CS196969B1 - Phosphatizing agent for metals surface treatment - Google Patents

Description

The invention relates to a phosphatizing agent for the treatment of metal surfaces, in particular for temporary corrosion protection and for pretreatment of the metal surface under coatings to be dissolved in a non-aqueous solvent.

Known phosphatizing agents of this type contain, in addition to a non-aqueous solvent such as an aromatic, aliphatic or chlorinated hydrocarbon, solubilizing components such as aliphatic alcohol and phosphoric acid, further additives to enhance the stability of the bath, optionally to improve the quality and structure of the phosphate layer formed. In particular, acetic acid, thiourea derivatives, organic nitro, nitroso- or azo compounds, dimethylglyoxime or indigo are used in the function of these additives. In addition to the purely organic compounds, compounds containing a divalent zinc cation such as oxide, acetate, phosphate or nitrate can also be applied.

These known phosphatizing agents have the disadvantage that only a small surface area of the metal to be protected can be treated, whereby the phosphate layers formed are amorphous or coarse crystalline and, due to the inhomogeneities in the layer, their protective efficacy is relatively low.

For example, only one liter of a known bath containing, in addition to trichlorethylene, ethanol, phosphoric acid and dimethylglyoxime, only 0.5 m of steel surface can be treated, whereby

196 969

198 989 The protective efficacy of the layers formed in this bath under indirect weathering conditions is 60 days. One liter of another known zinc ion-containing phosphatizing bath can be used to treat 1.3 m of steel surface, the protective efficacy of the layers resulting from the indirect weathering of the baths being 90 days.

These drawbacks are largely overcome by the phosphatizing agent for the metal surface treatment according to the invention, comprising phosphoric acid and divalent zinc compounds, characterized in that it contains from 0.01 to 2% by weight of divalent manganese compounds such as manganese carbonate and / or or from 0.01 to 1% by weight of calcium compounds, such as calcium oxide, and / or from 0.01 to 1% by weight of an alkali metal fluoride, such as sodium fluoride. It is also an object of the present invention to find an optimum concentration range of the composition in the solvent, after which the phosphatizing bath itself is formed. The principle of this solution consists in that, for 1 part by weight of said active ingredients, the preparation according to the invention contains 80 to 200 parts by weight of solvent.

By using the composition of the invention, an extended phosphatization bath can be prepared

About efficiency, so one liter. The bath can be treated with, for example, 2 m of steel surface. In addition, the phosphate layer formed is uniform and hydrogenic, so that its protective effect is considerably longer than that of amorphous or coarse-crystalline phosphate layers formed using known phosphatizing baths.

The phosphatizing agent for surface treatment of metals is further explained by describing examples of its composition.

Example 1

0.2250 g of zinc oxide and 0.0125 g of sodium fluoride were dissolved in 99.7625 g of 85% phosphoric acid. The phosphatizing agent thus formed was dissolved in an amount of 0.8 g in a mixture of 94.3 g of trichlorethylene and 4.9 g of n-amyl alcohol to form the actual phosphatizing bath. One liter of this phosphatizing bath has a surface area of 2 m? at 86 ° C over a one minute period. The resulting 1.8 g / m 2 layer provided good temporary protection of the steel surface for 120 days.

Example 2

0.2250 g of zinc oxide, 0.0125 g of sodium fluoride and 0.0125 g of manganese carbonate were dissolved in 99.7500 g of 85% phosphoric acid. The resulting phosphatizing agent was dissolved in a ratio of 1: 124 in a mixture of 94.3 g of perchlorethylene and 4.90 g of n-amyl alcohol

This phosphatizing bath was used to treat the steel surface at 120 ° C. In 120s arose 9.

a 1.5 g / m layer provided corrosion resistance of the steel product upon storage for 110 days.

Example 3

0.2250 g of zinc oxide was dissolved in 99.7625 g of 85% phosphoric acid and

0.0125 g of calcium oxide. The thus obtained phosphatizing agent in an amount of 0.8 g was dissolved in a mixture of 94.3 g of trichlorethylene and 4.90 g of n-amyl alcohol and 1 liter of this

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The steel surface was treated with an area of 1.8 m.

In all the described embodiments of the invention, the surface area treated with 1 liter of bath was considerably larger than that of the known baths and the resulting phosphate layer exhibited a considerably higher grain fineness. The coating applied to the phosphate layer has a higher adhesion to the metal surface than phosphate formed in an aqueous medium, and the corrosion resistance of the metal-non-aqueous phosphate-coating system is higher.

The phosphatizing agent according to the invention can be used in the form of a dip or spray at the boiling point of a bath in all industries, both for temporary protection of the metal surface against corrosion and for pretreatment of the metal surface under coating.

SUBJECT OF THE INVENTION

Claims (2)

SUBJECT OF THE INVENTION Phosphatizing agent for the surface treatment of metals, containing phosphoric acid and divalent zinc compounds, characterized in that it contains from 0.01 to 2% by weight of divalent manganese compounds, for example manganese carbonate and / or from 0.01 to 1% by weight of compounds % of calcium, for example calcium oxide and / or from 0.01 to 1% by weight of an alkali metal fluoride, for example sodium fluoride. 2. Phosphatizing agent according to claim 1, characterized in that it contains from 80 to 200 parts by weight of solvent per part by weight of active substances.