ANTI-CORROSIVE PIGMENT COMPOSITION AND PROCESS FOR PRODUCING THE SAME

Abstract: The composition may be used for the purposes of dyestuff and varnish industry, particularly for the production of dyestuffs, lutes and other corrosion protecting coatings. The pigment composition comprises: (a) alumina hydrate AlOH3, (b) an amount of 10-100 parts by weight of at least one of the atoxic oxides, hydroxides, oxide hydroxides, carbonates or phosphates of amphoteric elements or metals of variable valency possessing less valency than the maximum - in case of aluminium the appropriate oxide or oxide hydroxide - related to 100 parts by weight of alumina hydrate, (c) an amount of 0-40 parts by weight of calcium and/or magnesium carbonate related to 100 parts by weight of alumina hydrate, and its grain size is less than 20 mu m. The pigment composition is made according to the invention by making: preground products having a grain size of substantially 160-200 mu m, from components (b) and (c) respectively, drying the preground products and alumina hydrate individually to contain a moisture amount less than 1 weight %, admixing the products at the ratios required and homogenizing and grinding the lot to a grain size less than 20 mu m.

Description: Anti-corrosive pigment composition and process for producing the same Technical- field The invention relates to an active anti-corrosive pigment composition which may be used for the purposes of dyestuff and varnish industry,-primarily for the production of dyestuffs and lutes, as well as corrosion protecting coatings. Further the invention relates to the process for • producing the active anti-corrosive pigment composition. Background of the invention As it is well known, recently the reσuirementes for corrosio resistant coatings are " increasing as the surfaces covered by such coatings have to be protected against ever more agg- ressive exposures, particularly, when they are installed in industrial equipments. It is also known that the possibilit of the application of anti-corrosive pigments proved best i practice, notably red lead /Pb,0./ and chromates, is more and more restricted because these materials are poisonous, particularly the process being harmful to health when adopt spraying methods in the use of same. At many places their us is strictly prohibited or restricted. Accordingly, there is a need for anti-corrosive pigments which meet the increased requirements of corrosion protection on one hand, and could be applied without causing hazard to health and to the environment, on the other hand. Summery of the invention The subject of the invention is an active corrosion protec¬ tive pigment composition which comprises: a/ alumina hydrate /Al/OH/.,/, b/ an amount of 10-100 parts by weight of at least one of the atoxic oxides, hydroxides, oxide hydroxides, carbonates or phosphates of amphoteric elements or metals of variable valency possessing less valency than the maximum - in case of aluminium the appropriate oxide of oxide hydroxide - related to lOO parts by weight of alumina hydrate c/ an amount of 0-40 parts by weight of.calcium and/or magnesium carbonate related to 100 parts by weight of alumina hydrate, and its grain size is less than 20 ,um. Detailed description of the invention The object of the invention is providing a pigment compositio which meets the foregoing requirements and is usable in any of the conventional corrosion protecting coatings and can be applied to the surface to be protected by the usual pro¬ cedures, respectively. Several tests have been carried out in,order to solve the task. Progress became difficult due to the condition that appropriate materials had to be selected of harmless compounds. During our tests, we σoυld surprisingly recocmize the following: When atoxic oxides, hydroxides, oxide hydroxi¬ des, carbonates or phosphates of the amphoteric elements or metals of variable valency, strictly those which posse s less valency than the maximum, are combined with adequate amounts of alumina hydrate and this blend is, optionally completed with calcium or ' agnesium carbonate and the blend is fine ground, a pigment composition is obtained which endows the surface coating materials with a strikingly more intensive corrosion protecting effect as the previously known anti-corrosive pigments exhibited. On +-he basis of this recognition, the active corrosion protective pigment composition comprises: a/ alumina hydrate /A1/0H/.,/, b/ an amount of 10-100 parts by weight of at least one of the amphoteric elements or atoxic oxides, hydroxides, oxide hydroxides, carbonates or phosphates of metals of variable valency possessing less valency than the maximum - in case of aluminium the appropriate oxide of oxide hyd- roxide - related to 100 parts by weight of alumina hydrate, c/ calcium and/or magnesium carbonate an amount of 0-40 parts by weight of related to 100 parts by weight of alumina hydrate, and its grain size is less than 20 ,um. By atoxic compounds, from the point of view of the invention compounds are meant which, applied in addition to alumina hydrate in a ratio usual in the surface protecting coatings ' 5 and mentioned also in this specification, are not harmful to healti whatever the method is of their application to the surface to be protected. As alumina hydrate component, the pigment composition ac¬ cording to the invention comprises advantageously alumina \Q . hydrate produced by the Bayer process. Namely, the weak alkality resulting in the course of the production of this metarial is advantageous .from the point of view of corrosion protection. If white pigment is required it is preferred to use carbonized alumina hydrate in certain amounts. This 15 amount may range up to 60 weight percent of the lot. The pigment composition according to the invention comprises advantageously as component b/ the above enumerated compound of metals which for* stable oxides, hydroxides and oxide hydroxides equally. Such metals are primarily aluminium, iro ~ pj and manganese the compounds of which are particularly advan¬ tageous in the anti-corrosion pigment composition. Compounds of these metals may also be used individually the pigment compositions, however, which comprise the coumpounds of alu¬ minium, iron and manganese all together, are more advanta- 25" geous. In additon to the foregoing, the pigment composition accor¬ ding to the invention may also comprise the above determined compounds of any other amphoteric elements, e.g. zinc or any other metal of variable valency, i.e. tin, cobalt or copper. The compounds enumerated as components b/ may be industrially produced meterials, possibly industrial by¬ products of wastes, however, they are preferably natural mi neral substances. The latter are of particular advantage if ' severeal compounds enumerated as components b/ are contained For component b/ of the pigment composition according to the invention, the following metarials have been considered to be of advantage: various kinds of bauxites, e.g. gibbsite-, goethite, hematite and particularly siderite bauxites, more¬ over, boehmite /AlO/OK//, magnetite /Fe.,0./, siderite /FeCO^/ lepidocrocite / V-' -FeO/OH//, anganite / L^ -Mn/OH/, rhodo- crosite .nCO-./, oyrolusite / .' -Mn0 / and zinc pho≤nhate. / Natural mineral substances which comprise compounds of se¬ veral metals are also cinsidered to be advantageous. Con¬ sequently for instance, jacobsite / nFe-0./,franklinite /ZnFe-O./ or chromite /FeCr„0 4 / may advantageously be used for components b/ of the pigment composition according to the invention. As already mentioned, ' the pigment composition according to the invention comprises at least one of the compounds ranked into the lot of components b/. If there is only one compound as component b/ in the composition, its amount is prefe¬ rably about 10-50 parts by weight related to 100 parts by weight of alumina hydrate. Were there more compounds cons¬ tituting component b/, their amount should preferably come to 20-90 parts- by weight related to 100 parts by weight of alumina hydrate. If there are no restrictions from other consideration, e.g. stipulations for a certain colour, it is advantageous to use a mixture of several compounds for com- . ponent b/. In certain cases, a pigment composition could be of advantage which comprises also calcium and/or magnesium carbonate in an amount of up to 40 parts by weight related to 100 parts by weight of alumina hydrate, beside the com- ponents-a/ and b/ outlined above. These compounds are advan¬ tageously also natural mineral substances. As such compounds the composition advantageously comprises limestone, dolomite, precipitated chalk or chalkstone or verious mistures of the substances enumerated. The grain size of the pigment composition is of importance from the point of view of the use of pigment composition according to the invention and the corrosion preventing effect of. coating materials comprising such pigment. The grain size of the pigment can be maximum 20 ,um. It is preferred, however, that the pigment comprises grains smal¬ ler than 10,urn, advantageously those smaller than- 5 ; m. Fine grains of this kind can, of course, be produced by grinding the substance under- appropriate conditions. The aim of the process according to the invention is assu¬ ring partly the grain size mentioned above, partly the perfect homogeneity of the components. Therefore, the pig- ment composition according to the invention is made in a way that preground products having a grain size of subs¬ tantially 160-200 ,um are made from components b/ and c/, respectively, the preground products and the alumina hyd¬ rate are individually dried to contain a moisture amount less than 1 weight % each, then they are admixed in a ratio required, then homogenized and finally ground to a grain siz less than 20 ,um, advantageously less than 10 ,um, however, most preferably less than 5 ,um. In certain cases /for some paint compositions/, addition of an anti-corrosive inhibitor to the . components during grin¬ ding may be advantageous. For this ' purpose, a 2-10 weight % aqueous solution of an alkyl pyridiniuπ halide , preferably cetyl pyridinium bromide or some kind of other known anti- -corrosive inhibitor is sprayed into the substances. Pregrinding, drying, admeasuring and ho ogenization of the compoments may be carried out by the usual methods and in the usual equipments. Fine grinding, however, should expe¬ diently be performed in an air jet mill being advantageously provided ' with an air sizer, the procedure be advantageously carried out in a closed circuit. During fine grinding the components get perfectly mixed, therefore, there is no need for subsequent homogenization. 5 Utilization of the invention The pigment composition of the invention may be used for making any kinds bf paints, lutes or other coating mate¬ rials. It can equally be used for oil-base or artificial 10 resin-base dyestuffs. The pigment according to the inven¬ tion is expediently used in an amount of about 50-85 weight percent for dyestuff compositions and in an amount of about 8-12 weight percent for lutes, however, ratios other than the former may also be adopted, if required. The pigment 15 according to the invention is compatible with the usual components of dyestuffs, lutes and other coating substances, thus with the colouring pigments and fillers. Along with the pigment composition according to the invention, the use of alumina as filler is particularly recommended, however, 20. the former can fairly be combined with other filler material The pigment composition according to the invention is easy and fast to get intermixed with dyestuffs and lutes. The advantage of the pigment composition according to the invention lies in its anti-corrosive feature. It not only 25 hinders the progress of existing corrosion, but forces back the same. Our experiments have pointed out that the pigmen composition according to the invention has made the exis¬ ting corrosion layer on the treated surface cease within a comparatively short time and after treatment a surface 5 clean to metal was obtained. It ensues from this that ther is no need for properly cleaning the surface to be protec¬ ted before the treatment with the dyestuffs, lutes and oth coating materials containing the pigment composition accor ding to the invention. Thus corrosion prevention can be 0 ' solved with considerably less labour compared with the pro cedure applying the conventional anti-corrosive materials. Further advantage of the pigment composition according to the invention is that, provided no fillers or pigments of larger grain size are admixed, the coating material made 15. of this substance is capable also for the treatment of bea ring surfaces. Namely, owing to its extremely fine grain size,- it prevents the bearing surface from abrasion. Considering that the pigment composition according to the invention does not comprise harmful materials to health, 20 the paints, lutes and other coating materials made by the use there of may be applied also under the strictest sti¬ pulations for health and could be applied by any means e.g spraying to the surface to be protected. Accordingly, the pigment composition according to the invention may be used 25 by any usual way in the corrosion protection. The invention should be illustrated by the examples hereunder without any restriction of the scope of same. The term "parts" is used in the sense parts by weight in the examples. Example 1 A pigment composition is prepared for lutes and priming paints with the composition below: 100 parts of alumina hydrate 67 parts of siderite bauxite /siderite content: 10 weight!/ 10 parts of siderite iron ore concentrate /manga- nese content: 3 weight!/ Siderite bauxite and siderite iron are concentrate are individually ground to grain size less than 200 ,um. Alumina hydrate need not be ground because its grain size meets the foregoing stipulation /it is approximately -160 ,um/ . The ground products, and the alumina hydrate respectively are dried to contain moisture less than 1 mas then the components are admixed at adequate ratios and homogenized in a homogenizer equipped with a spiral agita¬ tor. The homogenized mixture is fed into an air jet mill equipped with an air sizer. Here, it is ground in a closed circuit to a grain size less than 10, m. The ground produc is introduced into a dust filter connected with a dust separator. The finished pigment composition ready for further use may be withdrawn from the container of the dust filter. Example 2 A pigment composition is prepared for lutes with the com- position below: 100 parts of aluminate hydrate « 64 parts of bauxite 18 parts of siderite iron are concentrate /manganese content: 2 weight %/ The components are ground, homogenized and processed for pigment by the method given in Example 1. The final mixture is ground to 20 ,um grain size. Example 3 A pigment composition is prepared for synthetic base pri¬ ming paints, spray lutes and also for the protection aga¬ inst strong electrolytes /e.g. sea water/, with the follo- wing composition: 100 parts of alumina hydrate 55 parts of bauxite 22 parts of 95% siderite concentrate 11 parts of manganite 15 parts of limestone The components are dressed by grinding, drying and homo- genization according to Example 1. The homogeneous mix^ ture is introduced into an air jet mill equipped with an air sizer wherein it is ground to 10 ,um grain size. Du¬ ring grinding a 6 weight%aqueous solution of cetyl pyri- dinium bromide is sprayed into the pregrinding chamber by taking care of the added quantity not to exceed 10 weight% of the material to be ground. Namely, in this case, water gets evaporated during grinding and sizing thus no sepa¬ rate removal or water has to be provided for. Example 4 A pigment composition is prepared for priming paints, spary lutes in order to obtain smooth surface finis, with the following composition: 100 parts of alumina hydrate 66 parts of bauxite 16 parts of siderite 8 parts of yrolusite 10 parts of limestone - - The components are processed by the method given in Example 3 and are formed to obtain the pigment with the exception that fine grinding is made until 5 ,um grain size is obtained. Example 5 A pigment composition is prepared for the area of appli- cation mentioned is Example 4 with the following compo¬ sition: 100 parts of alumina hydrate 16 parts of siderite 8 parts of pyrolusite 11 parts of dolomite The components are processe ' d and formed to obtain the pigment by the method given in Example 4. Example 6 A pigment composition is prepared for the purpose of light colour priming paints or lutes for use at moderately corro sive conditions with the following composition: 100 parts of alumina hydrate 15 parts of boehmite 5 parts of rhodocrosite The components are processed and formed to obtain the pigment by the method given in Example 1. Fine grinding is made till 20 ,um grain size is obtained. Example 7 A pigment composition is prepared to achieve a very fast developing electrophoretic protecting effect with the following composition: 100 parts of alumina hydrate 25 parts of bauxite 10 parts of lepi ' docrocite . The components are processed and formed to obtain the pi ment by the method given in Example 1. Example 8 A pigment composition is prepared for priming paints with the following composition: 100 parts of alumina hydrate 30 parts of magnetite 5 parts of manganese dioxide 20 parts of dolomite The components are processed and formed to obtain the pigment by the method given in Example 3. Fine grinding is performed till 5 ,um grain size is obtained. Example 9 A pigment composition is prepared with the following composition: 100 parts of alumina hydrate /50 parts therein are carbonized alumina hydrate/ 40 parts of zinc phosphate 40 parts of limestone . The components are processed and formed to obtain the pigment according to Example 3. Fine grinding is perfor¬ med till 5 ,um grain size is attained. A pigment appli¬ cable for the production of white and coloured paints, respectively, is obtained. Example 10 A pigment composition is prepared for synthetic resin base light primers with the following composition: 100 parts of alumina hydrate - 40 parts of calcium zinc phosphate 15 parts of precipitated chalk The components are processed and formed to obtain the pigment by the method given in Example 3. Fine grinding is ^ performed till 10 ,um grain size is obtained. In order to examine the anti-corrosive effect of the pig- 5 ment composition according to the invention a lute has been prepared by the use of 10 weighβ of pigment composi¬ tion and the pigments enumerated in the examples 1-10. The lute has been applied in a 5 mm layer to the surface of steel specimens, havincr the measurements: 100x50x1.5 m 10. Part of the specimens was ground and degreased prior to applying the lute, the other part, however, was coated by the lute in the stained state. To carry out the weathering tests the specimens were sub¬ ject to cyclic ageing, carried out in 30 cycles during 15 which they were radiated by UV-light by a 300 τ . ~ lamp from a distance of 30 cm for 4 hours, kept for 4 hours in_ a space having 95% relative hu¬ midity and frozen at -20 C for 16 hours. 20 In order to test the specimens in a highly polluted in¬ dustrial atmosphere, they were treated according to the specification of the Standard: DIN 50,018, i.e. they were kept in a 330 litre cliamber having a humidity of 95-100% and being charged by sulfur dioxide at a rate of 0.2 25 litre/day, the procedure lasted for 30 days at 40°C. From the test results it has been experienced that the surfaces clean to metal remained stainless in all cases after the corrosion loading tests. Corrosion on the stained surfacesdid not intensify, however, it has been partly or entirely reversed. In the majority of instances, i.e. in the cases of lutes containing pigment compositions of Examples 1,2,3,4,5 and 7 a surface clean to metal has developed under the coating layer. The foregoing experiments give evidence of the condition that the coating materials made by the pigment composition according to the invention possess a very high anti-corro¬ sive effect and are capable of protecting the coated sur¬ faces against extremely severe corrosive exposures .

Claims: C l a i m s 1. An active anti-corrosive pigment composition comprisi a/ alumina hydrate /Al/0H/ 3 / b/ an amount of 10-100 parts by weight of at least o of the atoxic oxides, hydroxides, oxide hydroxides, car¬ bonates or phosphates of amphoteric elements or metals of variable valency possessing less valency than the maximum - in case of aluminium the appropriate oxide or oxide hydroxide - related to 100 parts by weight of- alu¬ mina hydrate, c/ an amount of 0-40 parts by weight of calcium and/ magnesium carbonate related to 100 parts by weight of al mina hydrate, and having grain size less than 20 ,um. 2. A pigment composition according to Claim 1, comprisin an alumina hydrate produced by the Bayer process, as cor.- ponent a/ . 3. A pigment composition according to Claims 1 or 2, comprising an alumina hydrate as component a/ that con¬ tains up to 60 weight % of carbonized alumina hydrate. 4. A pigment composition according to any of Claims 1-3, comprising at least one compound derived from metals capable of forming stable- oxides, hydroxides and oxide hydroxides, as component b/. 5. A pigment composition according to Claim 4, comprising at least one compound of aluminium iron and/or manganese as component b/. 6. A pigment ' composition according to Claim 1, comprising a natural mineral subastance, as component b/. 7. A pigment composition according, to Claim 1, comprisin a single compound in an amount of 10-50 parts by weight related to 100 parts by weight of alumina hydrate, as component b/. 8. A pigment composition according to Claim 1, •comprising at least two compounds in an amount of 20-90 parts by weight related to' 100 parts by weight of alumina hydrate, as component b/. 9. A pigment composition according to Claim 1, comprising limestone, dolomite, precipitated chalk or chalkstone or * the mixture of the same as component c/. 10. A pigment composition according to any of Claims 1-9, characterized in that its grain size is less than 10 ,um advantageously less than 5 ,um. 11. Process for producing a pigment composition accordin to any of Claims 1-10, characterized in that preground products having a grain size of substantially 160-200 ,u are made of components b/ and c/, respectively the pre- grodund products and alumina hydrate are individually dried to contain a moisture amount less than 1 weight, then the products are admi-xed at the ratios required, th lot is homogenized and ground to a grain size less than 20 ,um, advantageously less than 10 ,um but preferably less than 5 ,um. 12. Process according to Claim 11, characterized in that an anti-corrosive inhibitor is sprayed into the component during grinding. 13. Process according to Claim 12, characterized in that a 2-10 weight % aqueous solution of an alkyl pyridinium halogenide is used as anti-corrosive inhibitor.

Inventors: CSILLAG ZSOLT, KALMAN TIBOR, KIRALY LASZLO, KONIORCZYK BELA, LEGAT TIBOR, PATYI LAJOS, SZENTGYOERGYI GEZA, ZSEMBERY LASZLO, CSILLAG, ZSOLT, KALMAN, TIBOR, KIRALY, LASZLO, KONIORCZYK, BELA, LEGAT, TIBOR, PATYI, LAJOS, SZENTGYOERGYI, GEZA, ZSEMBERY, LASZLO
Applicants: CHEM EPITOEANYAGIPARI, MAGYAR ALUMINIUM, KEMIKAL EPITOEANYAGIPARI VALLALAT, MAGYAR ALUMINIUMIPARI TROESZT
Application year: 1986
Main classification: C09C1
IPC codes: C08K3, C09C1, C09C3, C09D5, C09D7