sodium carbonate, 50 parts barium sulfate, 20 parts zinc oxide, 50 parts lead tetroxide, 40 parts basic lead carbonate, 5 parts amorphous chromic oxide, 4 parts cupric oxide, 2 parts nickel cyanide, 10-25 parts lead oxide, and 1-3 parts non-acid titanium white.

3. A corrosion preventative of the type described, comprising zirconium dioxide, aluminium, aluminium silicate, talc, magnesium oxide, sodium carbonate, barium sulfate, zinc oxide, lead tetroxide, basic vlead carbonate, amorphous chromic oxide, cupric oxide, nickel cyanide, lead oxide, and ilmenite of the formula 4. A corrosion preventative comprising 5 parts zirconium dioxide, 4 parts aluminium, 120 parts aluminium silicate, 30 parts talc, 10 parts magnesium oxide, 1 part sodium carbonate, 50 parts barium sulfate, 20 parts zinc oxide, 50 parts lead tetroxide, 40 parts basic lead carbonate, 5 parts amorphous chromic oxide, 4 parts cupric oxide, 2 parts nickel cyanide, 10-25 parts lead oxide, and

l-5 parts ilmenite of the formula 5. A method of preventing corrosion of metals which comprises rolling into the surface of the metal to be protected, a composition comprising zirconium dioxide, aluminium, aluminium silicate, talc, magnesium oxide, sodium carbonate, barium sulfate, zinc oxide, lead tetroxide, basic lead carbonate, amorphous chromic oxide, cupric oxide, nickel cyanide, lead oxide, and titanium white.

6. A method of preventing corrosion of metals which comprises rolling into the surface of the metal to be protected, a composition comprising 5 parts zirconium dioxide, 4 parts aluminium, 120 parts aluminium silicate, 30 parts talc, 10 parts magnesium oxide, 1 part sodium carbonate, 50 parts barium sulfate, 20 parts zinc oxide, 50 parts lead tetroxide, 40 parts basic lead carbonate, 5

' parts amorphous chromic oxide, 4 parts cupric oxide, 2 parts nickel cyanide, 10-25 parts leadzirconium dioxide, aluminium, aluminium silicate, talc, magnesium oxide, sodium carbonate. barium sulfate, zinc oxide, lead tetroxide, basic lead carbonate, amorphous chromic oxide, cupric oxide, nickel cyanide, lead oxide, and titanium white.

8. A method of preventing corrosion of metals which comprises fusing into the surface of the metal to be protected a composition comprising 5 parts zirconium dioxide, 4 parts aluminium, 120 parts aluminium silicate, 30 parts talc, 10 parts magnesium oxide, 1 part sodium carbonate, 50 parts barium sulfate, 20 parts zinc oxide, 50 parts lead tetroxide, 40 parts basic lead carbonate, 5 parts amorphous chromic oxide, 4 parts cupric oxide, 2 parts nickel cyanide, 10-25 parts lead oxide, and 1-3 parts non-acid titanium white.

9. A method of preventing corrosion of metals which comprises applying to the surface of the metal to be protected, a composition comprising zirconium dioxide, aluminium, aluminium silicate, talc, magnesium oxide, sodium carbonate, barium sulfate, zinc oxide, lead tetroxide, basic lead carbonate, amorphous chromic oxide, cupric oxide, nickel cyanide, lead oxide, and titanium white. I

10. A method of preventing corrosion of metals which comprises applying to the surface of the metal to be protected, a composition comprising 5 parts zirconium dioxide, 4 parts aluminium, 120 parts aluminium silicate, 30 parts talc. 10 parts magnesium oxide, 1 part sodium carbonate, 50 parts barium sulfate, 20 parts zinc oxide, 50 parts lead tetroxide, 40 parts basic lead carbonate, 5 parts amorphous chromic oxide, 4 parts cupric oxide, 2 parts nickel cyanide, 10-25 parts lead oxide, and 1-3 parts non-acid titanium white.

11. A corrosion preventative according to claim 1, in which graphite is included.

12. A corrosion preventative according to claim 2, in which 1-5 parts graphite is included.

13. A method according to claim 9, in which the composition includes graphite.

14. A method according to claim 10, in which the composition includes 1 to 5 parts graphite.

15. A method according to claim 9, in which the composition is applied by brushing it onto the metal surface.

16. A method according to claim 10, in which the composition is applied by brushing it onto the metal surface.

17. A method according to claim 9, in which the composition is applied by brushing it onto the metal surface, and in which the composition includes graphite.

18. A method according to claim 10, in which the composition is applied by brushing it onto the metal surface, and in which the composition includes 1-5 parts graphite.

, ANTON BOPP.