CA1073610A - Low-temperature curing coating composition - Google Patents
Low-temperature curing coating compositionInfo
- Publication number
- CA1073610A CA1073610A CA219,799A CA219799A CA1073610A CA 1073610 A CA1073610 A CA 1073610A CA 219799 A CA219799 A CA 219799A CA 1073610 A CA1073610 A CA 1073610A
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- CA
- Canada
- Prior art keywords
- coating
- composition
- dissolved
- amine
- aluminum
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
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- 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
- C23C22/73—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 characterised by the process
- C23C22/74—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 characterised by the process for obtaining burned-in conversion coatings
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- 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
- 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
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
- C04B41/81—Coating or impregnation
- C04B41/85—Coating or impregnation with inorganic materials
-
- 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
- C23C22/24—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 hexavalent chromium compounds
- C23C22/33—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 hexavalent chromium compounds containing also phosphates
-
- 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
- C23C22/40—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 molybdates, tungstates or vanadates
- C23C22/42—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 molybdates, tungstates or vanadates containing also phosphates
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C2217/00—Coatings on glass
- C03C2217/20—Materials for coating a single layer on glass
- C03C2217/29—Mixtures
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C2218/00—Methods for coating glass
- C03C2218/10—Deposition methods
- C03C2218/11—Deposition methods from solutions or suspensions
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Ceramic Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Structural Engineering (AREA)
- Paints Or Removers (AREA)
- Chemical Treatment Of Metals (AREA)
- Organic Insulating Materials (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A coating composition which is capable of being used effectively in a wide variety of applications where heretofore known coating compositions could not be used, or where their use was accompanied by various disadvantages is disclosed. The curing temperature at which coatings (for example, corrosion resistant coatings) are formed from an aqueous coating composition containing dissolved phosphate, dissolved dichromate or molybdate, and solid particulate material is lowered by adding an amine to the composition The coating composition of the present invention can be used to effectively coat substrates which heretofore could not be coated or could not be coated satisfactorily as a re-sult of the substrate being destroyed or degraded by the relatively high temperatures that were required to satis-factorily cure heretofore known coating compositions.
A coating composition which is capable of being used effectively in a wide variety of applications where heretofore known coating compositions could not be used, or where their use was accompanied by various disadvantages is disclosed. The curing temperature at which coatings (for example, corrosion resistant coatings) are formed from an aqueous coating composition containing dissolved phosphate, dissolved dichromate or molybdate, and solid particulate material is lowered by adding an amine to the composition The coating composition of the present invention can be used to effectively coat substrates which heretofore could not be coated or could not be coated satisfactorily as a re-sult of the substrate being destroyed or degraded by the relatively high temperatures that were required to satis-factorily cure heretofore known coating compositions.
Description
~36~0 ~OW-TEMPERATVRE CURING COATING COMPOSITION
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F~eld of`the Invention ' ... .
This invention relates to improved coatings (for example, corrosion resistant coatings) which can he formed by curi~g an aqueous coating composition at a relat.i.vely low temperature. This invention relates also to lowering the curing temperature at which aqueous coating compositions can be cured into coatings haviny desired properties thereby permitting their.use in a wi.de variety of applications where`problems hereto~ore were encountered.
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It is known to apply to metallic and other types of .
substrates coatings which protect the substrate from corrosive elements, and/or which have otller beneficial properties. Some .coating compositions which form such coa~ings ~ust be cured at relatively high temperatures, for exam~le, in e~cess of 500F.
One type of coating composition that must be cured at rela- :
tively high temperatures and that is effective in -Forming corro-sion resistant coatings on various types o~ substrates is a composition containing dissolved phosphate, dissolved dichromate or molybdate, and solid particulate material such as powdered ;~
metal, powdered metallic alloys, and refractory metal oxides.
Examples of such coating compositions are disclosed in a publi-cation entitled "Investigation of Aluminum Phosphate Coatings for ThermalInsulation of Air Frames", by Eubanks and Moore, National Aeronautics and Space Administration (M~SA Technical Note D-106, 1959) and U.S. Patent No. 3,248,251 to A.llen. Coat-ings formed from the aforementioned type composition have corro-sion resistant and/or other beneficial properties depending :-on the specific solid particulate material used in the composi-tion and the amount applied to the substrate. For example, coatings having particularly high heat resistance or refractory :
properties can be obtained by utilizing refractory metal oxides such as powdered quart~ and alumina (A12O3).
Application of the aforementioned type of coatings to articles permits the articles to be used in applications where they otherwise would not be suitable for use or it improves the performance properties of the article. Examples of such properties include corrosion resistance, hi~h heat resistance, abrasion resistance and electrical characteristics.
~rticles coated with the aforementioned type of coating can be used in various applications, including aerospace, automotive, ~.
marine and metal working applications.
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One of the steps that is required in forming the aforementioned type of coating on the substrate is curing the coating composition at a relatively high temperature a~ter it has been applied to the substrate. If the composition is not properly cured, problems are encountered. The aforemen tioned Allen patent discloses that the composition described therein should be cured at a temperature of 500F to 1000F, preferably at 600F to 800F, and that if the composition is not cured completely, soluble ingredients of the coating ~re leached out when it is exposed to water. This results in a coating having poor moisture resistance. The aforementioned NASA article discloses the curing of compositions described therein at temperatures ranging from room temperature to 800F. Various of the examples disclosed in the article show that maximum hardness of the coatings is not attained unless the curing temperature is about 600F, and further that the coatings are not moisture resistant unless cured at a tempera ture of at least ~00F for at least one half hour.
In general, if the coating composition is not cured properly, the coating formed therefrom will not have the ability to survive in marine, salt spray, or highly humid environments for desired periods of time.
There are various disadvantages in having to cure the aforementioned coating compositions at such relatively high temperatures. Some types of substrates cannot be coated satisfactorily with the aforementioned type composition because they cannot withstand the high curing temperature, or their properties, such as dimensional stability, and strength, are affected adversely. Another disadvantage is that high energy requirements are needed to provide the high curing temperatures. ~lso, relatively long periods are needed to 61~
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oool the hot coated article; this increases processing time r and uses up space which is needed to allow the articles to cool. In coating articles which have areas which should be free of coating, areas such as flanges, threaded surfaces or holes, it is necessary to mask the areas. When applying two or more layers of coatings to such articles, such areas -have to be remasked because the high curing temperatures destroy tha mask. Appreciable savings in cost and labor could be realized if the coating composition were c~pable of being cured at lower temperatures which do not destroy the mask. Some industrial concerns have refrained from using the aforementioned type of coating composition because they do not have ovens or furnaces which are capable of providing the high curing temperatures.
This invention relates to a coating composition which is capable of being cured into an improved coating at relatively low temperatures. ~-Reported Developments .
Various methods have been reported for lowering the curing temperatures of the aforementioned type of coating compositions. As will be seen from the discussion which follows, these methods have one or more shortcominys.
In U.S. Patent No. 3,248,250 to Collins, one of the applicants herein, it is disclosed that the curing tempe~
rature of the coating composition described in the aforemen- ;
tioned Allen patent can be lowered by adding to the composition an alkali metal silicate. The Collins patent discloses that such compositions can be cured at a temperature as low as 250F, but preferably at a temperature of 300F to 500F fox 3 to 60 minutes.
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In U.S. Patent No. 3,248,249, also to Collins, one of the applicants herein, it is disclosed that the curing temperature of the coating composition described in the aforementioned Allen pa-tent can be reduced by adding to the composition a solid particulate material having a grain size on the order of 0.1 micron or finer. The preferred particu-late materials are colloidal silica and colloidal alumina.
Such compositions can be cured at a temperature as low as 250F, but preferably at a temperature of 250F to 500E~
for 3 to 60 minutes.
In general, coatings formed from compositions described in the arorementioned Collins' patents, and cured at the lower temperatures described therein, tend to have better properties than coatings formed from the composition described in the aforementioned Allen patent, and cured at like temperatures~ Nevertheless, the use of lower tempera-tures to cure the compositions described in the Collins' patents results in sacrificing certain desired properties of the coatings formed from the compositions. By way of bac~ground, it is noted that for use in certain applications, industrial standards require that coatin~s of the aforemen-tioned type have excellent adhesive and corrosion resistant properties after being exposed to all of the following 5 test evaluations; (1) 5% salt spra~ for a minimum of 144 hours; (2) 100% relative humidity at 100F for a minimum of 144 hours; (3) hot water (180F) for a minimum of 2~ hours;
(4) steam vapor for a minimum o~ ~44 hours; and (5) hot saline condensates for a minimum of 24 hours. Coatings formed by curin~ the composition described in the aforementioned Collins' patents at temperatures of 300~ and below did not pass all of the above tests, with the most predominant failure being that of failure to survive the 5% salt spra~ test. (For example, after exposing the coated substrate to the 5~ salt spray test for a period of only 24 hours, the coatiny could be wiped oEf the substrate. Thus, the adhesive properties of such coatings were destroyed when exposed to the salt spray test for a very short period of tLme.) In general/ although certain improvements in corrosion resistance are realized, other important properties, such as abrasion and impact resistance, are affected adversely when the compositions are cured at the lower temperatures.
Thus, it is an object of this invention to provide a coating composition which is capable of being cured at relatively low temperatures, for example, below 400F. It is another object of this invention to provide a coating com-position which is capable of being cured at relatively low temperatures without significantly affecting adversely the desired properties of coatings formed from the composition.
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In accordance with this invention in ~n acidic aqueous coating composition comprisingJ in coating-forming proportions, materials which are a source of dissolved phosphate; dissolved dichromate or molybdate, or mixtures thereof; and solid particles of an inorganic particulate ma~erial;
wherein said composition is capable of being heat-cured at elevated temper-atures into a water insoluble coating, there is provided the improvement com-prising the addition of an amine in an amount at least sufficient to reduce the temperature at which said composition can be cured into said water insoluble coating.
The invention also provides an acidic aqueous coating composition which is capable of being heat-cured at elevated temperatures into a water insoluble coating having excellent adhesion to steel and excellent corrosion resistant propertiesl including sacrificial corrosion protection properties, and lqhich consists essentially of:
(a) phosphoric acid in an amount equivalent to at least about 1 m/l of dissolved phosphate;
~b) chromic anhydride in an amount equivalent to at least about O.l m/l of dissolved dichromate;
(c) at least about 20 g/l of aluminum metal powder, the particle si~e of which is -400 mesh (U.S. Standard Sieve Series);
~d) dissolved aluminum in an amount at least sufficient to im-part improved corrosion resistant and adhesive properties to said coating; and (e) diethanolamine in an amount at least sufficient to reduce the temperature at which said composition can be cured into said coating.
The invention further provides an acidic aqueous coating composi-tion which is capable of being heat-cured at elevated temperatures into a water insoluble coating and which consists essentially of:
~a) at least about l m/l of dissolved phosphate, (b) at least about 0.1 m/l of dissolved dichromate;
(c) at least about 20 g/l of inorganic solid particulate ma-~,,~ ,, _ 7 _ 3 61 ~
terial having a particle size of about one micron or more; and (d) an amine in an amount at least sufficient to reduce the temperature at which said composition can be cured into said coating.
Finally, the inventioD provides a method for coating substrate by applying a coating composition as defined above and thereafter curing the composition.
The addition of an amine to the coating composition is effective in permitting the composition to be cured at temperatures as low as about 180F. Furthermore, the low-temperature curing composition of this invention can be cured into coatings without significantly sacrificing desired proper-ties of the coatings.
Preferred amines for use in the composition of this invention are alkanol amines such as diethanolamine.
The low-temperature curing composition of this invention provides a number of advantages to industry. It is capable of being cured into coat-ings at relatively low temperatures without sacrificing desired properties of the coatings. The composition can be used to satisfactorily coat substrates ~0 which are not capable of being coated satisfactorily with heretofore known compositions which must be cured at high temperatures which affect properties of the substrate adversely. Since the coating composition can be cured at relatively low temperatures, energy requirements, cool-down time o~ the coated article, and space required for the cool-down time are reduced. Investment in high-temperature furnaces ~ ~ - 7a -.
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or ovens is unnecessary. And remasking of coating-free areas of the coated article is avoided because the compositions can be cured at temperatures which do not destroy the mask.
Detailed Description of the Invention .
The essential ingredients of the aqueous coating composition of this invention are water, dissol~ed phosphate, dissolved dichromate or molybdate, solid particulate material and an amine. As will be discussed more ully below, it is preferred that the composition contain dissolved metal also.
The term "dissolved phosphate" as used herein includes PO4~3, Hpo4-2 and ~2PO4-l. Any water soluble compound which is a source of dissolved phosphate can be used in prepar-ing the composition of this invention. Examples of such compounds are: ortho, meta, pyro, and hypo phosphoric acids;
anhydrous and hydrated metal phosphate salts such as the mono-basic phosphates o~ aluminum, magnesium, zinc, calcium, sodium, pokassium and lithium/ the dibasic phosphates of magnesium and calcium, and the tribasic phosphates of magnesium, zinc and lithium and mixtures thereof. The use of orthophosphoric acid is preferred. Excellent results are attained utilizing ortho-phosphoric acid and it is readily available and relatively inexpenslve.
Any water soluble compound which is a source of dissolved dichromate ~Cr2O7~2) can be used in preparing the composition of this invention. Examples o~ water soluble dichromate salts that can be used are sodium dichromate, potassium dichromate and other metal dichromates such as those of magnesium, calcium and zinc. Since the coating composition of the present invention is acidic, chromic acid and its anhydride (CrO3), and water soluble chromat~ compounds which in acidic medium are oxidized to dichromate can be used also as a source of ~he dichromate. Examples of m~tal chro-mates that can be used are those of potassium, sodium, magne-sium~ zinc and calcium. The use of chromic anhydride is preferred because its use provides excellent results, it is relativel~ low in cost and readily available, and it is easier to dissolve than certain other chromium compounds.
Dissolved molybdate may be substituted for dissolved dichromate or u~ed in combination therewith in the ComPoSitiOn of the present invention. However, it is preferred to use dichromate because compositions containing it tend to have better shelf-life properties than compositions containing molybdate, and the dichromate-containing compositions tend to passivate the substrate better than the molybdate-containing compositions. When molybdate is used in the composition, any water-soluble compound which is a source thereof can be used.
Examples of such compounds are molybdic acid, molybdic anhy dride and water-soluble metal molybdates such as those of sodium, potassium, magnesium, calcium and zinc.
The solid particulate materials for use in the com-position of the present invention are small particle inorganic materials such as refractory and non-refractory pigments, including metals, intermetallic or metal alloy compounds, cements, ceramics, and fillers. The small particle material can be colloidal in size or of larger size. Specific examples of the aforementioned types of particulate materials, which are completely insoluble or substantially insoluble in the aqueous composition, are as ~ollows: metals - aluminum, copper, silver and nickel; intermetallic or metal alloy compounds - cobalt/
aluminum alloy and aluminum/manganese alloy; cements - mixed or complex oxides, silicates, silica and zircon; ceramics -metal oxides such as chromic oxide, silica and powdered quartz, aluminum oxide, cerium oxide, zirconia and beryllia, and g ._ ~736~0 reractory carbides such as silicon carbide, molybdenum disilicide, tungsten c~rbide and boron nitride. Examples o~
other solid particulate materials that can be used are other metal nitrides, metal borides, titanates, zirconates, metal sulfides and graphite.
The particle size of the paxticulate material can vary over a wide range. Any particle size or distribution of particle sizes that permits the binding of the particulate material to the substrate can be used. In general, particle size selection will depend on the type of application for which the coated substrate is to be used. For example, the particle size of the particulate material can be within the range of about 20 to about 100 mesh when it is desired that the coatings have a rough surface for aesthetic or functional reasons. (Unless stated otherwise, the term "mesh" when used herein refers to U.S. Standard Sieve Series.) Smoother coatings can be attained by using a particle size of -200 mesh. For very smooth and denser coatings, it is preferred that the particle size of the particulate material be -400 mesh. It is noted that coatings for gas turbine parts, such as compressor, stator and rotary blades, and for other applica~
tions where aerodynamic flow is important, are generally required to be as fine and smooth as possible so that drag is minimized. A particulate material having a particle size within a range of about 1 to about 10 microns can be used to very good advantage in forming coatings on such parts.
The selection of the specific particulate material incorporated in the composition will depend on the specific application for which the coatings formed from the composition are intended to be used. In general, this selection can be made in accordance with known properties of the particulate materials.
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With respect to the amine ingredient of the ~resent invention, the term "amine" is used herein to mean those com-pounds which are generally considered to be derivatives of ammonia (NH3) by virtue o~ the substitution of an organic radical for one or more of the hydrogen atoms of the ammonia.
The amine can be an aliphatic or aromatic amine. Primary, secondary and tertiary amines can be used. The amine can be an alkylar~l amine or an alicyclic amine. Polyamines, for example, diamines and triamines can be used, as well as linear polyamines which contain recurring ~mine groups in the linear chain. ~nino derivatives of heterocyclic compounds containing nitrogen, or other substitutents in the rin~ can be used.
Examples of alkyl amines include methylamine, diethylamine, tripropylamine. Examples of aromatic amines include aniline, and toluidine, xylidine, and mesidine. Other aromatic amines that can be used are l-naphthylamine, 3-biphenylamine, benzylamine, and phenethylamine. Ethylenediamine, 1,2-butane-diamine, and 1,4-napthalenediamine, and 1, 2, 3-benzenetriamine are examples of polyamines that can be used. E~amples of ;
lînear polyamines include diethylenetriamine and triethylene-tetramine. Other amines which can be used are morpholine, piperidine and dic~clohexylamine. The amine can contain other groups such as, for example, h~droxy groups. Thus amines, such as alkanolamines, and hydroxylamines can be used also.
From the standpoint of overall performance characte-ristics, the use of alkanol amines, particularly, diethanol-amine, in the coating composition of the present invention is preferred. This is illustrated in certain of the e~amples below.
It has been found that the addition of an amine to the coating composition reduces hexavalent chromium of the dichromate constituent of the composition to trivalent chromium.
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This will be discussed more ~ully in connection with certain of the examples.
The dissolved metal can be convenientl~ provided by formulating the composition from solu~le metal salts which are a source of phosphate, dichromate and/or molybdate. How-ever, if the sources of ~he phosphate, dichromate and/or molybdate are the acids or anhydrides thereof, the source of the dissolved metal can be metal compounds which are soluble in the coating composition. ~xamples of such compounds are metal oxides, metal hydroxides, and metal carbonates. Other soluble metal compounds and the elemental ~orm of the metal can be used also. Specific examples of sources of the metal ion are magnesium oxide, magnesium hydroxide, zinc oxide, and zinc hydroxide, aluminum hydroxide, calcium hydroxide, lithium oxide, lithium carbonate and sodium hydroxide. Pow-d0red metal in its elemental state can be used conveniently.
Mixtures of the aforementioned metal compounds can be used also.
As to amounts of ingredients comprising the composi-tion, the dissolved phosphate should be present in an amount such that it functions to form a bond between the substrate and the particulate material. The dissolved dichromate and/or molybdate should be present in amounts such that it inhibits the reaction between the phosphate and th~ substrate and also the reaction between the par~iculate material and the phospl~ate.
B~v way of background, it is noted that if the reaction between the substrate and phosphate is too viyorous, the coating formed tends to be blistered ana tends to have poor adhesive prGperti~s.
Also, if the reaction between the phosphate and the particulate material is too vigorous, the particulate material is consumed by the reaction, and thus, its concentration in the composition is reduced. The amount of dichromate and/or molybdate should i0~ 0 not be so great that the formation of the phos~ha-te bond is prevented. The dissolved metal should be present in amounts such that appropriate improvements in corrosion resistance and adherency are realized. The particulate material should be used in an amount to impart to the substrate a coatin~ of the desired thickness. In general, this will in turn depend on the particular type of application for which the coating is to be used. For example/ if the primary function of the coating is to impart electrical conductivity to the substrate, -~
very small amounts of yraphite or other conductive material can be used in the composition. On the other hand substantial amounts of the particulate material should be used whsn it is desired that the coating impart high thermal insulation pro-perties to the substrate. Relatively low amounts of the par-ticulate material can be used in applications (for example, optic and aerodynamic flow applications) where it is desired that the coatings be relatively thin.
As to the amount of amine, it has been Eound that the mere presence of the amine appears to be effective in reducing the temperature at which the coating composition can be cured satisfactorily. For example, as little as one drop of diethylhydroxylamine per 100 ml of the aqueous solution was effective in reducing the temperature at which a coating com-position containing also a particulate material could be cured.
As to the upper concentration limit of the amine, this will generally be governed by the effect the amine has on the shelf lie of the composition and other factors hereafter discussed.
By way of background, it is noted that after the particulate material is mixed with the other ingredients comprising the composition, it will tend to settle from the composition.
(The time it takes Eor the dispersed particulate material to settle will depend on the particular material used and the . .
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particle size thereof.) A composition with a good shelf life is one wherein the settled particula~e materi~l can be readily redispersed in the composition even after standin~ ~or long periods of time, for example, many months. Excess amounts of amine which adversely affect the shelf life of the composi-tion twhen shelf life is considered important) should be avoided. Poor shelf life is cha~acterized by the particulate ~urning into a solid rock hard mass in a relativel~ short period of time which mass can't be redispersed in the composi-tion. It is noted tha~ there has been observed in some situa-tions the formation of agglomerates of the particulate material in the composition. While this is not particularly desirable, such agglomerates can be brol~en down and the particulate material redispersed in the composition for use by applyin~
high shear. Also, and as mentioned above, it is believed that -the amine reacts to reduce the hexavalent constituent of the composition to trivalent chromium. (This is evidenced by a green color which is observed after the amine is added to the composition. The addition of some amines cause the gree~
color to form immediately wher~as the green color forms after a prolonged period of time when other amines are used.) The amount of amine used should not be so great that the hexavalent chromium ingredient is depleted by this reaction to the extent that its contribution to corrosion resistance is significantly adversely affected. Generally speaking, it has been found that the effects the amines have on the shelf life of the com- ;
position and on the chromium constituent will depend on the specific amines used and the amounts thereof, that is~ the amount of amine to be used will depend on the specific amine used.
In general, it will be found that satisfactory coat-ing compositions can be formulated hy adding solid particulate material to the ~ollowing amounts of ingredients.
Amounts, m/l Preferred Amounts, m/l dissolved phos-phate at least about 1 about 1 to about 6 dissolved dichromate and/or molybdate " " " 0.1 " 0.15 to " 3.5 metal ion - - - - " 1 to " 6 amine " " " 0.02 " 0.02 to " ~.3 The above aqueous coating compositions o~ the pre-sent invention can be used to form glaze coatings on substrates and the presence therein of the amine is e~fective in reducing the temperature at which the composition can be cured. It is believed that widest use of the present invention will encompass the above compositions containing also about 20 to about 2000 g/l of particulate material. Such compositions can be prepared by standard high shear bulk mixing equipment.
It is believed that the coatin~ composition o~ the present invention will have its widest applicability of use in coating metallic substrates such as iron and ferrous alloys and other me~als which are subject to corrosion or require a specialty coating due to re~uirements of use. In addition, the coating composition can be used to coat other types oE
substrates such as, for example, glass, ceramics, refractories, wood and derivatives thereo~, and plastics.
The coating composition can be applied to the sub-strate according to any available or conventional technique.
It is believed that it will be most convenient to apply the composition by conventional procedures used for applying paint, for example, spray, roller and brush. E~amples of other tech- -niques for applying the coating composition are electrostatic spray ana electrophoretic deposition.
The coated substrate can be cured at temperatures as low as about 180F. The curing time is dependent on the ~ 3~
temperature used and can be best selected on the basis of experience. However, for guideline purposes, when curing at a temperature of about 180F, the curing should be continued for at least about 4 to 6 hours. When curing at a temperature of about 225F, the curing should be continued for at least about l hour. When curing at hiyher temperatures, for example, about 300F to about 500F, curing can be continued for about 15 to 30 minutes. It should be understood that due to its inorganic nature, the coating composition of the present invention can be cured at higher temperatures, for example, as high as about lO00F to about l600F.
In addition to curing the coating composition by exposing it to a heated environment, such as that provided in a hot oven, the composition can be cured also by other methods, examples of which include induction heating, infrared heatiny and resistance heating.
The thickness of the coating can be varied as desired. For example, the coating can have a thickness within the range of about 0.5 to about 15 mils. Speaking generally, coatings formed from the composition of the present invention will have a thickness of about 0.5 to about 4 mils/coat. For most applications, it is believed that a coating of about l to about 2 mils in thickness per coat will be satisfactory.
Between each coat the composition should be cured as described above, although shorter time periods may be used for curing between coats.
EX~PLES
Examples set forth below are illustrative of compo-sitions within the scope of the present invention.
There are described below 6 aqueous binding solutions (Solutions A to F) of the present invention to which can be added solid particulate materials to form coating compositions ~ 36~
within the scope of the present invention.
Solution H2O . . . . . . 25 ml aluminum phosphate and CrO3 solution* 100 ml (HOCH2CH2) 2NEI
*This aluminum phosphate/CrO3 solution was prepared by combining 300 g of hydrated alumina (A12O3 H O) with 558 ml of 75~ phosphoric acid and thereafter high spee~ mixing.
After standing overnight the solution was decanted from the insoluble Al(OH)3 which had settled to the bottom. The resulting solution was diluted with water to yield a 60 by weight aluminum phosphate solution. To 100 ml of this solution, 12 g of (CrO3) was added.
Solution A is an example of an a~ueous binding solution tha~
can be described as being versatile in that it can be used very effectively in binding a wide variety of particulate materials, both refractory and non-refractory, to metallic or ; other substrates. Such coating compositions prepared from Solution A can be cured effectivel~ at relatively low tempera-tures (for example, at about 180F for 4 to 6 hours or at 215F for 1 hour or at 300F for 1/2 hour) into coatings which maintain their corrosion resistant propertie;s after being exposed to corrosive environments.
Solution B
H2O . . . . . . 300 ml H3PO~(75%) . . . . . 100 ml NaOH . ~ 25 g CrO3 . . . . . . 8 g (HOCH2CH2)2NH . 8 g SOLUTION C
, H20 . . . . . .300 ml H3PO4 (75%) 100 ml MgO . . . . . . 20 g NaOH . . . . . . 5 g CrO3 . . . . . .10 y (HOCH2CH2)2NH (diethanolamine) . . 8 g The addition to Solution C of a solid particulate material such as silicon carbide in an amount of about 900 g/l produces a coating composition which can be cured into a coating of exceptional hardness and strength.
SOLUTION D
Solution D is the same as Solution B except that triethanolamine was substituted for diethanolamine. During mixing, there was a distinctive odor associated with Solution D, whereas Solution B did not have any noticeable odor. Other-wise, these two solutions behave in a very similar manner.
SOLUTION E
H2O . . . . . . 300 ml ~3PO4 (75%) . 100 ml NaOH . . . . . . 25 g CrO3 . . 8 g (C2Hs)2NOH . . 40 drops Solution E is an example of an aqueous binding solution wherein one drop of N,N-diethylhydroxylamine (85~ in water) per about 10 ml of solution was used to lower the curing tempera-ture. One drop per 10 ml of solution had the effect of immediately changing the dichromate to a very dark green. When a particulate material is added to Solution E, coatings formed from the resulting composition are satisfactory, but are not as corrosion resistant as coatings formed from compositions prepared from Solutions A to D. It is believed that the amine ~o~
used in Solution E reacts with and depletes chromium more quickly than the amines of Solutions A to D. Addin~ larger amounts, that is, from 0.1 to 8.0 grams of (C2H5)2NOH to Solution E (instead of 40 arops) adversely affects the shelf life properties when a particulate material is added to the composition.
SO~UTION F
H2O . . . . . . 300 ml H3PO4 (75%) . 100 ml NaO~ . . . . . . 25 g CrO3 . . . . . . 8 g HocH2cH~N~2 8 g Solution F is an example of an aqueous binding solution wherein monoethanolamine is used to lower the curing tempera-ture. Solutions using from 8 to 80 grams of this amine were effective in lowering the curing temperature. Solution F with pigment had a shelf life of less than about 2~ hours. Pig-mented Solutions A through D had no shelf life problem after six months. Solution F can be used effectivel~ by packing it separately from the particulate material, and using the compo-sition prepared by mixing solution F and the particulate material promptly after mixing.
Solutions A through F ~without particulate material) can be utilized as a glaze type coating, particularly as a top-coat to coatings such as, for example, those described in examples which follow.
Examples 1 to 7 below are illustrative of low tem-perature curing coating compositions within the scope of this invention, including compositions made from certain of the binding solutions described above. -~
Example 1 is illustrative of a coating composition containing a metal oxide. Such a composition can be used in : . .: . .. ..
' ` ~ : . .: ' '. ' ' ~ 36~0 forming coatings which have properties that make them parti-cularly effec-tive as electrical insulation coatings.
Example 1 Solution A . . . . . 100 ml aluminum oxide powder . . . 120 g (~400 mesh) Example 2 is illustrative of a coating composition containing a titanate. Such a composition can be used ln forming coatings which have properties that make them parti-cularly effective as thermal insulative coatings with high K
factors.
Example 2 Solution A . ~ . . . 100 ml barium titanate . . . . 100 g (-400 mesh) Example 3 is an illustration of a coating composition containing a metal alloy.
Example 3 Solution A . . . . . 100 ml Aluminum-manganese alloyed metal powder, 50~ Al-50% Mn ( 325 mesh) . 90 g The use of the aluminum-manganese alloy as the particulate material in the coating composition of Example 3 affords vari-ous advantages over the use of pure aluminum powder as particu-late material. Coatings including the alloy have a higher melting point than coatings including aluminum metal only.
The presence of the aluminum in the alloy provides excellent corrosion protection for metal substrates coated with the com~
position of Example 3 which substrates are exposed alternately to high and low temperatures (for example -100F to 1800F), and to salt spray environments. (An example of such an appli-cation is a coating for hot section parts of gas turbine -~0~
engines such as turbine blades.) In an application where the coated substrate is exposed to sulphur, such as in applica-tions where the substrate is exposed to sulphur-bearing gases, the manganese in the alloy functions to tie up the sulphur as MnS, thus reducing the susceptibility of the metal substrate to corrosive attack by the sulphur.
Example 4 is illustrative of a coating composition containing metal powder as the particulate material.
Example 4 Solution A . . . . . lO0 ml aluminum metal powder (-400 mesh) . 90 g Each of the coating compositions of Examples 1 to 4 above was applied to a steel panel by conventional paint spraying equipment. The coating compositions were then cured by placing the coated panels in an oven at 300F for 30 minutes. The coatings had thicknesses of about 1 to 2 mils.
Thereafter the corrosion resistant properties of coated sub-strates were evaluated by subjecting the substrates to a 5%
salt spray test (ASTM-117B) for 168 hours. It was found that there was no loss o~ adhesion and the coatings could not be removed readily.
The coating and test procedure described immediately ahove was repeated except that the coating compositions used did not contain diethanolamine. ~In all other respects the coating compositions of Examples l to 4 were the same.) It was found that the coatings after being exposed for only 24 hours to the aforementioned 5% salt spray test were washed off the steel panel or could be readily wiped therefrom. Thus the coatings, formed from the compositions of Examples 1-4, but without the amine, and cured at a relatively low tempera-ture completely lost their bond strength.
1~36~
In connection wi-th the compo~ition of Example 4 above, part of a steel panel was coated with this composition by spraying. The remainder of the panel was left uncoated.
The partly coated panel was cured at 350F for 30 minutes. In addition to exhibiting excellent adhesion to the steel panel after 168 hours exposure to the aforementioned 5% salt spray test, the coating exhibited excellent sacrificial corxosion protection, that is, it was responsible for inhibiting corro-sion of the uncoated portion of the panel. Sacrificial corro-sion protection of this type is generally considered ~o be dependent on the conductivity of the coating's metal particu-late material, which normally is above the metal comprising the substrate in the electromotive series of metals, that is, the particulate material is more anodic than the base metal.
However, in this case, the coating was found not to be conduc-tive before or after exposure to the salt spray environment.
Example 5 below is illustrative of a coating com-position containing a mixture of different solid particulate materials.
Example 5 Solution A ~ . . O . 125 ml silica (quartz, -325 mesh) . . 200 g Cr2O3 (-325 mesh) ~ . . . 15 g The coating composition of Example 5 can be cured into a refractory coating which has axcellent high temperature thermal insulative properties. The coating has satisfactory hardness and strength after being cured on a steel substrate at tempera-tures of 215-300F for one half hour. It has been found that when the coated steel substrate is subjected to use in appli-cations where it is subjected to temperatures as high as 1800~F, the coating continues to increase in hardness and has very high resistivity values, for e~ample, 2.2 x 106 ohm-cm at 1800F
~3~o and 300 x 106 ohm-cm at 1200F.
Example 6 is illustrative of a composition especi-all~ suited for bonding ceramic cements.
~ -.
phosphoric acial 85% . . . . 15 g CrO3 . . . . . . . . 5 g -diethanolamine . . . . . 3 g guartz (-325 mesh~ . . . . 50 g aluminum oxide (-325 mesh) . . 50 g aqueous suspension o colloidal silica*. . . . . 100 g *stable low-alkali suspension of colloidal silica in water sold by E. I. duPont de Nemours and Co., Inc. under the trademark Ludox, SM grade The composition of Example 6 is particularly suitable as a high temperature ceramic cement for use at temperatures as high as 2000F. At 1800F, a ~oating formed from the composi-tion had an average resistivity of 6.8 megohm-cm. At 1200F, the average resistivity was o~er 1000 megohm-cm, and the bond str~ngth was about 500 psi. It is noted that th~ composition of Example 6 does not have an indefinite shelf life since the collidal silica dispersion is not indefinitely stable in the acidic medium of the composition. However, the composition can be used satisfactoril~ a~ter aging for one month. After aging for two months, the composition can be thinned by adding thereto additional binding solution comprising the composition of Example 6.
Example 7 is illustrative of a particularly good ceramic coating composition.
' ' .. . . . .
~3~
Example 7 water . . ~ . . 70 ml phosphoric acid, 75~ . . 30 ml zinc chromate . . . . 5 g aluminum hydroxide . . . 20 g lithium carbonate . . . 5 g sodium dichromate . . . 20 g diethanolamine. . . . 3 g quartz, -325 mesh . . . 150 g chromic oxide, -325 mesh . . 5 g In summary, it can be said that the present invention affords a number of important industrial advantages. The coating composition of the present invention can be used in a wide variety of applications under conditions where energy requirement are reduced and excellent coating properties are realized.
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F~eld of`the Invention ' ... .
This invention relates to improved coatings (for example, corrosion resistant coatings) which can he formed by curi~g an aqueous coating composition at a relat.i.vely low temperature. This invention relates also to lowering the curing temperature at which aqueous coating compositions can be cured into coatings haviny desired properties thereby permitting their.use in a wi.de variety of applications where`problems hereto~ore were encountered.
736~
It is known to apply to metallic and other types of .
substrates coatings which protect the substrate from corrosive elements, and/or which have otller beneficial properties. Some .coating compositions which form such coa~ings ~ust be cured at relatively high temperatures, for exam~le, in e~cess of 500F.
One type of coating composition that must be cured at rela- :
tively high temperatures and that is effective in -Forming corro-sion resistant coatings on various types o~ substrates is a composition containing dissolved phosphate, dissolved dichromate or molybdate, and solid particulate material such as powdered ;~
metal, powdered metallic alloys, and refractory metal oxides.
Examples of such coating compositions are disclosed in a publi-cation entitled "Investigation of Aluminum Phosphate Coatings for ThermalInsulation of Air Frames", by Eubanks and Moore, National Aeronautics and Space Administration (M~SA Technical Note D-106, 1959) and U.S. Patent No. 3,248,251 to A.llen. Coat-ings formed from the aforementioned type composition have corro-sion resistant and/or other beneficial properties depending :-on the specific solid particulate material used in the composi-tion and the amount applied to the substrate. For example, coatings having particularly high heat resistance or refractory :
properties can be obtained by utilizing refractory metal oxides such as powdered quart~ and alumina (A12O3).
Application of the aforementioned type of coatings to articles permits the articles to be used in applications where they otherwise would not be suitable for use or it improves the performance properties of the article. Examples of such properties include corrosion resistance, hi~h heat resistance, abrasion resistance and electrical characteristics.
~rticles coated with the aforementioned type of coating can be used in various applications, including aerospace, automotive, ~.
marine and metal working applications.
3~
One of the steps that is required in forming the aforementioned type of coating on the substrate is curing the coating composition at a relatively high temperature a~ter it has been applied to the substrate. If the composition is not properly cured, problems are encountered. The aforemen tioned Allen patent discloses that the composition described therein should be cured at a temperature of 500F to 1000F, preferably at 600F to 800F, and that if the composition is not cured completely, soluble ingredients of the coating ~re leached out when it is exposed to water. This results in a coating having poor moisture resistance. The aforementioned NASA article discloses the curing of compositions described therein at temperatures ranging from room temperature to 800F. Various of the examples disclosed in the article show that maximum hardness of the coatings is not attained unless the curing temperature is about 600F, and further that the coatings are not moisture resistant unless cured at a tempera ture of at least ~00F for at least one half hour.
In general, if the coating composition is not cured properly, the coating formed therefrom will not have the ability to survive in marine, salt spray, or highly humid environments for desired periods of time.
There are various disadvantages in having to cure the aforementioned coating compositions at such relatively high temperatures. Some types of substrates cannot be coated satisfactorily with the aforementioned type composition because they cannot withstand the high curing temperature, or their properties, such as dimensional stability, and strength, are affected adversely. Another disadvantage is that high energy requirements are needed to provide the high curing temperatures. ~lso, relatively long periods are needed to 61~
': ' "
oool the hot coated article; this increases processing time r and uses up space which is needed to allow the articles to cool. In coating articles which have areas which should be free of coating, areas such as flanges, threaded surfaces or holes, it is necessary to mask the areas. When applying two or more layers of coatings to such articles, such areas -have to be remasked because the high curing temperatures destroy tha mask. Appreciable savings in cost and labor could be realized if the coating composition were c~pable of being cured at lower temperatures which do not destroy the mask. Some industrial concerns have refrained from using the aforementioned type of coating composition because they do not have ovens or furnaces which are capable of providing the high curing temperatures.
This invention relates to a coating composition which is capable of being cured into an improved coating at relatively low temperatures. ~-Reported Developments .
Various methods have been reported for lowering the curing temperatures of the aforementioned type of coating compositions. As will be seen from the discussion which follows, these methods have one or more shortcominys.
In U.S. Patent No. 3,248,250 to Collins, one of the applicants herein, it is disclosed that the curing tempe~
rature of the coating composition described in the aforemen- ;
tioned Allen patent can be lowered by adding to the composition an alkali metal silicate. The Collins patent discloses that such compositions can be cured at a temperature as low as 250F, but preferably at a temperature of 300F to 500F fox 3 to 60 minutes.
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36~
In U.S. Patent No. 3,248,249, also to Collins, one of the applicants herein, it is disclosed that the curing temperature of the coating composition described in the aforementioned Allen pa-tent can be reduced by adding to the composition a solid particulate material having a grain size on the order of 0.1 micron or finer. The preferred particu-late materials are colloidal silica and colloidal alumina.
Such compositions can be cured at a temperature as low as 250F, but preferably at a temperature of 250F to 500E~
for 3 to 60 minutes.
In general, coatings formed from compositions described in the arorementioned Collins' patents, and cured at the lower temperatures described therein, tend to have better properties than coatings formed from the composition described in the aforementioned Allen patent, and cured at like temperatures~ Nevertheless, the use of lower tempera-tures to cure the compositions described in the Collins' patents results in sacrificing certain desired properties of the coatings formed from the compositions. By way of bac~ground, it is noted that for use in certain applications, industrial standards require that coatin~s of the aforemen-tioned type have excellent adhesive and corrosion resistant properties after being exposed to all of the following 5 test evaluations; (1) 5% salt spra~ for a minimum of 144 hours; (2) 100% relative humidity at 100F for a minimum of 144 hours; (3) hot water (180F) for a minimum of 2~ hours;
(4) steam vapor for a minimum o~ ~44 hours; and (5) hot saline condensates for a minimum of 24 hours. Coatings formed by curin~ the composition described in the aforementioned Collins' patents at temperatures of 300~ and below did not pass all of the above tests, with the most predominant failure being that of failure to survive the 5% salt spra~ test. (For example, after exposing the coated substrate to the 5~ salt spray test for a period of only 24 hours, the coatiny could be wiped oEf the substrate. Thus, the adhesive properties of such coatings were destroyed when exposed to the salt spray test for a very short period of tLme.) In general/ although certain improvements in corrosion resistance are realized, other important properties, such as abrasion and impact resistance, are affected adversely when the compositions are cured at the lower temperatures.
Thus, it is an object of this invention to provide a coating composition which is capable of being cured at relatively low temperatures, for example, below 400F. It is another object of this invention to provide a coating com-position which is capable of being cured at relatively low temperatures without significantly affecting adversely the desired properties of coatings formed from the composition.
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0 ~ 3 ~ 1~
In accordance with this invention in ~n acidic aqueous coating composition comprisingJ in coating-forming proportions, materials which are a source of dissolved phosphate; dissolved dichromate or molybdate, or mixtures thereof; and solid particles of an inorganic particulate ma~erial;
wherein said composition is capable of being heat-cured at elevated temper-atures into a water insoluble coating, there is provided the improvement com-prising the addition of an amine in an amount at least sufficient to reduce the temperature at which said composition can be cured into said water insoluble coating.
The invention also provides an acidic aqueous coating composition which is capable of being heat-cured at elevated temperatures into a water insoluble coating having excellent adhesion to steel and excellent corrosion resistant propertiesl including sacrificial corrosion protection properties, and lqhich consists essentially of:
(a) phosphoric acid in an amount equivalent to at least about 1 m/l of dissolved phosphate;
~b) chromic anhydride in an amount equivalent to at least about O.l m/l of dissolved dichromate;
(c) at least about 20 g/l of aluminum metal powder, the particle si~e of which is -400 mesh (U.S. Standard Sieve Series);
~d) dissolved aluminum in an amount at least sufficient to im-part improved corrosion resistant and adhesive properties to said coating; and (e) diethanolamine in an amount at least sufficient to reduce the temperature at which said composition can be cured into said coating.
The invention further provides an acidic aqueous coating composi-tion which is capable of being heat-cured at elevated temperatures into a water insoluble coating and which consists essentially of:
~a) at least about l m/l of dissolved phosphate, (b) at least about 0.1 m/l of dissolved dichromate;
(c) at least about 20 g/l of inorganic solid particulate ma-~,,~ ,, _ 7 _ 3 61 ~
terial having a particle size of about one micron or more; and (d) an amine in an amount at least sufficient to reduce the temperature at which said composition can be cured into said coating.
Finally, the inventioD provides a method for coating substrate by applying a coating composition as defined above and thereafter curing the composition.
The addition of an amine to the coating composition is effective in permitting the composition to be cured at temperatures as low as about 180F. Furthermore, the low-temperature curing composition of this invention can be cured into coatings without significantly sacrificing desired proper-ties of the coatings.
Preferred amines for use in the composition of this invention are alkanol amines such as diethanolamine.
The low-temperature curing composition of this invention provides a number of advantages to industry. It is capable of being cured into coat-ings at relatively low temperatures without sacrificing desired properties of the coatings. The composition can be used to satisfactorily coat substrates ~0 which are not capable of being coated satisfactorily with heretofore known compositions which must be cured at high temperatures which affect properties of the substrate adversely. Since the coating composition can be cured at relatively low temperatures, energy requirements, cool-down time o~ the coated article, and space required for the cool-down time are reduced. Investment in high-temperature furnaces ~ ~ - 7a -.
3~
or ovens is unnecessary. And remasking of coating-free areas of the coated article is avoided because the compositions can be cured at temperatures which do not destroy the mask.
Detailed Description of the Invention .
The essential ingredients of the aqueous coating composition of this invention are water, dissol~ed phosphate, dissolved dichromate or molybdate, solid particulate material and an amine. As will be discussed more ully below, it is preferred that the composition contain dissolved metal also.
The term "dissolved phosphate" as used herein includes PO4~3, Hpo4-2 and ~2PO4-l. Any water soluble compound which is a source of dissolved phosphate can be used in prepar-ing the composition of this invention. Examples of such compounds are: ortho, meta, pyro, and hypo phosphoric acids;
anhydrous and hydrated metal phosphate salts such as the mono-basic phosphates o~ aluminum, magnesium, zinc, calcium, sodium, pokassium and lithium/ the dibasic phosphates of magnesium and calcium, and the tribasic phosphates of magnesium, zinc and lithium and mixtures thereof. The use of orthophosphoric acid is preferred. Excellent results are attained utilizing ortho-phosphoric acid and it is readily available and relatively inexpenslve.
Any water soluble compound which is a source of dissolved dichromate ~Cr2O7~2) can be used in preparing the composition of this invention. Examples o~ water soluble dichromate salts that can be used are sodium dichromate, potassium dichromate and other metal dichromates such as those of magnesium, calcium and zinc. Since the coating composition of the present invention is acidic, chromic acid and its anhydride (CrO3), and water soluble chromat~ compounds which in acidic medium are oxidized to dichromate can be used also as a source of ~he dichromate. Examples of m~tal chro-mates that can be used are those of potassium, sodium, magne-sium~ zinc and calcium. The use of chromic anhydride is preferred because its use provides excellent results, it is relativel~ low in cost and readily available, and it is easier to dissolve than certain other chromium compounds.
Dissolved molybdate may be substituted for dissolved dichromate or u~ed in combination therewith in the ComPoSitiOn of the present invention. However, it is preferred to use dichromate because compositions containing it tend to have better shelf-life properties than compositions containing molybdate, and the dichromate-containing compositions tend to passivate the substrate better than the molybdate-containing compositions. When molybdate is used in the composition, any water-soluble compound which is a source thereof can be used.
Examples of such compounds are molybdic acid, molybdic anhy dride and water-soluble metal molybdates such as those of sodium, potassium, magnesium, calcium and zinc.
The solid particulate materials for use in the com-position of the present invention are small particle inorganic materials such as refractory and non-refractory pigments, including metals, intermetallic or metal alloy compounds, cements, ceramics, and fillers. The small particle material can be colloidal in size or of larger size. Specific examples of the aforementioned types of particulate materials, which are completely insoluble or substantially insoluble in the aqueous composition, are as ~ollows: metals - aluminum, copper, silver and nickel; intermetallic or metal alloy compounds - cobalt/
aluminum alloy and aluminum/manganese alloy; cements - mixed or complex oxides, silicates, silica and zircon; ceramics -metal oxides such as chromic oxide, silica and powdered quartz, aluminum oxide, cerium oxide, zirconia and beryllia, and g ._ ~736~0 reractory carbides such as silicon carbide, molybdenum disilicide, tungsten c~rbide and boron nitride. Examples o~
other solid particulate materials that can be used are other metal nitrides, metal borides, titanates, zirconates, metal sulfides and graphite.
The particle size of the paxticulate material can vary over a wide range. Any particle size or distribution of particle sizes that permits the binding of the particulate material to the substrate can be used. In general, particle size selection will depend on the type of application for which the coated substrate is to be used. For example, the particle size of the particulate material can be within the range of about 20 to about 100 mesh when it is desired that the coatings have a rough surface for aesthetic or functional reasons. (Unless stated otherwise, the term "mesh" when used herein refers to U.S. Standard Sieve Series.) Smoother coatings can be attained by using a particle size of -200 mesh. For very smooth and denser coatings, it is preferred that the particle size of the particulate material be -400 mesh. It is noted that coatings for gas turbine parts, such as compressor, stator and rotary blades, and for other applica~
tions where aerodynamic flow is important, are generally required to be as fine and smooth as possible so that drag is minimized. A particulate material having a particle size within a range of about 1 to about 10 microns can be used to very good advantage in forming coatings on such parts.
The selection of the specific particulate material incorporated in the composition will depend on the specific application for which the coatings formed from the composition are intended to be used. In general, this selection can be made in accordance with known properties of the particulate materials.
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With respect to the amine ingredient of the ~resent invention, the term "amine" is used herein to mean those com-pounds which are generally considered to be derivatives of ammonia (NH3) by virtue o~ the substitution of an organic radical for one or more of the hydrogen atoms of the ammonia.
The amine can be an aliphatic or aromatic amine. Primary, secondary and tertiary amines can be used. The amine can be an alkylar~l amine or an alicyclic amine. Polyamines, for example, diamines and triamines can be used, as well as linear polyamines which contain recurring ~mine groups in the linear chain. ~nino derivatives of heterocyclic compounds containing nitrogen, or other substitutents in the rin~ can be used.
Examples of alkyl amines include methylamine, diethylamine, tripropylamine. Examples of aromatic amines include aniline, and toluidine, xylidine, and mesidine. Other aromatic amines that can be used are l-naphthylamine, 3-biphenylamine, benzylamine, and phenethylamine. Ethylenediamine, 1,2-butane-diamine, and 1,4-napthalenediamine, and 1, 2, 3-benzenetriamine are examples of polyamines that can be used. E~amples of ;
lînear polyamines include diethylenetriamine and triethylene-tetramine. Other amines which can be used are morpholine, piperidine and dic~clohexylamine. The amine can contain other groups such as, for example, h~droxy groups. Thus amines, such as alkanolamines, and hydroxylamines can be used also.
From the standpoint of overall performance characte-ristics, the use of alkanol amines, particularly, diethanol-amine, in the coating composition of the present invention is preferred. This is illustrated in certain of the e~amples below.
It has been found that the addition of an amine to the coating composition reduces hexavalent chromium of the dichromate constituent of the composition to trivalent chromium.
~3~
This will be discussed more ~ully in connection with certain of the examples.
The dissolved metal can be convenientl~ provided by formulating the composition from solu~le metal salts which are a source of phosphate, dichromate and/or molybdate. How-ever, if the sources of ~he phosphate, dichromate and/or molybdate are the acids or anhydrides thereof, the source of the dissolved metal can be metal compounds which are soluble in the coating composition. ~xamples of such compounds are metal oxides, metal hydroxides, and metal carbonates. Other soluble metal compounds and the elemental ~orm of the metal can be used also. Specific examples of sources of the metal ion are magnesium oxide, magnesium hydroxide, zinc oxide, and zinc hydroxide, aluminum hydroxide, calcium hydroxide, lithium oxide, lithium carbonate and sodium hydroxide. Pow-d0red metal in its elemental state can be used conveniently.
Mixtures of the aforementioned metal compounds can be used also.
As to amounts of ingredients comprising the composi-tion, the dissolved phosphate should be present in an amount such that it functions to form a bond between the substrate and the particulate material. The dissolved dichromate and/or molybdate should be present in amounts such that it inhibits the reaction between the phosphate and th~ substrate and also the reaction between the par~iculate material and the phospl~ate.
B~v way of background, it is noted that if the reaction between the substrate and phosphate is too viyorous, the coating formed tends to be blistered ana tends to have poor adhesive prGperti~s.
Also, if the reaction between the phosphate and the particulate material is too vigorous, the particulate material is consumed by the reaction, and thus, its concentration in the composition is reduced. The amount of dichromate and/or molybdate should i0~ 0 not be so great that the formation of the phos~ha-te bond is prevented. The dissolved metal should be present in amounts such that appropriate improvements in corrosion resistance and adherency are realized. The particulate material should be used in an amount to impart to the substrate a coatin~ of the desired thickness. In general, this will in turn depend on the particular type of application for which the coating is to be used. For example/ if the primary function of the coating is to impart electrical conductivity to the substrate, -~
very small amounts of yraphite or other conductive material can be used in the composition. On the other hand substantial amounts of the particulate material should be used whsn it is desired that the coating impart high thermal insulation pro-perties to the substrate. Relatively low amounts of the par-ticulate material can be used in applications (for example, optic and aerodynamic flow applications) where it is desired that the coatings be relatively thin.
As to the amount of amine, it has been Eound that the mere presence of the amine appears to be effective in reducing the temperature at which the coating composition can be cured satisfactorily. For example, as little as one drop of diethylhydroxylamine per 100 ml of the aqueous solution was effective in reducing the temperature at which a coating com-position containing also a particulate material could be cured.
As to the upper concentration limit of the amine, this will generally be governed by the effect the amine has on the shelf lie of the composition and other factors hereafter discussed.
By way of background, it is noted that after the particulate material is mixed with the other ingredients comprising the composition, it will tend to settle from the composition.
(The time it takes Eor the dispersed particulate material to settle will depend on the particular material used and the . .
- . . . .: .
i~3~
particle size thereof.) A composition with a good shelf life is one wherein the settled particula~e materi~l can be readily redispersed in the composition even after standin~ ~or long periods of time, for example, many months. Excess amounts of amine which adversely affect the shelf life of the composi-tion twhen shelf life is considered important) should be avoided. Poor shelf life is cha~acterized by the particulate ~urning into a solid rock hard mass in a relativel~ short period of time which mass can't be redispersed in the composi-tion. It is noted tha~ there has been observed in some situa-tions the formation of agglomerates of the particulate material in the composition. While this is not particularly desirable, such agglomerates can be brol~en down and the particulate material redispersed in the composition for use by applyin~
high shear. Also, and as mentioned above, it is believed that -the amine reacts to reduce the hexavalent constituent of the composition to trivalent chromium. (This is evidenced by a green color which is observed after the amine is added to the composition. The addition of some amines cause the gree~
color to form immediately wher~as the green color forms after a prolonged period of time when other amines are used.) The amount of amine used should not be so great that the hexavalent chromium ingredient is depleted by this reaction to the extent that its contribution to corrosion resistance is significantly adversely affected. Generally speaking, it has been found that the effects the amines have on the shelf life of the com- ;
position and on the chromium constituent will depend on the specific amines used and the amounts thereof, that is~ the amount of amine to be used will depend on the specific amine used.
In general, it will be found that satisfactory coat-ing compositions can be formulated hy adding solid particulate material to the ~ollowing amounts of ingredients.
Amounts, m/l Preferred Amounts, m/l dissolved phos-phate at least about 1 about 1 to about 6 dissolved dichromate and/or molybdate " " " 0.1 " 0.15 to " 3.5 metal ion - - - - " 1 to " 6 amine " " " 0.02 " 0.02 to " ~.3 The above aqueous coating compositions o~ the pre-sent invention can be used to form glaze coatings on substrates and the presence therein of the amine is e~fective in reducing the temperature at which the composition can be cured. It is believed that widest use of the present invention will encompass the above compositions containing also about 20 to about 2000 g/l of particulate material. Such compositions can be prepared by standard high shear bulk mixing equipment.
It is believed that the coatin~ composition o~ the present invention will have its widest applicability of use in coating metallic substrates such as iron and ferrous alloys and other me~als which are subject to corrosion or require a specialty coating due to re~uirements of use. In addition, the coating composition can be used to coat other types oE
substrates such as, for example, glass, ceramics, refractories, wood and derivatives thereo~, and plastics.
The coating composition can be applied to the sub-strate according to any available or conventional technique.
It is believed that it will be most convenient to apply the composition by conventional procedures used for applying paint, for example, spray, roller and brush. E~amples of other tech- -niques for applying the coating composition are electrostatic spray ana electrophoretic deposition.
The coated substrate can be cured at temperatures as low as about 180F. The curing time is dependent on the ~ 3~
temperature used and can be best selected on the basis of experience. However, for guideline purposes, when curing at a temperature of about 180F, the curing should be continued for at least about 4 to 6 hours. When curing at a temperature of about 225F, the curing should be continued for at least about l hour. When curing at hiyher temperatures, for example, about 300F to about 500F, curing can be continued for about 15 to 30 minutes. It should be understood that due to its inorganic nature, the coating composition of the present invention can be cured at higher temperatures, for example, as high as about lO00F to about l600F.
In addition to curing the coating composition by exposing it to a heated environment, such as that provided in a hot oven, the composition can be cured also by other methods, examples of which include induction heating, infrared heatiny and resistance heating.
The thickness of the coating can be varied as desired. For example, the coating can have a thickness within the range of about 0.5 to about 15 mils. Speaking generally, coatings formed from the composition of the present invention will have a thickness of about 0.5 to about 4 mils/coat. For most applications, it is believed that a coating of about l to about 2 mils in thickness per coat will be satisfactory.
Between each coat the composition should be cured as described above, although shorter time periods may be used for curing between coats.
EX~PLES
Examples set forth below are illustrative of compo-sitions within the scope of the present invention.
There are described below 6 aqueous binding solutions (Solutions A to F) of the present invention to which can be added solid particulate materials to form coating compositions ~ 36~
within the scope of the present invention.
Solution H2O . . . . . . 25 ml aluminum phosphate and CrO3 solution* 100 ml (HOCH2CH2) 2NEI
*This aluminum phosphate/CrO3 solution was prepared by combining 300 g of hydrated alumina (A12O3 H O) with 558 ml of 75~ phosphoric acid and thereafter high spee~ mixing.
After standing overnight the solution was decanted from the insoluble Al(OH)3 which had settled to the bottom. The resulting solution was diluted with water to yield a 60 by weight aluminum phosphate solution. To 100 ml of this solution, 12 g of (CrO3) was added.
Solution A is an example of an a~ueous binding solution tha~
can be described as being versatile in that it can be used very effectively in binding a wide variety of particulate materials, both refractory and non-refractory, to metallic or ; other substrates. Such coating compositions prepared from Solution A can be cured effectivel~ at relatively low tempera-tures (for example, at about 180F for 4 to 6 hours or at 215F for 1 hour or at 300F for 1/2 hour) into coatings which maintain their corrosion resistant propertie;s after being exposed to corrosive environments.
Solution B
H2O . . . . . . 300 ml H3PO~(75%) . . . . . 100 ml NaOH . ~ 25 g CrO3 . . . . . . 8 g (HOCH2CH2)2NH . 8 g SOLUTION C
, H20 . . . . . .300 ml H3PO4 (75%) 100 ml MgO . . . . . . 20 g NaOH . . . . . . 5 g CrO3 . . . . . .10 y (HOCH2CH2)2NH (diethanolamine) . . 8 g The addition to Solution C of a solid particulate material such as silicon carbide in an amount of about 900 g/l produces a coating composition which can be cured into a coating of exceptional hardness and strength.
SOLUTION D
Solution D is the same as Solution B except that triethanolamine was substituted for diethanolamine. During mixing, there was a distinctive odor associated with Solution D, whereas Solution B did not have any noticeable odor. Other-wise, these two solutions behave in a very similar manner.
SOLUTION E
H2O . . . . . . 300 ml ~3PO4 (75%) . 100 ml NaOH . . . . . . 25 g CrO3 . . 8 g (C2Hs)2NOH . . 40 drops Solution E is an example of an aqueous binding solution wherein one drop of N,N-diethylhydroxylamine (85~ in water) per about 10 ml of solution was used to lower the curing tempera-ture. One drop per 10 ml of solution had the effect of immediately changing the dichromate to a very dark green. When a particulate material is added to Solution E, coatings formed from the resulting composition are satisfactory, but are not as corrosion resistant as coatings formed from compositions prepared from Solutions A to D. It is believed that the amine ~o~
used in Solution E reacts with and depletes chromium more quickly than the amines of Solutions A to D. Addin~ larger amounts, that is, from 0.1 to 8.0 grams of (C2H5)2NOH to Solution E (instead of 40 arops) adversely affects the shelf life properties when a particulate material is added to the composition.
SO~UTION F
H2O . . . . . . 300 ml H3PO4 (75%) . 100 ml NaO~ . . . . . . 25 g CrO3 . . . . . . 8 g HocH2cH~N~2 8 g Solution F is an example of an aqueous binding solution wherein monoethanolamine is used to lower the curing tempera-ture. Solutions using from 8 to 80 grams of this amine were effective in lowering the curing temperature. Solution F with pigment had a shelf life of less than about 2~ hours. Pig-mented Solutions A through D had no shelf life problem after six months. Solution F can be used effectivel~ by packing it separately from the particulate material, and using the compo-sition prepared by mixing solution F and the particulate material promptly after mixing.
Solutions A through F ~without particulate material) can be utilized as a glaze type coating, particularly as a top-coat to coatings such as, for example, those described in examples which follow.
Examples 1 to 7 below are illustrative of low tem-perature curing coating compositions within the scope of this invention, including compositions made from certain of the binding solutions described above. -~
Example 1 is illustrative of a coating composition containing a metal oxide. Such a composition can be used in : . .: . .. ..
' ` ~ : . .: ' '. ' ' ~ 36~0 forming coatings which have properties that make them parti-cularly effec-tive as electrical insulation coatings.
Example 1 Solution A . . . . . 100 ml aluminum oxide powder . . . 120 g (~400 mesh) Example 2 is illustrative of a coating composition containing a titanate. Such a composition can be used ln forming coatings which have properties that make them parti-cularly effective as thermal insulative coatings with high K
factors.
Example 2 Solution A . ~ . . . 100 ml barium titanate . . . . 100 g (-400 mesh) Example 3 is an illustration of a coating composition containing a metal alloy.
Example 3 Solution A . . . . . 100 ml Aluminum-manganese alloyed metal powder, 50~ Al-50% Mn ( 325 mesh) . 90 g The use of the aluminum-manganese alloy as the particulate material in the coating composition of Example 3 affords vari-ous advantages over the use of pure aluminum powder as particu-late material. Coatings including the alloy have a higher melting point than coatings including aluminum metal only.
The presence of the aluminum in the alloy provides excellent corrosion protection for metal substrates coated with the com~
position of Example 3 which substrates are exposed alternately to high and low temperatures (for example -100F to 1800F), and to salt spray environments. (An example of such an appli-cation is a coating for hot section parts of gas turbine -~0~
engines such as turbine blades.) In an application where the coated substrate is exposed to sulphur, such as in applica-tions where the substrate is exposed to sulphur-bearing gases, the manganese in the alloy functions to tie up the sulphur as MnS, thus reducing the susceptibility of the metal substrate to corrosive attack by the sulphur.
Example 4 is illustrative of a coating composition containing metal powder as the particulate material.
Example 4 Solution A . . . . . lO0 ml aluminum metal powder (-400 mesh) . 90 g Each of the coating compositions of Examples 1 to 4 above was applied to a steel panel by conventional paint spraying equipment. The coating compositions were then cured by placing the coated panels in an oven at 300F for 30 minutes. The coatings had thicknesses of about 1 to 2 mils.
Thereafter the corrosion resistant properties of coated sub-strates were evaluated by subjecting the substrates to a 5%
salt spray test (ASTM-117B) for 168 hours. It was found that there was no loss o~ adhesion and the coatings could not be removed readily.
The coating and test procedure described immediately ahove was repeated except that the coating compositions used did not contain diethanolamine. ~In all other respects the coating compositions of Examples l to 4 were the same.) It was found that the coatings after being exposed for only 24 hours to the aforementioned 5% salt spray test were washed off the steel panel or could be readily wiped therefrom. Thus the coatings, formed from the compositions of Examples 1-4, but without the amine, and cured at a relatively low tempera-ture completely lost their bond strength.
1~36~
In connection wi-th the compo~ition of Example 4 above, part of a steel panel was coated with this composition by spraying. The remainder of the panel was left uncoated.
The partly coated panel was cured at 350F for 30 minutes. In addition to exhibiting excellent adhesion to the steel panel after 168 hours exposure to the aforementioned 5% salt spray test, the coating exhibited excellent sacrificial corxosion protection, that is, it was responsible for inhibiting corro-sion of the uncoated portion of the panel. Sacrificial corro-sion protection of this type is generally considered ~o be dependent on the conductivity of the coating's metal particu-late material, which normally is above the metal comprising the substrate in the electromotive series of metals, that is, the particulate material is more anodic than the base metal.
However, in this case, the coating was found not to be conduc-tive before or after exposure to the salt spray environment.
Example 5 below is illustrative of a coating com-position containing a mixture of different solid particulate materials.
Example 5 Solution A ~ . . O . 125 ml silica (quartz, -325 mesh) . . 200 g Cr2O3 (-325 mesh) ~ . . . 15 g The coating composition of Example 5 can be cured into a refractory coating which has axcellent high temperature thermal insulative properties. The coating has satisfactory hardness and strength after being cured on a steel substrate at tempera-tures of 215-300F for one half hour. It has been found that when the coated steel substrate is subjected to use in appli-cations where it is subjected to temperatures as high as 1800~F, the coating continues to increase in hardness and has very high resistivity values, for e~ample, 2.2 x 106 ohm-cm at 1800F
~3~o and 300 x 106 ohm-cm at 1200F.
Example 6 is illustrative of a composition especi-all~ suited for bonding ceramic cements.
~ -.
phosphoric acial 85% . . . . 15 g CrO3 . . . . . . . . 5 g -diethanolamine . . . . . 3 g guartz (-325 mesh~ . . . . 50 g aluminum oxide (-325 mesh) . . 50 g aqueous suspension o colloidal silica*. . . . . 100 g *stable low-alkali suspension of colloidal silica in water sold by E. I. duPont de Nemours and Co., Inc. under the trademark Ludox, SM grade The composition of Example 6 is particularly suitable as a high temperature ceramic cement for use at temperatures as high as 2000F. At 1800F, a ~oating formed from the composi-tion had an average resistivity of 6.8 megohm-cm. At 1200F, the average resistivity was o~er 1000 megohm-cm, and the bond str~ngth was about 500 psi. It is noted that th~ composition of Example 6 does not have an indefinite shelf life since the collidal silica dispersion is not indefinitely stable in the acidic medium of the composition. However, the composition can be used satisfactoril~ a~ter aging for one month. After aging for two months, the composition can be thinned by adding thereto additional binding solution comprising the composition of Example 6.
Example 7 is illustrative of a particularly good ceramic coating composition.
' ' .. . . . .
~3~
Example 7 water . . ~ . . 70 ml phosphoric acid, 75~ . . 30 ml zinc chromate . . . . 5 g aluminum hydroxide . . . 20 g lithium carbonate . . . 5 g sodium dichromate . . . 20 g diethanolamine. . . . 3 g quartz, -325 mesh . . . 150 g chromic oxide, -325 mesh . . 5 g In summary, it can be said that the present invention affords a number of important industrial advantages. The coating composition of the present invention can be used in a wide variety of applications under conditions where energy requirement are reduced and excellent coating properties are realized.
.
Claims (35)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS.
1. In an acidic aqueous coating composition compris-ing, in coating-forming proportions, materials which are a source of dissolved phosphate; dissolved dichromate or molyb-date, or mixtures thereof; and solid particles of an inorganic particulate material; wherein said composition is capable of being heat-cured at elevated temperatures into a water in-soluble coating, the improvement comprising the addition of an amine in an amount at least sufficient to reduce the tem-perature at which said composition can be cured into said water insoluble coating.
2. A composition according to Claim 1 comprising:
(A) at least about 1 m/l of dissolved phos-phate;
(B) at least about 0.1 m/l of dissolved di-chromate or molybdate or mixtures thereof;
(C) at least about 20 g/l of particulate material; and (D) at least about 0.02 m/l of amine.
(A) at least about 1 m/l of dissolved phos-phate;
(B) at least about 0.1 m/l of dissolved di-chromate or molybdate or mixtures thereof;
(C) at least about 20 g/l of particulate material; and (D) at least about 0.02 m/l of amine.
3. A composition according to Claim 1 comprising:
(A) about 1 to about 6 m/l of dissolved phos-phate;
(B) about 0.15 to about 3.5 m/l of dissolved dichromate or molybdate or mixtures thereof;
(C) about 20 to about 2000 g/l of particulate material;
(D) about 0.02 to about 0.3 m/l of amine; and (E) 0 to about 6 m/l of dissolved metal.
(A) about 1 to about 6 m/l of dissolved phos-phate;
(B) about 0.15 to about 3.5 m/l of dissolved dichromate or molybdate or mixtures thereof;
(C) about 20 to about 2000 g/l of particulate material;
(D) about 0.02 to about 0.3 m/l of amine; and (E) 0 to about 6 m/l of dissolved metal.
4. A composition according to Claim 1, also containing dissolved metal.
5. A composition according to Claim 1 wherein said amine is selected from the group consisting of alkylhydroxyamines and alkanolamines.
6. A composition according to Claim 5 wherein said amine is an alkanol-amine.
7. A composition according to Claim 6 wherein said amine is diethanol-amine.
8. A method for coating a substrate comprising:
(A) applying to said substrate the coating composition of Claim 1;
and (B) thereafter curing said composition into said coating.
(A) applying to said substrate the coating composition of Claim 1;
and (B) thereafter curing said composition into said coating.
9. A method according to Claim 8 wherein said composition is cured at a temperature of at least about 180°F.
10. A method according to Claim 9 wherein said composition is cured at a temperature of about 215°F to about 300°F.
11. A composition according to Claim 2 including also at least about 1 m/l of dissolved metal.
12. A composition according to Claim 1 including at least about 0.1 m/l of dissolved dichromate.
13. A composition according to Claim 12 including also at least about 1 m/l of dissolved metal.
14. A composition according to Claim 13 comprising:
(A) about 1 to about 6 m/l of dissolved phosphate;
(B) about 0.15 to about 3.5 m/l of dissolved dichromate;
(C) about 20 to about 2000 g/l of particulate material;
(D) about 0.02 to about 0.3 m/l of amine; and (E) about 1 to about 6 m/l of dissolved metal.
(A) about 1 to about 6 m/l of dissolved phosphate;
(B) about 0.15 to about 3.5 m/l of dissolved dichromate;
(C) about 20 to about 2000 g/l of particulate material;
(D) about 0.02 to about 0.3 m/l of amine; and (E) about 1 to about 6 m/l of dissolved metal.
15. A composition according to Claim 13 wherein said amine is an alkyl-hydroxyamine or an alkanolamine, wherein said particulate material is alu-minum, aluminum oxide, Cr2O3, boron nitride, silicon carbide or titanium di-oxide and wherein said dissolved metal is sodium, potassium, calcium, mag-nesium, zinc or aluminum.
16. A composition according to Claim 14 wherein said amine is an alkyl-hydroxyamine or an alkanolamine, wherein said particulate material is aluminum, aluminum oxide, Cr2O3, boron nitride, silicon carbide or titanium dioxide and wherein said dissolved metal is sodium, potassium, calcium, magnesium, zinc or aluminum.
17. A composition according to Claim 16 wherein said amine is diethanol-amine wherein said particulate is aluminum or aluminum oxide and wherein said dissolved metal is aluminum or magnesium.
18. A composition according to Claim 1, 2 or 3 wherein said particulate material is selected from the group consisting of one or more of the following:
aluminum, copper, silver, nickel, cobalt/aluminum alloy, aluminum/manganese alloy, mixed or complex oxide cements, silicate cements, silica cements, zir-con cements, chromic oxide, silica, powdered quartz, aluminum oxide, cerium oxide, zirconia, beryllia, silicon carbide, molybdenum disilicide, tungsten carbide, metal nitrides, metal borides, titanates, zirconates, metal sulfides and graphite.
aluminum, copper, silver, nickel, cobalt/aluminum alloy, aluminum/manganese alloy, mixed or complex oxide cements, silicate cements, silica cements, zir-con cements, chromic oxide, silica, powdered quartz, aluminum oxide, cerium oxide, zirconia, beryllia, silicon carbide, molybdenum disilicide, tungsten carbide, metal nitrides, metal borides, titanates, zirconates, metal sulfides and graphite.
19. A composition according to Claim 12, 13 or 14 wherein said partic-ulate material is selected from the group consisting of one or more of the following: aluminum, copper, silver, nickel, cobalt/aluminum alloy, aluminum/
manganese alloy, mixed or complex oxide cements, silicate cements, silica cements, zircon cements, chromic oxide, silica, powdered quarts, aluminum oxide, cerium oxide, zirconia, beryllia, silicon carbide, molybdenum disil-icide, tungsten carbide, metal nitrides, metal borides, titanates, zirconates, metal sulfides and graphite.
manganese alloy, mixed or complex oxide cements, silicate cements, silica cements, zircon cements, chromic oxide, silica, powdered quarts, aluminum oxide, cerium oxide, zirconia, beryllia, silicon carbide, molybdenum disil-icide, tungsten carbide, metal nitrides, metal borides, titanates, zirconates, metal sulfides and graphite.
20. A composition according to Claim 1, 2 or 3 including said dissolved metal which is selected from the group consisting of magnesium, zinc, alu-minum, calcium, lithium, sodium, and potassium.
21. A composition according to Claim 12, 13 or 14 including said dis-solved metal which is selected from the group consisting of magnesium, zinc, aluminum, calcium, lithium, sodium, and potassium.
22. A composition according to Claim 1 including at least about 0.02 m/l of said amine.
23. An acidic aqueous coating composition which is capable of being heat-cured at elevated temperatures into a water insoluble coating having ex-cellent adhesion to steel and excellent corrosion resistant properties, in-cluding sacrificial corrosion protection properties, and which consists es-sentially of:
(A) phosphoric acid in an amount equivalent to at least about l m/l of dissolved phosphate;
(B) chromic anhydride in an amount equivalent to at least about 0.1 m/l of dissolved dichromate;
(C) at least about 20 g/l of aluminum metal powder, the particle size of which is -400 mesh (U.S. Standard Sieve Series);
(D) dissolved aluminum in an amount at least sufficient to impart improved corrosion resistant and adhesive properties to said coating; and (E) diethanolamine in an amount at least sufficient to reduce the temperature at which said composition can be cured into said coating.
(A) phosphoric acid in an amount equivalent to at least about l m/l of dissolved phosphate;
(B) chromic anhydride in an amount equivalent to at least about 0.1 m/l of dissolved dichromate;
(C) at least about 20 g/l of aluminum metal powder, the particle size of which is -400 mesh (U.S. Standard Sieve Series);
(D) dissolved aluminum in an amount at least sufficient to impart improved corrosion resistant and adhesive properties to said coating; and (E) diethanolamine in an amount at least sufficient to reduce the temperature at which said composition can be cured into said coating.
24. A composition according to Claim 23 wherein the amount of said amine is at least about 0.02 m/l.
25. A composition according to Claim 24 wherein the ingredients are present in amounts equivalent to:
(A) about 1 to about 6 m/l of dissolved phosphate;
(B) about 0.15 to about 3.5 m/l of dissolved dichromate;
(C) about 20 to about 2000 g/l of aluminum metal powder;
(D) about l to about 6 m/l of dissolved aluminum; and (E) about 0.02 to about 0.3 m/l of said amine.
(A) about 1 to about 6 m/l of dissolved phosphate;
(B) about 0.15 to about 3.5 m/l of dissolved dichromate;
(C) about 20 to about 2000 g/l of aluminum metal powder;
(D) about l to about 6 m/l of dissolved aluminum; and (E) about 0.02 to about 0.3 m/l of said amine.
26. An acidic aqueous coating composition which is capable of being heat-cured at elevated temperatures into a water insoluble coating and which consists essentially of:
(A) at least about l m/l of dissolved phosphate;
(B) at least about 0.1 m/l of dissolved dichromate;
(C) at least about 20 g/l of inorganic solid particulate material having a particle size of about one micron or more; and (D) an amine in an amount at least sufficient to reduce the temper-ature at which said composition can be cured into said coating.
(A) at least about l m/l of dissolved phosphate;
(B) at least about 0.1 m/l of dissolved dichromate;
(C) at least about 20 g/l of inorganic solid particulate material having a particle size of about one micron or more; and (D) an amine in an amount at least sufficient to reduce the temper-ature at which said composition can be cured into said coating.
27. A composition according to Claim 26 including dissolved metal in an amount at least sufficient to impart improved corrosion resistant and ad-hesion properties to said coating.
28. A composition according to Claim 27 wherein the amount of said amine is at least about 0.02 m/l.
29. A composition according to Claim 27 wherein the ingredients are present in amounts equivalent to:
(A) about l to about 6 m/l of dissolved phosphate;
(B) about 0.15 to about 3.5 m/l of dissolved dichromate;
(C) about 20 to about 2000 g/l of said particulate material;
(D) about 0.02 to about 0.3 m/l of said amine; and (E) about 1 to about 6 m/l of said dissolved metal.
(A) about l to about 6 m/l of dissolved phosphate;
(B) about 0.15 to about 3.5 m/l of dissolved dichromate;
(C) about 20 to about 2000 g/l of said particulate material;
(D) about 0.02 to about 0.3 m/l of said amine; and (E) about 1 to about 6 m/l of said dissolved metal.
30. A method for coating a metallic substrate comprising:
(A) applying to said substrate the coating composition of claim 23, 24 or 25; and (B) thereafter curing said composition into said insoluble coating.
(A) applying to said substrate the coating composition of claim 23, 24 or 25; and (B) thereafter curing said composition into said insoluble coating.
31. A method for coating a metallic substrate comprising:
(A) applying to said substrate the coating composition of Claim 23, 24 or 25; and (B) thereafter curing at a temperature of at least about 180°F
said composition into said insoluble coating.
(A) applying to said substrate the coating composition of Claim 23, 24 or 25; and (B) thereafter curing at a temperature of at least about 180°F
said composition into said insoluble coating.
32. A method for coating a metallic substrate comprising:
(A) applying to said substrate the coating composition of Claim 23, 24 or 25; and (B) thereafter curing at a temperature of about 215°F to about 300°F said composition into said insoluble coating.
(A) applying to said substrate the coating composition of Claim 23, 24 or 25; and (B) thereafter curing at a temperature of about 215°F to about 300°F said composition into said insoluble coating.
33. A method for coating a metallic substrate comprising:
(A) applying to said substrate the coating composition of Claim 26, 27 or 29; and (B) thereafter curing said composition into said insoluble coating.
(A) applying to said substrate the coating composition of Claim 26, 27 or 29; and (B) thereafter curing said composition into said insoluble coating.
34. A method for coating a metallic substrate comprising:
(A) applying to said substrate the coating composition of Claim 26, 27 or 29; and (B) thereafter curing at a temperature of at least about 180°F said composition into said insoluble coating.
(A) applying to said substrate the coating composition of Claim 26, 27 or 29; and (B) thereafter curing at a temperature of at least about 180°F said composition into said insoluble coating.
35. A method for coating a metallic substrate comprising:
(A) applying to said substrate the coating composition of Claim 26, 27 or 29; and (B) thereafter curing at a temperature of about 215°F to about 300°F said composition into said insoluble coating.
(A) applying to said substrate the coating composition of Claim 26, 27 or 29; and (B) thereafter curing at a temperature of about 215°F to about 300°F said composition into said insoluble coating.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US44188774A | 1974-02-12 | 1974-02-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1073610A true CA1073610A (en) | 1980-03-18 |
Family
ID=23754686
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA219,799A Expired CA1073610A (en) | 1974-02-12 | 1975-02-11 | Low-temperature curing coating composition |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS50121326A (en) |
| BE (1) | BE825180A (en) |
| CA (1) | CA1073610A (en) |
| DE (1) | DE2505438A1 (en) |
| FR (1) | FR2260609B1 (en) |
| GB (1) | GB1503934A (en) |
| IT (1) | IT1031668B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4544408A (en) * | 1983-04-18 | 1985-10-01 | Sermatech International Inc. | Thixotropic alumina coating compositions, parts and methods |
| CA1266766A (en) * | 1983-11-28 | 1990-03-20 | Mark F. Mosser | Coating composition containing particles of leachable chromate figments |
| CA1278985C (en) * | 1985-04-30 | 1991-01-15 | Allegheny Ludlum Corporation | Grain-oriented silicon steel and stress coating therefor |
| US4881975A (en) * | 1986-12-23 | 1989-11-21 | Albright & Wilson Limited | Products for treating surfaces |
| AU2002361680A1 (en) * | 2001-12-13 | 2003-07-09 | Henkel Kommanditgesellschaft Auf Aktien | Use of substituted hydroxylamines in metal phosphating processes |
| CN102817063B (en) * | 2012-07-12 | 2015-04-22 | 华南理工大学 | Preparation method for light green superhydrophobic corrosion-resistant film on surface of magnesium-lithium alloy |
| CN105949833B (en) * | 2016-07-11 | 2017-12-26 | 丽水学院 | Solution of surface treatment for Longquan sword highly effective antirust and preparation method thereof |
| CN109594070B (en) * | 2017-09-30 | 2021-02-23 | 比亚迪股份有限公司 | Neodymium iron boron phosphating solution, preparation method thereof and neodymium iron boron phosphating method |
| GB201815832D0 (en) * | 2018-09-28 | 2018-11-14 | Rolls Royce Plc | Cement |
| US11225441B2 (en) * | 2018-10-18 | 2022-01-18 | Praxair S.T. Technology, Inc. | Chromium-free silicate-based ceramic compositions with reduced curing temperature |
| CN113683429B (en) * | 2021-09-29 | 2022-05-20 | 湖北瑞宇空天高新技术有限公司 | Modified antioxidant composite phosphate coating and preparation method and application thereof |
| CN115820091B (en) * | 2022-11-30 | 2023-08-25 | 南昌航空大学 | Preparation of GO-PDA-CeO 2 Method for preparing PU wear-resistant super-hydrophobic long-acting anti-corrosion coating |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1519390B2 (en) * | 1962-01-15 | 1972-01-20 | Teleflex Ine , North Wales, Pa (V St A) | STOVE-ON COATING MIXTURE |
| CH542910A (en) * | 1970-03-16 | 1973-10-15 | Pennwalt Corp | Coating composition |
| BE787186A (en) * | 1971-08-06 | 1973-02-05 | Teleflex Inc | CORROSION PROTECTIVE COATING COMPOSITION |
-
1975
- 1975-02-04 BE BE153058A patent/BE825180A/en not_active IP Right Cessation
- 1975-02-08 DE DE19752505438 patent/DE2505438A1/en not_active Withdrawn
- 1975-02-10 JP JP50016387A patent/JPS50121326A/ja active Pending
- 1975-02-11 CA CA219,799A patent/CA1073610A/en not_active Expired
- 1975-02-11 FR FR7504265A patent/FR2260609B1/fr not_active Expired
- 1975-02-12 GB GB5907/75A patent/GB1503934A/en not_active Expired
- 1975-02-12 IT IT20183/75A patent/IT1031668B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| GB1503934A (en) | 1978-03-15 |
| FR2260609A1 (en) | 1975-09-05 |
| IT1031668B (en) | 1979-05-10 |
| DE2505438A1 (en) | 1975-08-14 |
| JPS50121326A (en) | 1975-09-23 |
| FR2260609B1 (en) | 1978-12-29 |
| BE825180A (en) | 1975-08-04 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |