CZ170492A3 - Anti-corrosion molybdate, tungsten pigment - Google Patents

Abstract

Described is a non-toxic anti-corrosion molybdate, tungsten pigment, containing 90.0 to 99.5 % by weight of a bearer from the group including: calcium carbonate, magnesium carbonate, magnesium oxide, zinc oxide, zinc phosphate, calcium phosphate hydroxide, and their mixtures, designed for organic solution and water soluble coating materials and 0.5 to 10.0 % by weight of molybdate and tungsten lime and possibly zincate in a mass ratio of molybdate:tungsten of 4:1 to 1:4, preferably 2:1.

Description

Technical field

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-corrosion molybdenum, a tungstate pigment intended for use with organic diluents and water-based paints. BACKGROUND OF THE INVENTION

The wider application of non-toxic anticorrosive molybdate pigments has been made possible by their preparation on carriers, thereby increasing the effective surface area of the anticorrosive molybdenum component coupled with improved utilization and lowering the cost of the pigment to an acceptable level for conventional paint applications.

However, despite considerable progress in refining properties, these pigments have not yet achieved as good corrosion-inhibiting effects in water-borne coating systems as toxic chromate pigments. Therefore, they are used as a substitute for environmental reasons.

The developed tungstate anticorrosion pigments have not been adopted in practice because their corrosion inhibitory effects are worse in all types of paints in the corrosion area parameter than in their analogs containing molybdates as active ingredient.

SUMMARY OF THE INVENTION

The above disadvantage of the worse inhibitory effects of molybdate or tungstate anticorrosion pigments alone, compared to chromate pigments, largely eliminates the anticorrosive pigment containing carriers from the group of substances such as calcium carbonate, magnesium carbonate, magnesium oxide, zinc oxide, zinc phosphate and mixtures thereof, characterized in that it contains 0.5 to 10.0% by weight of molybdate and tungsten and optionally zinc tungstate in a weight ratio of molybdate: tungstate of 1: 4 to 4: 1, preferably 2: 1.

The essence of the higher anticorrosive effect of the above-mentioned pigment consists in utilizing the synergistic action of molybdate and tungstate ions.

The resulting effect of this synergistic effect is a slight improvement in the inhibitory effects of the pigment in the area corrosion parameter ”and a significant improvement in the section corrosion parameter. As a result, the aforementioned type of pigments is shifted to a higher quality level and, due to its non-toxic nature, it approximates its parameters with chromate anticorrosive pigments even in water-based paints.

In order to reduce the cost of the above-mentioned pigment, it is suitable to carry out its preparation on carriers by gradual or simultaneous precipitation of molybdate and calcium and / or zinc tungstate so that the final composition of the mixtures is 90.0 to 99.5% by weight of the carrier and 0.5 to 10.0% by weight of molybdate and calcium and / or zinc tungstate, wherein the weight ratio of molybdate: tungstate is 1: 4 to 4: 1, preferably 2: 1.

A wide variety of inorganic substances can be used as carriers, for example calcium carbonate, magnesium carbonate, magnesium oxide, zinc oxide, zinc phosphate tetrahydrate, calcium phosphate hydroxide and mixtures thereof.

The lower limit of the active molybdate and tungstate components can be achieved, while preserving the anticorrosive properties of the pigment, by using the calcium carbonate prepared on the surface of the phosphates according to CS 262 306 to maintain the surface reactivity before eliminating the above active ingredients.

A description of a possible procedure for the preparation of our anticorrosive pigment, including the processes and the composition of the resulting product, is given in the following example, which can be considered optimal in terms of the anticorrosion properties achieved and the minimization of molybdate and tungstate.

DETAILED DESCRIPTION OF THE INVENTION

To a suspension of 400 g of calcium carbonate and 15 g of zinc oxide in water, 130 ml of 8.5% phosphoric acid are added under stirring to treat the surface of the calcium carbonate to form dicalcium phosphate and zinc phosphate.

After the reaction between the surface of the support and the phosphoric acid was complete, the suspension was heated to 80 ° C, and solutions of ammonium molybdate (total Mo content 1.2 g) and sodium tungstate (total content V 0.9 g) were added thereto with stirring. then a suspension containing 15 g of zinc oxide.

After about 1 hour dwell, unreacted molybdenum and tungstate ions are precipitated by the addition of an equivalent amount of soluble calcium salt (eg calcium nitrate solution). After a further delay, the suspension is filtered, washed with water and dried at 105 ° C.

The pigment prepared by the above procedure was identified by phase and chemical analysis as follows:

86.64 % wt. calcium carbonate + recalculation 6.00 % wt. zinc phosphate tetrahydrate 3.20 % wt. zinc oxide 3.10 % wt. calcium phosphate hydroxide 0.67 % wt. calcium molybdate 0.39 % wt. calcium tungstate

The corrosion inhibiting effects of the thus prepared pigment have been verified with a very good result in a number of paints. An example of a comparison of the corrosion inhibitory effects of this pigment and its analogue containing 1.06 wt. only the molybdate or tungstate active ingredients in the water-borne acrylic binder-based mass are given in the following table:

pigment attack of test sheets corrosion in area (%) Corrosion in (MRA ²⁾ cut ) molybdate, tungstate 0.4 50 - 70 molybdate 0.6 120 - 130 tungstate 2.7. 70 - 90

Note: Test of corrosion attack of test sheets was performed according to ČSN 673094 / A and evaluation according to ČSN 673089.

Industrial applicability

The invention is industrially applicable for the preparation of anticorrosive non-toxic pigments which can be applied in both synthetic and water-based paints.

PATENTOV E N O R 0 K Y 1. Anti-corrosion molybdenum, tungstate pigment containing carrier from the group of substances: carbonate calcium, carbonate

Claims (2)

as well as water-based paints. PATENTOV E N O R 0 K Y 1. Anti-corrosion molybdenum, tungstate pigment containing carrier from the group of substances: carbonate calcium, carbonate magnesium, magnesium oxide, zinc oxide, zinc phosphate, dicalcium phosphate and mixtures thereof, characterized in that it contains from 90 to 99.5% by weight of the carrier ≥ 0.5 to 10.0% by weight of molybdate and calcium tungstate by weight of molybdate: tungstate 4: 1 to 1: 4, preferably 2: 1. Anti-corrosive molybdate, tungsten (II) pigment according to claim 1, characterized in that the content is 90 to 99.5% by weight of carrier 0.5 to 10.0% by weight of molybdate, tungstate and calcium zincate.