GB2114162A - Coating composition for sealing sacrificial coating - Google Patents
Coating composition for sealing sacrificial coating Download PDFInfo
- Publication number
- GB2114162A GB2114162A GB08201743A GB8201743A GB2114162A GB 2114162 A GB2114162 A GB 2114162A GB 08201743 A GB08201743 A GB 08201743A GB 8201743 A GB8201743 A GB 8201743A GB 2114162 A GB2114162 A GB 2114162A
- Authority
- GB
- United Kingdom
- Prior art keywords
- coating composition
- protective coating
- coating
- water soluble
- weight
- 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.)
- Withdrawn
Links
- 239000008199 coating composition Substances 0.000 title claims abstract description 24
- 238000000576 coating method Methods 0.000 title description 15
- 239000011248 coating agent Substances 0.000 title description 13
- 238000007789 sealing Methods 0.000 title 1
- 239000011253 protective coating Substances 0.000 claims abstract description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 14
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims abstract description 10
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 7
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims abstract description 5
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 claims abstract description 5
- GVALZJMUIHGIMD-UHFFFAOYSA-H magnesium phosphate Chemical compound [Mg+2].[Mg+2].[Mg+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O GVALZJMUIHGIMD-UHFFFAOYSA-H 0.000 claims abstract description 5
- CRGGPIWCSGOBDN-UHFFFAOYSA-N magnesium;dioxido(dioxo)chromium Chemical compound [Mg+2].[O-][Cr]([O-])(=O)=O CRGGPIWCSGOBDN-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 3
- 239000000203 mixture Substances 0.000 claims description 23
- 239000003960 organic solvent Substances 0.000 claims description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 4
- 239000000049 pigment Substances 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims 1
- 238000005260 corrosion Methods 0.000 abstract description 14
- 230000007797 corrosion Effects 0.000 abstract description 14
- 230000006866 deterioration Effects 0.000 abstract description 2
- 230000002401 inhibitory effect Effects 0.000 abstract description 2
- -1 magnesium chromate Chemical compound 0.000 abstract 1
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 230000002411 adverse Effects 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 238000005507 spraying Methods 0.000 description 4
- 239000012799 electrically-conductive coating Substances 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 235000011007 phosphoric acid Nutrition 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- 239000004640 Melamine resin Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- YOBAEOGBNPPUQV-UHFFFAOYSA-N iron;trihydrate Chemical compound O.O.O.[Fe].[Fe] YOBAEOGBNPPUQV-UHFFFAOYSA-N 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 229920002050 silicone resin Polymers 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/73—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
Landscapes
- Chemical & Material Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Paints Or Removers (AREA)
Abstract
The coating composition contains phosphoric acid, a water soluble chromate e.g. magnesium chromate, and optically magnesium orthophosphate, iron oxide and chromic oxide. The protective-coating inhibits any deterioration of the corrosion inhibiting properties of the sacrificial coating composition.
Description
SPECIFICATION
Coating composition
This invention relates to a coating composition and in particular to a coating composition which is suitable for application to a previously applied coating in order to inhibit any deterioration of the properties of that coating under certain adverse conditions.
It is common practice to protect metallic surfaces from corrosion by the application thereto of a coating which is electrically conductive so that it provides sacrificial protection. Whilst in most situations, conductive coatings provide effective protection against corrosion, they are somewhat less effective when they are subject to contamination by electrically conductive materials. For instance turbine discs in gas turbine engines are commonly protected against corrosion by the application thereto of an electrically conductive coating. However in use, turbine discs tend to be contaminated by carbon which is carried by the exhaust efflux passing in operation through the turbine. If carbon is deposited upon the conductive coating, a cell is defined, the operation of which results in the corrosion of the disc metal substrate.
It is an object of the present invention to provide a protective coating composition which, when applied to an electrically conductive protective coating, protects that electrically conductive coating from contamination by electrically conductive materials without adversely affecting the protective properties of the conductive coating.
According to the present invention, a protective coating composition comprises an aqueous mixture containing from 14.70 to 23.1% by weight phosphoric acid and from 18.9 to 20.1% by weight of a water soluble chromate.
The water soluble chromate, which is preferably magnesium chromate, provides the composition with properties of corrosion resistance in addition to providing a barrier between an electrically conductive coating and any electrically conductive contaminants. This corrosion resistance may be further enhanced by the addition to the coating composition of from 5.4 to 8.6% by weight of a water soluble orthophosphate. The preferred water soluble orthophosphate is magnesium orthophosphate.
The application of coating compositions in accordance with the present invention to a substrate which has previously been coated with an electrically conductive protective coating composition is enhanced by the addition thereto of from 3.0 to 3.7% by weight of pigments to provide a witness of coverage. It is preferable to utilise pigments which further enhance the corrosion resistance properties of the coating composition and mention may be made of iron oxide and chromic oxide as suitable pigments.
Coating compositions in accordance with the present invention preferably have a water soluble or water miscible organic solvent such as ethylene glycol added thereto prior to their application to the surface to be protected. The addition of the organic solvent improves the quality of the resultant coating and renders the coating composition amenable to application by spraying. We have found that the best results are achieved if 1 0 parts by volume of the aqueous coating composition are mixed with 1 part by volume of the organic solvent.
After the mixture of the aqueous coating composition and the organic solvent have been applied to the surface to be protected, it is heated at about 800C for twenty minutes. The coating surface is then visually examined in order to determine whether it is matt or glossy. A matt surface is indicative of the application of an insufficient amount of the coating composition. If this happens the coating and heating processes are repeated until a glossy surface is obtained. The coating is then further heat treated at about 3500C for 30 minutes.
In order to assess the properties of coating compositions in accordance with the present inventions, a mild steel test piece was coated with a conductive coating composition of the type described in UK Patent No. 1 513260 in accordance with the method of application described therein.
The coated test piece was then further coated by spraying with a coating composition in accordance with the present invention. The coating composition was as follows:- % by weight
Phosporic acid (H3PO4) S.G. 1.75 14.77
Magnesium chromate (MgCrO4) 19.69
Magnesium Orthophosphate (MgHOP4) 5.63
Iron oxide (Red) 0.56
Iron oxide (Ochre) 0.56
Chromic oxide (Cr203) 2.53
Distilled water Balance
Ten parts by volume of this mixture were mixed with 1 part by volume of ethylene glycol prior to spraying.
After spraying, the test piece was heated at 80"C for 20 minutes whereupon the coating was visually examined in order to determine whether it was glossy or matt. The coating was found to be glossy and consequently the second heating step of heating the test piece at 3500C for 30 minutes was carried out.
The coated test piece was then tested for its resistance to corrosion by heating it to 4000C and then placing it in a salt spray environment. This cycle was repeated twenty times without any trace of corrosion of the test piece, thereby demonstrating that the addition of the coating composition in accordance with the present invention had not adversely affected the corrosion resistance of the original coating.
Two further test pieces were then prepared in the same manner as the first test piece. The second test piece, however, was coated only with the coating composition in accordance with UK Patent No.
1 51 3260. Both of the test pieces were then spotted with graphite suspended in an epoxy/silicone/melamine resin mixture known as VX1497 and marketed by International Pinchin
Johnson Limited. They were then heated to 4000C and placed in a salt spray environment. This was repeated ten times whereupon the test pieces were removed and examined. It was found that the test piece which had been coated with the coating composition in accordance with the present invention showed no sign of corrosion. However the test piece which had not been coated with the coating composition in accordance with the present invention showed evidence of corrosion around the graphite spots.
Thus the coating composition in accordance.with the present invention seals sacrificial corrosion inhibiting coatings without adversely affecting their sacrificial properties.
Claims (10)
1. A protective coating composition comprising an aqueous mixture containing from 14.70 to 23.1% by weight phosphoric acid and from 18.9 to 20.1% by weight of a water soluble chromate.
2. A protective coating composition as claimed in claim 1 wherein said water soluble chromate is magnesium chromate.
3. A protective coating composition as claimed in claim 1 or claim 2 wherein said aqueous mixture additionally contains from 5.4 to 8.6% by weight a water soluble orthophosphate.
4. A protective coating composition as claimed in claim 3 wherein said water soluble orthophosphate is magnesium orthophosphate.
5. A protective coating composition as claimed in any one preceding claim wherein said coating composition additionally contains a total of from 3.0 to 3.7% by weight of iron oxide and chromic oxide pigments.
6. A protective coating composition as claimed in any one preceding claim wherein said aqueous mixture is mixed with a water soluble or water miscible solvent.
7. A protective coating composition as claimed in claim 6 wherein 10 parts by volume of said aqueous mixture is mixed with 1 part by volume of said organic solvent.
8. A method of applying a protective coating composition as claimed in any one preceding claim to a surface wherein said protective coating composition is applied to said surface, heated at about 800C for twenty minutes and then heated at about 3500for 30 minutes.
9. A protective coating composition substantially as hereinbefore described with reference to the accompanying exampie.
10. A method of applying a protective coating composition substantially as hereinbefore described with reference to the accompanying example.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08201743A GB2114162A (en) | 1982-01-21 | 1982-01-21 | Coating composition for sealing sacrificial coating |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08201743A GB2114162A (en) | 1982-01-21 | 1982-01-21 | Coating composition for sealing sacrificial coating |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2114162A true GB2114162A (en) | 1983-08-17 |
Family
ID=10527787
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08201743A Withdrawn GB2114162A (en) | 1982-01-21 | 1982-01-21 | Coating composition for sealing sacrificial coating |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2114162A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0455419A1 (en) * | 1990-04-30 | 1991-11-06 | General Electric Company | Coating steel articles |
| US20230124773A1 (en) * | 2021-10-18 | 2023-04-20 | Robert Bosch Gmbh | Anti-corrosive, anti-reactive current conductors for electrochemical devices for removing ions from solutions |
-
1982
- 1982-01-21 GB GB08201743A patent/GB2114162A/en not_active Withdrawn
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0455419A1 (en) * | 1990-04-30 | 1991-11-06 | General Electric Company | Coating steel articles |
| US20230124773A1 (en) * | 2021-10-18 | 2023-04-20 | Robert Bosch Gmbh | Anti-corrosive, anti-reactive current conductors for electrochemical devices for removing ions from solutions |
| US12330965B2 (en) * | 2021-10-18 | 2025-06-17 | Robert Bosch Gmbh | Anti-corrosive, anti-reactive current conductors for electrochemical devices for removing ions from solutions |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |