FI75856B - ANTIKORROSIV BELAEGGNINGSKOMPOSITION, SOM INNEHAOLLER ETT METALLSALT AV EN ORGANISK POLYFOSFORSYRA OCH ANVAENDNING AV DETTA SALT I EN ANTIKORROSIV MAOLARFAERG. - Google Patents

Description

1 75856

This invention relates to anti-corrosion coating compositions for use as protective coatings on metal surfaces, in particular as coatings for iron and steel to prevent corrosion. Anti-corrosion coatings are used in particular on bridges, steel structures that are exposed to the weather for a long time during the erection of buildings, hulls and parts of cars, aircraft and other vehicles, agricultural machinery, oil plants and exposed steel parts of ships. The anti-corrosion coating ("workshop paint") 15 can be applied to freshly sandblasted steel sheet which is to be stored before use in construction or shipbuilding.

The anti-corrosion paint generally consists of a film-forming binder and one or more pigments.

20 Lead pigs and chromates, especially zinc chromate, are considered to be the most effective pigments in corrosion protection. Unfortunately, both lead ice and chromates are now considered dangerous to health. Many currently sold anti-corrosion paints contain zinc phosphate as an anti-corrosion pigment, but paints containing zinc phosphate have not been as effective as those containing lead ice or zinc chromate. The present invention is directed to a paint that provides better protection against iron and steel rust than zinc phosphate paints and does not use chemicals that are considered hazardous to health.

Many phosphates, phosphonates, and polyphosphates have been used as corrosion and flaking inhibitors in aqueous systems. These include hydroxyethylidene-1,1-diphosphonic acid, also known as etidronic acid, and its salts, the use of which is described in GB Patents 1,201,334 and 1,261,554 and U.S. Patents 3,431,217, 3,532,639 and 3,668,094. , e-ethylene-1,1-diphosphonic acid, described in GB Patent 1,261,554 and 2,755,56 amino compounds substituted with two or more methylenephosphonic acid groups, described in GB Patent 1,201,334 and U.S. Patent 3,483,133. the preparation of a deficient lead salt with a molar ratio of lead: phosphonate groups = 0.25: 1 is described in U.S. Patent 4,020,091, and its use as a gel-like pigment with good surface coverage is described, although anti-corrosion properties are not mentioned .

The coating compositions described in DE-A-2 710 498 contain a metal salt of a phosphonic acid, which may be a salt of a polyphosphonic acid. The compositions are intended for use as fire protective insulating coatings used in significantly thicker layers than anti-corrosion paints. The anti-corrosion properties of the salts used are not mentioned in the publication.

It has been found that certain organic polyphosphonate salts are particularly useful as anti-corrosion pigments.

The anti-corrosion coating composition of the invention consists of a pigment component dispersed in a film-forming binder. This pigment component comprises a) a polyvalent metal cation and a salt of an organic polyphosphonic acid containing at least two phosphonic acid groups of the general formula MR (PO-) H / O "wxjm um-xn) wherein M represents a metal ion which may be zinc, manganese, magnesium, calcium, barium, aluminum, cobalt, iron, strontium, tin, zirconium, nickel, cadmium or titanium, R represents an organic radical attached to phosphonate groups by carbon-phosphorus bonds, m is the valence of the radical R and at least 2, n is the valence of the metal ion M and x is 0.8 m / n to 2 m / n, and b) a corrosion passivator which is molybdate, tungstate, vanadate, stannate, manganate, titanate containing divalent metal cations. , phosphomolybdate or phosphovanadate, wherein the weight ratio of polyphosphonate salt a) to passivator b) is between 1: 1 and 50: 1.

3 75856

The corrosion resistance achieved with anti-corrosion paints consists of many phenomena, the relative importance of which may vary depending on the intended use of the paint. One effect of the paint is to prevent the appearance of rust and the resulting brown 5 color. This is especially important when an anti-corrosion paint is used as a primer that is covered with a paint whose main purpose is cosmetic. Another effect is the prevention of metal loss due to corrosion, which is particularly important when coating ships 10 or industrial steel structures. The third effect is to prevent the formation of corrosion products on the surface of the metal, which would impair the adhesion of subsequent paint layers. This is especially important when it comes to workshop paints. According to the invention, it is possible to produce paints which are substantially more effective than paints containing phosphates, such as paints containing a known anti-corrosion pigment, zinc phosphate, in order to achieve any of said effects. A polyphosphonate salt pigment can be selected to provide a certain anti-corrosion effect, although many polyphosphate salt pigments are superior to zinc phosphate in substantially all proportions.

The valence m of the organic group R in the polyphosphonate salt used according to the invention is preferably 2-5. The polyphosphonate may be derived from a diphosphonic acid, for example hydroxyalkylidene-1,1-phosphonic acid of the formula PO (OH) 0 i 2

R'-C-OH I

30 I

PO (OH) 2 wherein R 'is a monovalent organic group, preferably C 1-12 alkyl.

The polyphosphonate salt is preferably etidronate, since editronic acid has the most phosphonate groups per unit weight of the acids of formula I and is commercially available. The acids of formula I are readily prepared by reacting the carboxylic acid R'COOH with phosphorus trichloride and hydrolyzing the reaction product.

4 75856

An alternative polyphosphonic acid type is an amino compound containing at least two N-methylenephosphonic acid groups. Such polyphosphonic acids can be prepared by reacting ammonia or an amine with formaldehyde and phosphoric acid. Diphosphonic acid of formula ^ CH-PO (OH)

R "- N <" Z

CH 2 PO (OH) 2 where R "is a monovalent organic group, preferably a substituted or unsubstituted 2-alkyl group such as propyl, isopropyl, butyl, hexyl or 2-hydroxyethyl, can be prepared from a primary amine. As an example of tri-phosphonic acid R 1 PO N 2) is amino-tris (methylenephosphonic acid) N (CH 2 PO (OH) 2) 3 / prepared from ammonia Examples of tetraphosphonic acids RtPO 2) are alkylenediamine tetra (methylenephosphonic acids) of general formula 20 (( OH) 2P (O) CH2) ^ IQN (CH2PO (OH) 2> 2 where Q is a divalent organic group, preferably C1-4 alkylene, for example ethylenediamine tetra (methylenephosphonic acid) or hexamethylenediamine tetra (methylenephosphonic acid) alternative tetrafosphonic acid. form is alkylene bis (1-hydroxymethyldiphosphonic acid) of the formula PO (OH) 2 PO (OH) 2

HO-C-Q '- C-OH

I I

PO (OH) 2 PO (OH) 2 where Q 'is the same as Q. Examples of pentaphosphonic acids R (PO 2 H 2) 5 are dialkylenetriaminepenta (methylenephosphonic acids), for example diethylenetriaminepenta (methylenephosphonic acid) of formula (oh) 2p (o) ch2) 2nch2ch2nch2ch2n (ch2po (OH) 2) 2 ch2po (oh) 2 75856 5

Polyphosphonic acids having more than one functional group, including polymeric polyphosphonic acids, can be used, for example, a polyethyleneimine substituted by methylene phosphone groups of the formula 5 (oh) 2p (o) ch2 / n - ch2 - ch2 \ n (ch2po (oh) 2) 2 \ CH2PO (OH) 2 J y 10 where y is at least 3.

The optimal ratio of polyvalent metal to acid in salt may vary with different metals; for example, we have found that zinc etronate is most effective in preventing corrosion when the zinc: etidronate molar ratio is at least 1.2: 2, for example 1.4: 1 to 2: 1 (zinc: phosphonate group ratio is at least 0.6: 1, e.g. 0.7: 1 to 1: 1), while manganese etidronate is most effective at a molar ratio of manganese: etidronate of 1: 1 to 1.5: 1 (ratio of manganese: phosphonate group 0.5: 1 to 0.75: 1). Within these limits, salts with a lower ratio of polyvalent metal to acid are generally most effective in preventing rust discoloration, while salts with a higher ratio of polyvalent metal to acid allow the least total corrosion, as evidenced by the absence of base layer corrosion.

Complex polyphosphonate salts can be formed by reacting an M metal base salt of the desired metal, for example zinc, manganese, magnesium, barium or calcium oxide, hydroxide or carbonate, with an organic polyphosphonic acid, for example etidronic acid, in the desired molar ratio.

The salt formation reaction is preferably carried out in an aqueous medium and the sparingly soluble salt is collected as a precipitate. Examples of basic compounds are zinc oxide, calcium hydroxide and manganese carbonate. Mixtures of basic β 75856 compounds such as zinc oxide and calcium hydroxide can be used to prepare a complex salt containing more than one metal M. An aqueous solution of an 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 the basic compound with the acid of formula (I) may be heated, for example at 50-100 ° C, for 10 minutes to 24 hours, to ensure the completion of the salt formation reaction. The precipitated salt is separated and then dried; it is preferred to wash it with water before drying to remove any highly water-soluble substance, especially unreacted polyphosphonic acid.

Alternatively, the soluble salt of the metal M may be reacted with the polyphosphonic acid or its soluble salt, but the product should be washed thoroughly free of any ions (such as chloride) that could promote corrosion.

The crystal form of the complex salt varies depending on the nature of the metal M and the polyphosphonate anion and the relationship between the metal ion and the polyphosphonate 20. Some metals form salts that have a well-defined crystalline form and whose stoichiometry and crystalline form may vary depending on the method of preparation.

For example, calcium tetidronate forms two types of crystals with a ratio of calcium retidronate of 1: 1 and foils or very small plate-like crystals with a ratio of calcium: etidronate of 2: 1. Other metals tend to form precipitated salts whose crystalline form is less well defined and whose composition varies according to the ratio of metal to etidronate used in the preparation, without forming identifiable compounds of simple stoichiometry. For example, zinc etronate prepared from zinc and etidronate in a molar ratio of 1.5: 1 under varying reaction conditions forms predominantly agglomerated needle-like crystals with a total zinc: etidronate ratio greater than 1.3: 1, but not more than 1.6: 1.

75856

Alternatively, the polyphosphonate salt may contain an excess of base groups. The metal used in the basic polyphosphonate salt is preferably a metal whose oxide is not significantly alkaline, for example zinc 5 or manganese. For example, in a zinc-like metal etronate, the molar ratio of metal to acid can be as high as 3: 1. Such overbased salts may have a general form

M 2 ° (nz-2m) R * PO 3 ^ m '3 R * m and n are as defined above and z is 2m / n to 3m / n. They can be prepared by reacting an excess of a metal M basic compound #, for example zinc oxide, with a polyphosphonic acid R (pO 3) mH 2 m ', for example etidronic acid #. In some cases, the superbasic salts may be formed using an equivalent molar amount of the 15 basic metal compound and the polyphosphonic acid. For example, when zinc oxide and etidronic acid are reacted with each other in a molar ratio of 2: 1 #, an amorphous precipitate # can be formed with a zinc: etidronate ratio of 2.3: 1 to 2.7: 1 and at the same time small plate-like crystals with a zinc to etidronate ratio. is about 1.8: 1. Both forms or mixtures thereof are effective anti-corrosion pigments.

The invention includes coating compositions in which the Pigment component consists of salts containing both polyphosphonate anions and other anions, for example phosphate anions, and which are formed, for example, by co-precipitation.

The present invention also includes coating compositions having a pigment component consisting of particles formed by the reaction of a substantially insoluble metal of a polyvalent metal with an organic polyphosphonic acid such that the particles have a surface layer of metal polyphosphonate, although the core of the particles may be altered. Pigments of this type can be formed, for example, by reacting an organic polyphosphonic acid with an excess of a metal oxide. The product may consist of at least partially coated oxide particles instead of the actual overbased poly-8 75856 phosphonate salt. The metal oxide may be, for example, zinc oxide, tin oxide, iron oxide or a form of alumina, silicon or zirconia in which a certain number of hydroxyl groups are present on the surface of each particle. The particles of the water-insoluble metal compound used to make these types of pigments should preferably have a diameter of less than 100, most preferably 1 to 20.

The polyphosphonate salt used as a pigment preferably has a solubility in water of at most 2 g / l, for example 0.01 to 2 g / l. The preferred solubility of the salt may vary depending on the intended use of the coating composition. Salts used in paints which are in constant or repeated contact with water, for example metal primers used in the marine industry, preferably have a solubility of less than 0.6 g / l, for example 0.02 to 0.1 g / l. The solubility of salt is less critical when salt is used in paints that come into contact with water less frequently, such as paints used in automobiles, aircraft, or ground steel structures.

The film-forming binder used for the anti-corrosion coating is preferably an organic polymer, and can generally be any binder used in the paint industry, for example alkyd resin, epoxy resin, petroleum resin, chlorinated rubber, vinyl resin, for example polyvinyl butyral, polyurethane, polyester, polyester, polyester, polyamide or acrylic polymer. Two or more compatible film-forming organic polymers may be used in the paint. A filler resin such as a hydrocarbon resin or a coal tertiary derivative may be present. We have found that the polyphosphonate salts used according to the invention achieve particularly good corrosion protection compared to known anti-corrosion pigments such as zinc phosphate when 85 salts are used in alkyd resins, which are the most widely used binders for protective coatings, and that considerable improvement also occurs with epoxy salts.

9 75856

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

In addition to the polyphosphonate salt, the pigment used in the coating composition of the invention contains a corrosion aid. By passivator is meant a corrosion inhibitor that acts either alone or in combination with another chemical to make the oxide film on the surface of the metal to be protected more protective. The passivator 10 can operate without oxygen and can advantageously act as an oxidant of the metal to be protected.

As the anti-corrosion paints used with the compositions of the invention, which contain a polyphosphonate salt and a passivator, a superior anti-corrosion effect can be obtained compared to paints containing a known anti-corrosion phosphate pigment, such as zinc phosphate, and corrosion due to corrosion.

The passivators used in the composition according to the invention are molybdates, vanadates, tungstates, chromates, stannates, magnanates, titanates, phosphomolybdates and phosphovanadates, which preferably contain a divalent metal, for example zinc, calcium, magnesium, magnesium, barium or strontium. base cations such as sodium, potassium, ammonium or substituted ammonium cations. The passivator can be, for example, zinc molybdate, sodium zinc molybdate, calcium molybdate, zinc vanadate or zinc tungstate. Zinc chromate or potassium-30 zinc chromate may be used, although it may be desirable for the coating composition not to contain chromate to avoid potential health hazards.

10 75856

Molybdates and vanadates are preferred, especially metavanadates, especially zinc molybdate, sodium zinc molybdate or zinc methanadate. The passivator preferably contains zinc ions, unless the polyphosphonate salt contains them. The passivator may be in the form of a combination of particles in which molybdate or another passivator is precipitated on the surface of the pigment particles, for example sodium zinc chymolybdate may be coated with a carrier pigment such as zinc oxide, titanium oxide or talc, as described in GB the solubility is preferably less than 2 g / l, for example 0.02 1 g / l.

The polyphosphonate salt and the passivator have a synergistic effect and achieve better corrosion resistance when used in the paint together compared to either of the two used separately. The synergistic effect is particularly noticeable in the case of polyphosphonate salts with a low ratio of polyvalent metal ions to phosphonate groups, so that the ratio of metal ions to phosphonate groups in the polyphosphonate salt to be used in combination with the passivator may be lower than in the non-passivator. In general, 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 the metal ion when the salt is used with a passivator; Ratios between 0.8 / n: 1 and 2 / n: 1 are preferred.

Preferred phosphonate salts for use with a passivator include calcium, zinc, manganese, barium, magnesium and strontium salts containing 0.4 to 0.6 divalent metal ions per phosphonate group, for example calcium methidronate with a calcium: etidronate ratio. about 1: 1. We have identified two li 7 5 8 5 6 crystalline calcium methidronate of this type. When calcium hydroxide and etidronic acid are reacted in water in a molar ratio of 0.6: 1 to 1.2: 1 and at a temperature above 70 ° C, plate-like crystals with a particle size of less than 50 μm precipitate.

5 When calcium hydroxide and etidronic acid are reacted in the same molar ratio in water and at a temperature below 70 ° C, needle-like crystals precipitate. Both of these crystalline forms have been found in the analysis to contain calcium and etidronate in a molar ratio of 0.9: 1 to 1: 1. The needle-like crystals can be converted into plate-like crystals by heating them in water at a temperature above 70 ° C for, for example, 30 minutes. Although both of these calcium methidronates are particularly effective corrosion inhibitors when used in conjunction with a passivator, sheet-like crystals are preferred due to their lower water solubility (generally less than 0.5 g / L) and lower particle size.

The weight ratio of polyphosphonate salt: passivator in the pigment component of the paint is preferably 2: 1 to 20: 1, most preferably 4: 1 to 10: 1. Within the latter limits, an increase in the proportion of passivator, such as a molybdate salt, leads to an increase in the corrosion inhibitory effect, but when the weight proportion of the molybdate salt rises above 25% by weight of the polyphosphonate salt, e.g. etidronate, the corrosion inhibition no longer improves. When the weight fraction of molybdate rises above 25 to 50% by weight of etidronate, the corrosion inhibition may be impaired.

In addition, other known anti-corrosion pigments such as phosphates, for example zinc phosphate, silicates, borates, diethylthiocarbamates or lig-nosulfonates or zinc dust or an anti-corrosion organic additive, such as tannin, an organic additive such as tannin, or borate road ester. Small amounts of 12,755,56 any basic pigment, such as calcium carbonate or zinc oxide, may be used, especially if the pH is below 5 when the phosphonate salt is in contact with water. When calcium methidronates, in which the molar-5 ratio of calcium to etidronate is about 1: 1, come into contact with water, the pH is generally 4.5 to 5.1. Calcium tetidronate, with a molar ratio of calcium retidronate of about 2: 1, results in a basic pH. Zinc dietronates having a zinc: etronate molar ratio of less than about 1.4: 1 generally give a pH value of 3.5 or less. Zinc etronates with a zinc: etidronate molar ratio greater than 1.6: 1 give a pH of 6-7.

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

The coating compositions of the invention are most commonly used to prevent corrosion of iron and steel, but may also be used in anti-corrosion paints for metal surfaces other than iron, for example galvanized steel or aluminum, or in prestressed concrete.

The anti-corrosion coating is most commonly applied to the metal surface by spraying, roller or brush using an organic solvent as a medium in which the film-forming binder is dissolved or dispersed. The coating can be cured by evaporating the solvent by air drying and / or by a crosslinking mechanism depending on the nature of the binder. Alternatively, the coating may be applied as an aqueous dispersion, in which case it may be applied by spraying, roller or brush or electrodeposition using a film-forming binder of an anionic or cationic resin. Alternatively, the coating composition may be applied as a powder coating, for example by electrostatic spraying, and melted and cured on a metal surface.

The invention is illustrated by the following examples:

Examples 1-9

Manufacture of polyphosphonate salts

Example 1 184.8 g (2.28 mol) of zinc oxide were slurried in 10 volumes of water to a concentration of 20% by weight and heated to 70 ° C. A solution of 316 g (1.52 mol) of etidronic acid was diluted to 20% by weight and heated to 70 ° C. The zinc oxide suspension was pumped into the etidronic acid solution over a period of 45 minutes with continuous stirring of both the suspension and the solution. After about 20% zinc oxide was added, a precipitate formed. The resulting slurry was stirred for four hours at 60-70 ° C to allow the salt formation reaction to occur. The slurry was then cooled and filtered using a Bvichner funnel.

The resulting solid was washed four times with distilled water to wash etidronic acid out of the salt using 2 liters of water each time. The wet filter cake was broken up and dried in an oven at 110 ° C to give about 500 g of zinc etronate as white needle-like putty. The solubility of zinc-25 hardidronate was determined by soaking it in distilled water, centrifuging and measuring the dissolved metal ion content. The metal ion content was 0.165 g / l, which meant a pigment solubility of 0.5 g / l.

Example 2 Manganese (II) carbonate (87.0 g, 0.75 mol) was reacted with etidronic acid (154 g, 0.75 mol) using the procedure of Example 1 to prepare a pink solid manganese etidronate.

Example 3 Calcium hydroxide (0.84 mol) was reacted with etidronic acid (1 mol) using the procedure of Example 1 to prepare calcium methidronate calcium as a plate-like kit.

Example 4

Magnesium oxide (80.7 g, 2.00 mol) was reacted with 5 da etidronic acid (207.8 g, 1.01 mol) using the procedure of Example 1 to prepare magnesium etidronate as a white solid.

Example 5

The preparation process of Example 1 was repeated using 246.4 g (3.04 mol) of zinc oxide to prepare zinc dihydrate with a theoretical zinc: etidronate molar ratio of 2: 1.

Example 6

The preparation process of Example 1 was repeated using 369.6 g (4.56 mol) of zinc oxide to prepare zinc dihydrate with a theoretical zinc: etidronate molar ratio of 3: 1.

The solubilities of the pigments of Examples 3-6 were as follows: Solubility (g me- Pigment leach ion / l) solubility (g / l)

The calcium methidronate of Example 3 0.037 0.261

The magnesium etidronate of Example 4 0.069 0.355

Zinc dietronate of Example 5 0.045 0.114

Zinc dithronate of Example 6 0.034 0.078 Example 7

Manganese (II) carbonate was gradually added to a solution of etidronic acid (.78.0 g, 0.38 mol) in 42 ml of distilled water, which was stirred vigorously. During the addition, carbon dioxide evolved, and a purple-35 female solution was formed. After the addition of 39.6 g of carbonate, a light brown precipitate formed. Distilled water (500 ml) was added followed by a further 47.4 g of manganese (IX) carbonate to give a total of 0.75 mol. The mixture was stirred for half an hour 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 etidronate.

Example 8

Barium carbonate was gradually added to a solution of etidronic acid (136.3 g, 0.66 mol) in 1,584 ml of distilled water and stirred. After 64.9 g of barium carbonate was added, a precipitate formed. An additional 195.9 g of barium carbonate was added to give a total of 1.32 moles and the mixture was diluted with distilled water (1500 ml) with stirring.

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

The white solid was stirred in distilled water (1,000 mL) and 34.2 mL of concentrated hydrochloric acid was added. The mixture was stirred for 2.5 hours, filtered, washed with distilled water and dried at 100 ° C. 266.1 g of a white solid, barium methidronate, were obtained.

Example 9 A 20% solution of 316 g of etidronic acid was prepared as described in Example 1, and 1 mol of sodium hydroxide per 2 moles of etidronic acid was added to partially neutralize the acid. A 20% aqueous solution of zinc oxide containing 184.8 g of zinc oxide was then reacted with a partially neutralized etidronic acid solution using the procedure of Example 1 to prepare sodium ion-modified zinc etidronate.

Examples 1-9 35 Paint tests

Each etidronate prepared as described in Examples 1-9 was used as an anti-corrosion pigment in 16,755,556 anti-corrosion paints. Etidronate was ground in a ball mill with the following ingredients until the particle size of etidronate was 30-40 μm:

Weight% 5 Alkyd resin 20.0

Ethidronate 16.3 prepared according to any one of Examples 1-9

Talc 13.5

Titanium dioxide 9.6 10 Drying and additives 2.4

Xylene solvent 38.2

Each anti-corrosion paint was sprayed on steel plates so that the dry film thickness became 100-200 μm. When the paint film was dry, two scratches extending through the paint film were drawn, exposing the steel below and forming a cross-pattern. The plates were then subjected to a 500-hour salt spray test according to British Standard BS 3900. In a comparative experiment, paints were prepared having the composition mentioned above but using zinc phosphate (British Standard BS 5193) instead of etidronate.

After 500 hours in the salt spray test, the plates were judged for blistering, rust spots, corrosion in and around the scratch, including the retraction of the base film at the cross and the spread of rust discoloration at the scratch. The paints of Examples 1-9 had superior anti-corrosion performance compared to the zinc phosphate-containing paint, especially in terms of corrosion at and around the scratch and corrosion of the scratch. The plates coated with the paints of Examples 1, 2, 3, 5 and 9 showed less corrosion in all respects than the plates coated with zinc phosphate paint. The plates coated with the paint of Example 6 showed less corrosion in and around the scratch than the zinc phosphate coated plates and the plates 17 75856 were more or less similar in other respects. The sheets coated with the paints of Examples 4, 7 and 8 showed less scratch-staining rust discoloration than the zinc phosphate coated sheets and the sheets were otherwise approximately similar.

Example 10

The zinc dietronate prepared according to Example 1 above was ground in a ball mill with the following ingredients to have an anti-corrosion paint having a particle size of zinc dietronate of 10 to 40 μm:

Parts by weight

Alkyd resin 20.0

Zinc dietronate 16.3

Sodium zinc molybdate 4.0 15 Talc 13.5

Titanium dioxide 9.6

Desiccants and additives 2.4

Xylene solvent 38.2

Examples 11 and 12 Anti-corrosion paints were prepared as described in Example 10, but used in Example 11 manganese etidronate prepared according to Example 2 and in Example 12 calcium methidronate prepared according to Example 3. In both examples, zid-25 etidronate was completely replaced with an equivalent amount of manganese or calcium methidronate.

Example 13

An anti-corrosion paint was prepared according to Example 12, but the amount of sodium zinc molybdate was increased to 8.0 to 8.0 parts by weight.

Example 14

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

The anti-corrosion paint of each of Examples 10 to 14 was sprayed onto 18,755,56 sheets of low carbon steel so that the dry film thickness became 100 to 200. When the paint film was dry, two scratches were drawn through it, exposing the cross-section of the steel below. The plates were then subjected to a 1,200 hour salt spray test according to British Standard BS 3900. After the test, the plates were tested for resistance to rust discoloration and blistering, both in general and from scratches. The paint of Example 3 was tested in Senna as a comparative example without the use of 10 passivators.

Comparative experiments were performed in which the paint had the composition of Example 10 but in which zinc etronate had been replaced by an equal amount of sodium zinc molybdate (Comparative Example Y) or the composition of Example 10 in which calcium methidronate and sodium zinc molybdate had been hardened with zinc phosphate (Comparative Example Z). The results are shown below:

Example 10 - very little rust staining, no blisters or signs of corrosion spreading more than 20 mm from the scratch.

Example 11 - the results are the same as for the paint according to Example 10.

Example 12 - almost no rust discoloration (even less than in Examples 10 and 11), no blisters 25 and no signs of corrosion spreading outside the scratch.

Example 13 - slight rust discoloration (but slightly more than in Examples 10 and 11), no blisters or signs of corrosion spreading more than 11 mm from the scratch.

30 Example 3 - very little rust discoloration (no more than in Example 10), but some blisters around the scratch.

Example 14 - the results are the same as for the paint according to Example 12.

35 Comparative Example Y - considerably more rust discoloration than in Examples 10-14 and some corrosion extending more than 1 mm from the scratch.

75856

Comparative Example Z - more rust staining than in Example Y and some corrosion spreading more than 1 mm from the scratch.

The results show that the paints of Examples 10-14 containing etidronate and molybdate passivator provide better corrosion resistance of the steel sheet than the paint of Example 3 containing etidronate alone. The paint of Example 3 achieved better corrosion resistance, especially with respect to rust discoloration, than paints containing sodium zinc molybdate alone or zinc phosphate. One of the sheets coated with the paints of Examples 10-14 and Comparative Example z was also exposed to natural weather conditions in harsh marine climates on 15 Coquet Island, a small island off the coast of Northumberland in England. After nine months, the plates coated with the paints of Examples 10-14 showed very little rust staining and no corrosion spread outside the scratch; in particular, the paints of Examples 11, 12 and 14 showed almost no rust staining outside the scratch. The paint of Comparative Example Z showed some corrosion around the scratch and spread of corrosion outside the scratch.

Example 15 1,177 g of calcium hydroxide was slurried in water (4,695 g) and the slurry was added at a rate of 130.5 g / min with stirring to a solution of 3,913 g of etidronic acid in 15.55 kg of water at 65-78 ° C. The mass of needle-like crystals precipitated after 30 minutes, and the addition of slurry was stopped to disperse and redissolve the crystals. As the slurry was continued, a precipitate formed in the form of plate-like calcium methidronate crystals. These were filtered, washed with water and dried in a fluid bed dryer. When analyzing the product, the molar ratio of calcium: etidronate was found to be 0.94: 1.

20 7585 6

Example 16 605 g of a 60% aqueous solution of etidronic acid were added over 100 minutes with stirring to a slurry of 107.4 g of calcium hydroxide in 2 l of distilled water, the temperature of which was kept at 20-35 ° C. A precipitate formed by needle-like crystals formed. The crystals were filtered, washed with water and dried in a fluid bed drier. Analysis of the product showed that the molar ratio of calcium to etidronate was 0.94: 1.

Anti-corrosion paints were prepared by grinding the following ingredients in a ball-10 mill.

Weight parts Example 15 Example 16

Weakly polymerized alkyd resin

Plate-shaped calcium methidronate crystals 16.3 15 Needle-shaped calcium methidronate crystals - 16.3

Sodium zinc molybdate precipitated on zinc oxide 2.0 2.0

Talc 13.5 13.5

Titanium dioxide 9.6 9.6 20 Desiccants and additives 2.4 2.4

Xylene solvent 38.2 38.2

The anti-corrosion paints of Examples 15 and 16 were sprayed onto low carbon steel sheets to a dry film thickness of about 25 to 100. When the film was dry, two scratches were drawn through the paint film, revealing the cross-shaped area of the steel below.

The coated sheets were subjected to a salt spray test at 90 ° C according to ASTM-B117.

30 After being painted for 250 hours in a hot salt spray, the paints of Examples 15 and 16 showed little or no corrosion or blistering at the scratch or at all in the intact areas of the film. Both paints were better in all respects 35 than the zinc phosphate-containing analogue country.

After 500 hours of the hot salt spray test, the paint of Example 16 showed some corrosion 75856 and the formation of blisters at the scratch and corrosion as much as my control la. The paint of Example 15 still showed very little corrosion or blistering, even at scratch, and 5 paint was significantly better than the reference paint.

Examples 15A and 16A

The 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. The paints were sprayed on low carbon steel plates into a 100 μm thick film and scratched, after which they were subjected to a weather resistance test on Coquet Island using a zinc phosphate coated plate as a control plate. After 10 months, the soils of Examples 15A and 16A showed very little rust even at scratch and were superior to the control sample with some corrosion spread outside the scratch.

Example 17 20,682 g of a 60% aqueous solution of etidronic acid were slowly added with stirring to a slurry of 400 g of zinc oxide in 1.45 kg of distilled water. A dense white, amorphous precipitate formed which settled on cessation of the stirring, allowing the solution to clear. The reaction was exothermic. The mixture was filtered and the precipitate was washed with distilled water and dried at 110 ° C. 863 g of zinc etronate were obtained with a molar ratio of zinc to etidronate of 2.4: 1.

As the filtered solution cooled, precipitate-like crystals precipitated and were filtered cold, washed and dried. 27.3 g of zinc etronate were obtained with a zinc: etidronate molar ratio of 1.8: 1.

An anti-corrosion paint was prepared with a solids content of 40% by volume and based on a weakly polymerized alkyd resin with a pigment content of 35% by volume (PVC) and the above-mentioned zinc diodonate (main precipitate with a zinc: etidronate molar ratio of 22,755,56). 2.4: 1) formed 40% by volume of pigment with the remainder consisting of titanium dioxide and a small amount of bentonite.

Example 18 A corrosion paint was prepared according to Example 17, but with 80% by volume of zinc etidronate in the pigment.

Example 19

The two-component anti-corrosion epoxy paint 10 was prepared from "Epikote 1001" (trademark) epoxy resin and pigment containing 40% by volume of the zinc etronate of Example 17 as well as titanium oxide and a small amount of bentonite. The curing agent of the epoxy resin was "Versamid" (trademark), a poly-15 amide containing amino functional groups and a total solids content of 51% by volume and P.V.C. 40%.

Example 20

The two-component anti-corrosion epoxy paint was otherwise prepared according to Example 19, but zinc-20 etidronate was used in 80% by volume of the pigment.

The anti-corrosion paint of each of Examples 17-20 was sprayed onto low carbon steel sheets to a dry film thickness of about 100, scratched and subjected to a ASTM B-117 bog glass spray test at 90 ° C. Similarly, coated plates were subjected to a moisture test according to British Standard 3900F2 (relative humidity 100%, temperature variation between 40 ° C and 48 ° C to ensure condensation).

Paints containing zinc phosphate instead of zinc etidronate were prepared as control samples (samples 17A-20A).

The plates were examined after a 1,000 hour test according to ASTM D-1654 (Procedure B). The results are shown in Table 1. The percentage of the surface area affected by corrosion or blistering is examined from the plate and graded accordingly.

23 7585 6

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Paints containing zinc etronate showed significantly less corrosion in both hot salt spray tests and moisture tests for both visible corrosion and sub-film corrosion.

Example 21 400 g of 50% by weight of amino-tri (methylenephosphonic acid) were diluted with distilled water to a 20% by weight solution and heated to 78-80 ° C. A slurry of 20% by weight (99.0%) of calcium hydroxide in distilled water was heated to 75-80 ° C and added to the phosphonic acid solution over 45 minutes with constant stirring. The molar ratio of calcium hydroxide: amino-tri (methylenephosphonic acid) was 2: 1 (ratio of calcium: phosphonic acid group 0.67: 1). When the slurry was completely added, the solution and the resulting precipitate were kept at said temperature and stirred for another two hours. The precipitate was separated and dried.

Examples 22-29

The calcium and zinc salts of various organic polyphosphonic acids were prepared according to Example 21 and from the amounts shown in Table 2.

26 7585 6

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Each of the polyphosphonate salts of Examples 21-29 can be used in place of calcium methidronate in the paint composition of Example 3 to give a paint having corrosion protection properties similar to those of the paint of Example 3.

Example 30 1 mole of sodium hydroxide was added to 1 mole of etidronic acid in aqueous solution to give a solution having a concentration of 20% by weight. 1 mole of calcium hydroxide-10 was slurried in water for 30 minutes to give a precipitate of calcium etidronate sodium, which was filtered, washed and dried. This polyphosphonate salt could be used instead of calcium methidronate in the paint compositions of Examples 3 and 12, in both cases to obtain a paint with similar anti-corrosion properties.

Example 31

The type of fast air-drying industrial primer used, for example, as a primer for agricultural tools, was prepared by grinding in a ball mill with the following ingredients:

Weight-%

Drying oil alkyd 50.23

Calcid-25 etidronate 12.40 prepared according to Example 15

Sodium zinc molybdate 1.55

Inert pigments and fillers (calcium carbonate, titanium dioxide, talc and iron oxide yellow) 10.07 30 Drying and additives 2.39

Xylene solvent 13.36

The paint was applied to plates made of phosphatized steel and scratched as described in Example 1. The plates were then subjected to a 240 hour salt spray test 35 using conditions according to ASTM B-117. For comparison, a paint containing the same ingredients except for calcium methidronate 28 7 5 8 5 6 and sodium zinc molybdate and zinc chromate as the anti-corrosion pigment (16% by weight of the pigment) was used.

The sheets coated with the paint of Example 31 showed hardly any signs of corrosion after the salt spray test, even at scratch, and were equal to or better than the zinc chromate-containing paint in both overall appearance and the absence of rust at scratch.

10 Example 32

A car abrasive paint / primer was prepared from the following ingredients for application to phosphatized steel, on which an acrylic topcoat is to be applied: 15 parts by weight

Sodium zinc molybdate 1.32

Calcium etidronate 12.68 prepared according to Example 15

Inert pigments (barite, kaolin, 20 titanium dioxide and iron oxide yellow) 22.64

Bentonite gel (10%) 2.57

Carbon black pre-dispersion (10%) 4.93 Tall oil epoxy ester resin 20.94

Urea-formaldehyde resin 1.37 Benzoguanamine resin 2.13

Drying and additives 1.24 n-butanol 0.69

Ethyl glycol monoethyl ether 0.69

Xylene 28.80 Pigments, bentonite gel and soot dispersion were dispersed in epoxy ester resin. Xylene was added to the dispersion, which was treated with a sand mill until a Hegmann reading of 7 was reached. The other ingredients were added with stirring.

The paint was sprayed onto sheets made of phosphatized steel to a dry film thickness of 30-40 m and cured by holding the sheets at 163 ° C for 29 75 8 5 6 20 minutes. The plates were scratched and subjected to a 300 hour salt spray test ASTM. According to B-117 for the above plates and for the reference plates / zinc phosphate was used instead of calcium methidronate and sodium zinc molybdate 5. The boards painted according to the invention showed no corrosion in the area of the intact surface and little corrosion around the scratch and the boards were significantly less corroded than the reference boards in both areas.

Claims (8)

An anticorrosive coating composition comprising a pigment component dispersed in a film-forming binder, characterized in that the pigment component comprises a) a salt formed from a polyvalent metal cation and an organic polyphosphonic acid containing at least two phosphoric acid groups, has the general formula MR (PO) H, ~, wherein M represents a metal ion which may be zinc, manganese, magnesium, calcium, barium, aluminum, cobalt, jam, strontium, tin, zirconium, nickel, cadmium or titanium, R represents an organic radical bonded to the phosphonate groups by carbon phosphorus compounds, m is the valence of the radical R and is at least 2, n is the valence of the metal ion M and x is 0.8 m / n - 2 m / n and b) a corrosion passivator which is a molybdate, tungsten gauge, vanadate, halted, manganate, titanate, phospho molybdate or phosphovanadate containing cations of a cross-linked metal, the weight ratio of the polyphosphonate salt a) to the passivator b) is 1: 1 - 50: 1. Anti-corrosive coating composition according to claim 1, characterized in that the polyphosphonate salt is a calcium salt, the mole ratio of calcium to phosphonate groups being 0.4: 1 - 0.6: 1. Anti-corrosive coating composition according to claim 2, characterized in that the polyphosphonate salt is a calcium etidronate. Anti-corrosive coating composition according to claim 1, 2 or 3, characterized in that the passivator is sodium zinc molybdate or zinc molybdate. Use of a site formed by a plurality of host metal cation and an organic polyphosphoric acid containing at least two phosphonic acid groups, which site has the general formula MXR ίρ03 ^ mH (2m-xn) 'var; * - M denotes