Classifications

• • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/08—Anti-corrosive paints
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/34—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing cold phosphate binders
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D1/00—Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
  • C09D1/06—Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances cement
• • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
  • C23C22/08—Orthophosphates
  • C23C22/22—Orthophosphates containing alkaline earth metal cations
• • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/68—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous solutions with pH between 6 and 8
• • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/78—Pretreatment of the material to be coated
• • 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
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/00482—Coating or impregnation materials
  • C04B2111/00525—Coating or impregnation materials for metallic surfaces
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/32—Phosphorus-containing compounds

Definitions

• This disclosure relates to coatings comprising acidic phosphate and alkaline metal oxide/hydroxide components that inhibit corrosion of metals, and specifically, the manufacture and method of coating on metal.
• well polished steel is immersed in phosphate bath of pH between 4 - 4.5 containing 2 -3 g/L phosphoric acid, 2 - 3 g/L of ammonium or zinc dihydrogen phosphate as buffer, and a small amount ( ⁇ 0.5 g/L) of oxidizer, to produce an iron phosphate passivation layer.
• phosphate bath of pH between 4 - 4.5 containing 2 -3 g/L phosphoric acid, 2 - 3 g/L of ammonium or zinc dihydrogen phosphate as buffer, and a small amount ( ⁇ 0.5 g/L) of oxidizer, to produce an iron phosphate passivation layer.
• hydrogen gas is liberated by the reaction of elemental iron with water in the extremely acidic environment. This produces a very thin passivation layer that is porous and not abrasion resistant, and as a result, an additional coating is required to make the surface of the passivated steel inaccessible to atmospheric oxygen.
• a method for preventing or reducing corrosion of a corrodible metal surface comprises contacting the corrodible metal surface with a mixture of an acidic phosphate component and a basic component comprising at least one of a metal oxide, a basic metal hydroxide, or basic mineral.
• a metal oxide e.g., aluminum oxide
• a basic metal hydroxide e.g., calcium oxide
• basic mineral e.g., calcium carbonate
• the acidic phosphate component is phosphoric acid, alkali metal dihydrogen phosphate MH 2 PO 4 , alkali earth dihydrogen phosphate M(H 2 P0 4 ) 2 or its hydrate, transition metal trihydrogen phosphate ⁇ 3 ( ⁇ 0 4 ) 2 or its hydrate, or mixtures thereof.
• the acidic phosphate component is mono potassium phosphate or its hydrate.
• the basic component is at least one of magnesium oxide, barium oxide, zinc oxide, calcium oxide, copper oxide, iron oxide, and hydroxides thereof, or magnesium brine containing an effective amount of magnesium hydroxide.
• the basic component is at least one of magnesium oxide and magnesium hydroxide.
• the acidic phosphate component is mono potassium phosphate or its hydrate
• the basic component is magnesium brine having a pH of about 9 to about 11 , wherein the magnesium brine contains an effective amount of magnesium hydroxide.
• the mixture of acidic phosphate component and basic component forms at least one of magnesium potassium phosphate, magnesium sodium phosphate, magnesium hydrogen phosphate, copper hydrogen phosphate, zinc hydrogen phosphate, barium hydrogen phosphate, or iron hydrogen phosphate.
• the surface is steel or aluminum.
• An eighth aspect alone or in combination with any one of the previous aspects of the first embodiment, further comprises producing on the contacted corrodible surface a magnesium-glass-phosphate, glossy coating.
• the contacting is with a slurry, paste, spray, or vapor thereof, independently, of the acidic phosphate component or the at least one of the basic metal oxide or the basic metal hydroxide component.
• a corrosion-inhibiting coating composition comprises a slurry of a combination of one or more iron oxides with magnesium dihydrogen phosphate.
• the iron oxide is a mixture of magnetite (Fe 3 0 4 ) or wustite FeO, and hematite (Fe 2 0 3 ).
• the total amount of hematite used is greater than the amount of magnetite or wustite.
• a method comprising contacting a corrodible surface with coating consisting essentially of a mixture of magnetite or wustite, and hematite; with a solution of phosphoric acid or magnesium dihydrogen phosphate, wherein the corrodible surface is essentially without a primer layer; and providing a corrosion-inhibiting coating, the coating comprising iron hydrogen phosphate.
• a method of providing corrosion inhibition comprises providing a combination of at least one of the following: (i) magnesium oxide (MgO) and mono potassium phosphate (KH 2 PO 4 ); (ii) magnesium oxide (MgO) and phosphoric acid solution (H 3 PO 4 solution); (iii) magnesium oxide (MgO) and magnesium dihydrogen phosphate; (iv) ferric oxide (Fe 2 0 3 ) and phosphoric acid (H 3 PO 4 ); (v) magnesium brine containing an effective amount of magnesium hydroxide and mono potassium phosphate (KH 2 PO 4 ); (vi) magnesium brine containing an effective amount of magnesium hydroxide and phosphoric acid (H 3 PO 4 ); or (vii) magnesium brine containing an effective amount of magnesium hydroxide and magnesium dihydrogen phosphate; and contacting the surface of a corrodible metal with at least one of the combinations (i)-(vii).
• the combination is presented as a slurry, paste, spray, or vapor.
• an article comprising a corrosion-inhibiting coating formed by the combination of an acidic phosphate with a basic metal oxide or basic metal hydroxide is provided.
• the coating is at least one of magnesium potassium phosphate, magnesium sodium phosphate, magnesium hydrogen phosphate, barium hydrogen phosphate, copper hydrogen phosphate, zinc hydrogen phosphate, or iron hydrogen phosphate.
• polyphosphates are present at the interface of the article surface and the corrosion-inhibiting coating.
• magnesium chromates are present at the interface of the article surface and the corrosion-inhibiting coating.
• a steel or iron-based article having a coating comprising a berlinite phase (A1P0 4 ) detectable by x-ray diffraction is provided.
• a method comprises contacting a previously corroded surface overlaying a metal with a composition comprising a mixture of an acidic phosphate and a basic metal oxide or a basic metal hydroxide, wherein an excess of the composition and a portion of the previously corroded surface is rendered readily removable and/or dislodges from the surface.
• a first aspect of the seventh embodiment further comprises forming a thin, corrosion protection layer on the surface.
• the mixture provides at least one of magnesium potassium phosphate, magnesium sodium phosphate, magnesium hydrogen phosphate or iron hydrogen phosphate to the metal surface.
• the corrosion protection layer is capable of self regenerating the corrosion protection layer from defects formed therein.
• any of the first, second, third, fourth, fifth, sixth or seventh embodiment alone or in combination with any of their respective aspects, methods and articles of improved abrasion resistance or in combination, improved corrosion and abrasion resistance is provided.
• FIG. 1 is a depiction of the redox potential vs. pH diagram for iron showing passivation and corrosion regions and comparing conventional phosphate coating and the methods disclosed and described herein.
• FIG. 2 is an X-ray diffraction pattern diagram illustrating a corrosion protection layer of a coating composition as disclosed and described herein.
• FIG. 3 is an X-ray diffraction pattern diagram illustrating a coating composition as disclosed and described herein.
• FIG. 4 is an X-ray diffraction pattern diagram illustrating a coating composition as disclosed and described herein.
• FIG. 5 is SEM image illustrating a coating composition as disclosed and described herein.
• FIG. 6 is SEM image illustrating a coating composition as disclosed and described herein.
• FIG. 7 is SEM image illustrating a coating composition as disclosed and described herein.
• FIG. 8 is SEM image illustrating a coating composition as disclosed and described herein.
• FIG. 9 is diagram illustrating a self-regenerating coating as disclosed and described herein.
• FIG. 10 is a Raman spectrograph of a coating as disclosed and described herein.
• the uniquely-suited formulations and methods disclosed and described herein are based on acid-base inorganic phosphate compositions.
• the coatings provided herein include magnesium potassium phosphate coating, and iron hydrogen phosphate coating. These compositions are used as coatings on steel and other metals as corrosion inhibitors. When applied to a metal surface as a coating, the paste formed by any of these compositions reacts with the metal, bonding therewith and forming a thin layer/coating to the surface of the metal. The bonded layer is hard and inhibits corrosion of the metal surface.
• a range of phosphate-based formulations may be used to coat and prevent or minimize the corrosion of metal surfaces.
• FIG. 1 is a representation showing stability regions of various phases of iron as a function of pH and the redox potential Eh.
• the black bold curves separate immunity, corrosion, and passivation regions for steel, where the lower region represents the immunity region where iron remains in metal form, the left hand side of this
• region is the corrosion region where iron is dissociated into Fe (aq) ions, and the right hand side representing the passivation region where iron becomes iron trihydroxide Fe(OH)3.
• the surface is generally porous and smooth and therefore needs a coating to plug in the porosity in order to protect the passivated surface completely from atmospheric corrosion.
• This also represents the process in which an oxidant, such as potassium permanganate, is used.
• Conventional polymeric coatings can be characterized as moving the steel surface from the corrosion region to passivation region by oxidizing the steel surface to Fe(OH)3.
• the passivation layer formed from this process is fairly close to the region of corrosion for steel and thus, explains at least in part, some of the inferior characteristics of this method.
• the process disclosed and described herein is based on an inorganic phosphate coating produced by acid-base reaction of an acidic phosphate and a metal oxide or metal hydroxide, or oxide mineral. Since the instant process is essentially based on an acid- base reaction, the end reaction product is near neutral, and the pH of coatings prepared therefrom are believed to be between 8 and 9, which is further positioned in the passivation region as shown in FIG. 1. In certain aspects, there is present an excess of alkaline precursor (e.g., magnesium hydroxide) distribution in the coating that has not reacted, which is believed beneficial in raising the pH of the coating beyond 7 to further position the coating in the passivation region as represented in FIG. 1.
• alkaline precursor e.g., magnesium hydroxide
• the instant coatings can protect against intrusion of acidic solutions, at least in part due to the excess Mg(OH) 2 present, which can function as a buffer to protect steel from corrosion.
• the instant coatings are superior to current commercial coatings containing zinc hydroxides with regard to buffering capacity, because zinc hydroxide is not stable below pH of 5.
• zinc oxide coatings can place steel substrate in the corrosion region in acidic environments.
• magnesium-based coatings as disclosed herein, will provide better protection than zinc-based coatings . Protection of steel in the reduction environment using the instant coatings is beneficial for applications requiring high temperatures, such as waste to energy incinerators, turbines, in any hydro carbon combustion environment, and in some chemical processes.
• the instant coatings disclosed herein can comprise, in part, the formation of poly phosphates, and in particular, poly phosphates formed by phosphites at the interfacial regions of the substrate surface in the instant coating.
• Polyphosphate can provide abrasion resistance and impermeablity to water and humidity, thus improving abrasion resistance as well as improving corrosion resistance to the substrate surface.
• an acid-phosphate composition one acidic with a pH between about 3 to about 4.5, and the other, an alkaline component with a pH between about 10 and about 11.
• these two components are contacted with the substrate surface, where they combine form a coating.
• mono potassium phosphate (KH 2 P0 4 ) and a magnesium hydroxide (Mg(OH) 2 , or its brine) composition with or without fillers such as wollastonite (CaSi0 3 ) or fly ash can be combined and contacted with a corrodible metal surface (e.g., steel). Once the compositions contact the surface, a coating forms that bonds instantly to the substrate.
• Line 2 in FIG. 1 shows at least in part, a typical result of the process disclosed and described herein.
• a first step of the instant process when the mixture of the acid and base is sprayed on the substrate, the acid solution lowers the pH of the substrate.
• reaction products such as magnetite, or iron hydroxides, react with the phosphate and form iron phosphate.
• the acid base chemistry of the instant process increases the pH to approximately 8, and in turn, drives the steel substrate pH beyond the corrosion region to the passivation region.
• the instant process also produces a phosphate-based abrasion resistant coating, thus resistant to both corrosion and abrasion. Therefore, the instant method eliminates the need for baths of acid solution, sludge to be disposed, the regimental time frame for dipping and drying, and after-coating of the steel.
• A may also be a reduced oxide phase when higher-valent oxides are used.
• A can be the metal of lower oxidation state. It can also be a cation of oxides of four-valent metal oxide
• nH 2 0 in the formula above is simply the bound water, where n can be any number, normally ranging from 0 to 25.
• hydro phosphates of trivalent metals such as aluminum, iron and manganese represented by the formula AH 3 (P0 4 ) 2 .nH 2 0, where A is a transition metal that includes aluminum, iron, manganese, yttrium, scandium, and all lanthanides such as lanthanum, cerium, etc.
• phosphoric acid may be added and the pH may be adjusted to bring down the pH.
• a preferred pH selected is between 3 and 4, and the most preferred pH is between 3 and 3.5.
• elevating the pH of phosphoric acid or that of an acid-phosphate such as magnesium dihydrogen phosphate (Mg(H 2 P0 4 ) 2 ) or aluminum trihydrogen phosphate (A1H 3 (P0 4 ) 2 ) by neutralizing partially using an alkaline oxide, hydroxide, or a mineral, or by acidifying a dihydrogen phosphate such as mono potassium phosphate (KH 2 PO 4 ) that has a pH > 3.5 by adding a small but appropriate amount of phosphoric acid or a low pH acid phosphate such as Mg(H 2 P0 4 ) 2 or aluminum trihydrogen phosphate A1H 3 (P0 4 ) 2 . Examples described later in this document provide the art of adjusting this pH.
• the acid-phosphate used in the precursor is only partially soluble.
• the precursor is wet-milled so that the average particle size passes through 230 mesh sieve (less than 70 micron).
• the acidic component consists of magnesium oxychloride, and magnesium oxysulfates appropriately acidified with either hydrochloric acid or sulfuric acid to reduce the pH.
• Water may be added to the precursor component to reduce the viscosity thereof, or other types of viscosity reducing agents may be used. Commercial additives that prevent algae growth may also added to this precursor so that no algae growth occurs during storage of this precursor.
• Basic precursor generally consists of a sparsely soluble oxide, or preferably a hydroxide with a particle size less than 230 micron.
• a range of phosphate compositions may be used as the corrosion inhibitor coatings commensurate with the spirit and scope of that disclosed and described herein, the following four exemplary, non-limiting examples are provided:
• Magnesium potassium phosphate coating formed by the combination and/or reaction of magnesium oxide (MgO) and mono potassium phosphate (KH2P04), which in the presence of water combine to produce magnesium potassium phosphate cement, comprising MgKP04.6H20.
• MKP magnesium oxide
• MKP04 mono potassium phosphate
• Magnesium hydrogen phosphate (newberyite) coating formed by the combination and/or reaction of magnesium oxide (MgO) and phosphoric acid solution (H3P04 solution), which when mixed well and allowed to dry, combine to produce a magnesium hydrogen phosphate coating comprisingMgHP04.3H20.
• Magnesium hydrogen phosphate (newberyite) coating formed by the combination and/or reaction of Magnesium dihydrogen phosphate compositions usually have an aqueous pH between about 2.5 and about 5.0. MHP solutions with a pH of about 3 or slightly higher are generally believed more effective in the production of corrosion resistant products and, for at least that reason, tend to be preferred. Magnesium hydrogen phosphate is also referred to hereafter as "MHP".
• Iron hydrogen phosphate coating formed by the combination and/or reaction of wustite (FeO) or magnetite (Fe304) and phosphoric acid (H3P04), which when mixed well and allowed to dry combine to produce iron hydrogen phosphate coatings comprising FeHP04.
• Iron hydrogen phosphate is also referred to hereafter as “mono- iron phosphate", or "MIP”.
• magnesium potassium phosphate compositions, magnesium hydrogen phosphate compositions and iron hydrogen phosphate compositions exhibit a paste-like consistency.
• a surface e.g., steel
• the thin layer coating is very hard, resistant to abrasion, and inhibits corrosion of the surface.
• this thin layer acts like a primer, protecting the metallic surface from corrosion. Similar results are observed when these compositions are applied to the surface of other metals besides steel, such as aluminum.
• a primer is formed by the reaction of chromium from the steel surface and the oxide from the coating. Therefore, in one aspect, an oxide-rich coating, whereby some of the oxide is used in forming a primer and the rest is used in the reaction that forms a acid-base phosphate coating, protective (corrosion/abrasion-resistant) coating, is provided .
• a "primer and paint” can be accomplished in just one step (or one coat), where the primer and/or paint provides corrosion resistance for corrodible surfaces.
• the instant corrosion resistant coatings can be formulated to provide aesthetic properties, such as proper shine and texture on them. This effect may be achieved, for example, by adding crushed glass or any other high solubility glass to the instant acidic phosphate/alkaline metal oxide/hydroxide formulations.
• the resulting coating comprising crushed glass prepared by the processes disclosed herein is a very dense glassy surface. Additional suitable ceramic pigments may be further added to produce colored paints.
• Soluble glass in combination with the instant compositions above can also be used in formulations for coating of solid objects, to provide very dense, glassy solid coatings having corrosion resistance.
• Example 1 MHP-based Corrosion Protection Layer
• MHP Mg(H 2 P0 4 ) 2 2H 2 0
• the amount of water used in diluting the MHP-based material can vary, depending on the amount of water contained in the material to begin with (most MHP-based materials are difficult to dry when made and, therefore, usually contain some water.)
• dilution water should be added in an amount equivalent to about 20% by weight of MHP.
• the amounts of calcium silicate and aluminum oxide added as fillers to form a thin paste may also vary. In this example, 80 grams of calcium silicate and 60 grams of aluminum oxide were added for each 100 grams of MHP.
• FIG. 2 shows the X-ray diffraction pattern of this layer on steel, where distinct peaks of magnesium chromate are observed. As discussed above, it is believed that chromium from the steel reacts with magnesium oxide in the acid environment, providing a chemically very stable magnesium chromate product, which may contribute in part to the corrosion protection afforded by the coating.
• Example 2 Corrosion Protection Layer On Rusted Steel Surface
• an MKP -based formulation prepared as a paste comprising calcium silicate was applied on a rusted surface of steel.
• the MKP paste was formed by mixing one part of dead-burnt magnesium oxide (calcined at temperatures higher than about 1,300 °C), three parts of mono potassium phosphate and six parts of calcium silicate. To this powder mixture was added two parts of water to provide a paste. As mixing was continued, the paste cooled by a couple of degrees initially, indicating dissolution of mono potassium phosphate; but, as magnesium oxide began to react, the temperature began to rise. Mixing was continued until the temperature of the paste rose to about 85°F and, at this point, the paste was applied to the rusted surface of the steel.
• FIG. 3 shows various phosphate phases contained in this corrosion preventing layer. Noteworthy is that the steel surface did not corrode when kept in humid and hot atmosphere, indicating the acid-base phosphate formation provided a corrosion protection layer.
• Example 3 Iron Oxide Based Corrosion Protection Paint
• Example 4 Magnesium-glass phosphate composite formulation
• FIG 4 shows a section of the X-ray diffraction pattern clearly indicating that MgKP0 4 .6H 2 0 was formed, as well as several phases of hydrated silico-phosphate minerals. These include, H 2 Si 2 0 5 , H 2 S1O 3 O 7 , and unhydrated phases SiP 2 0 7 and Si0 2 .
• This composition is unique and can be used in one or more applications, for example, as an electrical insulator, a glossy paint, and/or a corrosion resistant paint.
• Example 5 Use of MHP As Corrosion Protective Layer
• MHP magnesium dihydrogen phosphate material
• Example 6 Methods of Forming Berlinite Coatings on Steel
• the pH of the paste can adjusted to between 3-4 to reduce or prevent formation of a scale layer of ferric oxides that may reduce the coating effectiveness.
• This paste was brushed on mild steel substrate pre-heated at 175 °C. Initially, some water fraction from the paste evaporated, but the subsequent coating bonded well to the steel. The entire assembly was maintained at 175 °C for about three hours. Once all degassing and evaporation had occurred, a second coat was applied and cured for about three hours at 175 °C. The resulting thick coating formed on the steel surface was hard, dense and extremely well bonded to the steel. X-ray diffraction studies of the formed coating indicated that the coating was essentially berlinite.
• the methods disclosed and described herein provides for a relatively simple means for preparing berlinite-precursor formulations and thereafter forming berlinite coatings useful for providing high-temperature protection or improving high temperature service of articles, such as steel and other iron-based building materials.
• Aluminum hydrophosphate was produced by dissolving aluminum hydroxide in 50% dilute phosphoric acid solution. Aluminum oxide in three times excess to that of the acid solution was then added to this stream and resulting paste was sprayed on standard steel panels. The dried panel was heated slowly to get rid of all water. It was then heated to 350 F. The dried coating bonded to steel but with lot of cracks. A second coat of the same was sprayed on the first coat, again dried and then heated again. The second coat bonded to the first coat, did not crack and the resulting coat was dense and smooth. The measured abrasion resistance: 1000 cycles/mil, > 8 times that of organic commercial coatings.
• Example 9 To prove the concept of the material sustaining very high temperature, calcined magnesium oxide and mono potassium phosphate were mixed as powders in equimolar ratio and were then mixed in water. The resulting paste set into hard ceramic. It was then heated to 3000 F for three hours. It shrunk 10 vol.%, but was a dense and hard ceramic. The measured density of this sample was 2.1 g/cm
• Tables 1 and 2 summarizes the analysis of FIGs 5 and 6 respectively, of positions remote and near from the coating-surface interface, respectively, e.g., elements detected, the wt% and atom % of the coating.
• the composition of this coating immediate to the substrate is observed to be richer in iron indicating it is a compound of iron and phosphorous.
• Potassium and calcium contents are observed to be lower in this layer, and magnesium and silicon layers are higher, which indicates the presence of magnesium silicate.
• One or both of the acid phosphate or basic components can be vapor deposited, for example from an aqueous solution.
• This vapor deposition method can provide coats at nano- or micrometer thicknesses.
• each component is heated separately to produce vapors.
• These vapors are then funneled into a common tube, so that the vapors are mixed and then are deposited on the substrate. This coating should form that after reaction on the substrate will mimic the prime coat.
• Advantage of vapor deposition methods are, a) thin passivating coats, b) minimum use of material, c) uniformity of coats, d) assembly line coating, e) automation of the process.
• FIG. 9 a schematic of self-regeneration of the corrosion inhibiting layer is shown on a surface (10) of iron.
• any defects (20) developed in the iron phosphate primer coating (40) can be healed by tocoat (30) of MgKP0 4 .6H 2 0 as phosphate ions and iron migrate to the defect (as indicated by step 200) and reform (50) the iron phosphate primer coating (40) (as indicated by step 300).
• this MgKP0 4 .6H 2 0 top coat essentially heals defects in the thin prime coat on the substrate after a predetermined time.

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• 2010
  • 2010-08-20 EP EP10836345.8A patent/EP2510134B1/en active Active
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