Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
  • B24C11/00—Selection of abrasive materials or additives for abrasive blasts
  • B24C11/005—Selection of abrasive materials or additives for abrasive blasts of additives, e.g. anti-corrosive or disinfecting agents in solid, liquid or gaseous form
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/02—Coating starting from inorganic powder by application of pressure only
  • C23C24/04—Impact or kinetic deposition of particles

Definitions

• the present invention relates to a process for improving the corrosion resistance of metal surfaces simultaneously with cleaning the metal surfaces, and more particularly the invention relates to the depositing of a protective metal on a surface part of another metal which is to be made more corrosion-resistant.
• the protective metal may be distributed on the abrasive particles in various manners, so that the highest efficiency for a given end use may be reached. (On top of the binder or embedded in the binder or in multiple or sandwich layers.)
• Dust amount and dust danger in the blasting process are decreased due to better adhesion of protective metal to abrasive particles.
• the amount of protective metal deposited on the abrasive particles can be regulated by varying the amount and/or type of binder.
• the invention relates to a process for blasting metal surfaces and simultaneously applying a corrosion-protective metal thereto by blasting abrasive particles carrying the protective metal onto said surfaces, which process is characterized by using abrasive particles to which the protective metal is bound by means of a binder.
• blasting is to be interpreted in its broadest sense comprising as well abrasion by means of abrasive particles flung against the surface parts in question by means of, e.g., rotating wheels or other mechanical means as abrasion by means of abrasive particles conveyed against the surface parts in question by a current of air or another gas and/or a liquid current.
• the process according to the invention may be performed using any type of blast cleaning equipment or apparatus.
• An interesting aspect of the process of the invention is wet blasting," e.g., wet sandblasting," wherein a water spray is used for removing dust formed by disintegration of the abrasive particles. Without the corrosion protection obtained by the present invention, wet blasting is often of little interest because the humidity increases the corrosion of the surfaces being blasted.
• the abrasive particles may be of normally used types or of specially formulated types. Examples of abrasive particles are the following:
• Metallic abrasives e.g., cut-wire, cast iron shot and grit, steel shot and grit, etc.
• oxides synthetic or natural like alumina, zirconia, etc.
• silicas sand, glass shot and grit, flint, etc.
• conglomerates or slags e.g., mineral slag, copper slag, etc.
• the surfaces of the abrasive particles or bodies may be of any shape or type; they may for example be smooth, edged, porous, or grooved.
• a suitable abrasive material for a given purpose will depend upon considerations concerning, e.g., availability, cost, colour, and, especially, abrading properties, which are depending upon e.g. hardness (toughness), size, shape, chemical composition, specific gravity, etc.
• metal surfaces which may be treated by the process according to the invention are primarily surface parts of structural elements of iron or steel, such as steel plates, welding seams, cast iron, and the like. It is envisaged, however, that the advantages of the invention may also be obtained in treating surface parts on articles of other metals which are subject to corrosion.
• the protective metal is one which provides a distance-effect in corrosion protection, e.g., zinc, aluminum, cadmium, magnesium, or lead, but alsoother metals and alloys may be used, e.g., tin, and manganese.
• suitable alloys may be mentioned tin/zinc, copper/zinc, and Woods alloy (25 parts of lead, 12.5 parts of cadmium, 50 parts of bismuth, and 12.5 parts of tin), in the following called Woodmetal.
• zinc is the preferred protective metal used according to the invention, and the following description will, therefore, mainly be concerned with the use of zinc.
• the amount of binder present in the abrasive particles used according to the invention is usually of the order of 1 percent by weight or less, calculated on the total weight of the abrasive composition. As little as 0.05 percent by weight may in some cases be used, and the maximum amount of binder will usually be just below the one at which the abrasive particles start being bound together.
• the range of usable types of binders is surprisingly broad, and the only condition for a binder to be used according to the invention seems to be that it is a material which is able to adhere to the abrasive particles and to the protective metal particles so as to bind the protective metal particles to the abrasive particles to a greater extent than if no binder were present.
• the binder should, furthermore, be substantially non-evaporating and should preferably be of a type which will not vitiate the beneficial effect of the protective metal.
• Other desirable properties of the binders used according to the present invention are good wetting and penetrating properties under the conditions used when applying the binder to the abrasive particles, good stability, also at elevated temperatures, low toxicity, even when exposed at higher temperature's, and adequate resistance to adverse influence by water and alkali. Furthermore, it has been found preferable that the binder is not too brittle.
• binders which are oxidatively drying such as alkyd resins, varnishes, drying oils, standoil, phenolic resins, styrenated alkyd resins and epoxy ester resins
• binders which are physically drying such as chlorinated rubber with or without plasticizer, phenoxy resins, cyclized rubber, epoxy resins, polyamide resins, acrylic resins, isobutylene resins, and amine-epoxy adduct resins
• binders which are reactively drying such as polyamidecured epoxy resins, amine-cured epoxy resins, sodium silicate, and alkyl silicates such as ethyl silicate, and also non-drying binders such as plasticizers (e.g., dialkylphthalates), tar, asphalt, surface active compounds like silicone oil and lecithin, wax, and vegetable and mineral oils, as well raw and refined.
• binders such as, e.g., dialkylphthalates seem to be more suitable than harder binders such as, e.g., alkyl silicates, and chemically, the epoxy group is present in many binders found suitable.
• binders which at present seems especially interesting may be mentioned dibutylphthalate.
• the use of the binder opens new possibilities which did not exist with the known processes.
• the amount of protective metal may be increased almost to any desired value, and also special distributions of the protective metal of the abrasiveparticles may be obtained.
• the amount of protective metal it has been found that the anti-corrosion effect increases with the amount of protective metal applied.
• this proportionality continues up to 30 40 percent by weight on sand as abrasive.
• the process according to the invention may result in corrosion protection of treated steel surfaces for up to several months under normal outdoor exposure conditions. It is, however, especially remarkable that also low amounts of zinc will give surprisingly good corrosion protection in the process according to the invention.
• An interesting technique made possible through the present invention is to bind a mixture of particles of the protective metal and a particulate paintabilityimproving material to the abrasive particles.
• the paintability-improving material is a material which will improve the adhesion between the treated surfaces and the primer or other paint coatings applied after the blasting treatment.
• a paintabilityimproving material may be mentioned zinc oxide.
• blends of 50 percent of zinc and 50 percent of zinc oxide will, in addition to the improved paintability, still give good corrosion protection.
• it is believed to be necessary that the zinc particles are present in the primer in such amount that they are in contact with each other after the application.
• Such contact between the zinc particles is, as shown by the good protection obtained when using the mixture of zinc and zinc oxide, not necessary in the zinc deposits made according to the present invention.
• the paintability improvement obtained through the use of the zinc oxide together with the zinc is a highly interesting advantage, but it should be noted, however, that surfaces treated by the process according to the invention are, also without the use of a paintability-improving material, easy to paint because they possess the roughness imparted by the blasting process. In contrast, zinc primers painted on a blasted steel surface will result in a smoothening of the surface.
• the invention also relates to a composition for use in blasting metal surfaces and comprising abrasive parti cles carrying corrosion-protective metal on their outer surfaces, which composition is characterized in that said protective metal is bound to the abrasive particles by means of a binder.
• composition according to the invention may be prepared in various manners, and the use of the adhesive binder opens several possibilities of obtaining special advantageous effects.
• One method for preparing the composition according to the invention is to apply, to abrasive particles, a mixture of protective metal and binder, usually a dispersion of finely divided metal in liquid state of binder.
• the binder may be liquid perse, or the binder may be brought into the liquid state either by heating (for thermoplastic materials) or by being dissolved in a suitable solvent.
• a suitable solvent for thermoplastic materials
• the resulting mixture of abrasive particles and dispersion is suitably rotated in a rotating drum or otherwise agitated, e.g., by shaking or vibrating, until the mixture is evenly distributed on the particles.
• the solvent may be evaporated during the agitation or rotation of the mixture, for example by passing hot air through the mixture.
• Another method of preparing a composition according to the invention is to apply the protective metal to the abrasive particles subsequently to the application of the binder.
• the binder is first evenly distributed on the abrasive particles, and thereafter the protective metal is added, for example as a finely divided powder, which will then be concentrated at the outer surface of the binder coating.
• This concentration of the protective metal at the outer surface of the binder coating may be especially pronounced if the binder is allowed to obtain a higher viscosity before the metal is added.
• the binder is a thermoplastic material, it may be applied at an elevated temperature and may then be allowed to cool to for example room temperature before the metal particles are added. This will result in a material having a significant concentration of metal particles at the outer surface of the binder.
• compositions of the above-mentioned type in which the protective metal is concentrated at the outer surface of the binder are highly interesting because of the especially good corrosion protection obtained with such compositions.
• abrasive materials to be used only once such as sand and copperslag, it is preferred that the protective metal is concentrated at the outer surface of the binder.
• abrasive and protective metal Another interesting possibility with certain combinations of abrasive and protective metal is to concentrate the protective metal on one side of each abrasive particle. If, for example, sand is used as abrasive, and zinc is used as protective metal, the single particles carrying the zinc concentrated on one side thereof will, because of the difference between the higher specific weight of the zinc and the lower specific weight of the sand, have a tendency to be orientated with the zinc-rich side towards the surface to be treated immediately before the collision with said surface. In this manner, the probability that a high proportion of the zinc present of the particles will be forced onto and into the surface being treated is high, and, accordingly, less zinc may be needed to obtain a desired corrosion protection, compared to the amount necessary with particles on which the zinc is evenly distributed over the surface.
• compositions according to the invention having the protective metal concentrated on one side of each abrasive particle may be prepared in various suitable manners.
• One method is to spray a mixture of protective metal and binder on a bed of abrasive particles and moving the bed in relation to the spray of mixture.
• bed may, for example, be a thin layer of particles placed on a moving belt, or the bed may be a curtainlike bed of falling abrasive particles on which the mixture of protective metal and binder is sprayed from one direction.
• the blasting process according to the invention may be carried out using any type of blast cleaning equipment and apparatus, and the abrasives used may be of a type used only once (not recycled for renewed blasting against the surface being treated), or of a type used several times (recycled for renewed blasting against the surface being treated).
• the blasting process may be performed either with abrasive particles which all or substantially all carry the protective material bound to the particles by means of the binder, or with a mixture of abrasive particles provided with protective metal and binder and abrasive particles without metal and binder.
• the concentration of protective metal may become too low during blasting because of loss resulting from deposition on the surfaces being treated and disintegration of the particles.
• replenishing may be carried out by adding fresh particles having protective metal bound thereto, and most suitably the amount of particles added and the concentration of protective metal on the particles added are so chosen that the loss of protective metal is continuously compensated for so that the desired degree of protection is constantly obtained.
• Another way to compensate for loss of protective metal, especially in cases where there is little loss of the abrasive itself is to add fresh binder and fresh protective metal to the recycled abrasive and thus apply a new layer of protective metal on the abrasive particles.
• a further suitable way of maintaining the desired corrosion protection efficiency of the blasting process according to the invention when using an abrasive which is recycled is to apply the protective metal in such amounts and in such a way that the deposition of protective metal on the surfaces treated is substantially constant over the total working life of the abrasive. It is envisaged that this may be obtained by applying several layers of protective metal on the abrasive particles, and/or by using rather high amounts of binder, e.g., of
• compositions containing less binder may have a smaller initial protection efficiency, but this efficiency may be retained substantially unchanged during the total working life of the composition.
• the abrasive particles will descale or clean the metal surfaces in substantially the same manner as non-coated abrasive particles, and the protective metal carried by the abrasive particles will simultaneously come into contact with and be deposited on the cleaned surface.
• One of the disadvantages of conventional blast cleaning of steel surfaces is that the freshly cleaned steel surface is highly active and will immediately start reacting with air moisture and any other corroding components of the atmosphere in which the blasting is carried out.
• the application of a primer paint coat may stop corrosion, but some degree of corrosion, although perhaps invisible, will usually have taken place in the time interval between blasting and priming.
• the process according to the present invention can be said to prevent corrosion because there is no time interval between the blasting and deposition of the protective metal. Because of the intimate contact between the protecting metal and the treated surface a less amount of protecting metal is needed for sufficient protection which leads to a less decrease of speed in cutting and welding operations, a higher quality of welding seams and less development of toxic fumes during burning, cutting and welding than when using ordinary preconstruction primers.
• the process of the invention will prove an attractive and efficient process for cleaning old steelwork, especially steelwork which has been exposed to marine atmosphere and which shows deep rust pockets generally containing deliquescent iron salts like chloride, sulphate, etc., as it is envisaged that the treatment according to the invention will neutralize the harmfuls effect of these salts.
• the beneficial effect of the protective metal may in certain cases be enhanced by additionally applying, on the abrasive particles or bodies, catalysts or other additives which cooperate with the protective metal.
• a tracing means for example a tracing compound
• a tracing compound may, for example, be a pigment having a high colour strength, which may suitably be bound to the abrasive particles by means of the binder used.
• the blasting was carried out using one of the following blasting equipments:
• Educt-O-Matic a small suction-pressure unit. Recirculation. Made by Clementine USA.
• MIBK Abbreviation of methylisobutylketone.
• Oxitol (Shell): Ethyleneglycolmonoethylether.
• Zincoli 620 (Morris Ashby, England): Superfine grade of zinc dust.
• Zinc flake 83% (Eckart Maschinene, Federal Republic of Germany): Stepa Zinc 8, paste containing 83% af zinc.
• Woodmetal AS 31 (Eckart Maschinene, Federal Republic of Germany).
• Epicote 828 (Shell): Epoxy resin, epoxide equivalent 175 210.
• Epicote 834 (Shell): Epoxy resin, epoxide equivalent 225 290.
• Epicote 1001 (Shell): Epoxy resin, epoxide equivalent Epicote 1001-501: 50 grams of Epicote 1001 dissolved in 25 grams of xylene and 25 grams of MIBK.
• Zinc oxide (Ranaes Bruk. Sweden).
• Epoxyester 50% (Celanese, USA): Epi-Tex 183. Made by esterification of the epoxide groups and hydroxyl groups of epoxy resin with fatty acids of drying oils. Contains 35 40% fatty acid and is dissolved in 50% by weight of xylene.
• Acryloid All (Rohm & Haas, USA): Polymer of acrylic acid and methacrylic acid. Viscosity 1200 1900 cPs at C, 35% solids in methylethylketone.
• Chlorinated rubber (1C1, England): Alloprene R20. Chlorinated natural rubber with a chlorine content of about 76%. Viscosity 2O cPs at 25 C, 20% solids in toluene.
• Chlorinated paraffin (Hoechst, Federal Republic of Germany): Hordaflex LC. Contains about 50% chlorine. Viscosity about 20,000 cPs at 20 C.
• Antracene oil (Superfos, Denmark): High boiling grade.
• Soya lecithin (Dansk Sojakagefabrik, Denmark): Lecithin DS.
• Copperslag (Melchemie, the Netherlands): Semo- Arum. 0.5 3.5 mm.
• Cut-wire (Harrison Ltd., England): Supral, 0.6
• Ethylsilicate (Dynamit Nobel AG, Fed.Rep. of Germany): Dynasil 40. Composed of mixed ethylpolysilicates with an average of five silicon atoms per molecule. Contains about 40% SiO EXAMPLE 1.
• Metal Procedure Sand (0.5 1.5 mm) is mixed with Epicote 828 (preheated to 60 C) and rotated until all particles are wetted completely.
• the metal powder is added, and the mixture is rotated until it is dustfree, i.e., 2 minutes.
• the zinc flake, magnesium and Woodmetal are mixed with Epicote-sol and solvents before added to the sand and rotated.
• the treated sand is blasted with .Educt-O-Matic for 3 seconds on shopprimed steel.
• the shopprimer is based on polyvinylbutyral-phenolic resin and is only applied in 5 microns, just enough to indicate the blasted area.
• the blasted panels are exposed to salt spray (ASTM B 1 17-4), and hours to reach rust degree 8 and 6 are measured.
• the other binders (Epicote 828 dibutylphthalate, Antracene oil, soya lecithin) are added directly to the sand, and after distribution on the particles the zinc powder is added and rotated until dustfree, i.e., 2 5 minutes.
• the binder may be a liquid or'easy to liquefy (e.g., by heating as done with Epicote 828) so it can be added and easily distributed on the sand particles under rotation. Then the zinc powder is added and rotated until it is dustfree, i.e. 2 5 minutes.
• This method can be carried out with solvents and without solvents, and there is no limitation in number and type of layers.
• Amounts in grams 2 A process according to claim I, wherein the protective metal is zinc. sand I 3.
• Abrasives Used Once partially coated with said binder, and on which the pro- Testings are carried out using Educt o Matic which tective metal is concentrated at the outer surface of has shown results equivalent to results from open-blast Sald binder coatmgcleaning when using a blasting time of 3 seconds.
• Amounts in grams 8 A process according to claim 1, wherein blasting sand 1000 is effected with a mixture of abrasive particles d Copperslag 1000 40 rasive particles having a protective m t l b d Corundum 1000 thereto with a binder.
• a composition according tofllaim 9 wheliein the hour, h rotation Stopped ft 2 hours abrasive particles are at least partially coated with said The i fl f blasting time was measured by binder, and the zinc is concentrated at the outer surcleaning corroded panels after the abrasive has been in face of the bmdel' coatmguse 5,5 d 1 hour, respectively 7 13.
• a process for preparing a composition for use in blasting a metal surface comprising providing a bed of abrasive particles, spraying a mixture of a protective metal and a binder onto one side of said bed, and moving said bed in relation to the spray of said mixture.
• a binder layer is applied 64: "in number” should read in the "defined more closely below” Column Column “and hours to reach rust degree 8 and 6 are to "liquefy” should read easily liquefiablezinc, a binder layer is first applied on d '7 M115 I UNHE'E STA'EES PATENT OFFICE CERTEFIQATE @F CORRECTION PacmuzNob 3,765,923 Datai October 16, 1973 lnvmmorug Bent Bender-hristensen It is certified that'error appears.in the above-idfitified patent and that said Letters Patent axe hereby corrected as shown below:

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Paints Or Removers (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

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Citations (5)

• 1970
  • 1970-12-14 GB GB5932870A patent/GB1377484A/en not_active Expired
• 1971
  • 1971-12-07 SE SE15699/71A patent/SE363127B/xx unknown
  • 1971-12-09 ZA ZA718255A patent/ZA718255B/xx unknown
  • 1971-12-13 BR BR8245/71A patent/BR7108245D0/pt unknown
  • 1971-12-13 CA CA129,932A patent/CA945015A/en not_active Expired
  • 1971-12-13 DE DE19712161848 patent/DE2161848A1/de active Pending
  • 1971-12-13 ES ES397905A patent/ES397905A1/es not_active Expired
  • 1971-12-13 DK DK608871AA patent/DK130543B/da unknown
  • 1971-12-13 US US00207556A patent/US3765923A/en not_active Expired - Lifetime
  • 1971-12-13 IT IT32303/71A patent/IT943881B/it active
  • 1971-12-13 NL NL7117041A patent/NL7117041A/xx unknown
  • 1971-12-13 NO NO04583/71*[A patent/NO130194B/no unknown
  • 1971-12-14 BE BE776662A patent/BE776662A/xx unknown
  • 1971-12-14 FR FR7146245A patent/FR2118826A5/fr not_active Expired
  • 1971-12-14 RO RO7100069053A patent/RO62740A/ro unknown
  • 1971-12-20 AU AU37081/71A patent/AU3708171A/en not_active Expired

Patent Citations (5)

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