Anticorrosive pigment for coatings on metal

 

(57) Abstract:

The invention relates to the protection of metal from corrosion coating. Describes anticorrosive pigment for coatings on metal, comprising a pigment component-inhibitor. And as a pigment component inhibitor it contains pyrolusite powder and further comprises talc or iron oxide or mica, or a mixture in the following ratio, wt. %: pyrolusite 10-55; talcum powder or iron oxide or mica, or a mixture in any ratio of 45-90. The technical result - the assortment of low-toxic anticorrosive pigments inhibitors, protective properties are not inferior chromate pigments. table 1.

The invention relates to the field of protecting metal from corrosion coating.

It is known that the main protective function in the system of lacquer coating on metals perform primers, anti-corrosive action of which is largely determined by the content and type of pigments. The most effective in this aspect are anti-corrosive pigments and inhibitors present in the coating composition can suppress corrosion prisoneraa) are highly toxic.

Enhancing the environmental soundness of the materials used to produce coatings, in the last decade refers to the priority directions of development of the paint industry sub-sectors. Toxic pigments in the future should be completely eliminated from the formulations of anti-corrosive compositions. This makes urgent the problem of finding alternative low-toxic anticorrosive pigments and causes an increased interest in research on corrosion properties of various compounds which possess the characteristics necessary to perform the pigment functions in paint coatings.

The first connections among used to reduce the toxicity of anti-corrosion coatings instead of chromium and lead were phosphates.

As phosphate-containing pigments are mainly used phosphates of zinc and chromium, which are non-toxic crystalline [see the book of Korsun L. F., Kalin T. C., S. Stepin N. Inorganic pigments. Ref. ed. -SPb.: Chemistry, 1992. - 336 S., Smieszek E., Karminska E. Pigmenty fosforanowe do farb antikororuj nuch// Ochr. Koroz. - 1996. - Bd. 39. -14. C. 85-88]. The zinc phosphate Zn3(PO4) nH2O little soluble in water, but readily races is m Phosphate chromium is not used as an independent anti-corrosive pigment. It is used in pigment compositions, in particular in chromate, where there is a synergistic effect due to the increased solubility of chromates and enhance their corrosion resistance properties [see the book Rosenfeld, I. L., Rubinstein, F. I., Zhigalova K. A. Protection of metals from corrosion coating. - M.: Chemistry, 1987. S. 143].

Anti-corrosive properties in addition to the above salts of phosphoric acid are also others, including acidic phosphates of aluminum, barium, calcium, magnesium, manganese [Application 37317377 (Germany), D. Schuler Richtungsweisende Korrosionschutzpigmenten // Farbe und Lack. - 1986. - Bd.92. - N 8. - S. 703-705].

Known also use as anticorrosive pigments, condensed phosphates of metals. These compounds have a higher anti-corrosion properties, as are formed by their hydrolysis ions are more strongly expressed complexing ability towards Jonah Fe3+than PO43-. The resulting reactions of complex formation surface layer connection, for example, the General formula FexAly(PO4)zmakes the surface of the sheet m tripolyphosphate.//Corros. And Coat. S. Afr. - of 1991-92. - V. 18. -16. - P. 12].

Currently active research anti-corrosion properties of the condensed phosphates can be recommended for use in the field of protection against corrosion diphosphate copper Cu2P2O7, calcium Ca2P2O7magnesium Mn2P2O7; polyphosphates of the calcium Ca3(P3O10)21,5 H2O, zinc Zn3(P3O10)2H2O, aluminum Al3(P3O10)22H2O, cycloterpenic iron Fe2P4O12, copper Cu2P4O12, Nickel Ni2P4O12, zinc Zn2P4O12magnesium Mg2P4O12, calcium Ca2P4)12and manganese Mn2P4O12[see A. S. Czechoslovakia11, 262501, 256138, 259337, 247844, 253098, 259926, 245071, 259906, 260487, 259341; Takahashi M. Aluminium tripolyphosphate-anti-corroson pigment. //Polym. Paint Colour J. - 1987. - V. 177, N 4197. - P. 554, 556; Zotov F. B., Luganceva L. N., Petrov L. N. The protective properties of a number of passivating pigments // Paint-and-lacquer materials and their application. - 1987. - N 5. - S. 27-29].

Experience in the use of phosphate anticorrosive pigments in the coatings showed that their common disadvantage is the low efficiency in the initial stages of the times Anorganische Korrosionsschutzpigmente-Ubei-blick und neuere Entwicklung//Farbe und Lack. - 1982. Bd.88. - N 3. - S. 183-188].

A new group of anti-corrosion pigments are ferrites are mixed oxides of the spinel structure of the General formula MeOFe2O where Me is magnesium, zinc, tin, copper, calcium, cadmium, cobalt, barium, strontium, iron, manganese [see the book of Korsun L. F., Kalin T. C., S. Stepin N. Inorganic pigments. Ref. ed. - SPb.: Chemistry, 1992. S. 138, article; Freedom M. Properties of ferrites zinc and calcium as anticorrosive pigments // Protection of metals. - 1988. - So 24. - N 1. - S. 44-47; Nepesov K. K., Guriev L. N., Vasiliev L. C. Physico-chemical and protective properties of ferrites metals (calcium, magnesium, zinc) //g go active. chemistry. - 1991. - So 64. - N 2. - S. 422-425; Corrosion-electrochemical properties of systems steel-ferrites alkaline earth metals /K. K. Nepesov, L. N. Guriev, L. S. Vasilyev // Fo. Protection-92", M.: 6 - 11 Sept. 1992. EXT. proc. Dokl. - S. 158; Protective properties of some ferritic metals //K. K. Nepesov, L. N. Guriev, L. S. Vasilyev //Theory and practice. electrochim. processes and Ecol. aspects of their use: Proc. Dokl. Uses. scient. -practical Conf., Barnaul, - 1990. - S. 210]. Ferrites can be regarded as a ferrous salt acid HFeO2. However, it is noted that the ferrites on the protective properties inferior to lead and chromate pigmentosa time, full-fledged alternative to toxic pigments, effective in the aspect of protection of metals from corrosion, is not found. Therefore, the task of finding low-toxic pigments, anticorrosion effect is not inferior chromate, remains.

The present invention applies industrially produced anticorrosive primer GF-0119 (GOST 23343-78) pestiviruses type, widely used to protect metals [see the book Rosenfeld, I. L., Rubenstein, F. I. anti-Corrosion primer and inhibited paintwork. - M.: Chemistry, 1980. - 136]. As the pigment component of the inhibitor contains tetrachromat zinc and calcium chromate. The disadvantage of this primer is that these compounds hexavalent chromium, performing basic protective function in pigment mixtures belong to the first class of harmful substances, as their MAC is 0.01 mg/m3[see GOST 12.1.005-88; List of chemical and biological substances, passed state registration in the Russian register of potentially hazardous chemical and biological substances. M, 1996].

The objective of the invention is the expansion of the range of low-toxic anticorrosive pigments inhibitors, on the protective properties are not inferior to chromate pigment is rotovac on metal. And as a pigment component inhibitor contains natural ground pyrolusite and further comprises talc or iron oxide or mica, or a mixture in the following ratio, wt.%:

ground natural pyrolusite - 10 - 55

talcum powder or iron oxide or mica, or a mixture in any proportion - 45 - 90

An important difference ground natural pyrolusite from chrome-containing substances is significantly less toxicity: it belongs to the second class of harmful substances, its MAC is 0.3 mg/m3that is 30 times greater than the corresponding characteristic of chromate pigments. In addition, ground natural pyrolusite significantly cheaper tetrachromate zinc and chromate calcium obtained by synthetic.

It is established that natural ground pyrolusite has inhibitory ability, but due to the high hydrophilicity cannot be recommended for use as an anticorrosive pigment [see Stepin S. N., Svetlakov A. P., Smirnov, S. A. investigation of the corrosion properties of coatings, pigmented pyrolusite //M: Dept. in VINITI, N 2721-V from 28.08.98,].

High protective ability of the primer in theta and fine component with lamellar particle shape. This is explained in the following. A primer coating that is filled with crushed natural pyrolusite, have very low resistance coating to the charge transfer Rn, which is in the process of testing is reduced. Low isolation (barrier) properties of the coatings can be explained by the presence in the natural ground pyrolusite hydrophilic impurities that form in the amount of paint film frame from chain structures. Apparently, these chains contribute to the formation of transport channels for corrosive environment from the surface of the film to the surface of the steel. The additional introduction of the primer component plate (antomatically) particle shape helps, probably, the destruction of these channels. This increases the initial value of Rpand , most importantly, its stabilization in the testing process. As a component with lamellar particle shape used talcum powder or iron oxide or mica, or a mixture in any proportion. Iron oxide is a black, metallic iron oxide (a-Fe2O3), having the structure of hematite particles of lamellar form. Abroad an iron oxide called MIOX (Micaceus Iron Oxide - mica oxide jelly is a personal light and weather resistance [L. F. Korsunsky, So Century. Kalinsky, S. N. Stepin. Inorganic pigments, coatings. - SPb.: Chemistry, 1992. S. 138].

The methodology of testing. Surface preparation of samples of body steel 08 KP before applying primer was carried out by blasting and subsequent degreasing mineral spirits and acetone. Primers were prepared by dispersing the components of the pigment part in the solution of the foaming agent. As the foaming agent used alkyd varnish PF-060 (TU 6-10-612-76), copolymer a-15-Oh, bitumen varnish BT-577 (GOST 5631-79). In order to achieve maximum insulating ability of the primers to the filling level of the coatings were chosen equal to 0.8 of the value of the critical volume content of the pigment. This value was determined directly on the surface of the steel substrate by the dependence of the steady-state electric system capacity painted metal - electrolyte interface on the degree of filling of the coating [see Stepin S. N. , Svetlakov A. P., Smirnov, S. A. Method of assessing critical volume content of pigments in the primer coatings //Paint-and-lacquer materials and their application. - 1996. - N 11. - S. 12-15].

The obtained primer was applied centrifugal method, a coating was formed in natural conditions the quality of paint and varnish materials (definition of viscosity, the content of non-volatile and volatile substances, milling degree primers and coatings (definition of appearance, hardness, elasticity, Flexural strength, tensile impact, adhesion) were performed by standard techniques [see the book Livshits, M. L. Technical analysis and control of production of varnishes and paints: Textbook. a manual for technical schools. - M.: Higher. HQ., 1987. C. 206-227].

Comparative corrosion tests of painted steel samples was performed by immersion in a 0.5 molar aqueous solution of sodium chloride at a temperature of 205oC. the test Duration was 1500 hours.

The protective properties of the coatings obtained when applying primers based on the proposed pigmented parts and applying primer GF-0119, was estimated using index Rand index K, which characterizes the percentage of corrosion damage to the metal surface under the coating [method for determining K, see the book Karjakin M. I. tests of paints and coatings. - M.: Chemistry, 1988. C. 200].

The index KRfound by the formula KR= R1500/R10where R10, R1500- resistance of the coating to the charge transfer Rp(Momm2in the initial period (10 h) and after 1500 h of testing, matched with the metal in contact with the electrolyte (0.5 M NaCl), for registration which used the impedance meter VM-507 [see use of the method of impedance spectroscopy to assess the protective properties of coatings curable by the reaction of the oxidative polymerization /A. P. Svetlakov in. A. Terekhin, S. N. Stepin etc. //Paint-and-lacquer materials and their application. - 1991. - #4. - C. 24-26].

The composition of the investigated coatings and the results of the experiments are given in the table.

The results show that primers containing ground natural pyrolusite and fine component with lamellar particle shape, in the whole range of ratios provide effective corrosion protection to the steel surface, which is not inferior to the prototype - primer GF-0119.

Optimal is the following ratio of components in the pigment part: ground natural pyrolusite 35; component with lamellar particle shape 65 wt.%. Higher protective properties of the composition based on a copolymer of a-15-O.

Anticorrosive pigment for coatings on metal, comprising a pigment component-inhibitor, characterized in that the pigment component of the inhibitor contains ground pyrolusite and further comprises talc or iron with the Talc, or iron oxide or mica, or a mixture in any proportion - 45 - 90

 

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