DK172470B1 - Anti-corrosive coating compositions and their use to prevent corrosion, rusting and rust staining - Google Patents

Description

in DK PR 172470 B1

The invention relates to anti-corrosive coating compositions for use as a protective coating for metal surfaces, especially on iron and steel, in order to avoid rusting.

5 Anti-corrosive coatings are applied e.g. on bridges, steel structures that are exposed to the weather for long periods of time during the construction of buildings, bodies and components for cars, aircraft and other means of transport, agricultural machinery, oil installations and exposed 10 steel structures on ships. An anti-corrosion coating (a "factory primer") can be applied to freshly sandblasted steel sheets that must be stored before use for construction or shipbuilding.

Anticorrosive paints usually comprise a film-forming binder and one or more pigments. The pigments that have been considered the most effective in preventing corrosion are the moneys and the chromates, especially zinc chromate. Unfortunately, both moneys and chromatos are considered to be dangerous to health today. Many anticorrosive 20 paints sold today contain zinc phosphate as an anticorrosive pigment, but the properties of paints containing zinc phosphate have not been as good as the properties of paint containing zinc and zinc chromate. The present invention seeks to provide a paint which provides a better protection of iron and steel against rusting than zinc phosphate containing paints, which paint should not contain chemicals considered to be hazardous to health.

Many phosphates, phosphonates and polyphosphates have been used as corrosion inhibitors and flake formation inhibitors in aqueous systems. Among these are hydroxyethylidene-1,2-diphosphonic acid, also known as etidronic acid, and its salts, the use of which is disclosed in British Patent Specifications No. 1,201,334 and 1,261,554, and U.S. Patent No. 5,117,443.

3,431,217, 3,532,639 and 3,668,094, ethylene-1,1-diphosphonic acid disclosed in British Patent No. 1,261,554 and amino compounds substituted by two or more methylene-phosphonic acid groups described in British Patent

1 201 334 and US Patent 3,483,133. The preparation of a base salt-based lead salt of etidronic acid with a molar ratio of lead to etidronate of 0.5 (ratio of lead to phosphonate groups 0.25: 1) is described in U.S. Pat. Patent No. 4,020,091, and its use as a gelatinous pigment with high surface coverage is disclosed, although no mention is made of any anticorrosive properties.

DE 2 710 498 describes the application of paints containing 15 metal salts of phosphonecarboxylic acids and / or phosphonic acids to metal objects. The paint swells under heat to form a barrier layer which acts as a flame retardant. The preferred metals are magnesium, calcium, strontium, chromium, aluminum, zinc and iron, and the phosphonic acid may be a diphosphonic acid.

It has been found that salts comprising a polyvalent metal cation and an organic polyphosphonic acid having at least two phosphonic acid groups having a water solubility of not more than 2 g / l are useful as pigments in anti-corrosive coating compositions, especially with certain corrosive -sion passivators, to protect metal surfaces from corrosion, rust formation and rust staining.

The invention thus relates to an anti-corrosive coating composition which is of the kind specified in the preamble of claim 1 and which is characterized by the characterizing part of claim 1.

The present invention further relates to the use of salts comprising a polyvalent metal cation such as zinc, DK PR 172470 B1 3 and an organic polyphosphonic acid having at least two phosphonic acid groups in a film-forming binder dispersion to protect metal surfaces against corrosion, rusting and rust staining by application to metal surfaces. by 5 spray or with a brush.

The corrosion inhibition obtained by anticorrosive paints has several effects, the relative importance of which may differ for different applications of the paint. One effect is the inhibition of the appearance of 10 rust and the brown staining induced by the rust.

This is particularly important when using the anticorrosive paint as a primer to be covered by a paint whose main purpose is cosmetic. Another effect is the inhibition of metal loss by corrosion, which is especially important when coating ships or industrial steel structures. A third effect is inhibition of the formation of corrosion products at the surface of the metal, which would reduce the adhesion of subsequent coatings of paint. This is particularly important for a factory foundation.

Paintings according to the invention can be prepared which are substantially more effective than paints containing phosphates, such as the known anti-corrosive pigment zinc phosphate, in terms of achieving any of these effects. The polyphosphonate salt pigment can be selected to produce a special anti-corrosive effect, although many of the polyphosphonate salt pigments are better than zinc phosphate in virtually all respects.

One type of preferred polyphosphonate salts corresponds to the general formula: M * (R (PO3) BH (2B.xn)), where M represents a metal ion which is zinc, manganese, magnesium, calcium, barium, aluminum, cobalt, iron, strontium, tin, zirconium, nickel, cadmium or titanium, R represents an organic radical attached to the phosphonate groups by carbon-phosphorus bonds, m is the valence is the radical R and is at least 2, n is the valence of the metal ion M and is from 0.8 m / n to 2 m / n.

The valence m of the organic radical R is preferably 2 to 5. The polyphosphonate may be derived from a diphosphonic acid 10 R (PO 3 H 2) 2, e.g. a hydroxy-alkylidene-1,1-phosphonic acid of the formula: PO (OH) 2 R '- C - OH (I)

15 I

PO (OH) 2 wherein R 1 is a monovalent organic group, preferably an alkyl group having 1 to 12 carbon atoms.

The polyphosphonate salt is preferably an etidronate because 20 etidronic acid has most phosphonate groups per liter. weight unit of the acids of formula (I) and can be obtained commercially.

The acids of formula (I) can be readily prepared by reacting a carboxylic acid R'COOH with phosphorus trichloride and hydrolyzing the reaction product.

An alternative type of polyphosphonic acid is an amino compound containing at least two N-methylene phosphonic acid groups. Such polyphosphonic acids can be prepared by reaction of ammonia or an amine with formaldehyde and phosphoric acid. A diphosphonic acid of the formula: DK PR 172470 B1 CH2PO (OH) 2 /

R "- N

CH 2 PO (OH) 2 wherein R "is a monovalent organic group, preferably a substituted or unsubstituted alkyl group of 1-12 carbon atoms, such as propyl, isopropyl, butyl, hexyl or 2-hydroxyethyl, can be prepared from a primary amine. An example of a tri-phosphonic acid R (PO 3 H 2) 3 is amino-tris- (methylene-phosphonic acid) N (CH 2) PO (OH 2) 3 is prepared from ammonia. Examples of tetra-phosphonic acids R (PO 3 H 2) 4 are alkylene. diamine tetra (methylene phosphonic acids) of the general formula: ((OH) 2P (O) CH 2) 2N-QN (CH 2 PO (OH) 2) 2, where Q is a divalent organic group, preferably an alkylene group having. 1 to 12 carbon atoms, for example ethylene diamine tetra (methylene phosphonic acid) or hexamethylene diamine tetra (methylene phosphonic acid) An alternative form of tetraphosphonic acid is an alkylene bis (1-hydroxymethyl diphosphonic acid) of the formula: PO (OH) 2 P0 (OH) 2

I I

HO-C-Q '-C- OH 25 I I

PO (OH) 2 PO (OH) 2 where Q 'has the same definition as Q. Examples of penta-phosphonic acids R (PO3H2) 5 are dialkylene-triamine-penta (methylphosphonic acids), e.g., diethylene-triamine-penta (methylene phosphonic acid) of the formula: ((OH) 2P (o) CH2) 2nch2ch2nch2ch2n (CH2PO (OH) 2) 2, CH2PO (OH) 2 DK PR 172470 B1 6

Higher functionality polyphosphonic acids, including polymeric polyphosphonic acids, may be used, e.g. a polyethylene imine substituted with methylene phosphonic groups and of the formula: • 5 (OH) 2P (O) CH 2 N - CH 2 - CH 2 N (CH 2 PO (OH) 2) 2 CH 2 PO (OH) 2 Jy where y is at least 3.

The optimum ratio of polyvalent metal to acid in the salt may vary for different metals, e.g. For example, it has been found that zinc etidronate is most effective in preventing corrosion when the molar ratio of zinc to etidronate is at least 1.2: 1, e.g. 1.4: 1 to 2: 1 (ratio of zinc to phosphonate groups at least 0.6: 1, eg 0.7: 1 to 1: 1), whereas manganese etidronate is most effective at a molar ratio manganese to etidronate of 1: 1 to 1.5: 1 (ratio of manganese to phosphonate groups 0.5: 1 to 0.75: 1). Within these ranges, salts having a lower ratio of polyvalent metal to acid are generally more effective in preventing rust staining, but those salts having a higher ratio of polyvalent metal to acid allow the least total corrosion to be assessed. by the absence of corrosion in the interior film.

The complex polyphosphonate salt can be formed by adding a basic compound of the desired metal M, e.g. an oxide, hydroxide or carbonate of zinc, manganese, magnesium, barium or calcium, with an organic polyphosphonic acid, e.g. etidronic acid, in the desired molar proportions.

The salt-forming reaction is preferably carried out in aqueous medium and the heavily soluble salt is recovered as a precipitate. Examples of basic compounds are zinc oxide, calcium hydroxide and manganese carbonate. Mixtures of basic compounds, e.g. zinc oxide and calcium hydroxide, can be used to prepare a complex salt with more than 5 a metal M. An aqueous solution of organic polyphosphonic acid can be added to an aqueous slurry of the basic compound or vice versa. The slurry formed by the initial reaction of basic compound and acid of formula (I) can be heated, e.g. to 50-100 eC 10 for 19 minutes to 24 hours to ensure completion of the salt-forming reaction. The precipitated salt is then separated and dried; it is preferably washed with water prior to drying to remove any present, highly water-soluble material, especially unreacted polyphosphonic acid.

Alternatively, a soluble salt of the metal M can be reacted with the polyphosphonic acid or a soluble salt thereof, but care must be taken to wash the product free of any ion (such as chloride) which may promote corrosion.

The crystalline state of complex salts varies depending on the nature of the metal M, the polyphosphonate anion and the metal ion to polyphosphonate ratio. Some metals form salts of well-defined crystalline form, whose stoichiometry and crystalline form may vary depending on their mode of production. For example, calcium nitride night forms. two types of crystals having a ratio of calcium to etidronate of 1: 1, and flower-like formations of very small plate-like crystals having a ratio of calcium to etidronate of 2: 1. Other metals tend to form precipitated salts whose crystalline form is less well defined and whose composition varies depending on the ratio of lethal to etidronate used in the preparation thereof, whereby no identifiable compounds are present. B1 8 solutions with simple stoichiometry. Zinc tetronate, e.g. prepared from zinc and etidronate acid in molar ratio 1.5: 1 under varying reaction conditions, form mainly agglomerated needle-like crystals with a total zinc to etidronate ratio of over 1.3: 1 and up to 1.6: 1.

The polyphosphonate salt may alternatively have an excess of base. The metal used in polyphosphonate salt with an excess of base is preferably a metal whose oxide is not pronounced alkaline, e.g. zinc or manganese. Eg. For example, an ethidronate of a metal such as zinc may have a molar ratio of metal to acid of up to 3: 1. Such base-base salts may have the general formula MIQlzn, 2B1fi (PO3) m 15 2 where M, R, m and n are defined as before and z is from 2 m / n to 3 m / n. They can be prepared by reacting an excess of a basic compound of the metal M, e.g. zinc oxide, with a polyphosphonic acid P. (PO3) mH2u, e.g. etidronic. In 20 certain cases, salts with excess base can be formed using an equivalent amount of basic metal compound and polyphosphonic acid. Eg. For example, zinc oxide and etidronic acid, reacted in a molar ratio of 2: 1, may form amorphous precipitates with a ratio of zinc to etidronate in the range of 2.3: 1 to 2.7: 1 together with fine plate-like crystals having a ratio of zinc to etidronate of approx.

1.8: 1st Both forms, or a mixture of them, are effective anti-corrosion pigments. . .

The polyphosphonate salt may also contain cations from a strong base, such as sodium, potassium, ammonium or substituted ammonia cations derived from amines, including quaternary ammonia cations, especially when metals M are present in less a stoichiometric amount. These neutralize some or all of the excess acid groups in the salt so that the salt is less acidic in contact with water. Replacement of free acid groups with strong base cations usually increases the solubility of the salt. So-forming salts containing highly basic cations may have the general formula:

MxM * yR (PO3) BH (2B.xn.y) where M, R, n, m and x are defined as before, M 'is an alkali metal or ammonium or substituted ammonium ion 10 and the value of y is such that that (xn + y) is from m to 2 m.

Salts of this type can be prepared by the addition of a strong base, e.g. sodium hydroxide, potassium hydroxide or a quaternary ammonium hydroxide, such as tetrabutyl-ammonium hydroxide, for the slurry is formed by reaction between a basic compound of a polyvalent metal M and polyphosphonic acid R (PO 3) .H 2e or by reacting an aqueous solution of partial alkali metal salt of a polyphosphonic acid of the general formula: M'yR (PO3) wH (2.y), 20 having the desired amount of the basic compound of the metal M.

The invention comprises coating compositions whose pigment component comprises salts containing both polyphospho-ananates and other anions, e.g. phosphate anions, e.g. formed by coprecipitation.

The invention also encompasses coating compositions whose pigment component comprises particles of a substantially water-insoluble compound of a polyvalent metal reacted with an organic polyphosphinic acid such that the particles 30 have a surface layer of metal polyphosphonate, although the core of the particles may be unchanged in water-insoluble metal. 10 binding. Pigments of this type can e.g. is formed by reacting an organic polyphosphonic acid with an excess of a metal oxide. The product may consist, at least in part, of coated oxide particles and not a polyphosphonate salt having a true excess of base. The metal oxide may e.g. be zinc oxide, tin oxide, iron oxide or a form of alumina, silica or zirconia with a proportion of hydroxyl groups on the surface of each particle. The particles of the water-insoluble metal compound used to make pigments of this type preferably have a diameter less than 100 microns, preferably 1- 20 microns.

The aqueous solubility of polyphosphonate salt used as a pigment is preferably not more than 2 g / ml.

15 liters, e.g. 0.01 - 2 g per liter. The preferred solubility of the salt may vary according to the intended application of the coating mixture. Salts used in paints that come into contact with water continuously or frequently, e.g. metal foundations for maritime use, preferably have a solubility of less than 0.6 g per liter. liter, e.g. 0.02 - 0.1 g per liter. The solubility of the salt is less critical when used in paints which have less frequent contact with water, e.g. paints for use on cars or aircraft 25 or on steel structures on land.

The film-forming binder for the anticorrosive coating is preferably an organic polymer and can usually be any of the binders used in the paint industry, e.g. an alkyd resin, an epoxy resin, an oleo resin, a chlorinated rubber, a vinyl resin, e.g. polyvinyl butyral, a polyurethane, a polyester, an organic or inorganic silicate, a polyamide or an acrylic polymer. Two or more compatible film-forming organic polymers can be used in paint.

DK PR 172470 B1 11

A stretch resin, such as a hydrocarbon resin or a coal tar derivative, may be present. It has been found that the polyphosphonate salts used according to the invention provide a particularly improved corrosion protection in comparison with known anti-corrosive pigments such as zinc phosphate when used in alkyd resins which are the most universally used protective coatings agents, and that they also produce marked improvement when used in epoxy resins.

The polyphosphonate salt is usually used in an amount of between 2 and 100% by weight relative to the total pigment in the paint, preferably in an amount of between 5 and 50% by weight of the total pigment.

The polyphosphonate salt can be used with other anti-corrosive pigments. It has been found that a particularly good corrosion protection can be obtained in connection with paints containing as the pigments the polyphosphonate salt and a corrosion passivator. By a passivator, we mean a corrosion inhibitor that acts either alone or in association with another chemical to modify the metal oxide film on the metal to be protected to make it more protective. The passivator can operate without oxygen and is preferably capable of acting as an oxidizing agent for the metal to be protected.

The invention thus comprises an anti-corrosive coating composition comprising a pigment component dispersed in a film-forming binder, wherein the pigment component comprises a salt comprising a polyvalent metal cation and an organic polyphosphonic acid containing at least two phosphonic acid groups and inorganic corrosion passivator which is capable of modifying the metal oxide film on the metal to be protected to make it more protective, whereby the ratio of the polyphosphonate salt to the passivator is 1: 1 to 50: 1 by weight. Such anticorrosive paints containing a polyphosphonate salt and a passivator can produce a superior anticorrosive effect in paints containing a known anticorrosive phosphate pigment such as zinc phosphate both in the prevention of rust staining and in the prevention of metal loss by corrosion.

Examples of passivators are molybdates, vanadates, ramates, chromates, stannates, maganates, titanates, phosphololybdates and phosphovanadates. The passivator is preferably a salt of a divalent metal, e.g. zinc, calcium, manganese, magnesium, barium or strontium or a salt containing cations from a strong base such as sodium, potassium, ammonium or substituted ammonium cations 15, and cations of a divalent metal. The passivator can e.g. be zinc molybdate, sodium zinc molybdate, calcium molybdate, zinc vanadate, sodium zinc vanadate or zinc tungsten. Zinc chromate or potassium-zinc chromate may be used, although it may be desirable to have a chromate-free coating mixture to avoid any potential health risk. Molybdates and vanadates, especially meta-vanadates, are preferred, especially zinc-molybdate, sodium-zinc-molybdate or zinc-meta-vanadate. The passivator preferably contains zinc ions if the polyphosphonate salt does not.

The passivator may be present as composite particles in which a molybdate or other passivator is precipitated on the surface of the particles of a carrier pigment, e.g. For example, sodium zinc molybdate may be in the form of a coating on a carrier pigment, such as zinc oxide, titanium dioxide or talc, as disclosed in British Pat.

Preferably, the passivator has a solubility of less than 2 g / ml. liter, e.g. 0.02 to 1 g per liter.

The polyphosphonate salt and passivator have a synergistic effect and provide better corrosion inhibition when used together in a paint than when each pigment is used separately. This synergistic effect is particularly marked for polyphosphonate salts red low polyvalent metal ions to phosphonate groups, such that the ratio of metal ions to phosphonate groups in a polyphosphonate salt to be used with a passivator may be lower than when the polyphosphonate salt is used without a passivation. Usually, the ratio of polyvalent metal ions to phosphonate groups in the salt is at least 0.5 / n: 1, where n is the valence of metal ion when the salt is used with a passivator; ratios between 0.8 / n: 1 and 2 / n: l are preferred.

Among the preferred phosphonate salts for use with a passivator are calcium, zinc, manganese, barium, magnesium or strontium salts containing 0.4-0.5 divalent metal ions per mole. phosphonate group, e.g. calcium etidronate with a molar ratio of calcium to etidronate groups of approx. 1: 1. We have identified two crystalline calcium ethidronates of this type. When calcium hydroxide and etidronic acid are reacted in water at a molar ratio of 0.6: 1 - 1.2: 1 and at a temperature above 70 ° C, a precipitate of plate-like crystals having a particle size below 50 microns is formed. calcium hydroxide and etidronic acid are reacted in the same ratio in water below 70 ° C, a precipitate of needle-like crystals is formed.

Both of these crystal forms have been analyzed and they have been found to have a molar ratio of calcium to etidronate between 0.9: 1 and 1: 1. The needle-like crystals can be converted to the plate-like crystals 30 by heating in water to above 70 ° C, e.g. for 30 minutes. Although both of these calcium etidronates are particularly effective corrosion inhibitors when used in conjunction with a passivator, the plate-like crystals are preferred because of their lower solubility in water (generally less than 0.5 g per liter) and lower particle size.

The ratio of polyphosphonate salt to passivator in the pigment component of the paint is preferably 2: 1 to 20: 1 on a watch basis, especially 4: 1 to 10: 1. Within the last range, increasing passivator proportions, such as a molybdenum salt, have an increasing effect in inhibiting corrosion, but when the weight of the molybdenum salt increases above 25% based on the weight of the polyphosphonate salt, e.g. etidronate, there is no further increase in the corrosion inhibition. When the weight of molybdate is increased above 50%, based on the weight of etidronate, the corrosion inhibition may be reduced, although this surprising synergistic effect cannot be fully explained, the passivator is believed to catalyze the formation of a corrosion inhibiting layer at the metal surface.

The polyphosphonate salt can also be used with other known anticorrosive pigments, such as a phosphate, e.g. zinc phosphate, silicate, borate, diethyldithiocarbonate or lignosulphonate or zinc dust or with an organic anti-corrosive additive such as a tannin, oxazole, imidazole, triazole, lignin, phosphate ester or borate ester. Smaller amounts of a basic pigment such as calcium carbonate or zinc oxide can be used, especially if the polyphosphinate salt gives a pH below 5 upon contact with water. The calcium ethidronates with a molar ratio of calcium to etidronate of approx. Generally, 1: 1 gives a pH of 4.5 to 5.1 upon contact with water. Calcium etidronate with a molar ratio calcium etidronates with a molar ratio of 30 zinc to etidronate of less than approx. Generally, 1.4: 1 gives a pH of 3.5 or less. Zinc etidronates having a molar ratio of zinc to etidronate greater than 1.6: 1 generally give a pH of 6 to 7.

DK PR 172470 B1 15

The coating composition of the invention may contain substantially inert pigments in addition to the polyphosphonate salt, e.g. titanium dioxide, talc or barite, and optionally small amounts of colored pigments such as phthalocyanins. The pigment volume concentration of the paint is preferably 20-50%, depending on the film-forming polymer used.

The coating compositions of the invention are usually used to prevent rusting of iron and steel, but they can also be used in anti-corrosive paints for metal surfaces other than iron, such as galvanized steel or aluminum, and they can be used in prestressed concrete, either to coat stresses. the tongs to prevent corrosion or as an outer coating to the concrete to prevent rust staining.

The anti-corrosive coating is usually applied to a metal surface by spraying, rolling or brushing, using as an medium an organic solvent in which the film-forming binder is dissolved or dispersed. The coating may harden by evaporation of the solvent, by air drying and / or by a cross-linking mechanism, depending on the nature of the binder. The coating may alternatively be applied from an aqueous dispersion, in which case it may be applied as a spray, by roller or brush or by electro-precipitation using a film forming binder which is an anionic or cationic resin. Alternatively, the coating composition may be applied as a powder coating, e.g. by electrostatic spraying, and melted and cured on the metal surface.

The invention is illustrated by the following examples.

EXAMPLE 1-9 - Preparation of Polyphosphonate Salts EXAMPLE 1 184.8 g (2.28 moles) of zinc oxide were kept in slurry 1 at a concentration of 20% by weight in water and heated to 70 ° C.

An aqueous solution containing 316 g (1.52 mol) of etidronic acid was diluted to 20 wt% and heated to 70 ° C. The zinc oxide slurry was pumped into the etidronic acid solution over 45 minutes with continuous stirring of both the slurry and the solution. A precipitate formed after the addition of ca. 20% of the zinc oxide.

The resulting slurry was kept under stirring for 4 hours at 60-70 ° C to allow the salt-forming reaction to take place. The slurry was then cooled and filtered on a Buchner funnel. The obtained solid was washed 4 times with distilled water using 2 liters of water each time to wash the etidronic acid saline. The wet filter cake was broken up and oven-dried at 110 ° C to obtain ca. 500 g zinc tetronate as a white solid with needle-like crystals. The solubility of the zinc tetronate was measured by slurrying it in distilled water, centrifuging and measuring the dissolved metal ion content. The content of metal ion was 0.165 g / ml. per liter, corresponding to a pigment solubility of 0.5 g per liter. liter.

EXAMPLE 2

Manganese carbonate (87.0 g, 0.75 mole) was reacted with etidronic acid (154.0 g, 0.75 mole) using the same method as in Example 1 to prepare manganese nitrate as a pink solid.

EXAMPLE 3

Calcium hydroxide (0.84 mole) was reacted with etidronic acid (1 mole) using the method of calcium etidronate as described in Example 1 in the form of platelet-like crystals.

EXAMPLE 4 80.7 g (2.00 mole) of magnesium oxide was reacted with 207.8 g (1.01 mole) of etidronic acid using the method of Example 1 to prepare magnesium etidronate 10 as a white solid.

EXAMPLE 5

The procedure of Example 1 was repeated using 246.4 g of zinc oxide (3.04 mole) to prepare a zinc tetronate having a theoretical molar ratio of zinc to 15: 1 etidronate.

EXAMPLE 6

The procedure of Example 1 was repeated using 369.6 g of zinc oxide (4.56 mol) to prepare a zinc etidronate having a theoretical molar ratio of zinc 20 to etidronate of 3: 1.

The solubilities of the pigments from Examples 3 to 6 were as follows: DK PR 172470 B1 18

Solubility Solubility in g of metal ion of pigment in pr. liter per liter. Calcium Ethidronate in Example 3 0.037 0.261

Magne s in the urnet of drone in Example 4 0.069 0.355 10

Zinc tetrononate of Example 5 0.045 0.114

Zinc Tidronate 15 of Example 6 0.034 0.078 Example 7

Manganese carbonate was added portionwise to a solution of vigorously stirring etidronic acid (78.0 g, 0.38 mol) in 42 ml of distilled water. During the addition 20, carbon dioxide developed and a purple-colored solution appeared. After the addition of 39.6 g of carbonate, a leather-brown colored precipitate remained. 500 ml of distilled water was added, followed by an additional 47.4 g in manganocarbonate to give a total of 0.75 moles. The mixture was kept under stirring for 30 minutes and then allowed to stand overnight. The resulting slurry was filtered, washed with distilled water and dried to give 115.3 g of a pink solid manganese tetronate.

EXAMPLE B

30 barium carbonate was added portionwise to a stirring solution of etidronic acid (136.3 g, 0.66 mol) in 1.584 ml of distilled water. A precipitate remained after the addition of 64.9 g of the barium carbonate. Additional DK PR 172470 B1 19 re 195.9 g of barium carbonate was added, corresponding to a total of 1.32 moles, and the stirring mixture was diluted with 1500 ml of distilled water.

The mixture was heated to 50-55 ° C for 1 hour, cooled, filtered and washed with distilled water. After drying at 110 ° C, a white solid, weighing 313.7 g, was obtained.

The white solid was kept stirring in distilled water (1,000 ml) and 34.2 ml of concentrated hydrochloric acid 10 was added. The mixture was stirred for 2.5 hours, filtered, washed with distilled water and dried at 100 ° C. A white solid, barium ether sodium, weighing 266.1 g, was obtained.

EXAMPLE. 9 A 20% aqueous solution of 316 g of etidronic acid was prepared as described in Example 1, and sodium hydroxide was added thereto in a molar ratio of 1 mole of sodium hydroxide to 2 moles of etidronic acid to partially neutralize the acid. A 20% slurry of 184.8 g of zinc oxide in water was then reacted with the partially neutralized etidronic acid solution using the method of Example 1 to prepare a zinc tidronate modified with sodium ions.

EXAMPLES 1 to 9 - Paint Exercise 25 The etidronates prepared as described in Examples 1 to 9 above were used separately as the anti-corrosive pigment in an anti-corrosive paint. The etidronate was ball milled with the following ingredients until the particle size of the etidronate was 30-40 µm: DK PR 172470 B1 20% by weight

Alkyd Resin 20.0

Ethidronate as prepared in one of Examples 1-9 16.3

Talc 9.6 Drying aids 10 and additives 2.4

Xy len solvent 38.2

Each anticorrosive paint was sprayed onto steel sheets with a dry film thick Ise of 100-200 µm. When the paint film 15 was dry, two scratches were scratched through the paint film to expose the underlying steel in the form of a cross.

The plates were then subjected to a sample comprising 500 hours of salt spray as specified in English Standard BS 3900. In a comparative experiment, 20 paints having the specified formulation but using zinc phosphate (British Standard BS 5193) were substituted for etidronate. .

After the sample comprising the 500 hours of salt spray, the plates were evaluated for blistering, rust staining, corrosion in and around the scratch, including creep of the under film from the scratch and rust staining from the scratch. The paints of Examples 1 to 9 showed superior anticorrosive properties as compared to the paint containing zinc phosphate, especially with respect to corrosion in and around the scratch and rust staining of the scratch. The sheets coated with the paint from Examples 1, 2, 3, 5 and 9 showed less corrosion in all respects than the sheets coated with zinc phos- paint PR 172470 B1 21 phat paint. The sheets coated with the paint from Example 6 showed less corrosion in and around the scratch than the sheets coated with the zinc phosphate paint and in other respects had substantially the same properties as these. The plates coated with the paints of Examples 4, 7 and 8 showed less rust staining from the scratch than the plates coated with the zinc phosphate paint, and in other respects had substantially the same properties as these.

EXAMPLE 1Q

Zinc tetronate prepared as described in Example 1 above was ball milled with the following ingredients to form an anticorrosive paint wherein the particle size of the zinc tetronronate was 30-40 µm: 15 parts by weight

Alkyd Resin 20.0

Zinc tetronone 15.3

Sodium zinc molybdate 4.0

Talc 13.5 20 Titanium Dioxide 9.6 Drying aids and additives 2.4

Xylene Solvent 38.2 EXAMPLES 11 and 12

Anti-corrosive paints were prepared as described in Example 10, but using Example 11, the manganese etidronate prepared in Example 2 and in Example 12 the calcium etidronate produced in Example 3. In each of these examples, the entire amount was of zinc tetidronate replaced by the same amount of weight of the manganese or calcium etidronate.

Example PR 172470 B1 22 EXAMPLE 13

An anticorrosive paint was prepared according to Example 12, but increasing the amount of sodium zinc molybdate to 8.0 parts by weight.

EXAMPLE 14

An anti-corrosive paint was prepared according to Example 12, but reducing the amount of sodium zinc molybdate to 2.0 parts by weight.

The anticorrosive paints corresponding to each of Examples 10 to 14 were sprayed onto soft steel sheets having a dry film thickness of 100 to 200 µm. When the paint film was dry, two scratches made scratches through the paint film to expose the underlying steel in the form of a cross. The plates were then subjected to a test comprising 1200 hours of salt spray as specified in British Standard BS3 3900. The plates were evaluated after testing for rust and blister resistance, both generally and by scratch. The paints of Example 3 were similarly examined as a comparison where no passivator was used.

Comparative tests were carried out in which the paint had the composition of Example 10 but in which the zinc tetidronate was replaced by an equal 25 wt. Sodium zinc molybdate (Comparative Example · Y), or the composition of Example 10, but in which the calcium etidronate and the sodium zinc molybdate was replaced with zinc phosphate (Comparative Example Z). The results are shown in the following: Example 10 - very little rust staining, no blistering and before suggestion of corrosion.

DK PR 172470 B1 23 extending more than 1 mm from the scratch,

Example 11 - Results such as Example 10,

Example 12 - substantially no rust staining (end-5 and less than in Examples 10 and 11), no blistering, and no signs of corrosion extending away from the scratch,

Example 13 - slight rust staining (but slightly more than in Examples 10 and 11), no blistering 10, and no evidence that the corrosion extends more than 1 mm away from the scratch.

Example 14 - Results such as Example 13,

Example 3 - very little rust staining (no more than Example 10), but some blistering around the scratch,

Comparative Example Y - considerably more rust staining than in Examples 10 to 14, and any corrosion extending more than 1 mm from the scratch, 20 Comparative Example Z - more rust dyeing than in Example Y and any corrosion extending more than 1 mm away scratch.

The results show that the paints of Examples 25 10 to 14 containing an etidronate and a molybdate passivator produced better resistance to corrosion of the steel plate than the paint of Example 3 containing an etidronate alone. The paint from Example 3 produced better grating against corrosion and especially against rust stains than the paints containing sodium zinc molybdate alone or zinc phosphate. Some of the plates painted according to Examples 10 to 14 and Comparative Example Z were exposed to natural weather conditions in an extremely maritime environment off Coquet Island, a small island off the coast of Northumberland, England. After nine months, the sheets coated with the paints of Examples 10 to 14 showed very little rust staining and no creep of the corrosion from the scratch; Examples 11, 12 10 and 14 in particular showed essentially no rust staining around the scratch. Comparative Example Z showed some rusting around the scratch and creep corrosion from the scratch.

EXAMPLE 15 1,177 g of calcium hydroxide was dissolved in 4.695 g of water and the slurry was removed at a rate of 130.5 g / ml. per minute added to a stirred solution of 3.913 g of etidronic acid in 15.55 kg of water in the temperature range 65-78 ° C. A lot of matted needles were precipitated 20 after 30 minutes and the addition of the slurry was interrupted while dispersing and redissolving in the solution. As the addition of the slurry continued, a precipitate of plate-like crystals of calcium etidronate formed. These were filtered off, washed with 25 water and dried in a fluid mass drier. Analysis of the product showed a molar ratio of calcium to etidronate of 0.94: 1.

EXAMPLE 16 605 g of a 60% aqueous solution of etidronic acid was added over 30 minutes to a stirred slurry of 107.4 g of calcium hydroxide in 2 liters of distilled water maintained in the temperature range of 20-35 ° C.

A precipitate of needle-like crystals formed. Dispenser PR 172470 B1 25 was filtered off, washed with water and dried in a fluid mass dryer. Analysis of the product showed a molar ratio of calcium to etidronate of 0.94: 1.

Anti-corrosive paints were prepared by ball-milling the following ingredients:

Yagtdele

Example 15 Example 16

Alkyd resin with 10 short-chain oil 20.0 20.0

Calcium Ethidronate, plate-like crystals 16.3 Calcium Ethidronate, needle-shaped crystals - 16.3

Sodium zinc molybdate precipitated on zinc oxide 2.0 2.0 20

Talc 13.5 13.5

Titanium dioxide 9.6 9.6 25 Drying aids and additives 2.4 2.4

Xylene solvent 38.2 38.2

The anticorrosive paints of Examples 15 and 16 were sprayed onto soft steel sheets having a dry film thickness of approx. 100 pm. When the paint film was dry, two scratches were scratched through the paint film, exposing the underlying steel in the form of a cross.

DK PR 172470 B1 26

The coated plates were subjected to a salt spray test conducted at 90 ° C as specified in ASTM B-117.

After 250 hours in the hot salt spray sample, the paints of Examples 15 and 16 showed virtually no corrosion or blistering at the scratch and none in the intact areas of the film. Both paints were better in all respects than the zinc phosphate comparison paints.

After 500 hours in the hot salt spray sample, the paint from Example 16 showed some corrosion and blistering at the scratch, and it showed as much corrosion as the comparison paint. The paint from Example 15 still showed very little corrosion or blistering, even at the scratch, and was significantly superior to the comparison paint.

EXAMPLES 15A and 11A

Paints were prepared according to Examples 15 and 16, except that the amount of sodium-zinc-molybdate precipitated on zinc oxide was increased to 4.0 parts by weight.

20 The paints were sprayed onto soft steel sheets 100 µm thick and scratched and then subjected to a weather test at Coquet Island with a comparison plate painted with a zinc phosphate paint. After 10 months, the paints of Examples 15A and 16A showed very slight rusting, even at the scratch, and were superior to the comparison showing some degree of creep corrosion from the scratch.

EXAMPLE 17

682 g of a 60% aqueous solution of etidronic acid was slowly added to a stirred slurry of 400 g of zinc oxide in 1.45 kg of distilled water. A heavy white amorphous precipitate was produced and this precipitated when the stirring was stopped, leaving a clear liquid. The reaction was exothermic. The mixture was filtered and the precipitate was washed with distilled water and dried at 110 ° C to give 863 g of a zinc to etidronate molar ratio of 2.4: 1.

As the filtered liquid cooled, fine plate-like crystals precipitated and these were filtered cold, washed and dried. There was thus obtained 27.3 g of a zinc tetidronate having a molar ratio of zinc to etidronate of 1.8: 1.

An anticorrosive paint with 40% by volume of solids was prepared, based on an alkyd resin with short-chain oils and with a pigment volume concentration (PVC) of 40% with the above zinc tetronate (the molar ratio of zinc to etidronate). the major precipitate was 2.4: 1) used as 40% by volume of the pigment, with the remainder of the pigment being titanium dioxide with a small amount of bentonite.

EXAMPLE 18

An anti-corrosive paint was prepared according to Example 17, but zinc tidronate was used as 80% by volume of the pigment.

EXAMPLE 19

An anti-corrosion epoxy paint present in two packages was prepared from "Epikote 1001" (trademark) epoxy resin and a pigment comprising 40% by volume of the zinc-timronate of Example 17 with titanium dioxide and a small amount of bentonite. The curing agent for the epoxy material was a "Versmid" (trademark) amino-functional polyamide, and the total dry matter content was 51% by volume and P.V.C. was 40%.

EXAMPLE 20

Two anti-corrosive 5 epoxy-based paints were prepared in accordance with Example 19, but using the zinc tetidronate as 80% by volume of the pigment.

The anticorrosive paints of each of Examples 17 to 20 were sprayed onto soft steel sheets with a dry film thickness of about 10 mm. 100 μπ>, and they were scratched and subjected to a salt spray test at 90 eC, as specified in ASTM B-117. Similarly coated sheets were subjected to a humidity test according to British Standard 3900 F 2 (100% relative humidity with temperatures cycling in a cyclic manner between 40 ° C and 48 ° C to ensure condensation).

By comparison, zinc phosphate-containing paints were prepared and tested instead of zinc tetrononate (samples 17A to 20A).

The plates were evaluated after 1000 hours of testing according to ASTM D-1654 (Method B). The results are shown in% of the following Table 1. The plate is evaluated according to the percentage of area exhibiting defects resulting from corrosion or blistering and rated accordingly. The film is then peeled down with a scalpel to judge whether there is corrosion in the underlying film, which is characterized as: * x - severe corrosion + - moderate corrosion 30 0 - no corrosion 29 DK PR 172470 B1 -1 is- iiii Ί iio C tn O o ^ u. c tf) Lt OOO u ^ U) i- oouu

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The zinc tidronate-containing paints showed significantly less corrosion both in hot salt spray and in moisture samples, both in terms of visible corrosion and corrosion in the underlying film.

EXAMPLE 21 400 g of a 50 wt% solution of amino tri (methylene phosphonic acid) was diluted with distilled water to form a 20 wt% solution and heated to 75-80 ° C. A 20 wt% slurry of 99.0 g of calcium hydroxide in 10 distilled water was heated to 75-80 ° C and added to the phosphonic acid solution over 45 minutes of continuous stirring The molar ratio of calcium hydroxide to amino-tri (methylene phosphonic acid) was 2: 1 (calcium to phosphonic acid groups ratio 0.67: 1) After complete addition of the slurry, the solution and the resulting precipitate were kept at temperature and kept under stirring for an additional 2 hours The precipitate was isolated and dried.

EXAMPLES 22 to 29 20 Calcium and zinc salts of various organic polyphosphonic acids were prepared using the method of Example 21, as shown in the following Table 2: DK PR 172470 B1 31 u I C 01 - i rsj I Q.

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DK PR 172470 B1 32

Each of the polyphosphonate salts prepared in Examples 21-29 can be used in place of calcium etidronate in the paint formulation of Example 3 to form a paint having anti-corrosive properties similar to those of the paint of Example 3.

EXAMPLE 3Q

1 mole of sodium hydroxide was added to 1 mole of etidronic acid in aqueous solution to provide a 20 wt% solution. 1 mole of an aqueous slurry of calcium hydroxide 10 was added over 30 minutes to prepare a precipitate of calcium sodium etidronate which was filtered, washed and dried. This polyphosphonate salt could be used instead of calcium etidronate in the paint formulations of Examples 3 and 12 to form a paint which in each case had the same anti-corrosive properties.

EXAMPLE 31

A fast air-drying industrial foundation of the type which e.g. used as primer coatings for agricultural implements, was manufactured by ball mill treatment of 20 of the following ingredients: DK PR 172470 B1 33

Vgqt% Drying Oil Elk 50.23

Calcium Ethidronate Soro Prepared in Example 15 12.40 5 Sodium Zinc Molybdate 1.55

Inert pigments and fillers (calcium carbonate, titanium dioxide, talc and yellow iron oxide) 20.07 Dry aid 10 and additives 2.39

Xylene solvent 13.36

The paint was applied to phosphated steel sheets and scratched as described in Example 1. The plates were then subjected to a salt spray test for 240 hours using the conditions specified in ASTM B-117.

In comparison, a paint having the same constituents was used except for the calcium etidronate and sodium zinc molybdate and with zinc chromate (16% by weight of the pigment) as the anticorrosive pigment.

The plates coated with the paint of Example 31 showed hardly any sign of corrosion after the salt spray test, even at the scratch, and they were as good or better than the paint containing zinc chromate, both in appearance and overall. absence of rust 25 at the scratch.

EXAMPLE 32

An eraser / primer was made for automobiles, designed for application to phosphated steel and for applying an acrylic overlay coating on top of this, based on the following components: parts by weight

Sodium Zinc Molybdate 1.32 5 Calcium Ethidronate as Prepared in Example 15 12.68

Inert pigments (barites, kaolin, titanium dioxide and yellow iron oxide) 22.64 10 Bentonite gel 10% 2.57 Carbon black predisposition 10% 4.93

Number 1 oil epoxy ester resin 20.94

Urea Formaldehyde Resin 1.37

Benzoguanamine Resin 2.13 Drying Aids and Additives 1.24 n-Butanol 0.69

Ethylglycol monoethyl ether 0.69

Xylene 28.80

The pigments, bentonite gel and carbon black dispersion were dispersed in the epoxy ester resin. Xylene was added to the dispersion and passed through a sand mill to obtain a Hegmann grade of 7. The remaining ingredients were added with stirring.

The paint was sprayed onto phosphated steel sheets to form a dry film thickness of 30-40 microns and DK PR 172470 B1 was cured at 163 ° C for 20 minutes. The plates were scratched and subjected to a 300 hour salt spray test according to ASTM B-117, together with a comparator using zinc phosphate instead of the calcium 5 etidronate and sodium zinc molybdate. The plates painted in accordance with the invention showed no corrosion on the intact surface area and little corrosion around the scratch, and they were significantly less corroded than the comparison plates in both areas.

Claims (35)

An anticorrosive coating composition comprising a pigment component containing a phosphorus compound and a corrosion passivator dispersed in a film-forming binder, characterized in that the pigment component comprises (a) a salt comprising a polyvalent metal cation and an organic polyphosphonic acid having at least two phosphonic acid groups, salt has a water solubility of 10 at most 2 g / l, and (b) a corrosion passivator in the form of a molybdate, tungsten, vanadate, stannate, chromate, manganate, titanate, phosphomolybdate or phosphovanadate containing cations from a divalent metal, the weight ratio of the polyphosphonate salt (a) and the passivator (b) are 1: 1-50: 1. Anti-corrosive coating composition according to claim 1, characterized in that the salt has the general formula M + R (PO 3 where M represents a metal ion selected from zinc, manganese, magnesium, calcium, barium, aluminum, cobalt, iron, strontium, tin, zirconium, nickel, cadmium and titanium, R represents an organic radical bonded to the phosphonate groups by carbon-phosphorus bonds, m is the valence of the radical R and is at least 2, n 25 is the valence of the metal ion M, and x has a value of 0.8 m / n to 2 m / n. Anti-corrosive coating composition according to claim 1 or 2, characterized in that the salt is a salt of a diphosphonic acid of the formula 30 R 1 - C - OH (I) 5 (OH) 2 wherein R 1 is a monovalent organic group. Anti-corrosive coating composition according to claim 3, characterized in that the salt is a salt of ethidronic acid. Anti-corrosive coating composition according to claim 1 or 2, characterized in that the salt is a salt of an amine compound containing at least two N-methylenephosphonic acid groups. Anti-corrosive coating composition according to claims 1-5, 15, characterized in that the salt is a zinc salt. Anti-corrosive coating composition according to claims 1-5, characterized in that the salt is a manganese salt. Anti-corrosive coating composition according to claims 1-5, characterized in that the polyphosphonate salt is a calcium salt. Anti-corrosive coating composition according to claim 8, characterized in that the ratio of calcium to phosphonate groups is 0.4: 1-0.6: 1. Anti-corrosive coating composition according to claim 9, 25, characterized in that the polyphosphonate salt is a calcium etidronate having a molar ratio of calcium to etidronate groups of approx. 1: 1 and that the salt is mainly in the form of plate-like crystals. Anti-corrosive coating composition according to claim 1, 30, characterized in that the salt is present as granular particles formed by precipitation of the polyphosphonate salt on the surface of the metal oxide particles. Anti-corrosive coating composition according to claims 1-11, characterized in that either the polyphosphonate salt 5 or the passivator contains zinc ions. Anti-corrosive coating composition according to claims 1-12, characterized in that the passivator further contains sodium, potassium, ammonium or substituted ammonium cations. Anti-corrosive coating composition according to claims 1-13, characterized in that the passivator is sodium-zinc-molybdate or zinc-moblybdate. Anti-corrosive coating composition according to claims 1-14, characterized in that the passivator is present as composite particles formed by precipitation of a molybdate of a divalent metal on the surface of particles of a carrier pigment. Anti-corrosive coating composition according to claims 1-15, characterized in that the weight ratio of polyphosphonate salt to passivator is 2: 1-20: 1. Anti-corrosive coating composition according to claim 16, characterized in that the weight ratio of polyphosphonate salt to passivator is 4: 1-10: 1. Use of an anticorrosive coating composition 25 according to claims 1-17 to apply to a metal surface by spraying or brush coating a paint which is protective against corrosion, rusting and rusting. Use of a salt of zinc and an organic polyphosphonic acid containing at least two phosphonic acid groups as a pigment component dispersed in a film-forming binder part as a liquid anti-corrosive coating composition to apply to a metal surface by spraying or brush coating. which is protective against corrosion, rusting and rust staining, which salt has a 5 molar ratio of zinc to phosphonate groups of 0.7: 1-1.5: 1 and a water solubility of not more than 2 g / l, with coating composition no such being applied. that a thickness of the finished dry film of 30-100 μιη is provided. Use according to claim 19, characterized in that the salt has a molar ratio of zinc to phosphonate groups of 0.7: 1-1.0: 1. Use according to claim 19, characterized in that the salt is a zinc tetidronate having a molar ratio of zinc to etidronate groups of 2: 1-3: 1. Use of a salt comprising a polyvalent metal cation and an organic polyphosphonic acid containing at least two phosphonic acid groups as a pigment component dispersed in a film-forming binder as a liquid anticorrosive coating composition to apply to a metal surface by spraying or brush coating which is protective against corrosion, rusting and rusting, which salt has the general formula MsR (PO3) BH (2 ° xn), wherein M represents a metal ion selected from zinc, manganese, magnesium, calcium, barium, aluminum, cobalt , iron, strontium, tin, zirconium, nickel, cadmipm and titanium, R represents an organic radical attached to the phosphonate groups via carbon and phosphorus bonds, m is the valence of the radical R and at least 2 is n, the valence of the metal ion M and x is from 0.8 m / n to 2 m / n, which salt 30 has a water solubility of not more than 2 g / l, the coating mixture being applied to provide a thickness of the liquid. ready dry films of 30-100 μιη. DK PR 172470 B1 Use according to claim 19, 20 or 22, characterized in that the salt is a salt of a diphosphonic acid of the formula PO (OH) 2 In R * - C - OH (I) PO (OH) 2 wherein R 'is a monovalent organic group. Use according to claim 23, characterized in that the salt is a salt of ethidronic acid. Use according to claim 19, 20 or 22, characterized in that the salt is a salt of an amine compound containing at least two N-methylene phosphonic acid groups. Use according to claims 19-25, characterized in that the salt is present as composite particles formed by precipitation of the polyphosphonate salt on the surface of particles of a metal oxide. Use according to claims 19-26, characterized in that the salt has a water solubility of less than 0.6 g / l. Use according to claim 27, characterized in that the salt has a water solubility of 0.02-0.1 g / l. Use according to claims 18-28, characterized in that the coating composition is applied to a metal surface as a basis for preventing the appearance of rust and brown stains caused by it. Use according to claims 18-28, characterized in that the coating composition is applied to the surface of a DK PR 172470 B1 vessel or an industrial steel structure to prevent rust loss due to corrosion. Use according to claims 18-28, characterized in that the coating composition is applied as a factory primer to prevent the formation of corrosion products on the metal surface, which reduces the adhesion of subsequent paint coatings. Use according to claims 18-31, characterized in that the coating composition is applied to an iron or steel surface. Use of a coating composition according to claims 1-17 for application on the exterior of prestressed concrete to prevent rust staining.