DE480995C - Process for coating and coloring metals - Google Patents

Description

Process for coating and coloring metals The invention relates to specializing in the plating and coloring of metals and metal objects that are entirely or mainly of iron, steel, tin, aluminum, lead, magnesium, zinc and Caclmium, either alone or in a mixture with one another or in smaller proportions alloyed with other metals.

It is known that the metals cadtnium and zinc when combined into one Solution of a molybdate are immersed to obtain an adherent coating, but this procedure either has no result at all when applied to other metals or give a powdery, non-adherent precipitate unless used an electrical potential, which either by contact with a suitable metal in the solution or by connection with an electrical one lying outside Energy source has been achieved.

The object of the present invention is a simple, cheap, Fast and technically convenient process, creating a tightly adhering and protective Plating on common metals using molybdenum compounds and can be produced without using an electrical potential. Execution The procedure is so simple and safe that it can be carried out even by untrained personnel can be done.

It has been found that the above-identified object has been achieved when certain other substances are used in conjunction with the molybdate solution used either alone or in combination with each other.

The effect of these substances is likely to be that they with the Malybdate form complex compounds, with the individual embodiments of the Kind of after the same effect is achieved.

The molybdates used are those of the alkali metals (sodium, potassium, lithium, ammonium). It makes no difference which alkali is used. Handiness and cheapness are the only factors into consideration. Leave the added modifying or controlling salts, which are preferred. are classified as follows: r. Salts of oxalic acid. These are preferably the alkali salts of this radical, although if carried out carefully, the acid itself can be used and forms an oxalate with the base already in the bath. The molybdate is used in a concentration of% a to il / "and the oxalate in a concentration of - /, to 111, although this information is not intended to delimit the area of use or protection. However, it is preferable to use dilute solutions because the coatings obtained are harder and denser and there is also less loss when rinsing .. In general, it is most advantageous to choose the percentage of the oxalate at least as high as that of the molybdate.

2. Soluble fluorides. These are preferably in the form of double fluorides used, e.g. B. the double fluoride of an alkali metal, such as sodium with silicon, Iron, aluminum, zirconium, titanium, etc. In some cases a single fluoride alone, particularly sodium fluoride, may be used, but is generally a mixture a single fluoride with a double fluoride for any cheap and useful dyeing method except in the event that lead is treated. It was found, that fluorosilicates are the cheapest and most economical compounds, and these Substance alone is completely sufficient when combined with the molybdate solution for objects made of aluminum or tin hzw. substances containing these metals are used will. In the case of tin, the individual fluoride completes the same way as sodium fluoride the desired result when used with the molybdate solution, though Sodium fluoride is a more expensive compound. Sodium fluoride also scores one very hard, adhesive coating when combined with soluble molybdates for iron objects, etc., is used although its effectiveness is poor. In the case of iron, the coating provided by sodium silicon fluoride alone is insufficient firmly adhering, but which effect can be achieved if sodium fluoride or, which is essentially the same, an alkali carbonate, that with the sodium silicon fluoride reacts, is added. Accordingly, it is recommended for practical implementation, to use a mixture of sodium silicon fluoride and a second alkali compound, which is able to react with such a double fluoride, wherein in connection with the molybdate solution is a satisfactory coating solution for the above-mentioned ordinary ones Metals is achieved. Contains a very effective, cheap and reliable solution per liter of water 2 g sodium silicon fluoride, 2 g alkali carbonate, 2 g soluble Molybdate. This information does not constitute any limitation. 3. Increased acidification. For example forms added molybdic acid, tungsten or boric acid with the soluble molybdate an acid salt, and this achieves better adhesion for various reasons of the coating than is possible when using a neutral salt. The effect is not as satisfactory as with the oxalate or the double fluoride, but it is commercially successful results can be achieved with it. Such successful ones Results were e.g. B. obtained with a content of these acids of one tenth up to a quarter of the molybdate present.

Aluminum chloride. Advantageously, this becomes the major used for metals or objects made of lead or its alloys. There is remarkable results also with iron. As for lead, there is obviously better results than any other substance, like even the oxalates. B e i s p i e 1: Is a solution with i g of soluble molybdate and 5 g of aluminum chloride on i 1 Water. This solution gives the whole gamut of colors with lead from blue to yellow, red, green, brown to black. The oxalates often only bring the coating to the red stage. Certain other salts can also be used with lead, such as: B. aluminum sulfate, Alums, magnesium salts and manganese salts (such as disulfates or chlorides), but give most of these only half the color gamut.

Soluble polysilicates. These appear beneficial in use for iron and such objects. Such polysilicates are by adding a Excess silica made into a sodium silicate solution. A useful one Treatment bath contains 2 g soluble molybdate, 2% 10 g polysilicate, i 1 water.

In any case, the solution is preferably applied hot, and the Metals or objects to be treated are first completely cleaned and then dipped in the solution for half a minute to five minutes. The longer or shorter Immersion time depends on the depth and thickness of the desired coating. It hurts also nothing if the immersion is carried out for too long, as the procedure is self-contained brings to a standstill. The type of preparatory treatment must of course be such so that it does not collide with the effect of the bath. This prevents z. B. that Picking iron or objects made of it in chromic acid or its soluble compounds the successful formation of a layer. On the other hand, it shows, although the procedure not for the production of coatings on copper that a previous treatment is used des eisertien Object by immersion in a copper-containing Solution, so that a shiny copper coating is formed on it, has the consequence that the precipitation in the molybdenum bath is improved. With aluminum is the most beneficial Pickelbad the solution of a double fluoride, such as silicofluorosodium, although this no restriction means.

The coating obtained in the above way is dense, hard, impenetrable, firmly adhering and protecting against corrosive influences, it is also attractive for the eye even in the untreated state and forms a suitable basis for Paint, varnish, enamel, Japanese varnish and other subsequent coatings.

The protective effect of iron Gegens '' t in (J s applied coating can also be improved by the following chemical treatment "-erden It would found that despite the inability of a satisfactory coating by treatment-in a solution of chromic acid or the compounds of the resistance. Of Metal against damp or atmospheric corrosion is significantly increased if the object after coating is treated for a short time, i.e. 5 to 10 minutes, in a solution of soluble chromate (e.g. sodium or potassium chromate or dichromate) will. Excellent results have been obtained when the Gogen stands have been boiled in a 5 percent chromate solution for the length of the appropriate time. The best results in this rust prevention method have been obtained when the iron object is first picked in a suitable bath such as sulfuric acid, then a shiny copper coating was applied in the solution of copper sulphate, the copper solution was then rinsed off, the object was then immersed for half a minute to five minutes in a bath containing molybdenum and one of the above modifying ingredients, after which it was finally boiled in a solution of a chromium salt Forged cast iron is particularly suitable for this process.

Of course, the invention is not limited to the complete one Series of individual work steps, as the objects are immersed in a molybdate solution, modified by suitable energizing or activating reagents was, forms the basic idea of the invention and the addition of the other operations or modifications in the reagents are only regarded as color-changing conditions will.

In the treatment of zinc and cadmium it is advantageous use the combination of 1Volybdate with ammonium sulfate as a coloring solution, while with the other metals, ammonium sulfate, is expediently used together with molybdates and acids will.

Claims (1)

PATENT CLAIMS: i. Process for the production of an adhesive coating on metals or objects made of one or more of the metals iron, aluminum, Tin, lead; Magnesium, zinc and cadmium are made using molybdate solvents without application of an electrical potential, characterized in that this one or more salts of oxalic, polysilicic, hydrofluoric, silicofluoric acid contain. a. Method according to claim i, characterized in that the solution in addition to or in place of the salts of oxalic, polysilicic, hydrofluoric, silicofluoric acid Contains ammonium sulphate. 3. The method according to claim i, characterized in that the solution in addition to the soluble molybdate a soluble silica fluoride and a second Contains alkali compound capable of reacting with the soluble silica fluoride. 4: The method according to claim i, characterized in that the treatment with the hot solution of a molybdate in the presence of hydrofluoric acid. 5. The method according to claim i, characterized in that the metal with lead the solution of a soluble molybdate and a soluble salt of the metals aluminum (Aluminum chloride), magnesium, manganese with acids other than those mentioned in claim z is treated. 6. The method according to claim i, characterized in that in the Treatment of iron this is first provided with a smooth coating of copper and then treated with a solution of molybdenum salts and fluorides, on which treatment with a chromate solution can follow. 7. Procedure according to Claim i, characterized in that in the treatment of iron the objects first with a solution containing soluble salts of molybdenum and fluorine, and then treated with the solution of chromates. B. The method according to claim i, characterized in that when treating iron the objects first with a smooth coating of copper be provided on what a layer containing a molybdenum compound is deposited. . G. Method according to claim i, - characterized in that in the treatment of Iron objects first have a coating on them, which is a molybdenum compound contains, is precipitated, whereupon the same with a hot solution of a chromate is treated.